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UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-Q

(Mark One)

​ | ​
☒ | QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

​

For the quarterly period ended September 30, 2025

OR

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​ | ​
☐ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES ACT OF 1934

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For the transition period from ____________ to ____________

Commission File Number: 001-12584

THERIVA BIOLOGICS, INC.

(Exact name of registrant as specified in its charter)

​

Nevada | 13-3808303
(State or other jurisdiction of incorporation or organization) | (I.R.S. Employer Identification No.)
​ | ​
9605 Medical Center Drive, Suite 270 | ​
Rockville, MD | 20850
(Address of principal executive offices) | (Zip Code)

​

(301) 417-4364

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class | Trading Symbol(s) | Name of each exchange on which registered
Common Stock | TOVX | NYSE American

​

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer, “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large Accelerated Filer | ☐ | ​ | Accelerated Filer | ☐
​ | ​ | ​ | ​ | ​
Non-accelerated Filer | ☒ | ​ | Smaller Reporting Company | ☒
​ | ​ | ​ | ​ | ​
​ | ​ | ​ | Emerging growth company | ☐

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If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

Yes ☐ No ☒

As of November 7, 2025, the registrant had 33,739,643 shares of common stock, $0.001 par value per share, outstanding.

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Table of Contents

THERIVA BIOLOGICS, INC.

NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). In particular, statements contained in this Quarterly Report on Form 10-Q, including but not limited to, statements regarding the timing of our clinical trials, the development and commercialization of our pipeline products, the sufficiency of our cash, our ability to finance our operations and business initiatives and obtain funding for such activities and the timing of any such financing, our future results of operations and financial position, business strategy and plans prospects, or costs and objectives of management for future research, development or operations, are forward-looking statements. These forward-looking statements relate to our future plans, objectives, expectations and intentions and may be identified by words such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “intends,” “targets,” “projects,” “contemplates,” “believes,” “seeks,” “goals,” “estimates,” “predicts,” “potential” and “continue” or similar words. Readers are cautioned that these forward-looking statements are based on our current beliefs, expectations and assumptions and are subject to risks, uncertainties, and assumptions that are difficult to predict, including those identified below, under Part II, Item 1A. “Risk Factors” and elsewhere in this Quarterly Report on Form 10-Q, and those identified under Part I, Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2024 filed on March 6, 2025 (the “2024 Form 10-K”). Therefore, actual results may differ materially and adversely from those expressed, projected or implied in any forward-looking statements. We undertake no obligation to revise or update any forward-looking statements for any reason.

NOTE REGARDING COMPANY REFERENCES

Throughout this Quarterly Report on Form 10-Q, “Theriva Biologics,” the “Company,” “we,” “us” and “our” refer to Theriva Biologics, Inc. and our subsidiaries Theriva Biologics, S.L. (“VCN”, formerly known as VCN Biosciences, S.L.), Pipex Therapeutics, Inc. (“Pipex Therapeutics”), Effective Pharmaceuticals, Inc. (“EPI”), Solovax, Inc. (“Solovax”), CD4 Biosciences, Inc. (“CD4”), Epitope Pharmaceuticals, Inc. (“Epitope”), Healthmine, Inc. (“Healthmine”), Putney Drug Corp. (“Putney”) and Synthetic Biomics, Inc. (“SYN Biomics”).

NOTE REGARDING TRADEMARKS

All trademarks, trade names and service marks appearing in this Quarterly Report on Form 10-Q are the property of their respective owners.

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Table of Contents

THERIVA BIOLOGICS, INC.

FORM 10-Q

TABLE OF CONTENTS

​

|  | Page
​ | PART I. FINANCIAL INFORMATION | 3
​ | ​ | ​
Item 1. | Financial Statements (Unaudited) | 3
| Condensed Consolidated Balance Sheets as of September 30, 2025 and December 31, 2024 | 3
| Condensed Consolidated Statements of Operations and Comprehensive Loss for the Three and Nine Months ended September 30, 2025 and 2024 | 4
| Condensed Consolidated Statements of Stockholders’ Equity for the Three and Nine Months ended September 30, 2025 and 2024 | 5
| Condensed Consolidated Statements of Cash Flows for the Nine Months ended September 30, 2025 and 2024 | 7
| Notes to Condensed Consolidated Financial Statements | 8
Item 2. | Management’s Discussion and Analysis of Financial Condition and Results of Operations | 28
Item 3. | Quantitative and Qualitative Disclosures About Market Risk | 48
Item 4. | Controls and Procedures | 48
​ | ​ | ​
​ | PART II. OTHER INFORMATION | 49
​ | ​ | ​
Item 1. | Legal Proceedings | 49
Item 1A. | Risk Factors | 49
Item 2. | Unregistered Sales of Equity Securities and Use of Proceeds | 51
Item 3. | Defaults Upon Senior Securities | 52
Item 4. | Mine Safety Disclosures | 52
Item 5. | Other Information | 52
Item 6. | Exhibits | 53
SIGNATURES | 55

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2

Table of Contents

PART I–FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS (UNAUDITED)

Theriva Biologics, Inc. and Subsidiaries

Condensed Consolidated Balance Sheets

(In thousands except share and par value amounts)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, 2025 |  | December 31, 2024
Assets |  | ​ |  |  | ​ |
​ | ​ | ​ | ​ | ​ | ​ | ​
Current Assets |  | ​ |  |  | ​ |
Cash and cash equivalents | ​ | $ | 7,528 | ​ | $ | 11,609
Tax credit receivable | ​ | ​ | 1,721 | ​ | ​ | 3,228
Prepaid expenses and other current assets | ​ |  | 654 | ​ | ​ | 1,444
Total Current Assets | ​ |  | 9,903 | ​ | ​ | 16,281
​ | ​ | ​ | ​ | ​ | ​ | ​
Non-Current Assets | ​ | ​ | ​ | ​ | ​ | ​
Property and equipment, net | ​ |  | 249 | ​ | ​ | 270
Restricted cash | ​ | ​ | 46 | ​ | ​ | 96
Right of use asset | ​ | ​ | 942 | ​ | ​ | 1,272
In-process research and development | ​ |  | 19,614 | ​ | ​ | 17,358
Deposits and other assets | ​ |  | 82 | ​ | ​ | 75
Total Assets | ​ | $ | 30,836 | ​ | $ | 35,352
​ | ​ | ​ | ​ | ​ | ​ | ​
Liabilities and Stockholders’ Equity | ​ |  | ​ | ​ |  |
​ | ​ | ​ | ​ | ​ | ​ | ​
Current Liabilities: | ​ |  | ​ | ​ |  |
Accounts payable | ​ | $ | 795 | ​ | $ | 859
Accrued expenses | ​ |  | 7,685 | ​ | ​ | 3,368
Accrued employee benefits | ​ |  | 747 | ​ | ​ | 1,144
Deferred research and development tax credit-current portion | ​ | ​ | 1,101 | ​ | ​ | 1,614
Loans payable-current | ​ | ​ | 57 | ​ | ​ | 61
Operating lease liability-current portion | ​ |  | 618 | ​ | ​ | 539
Total Current Liabilities | ​ |  | 11,003 | ​ | ​ | 7,585
​ | ​ | ​ | ​ | ​ | ​ | ​
Non-current Liabilities | ​ | ​ | ​ | ​ | ​ | ​
Non-current contingent consideration | ​ | ​ | 10,793 | ​ | ​ | 6,973
Loan Payable - non-current | ​ | ​ | 1,654 | ​ | ​ | 92
Non-current deferred research and development tax credit | ​ | ​ | 215 | ​ | ​ | 762
Non-current operating lease liability | ​ | ​ | 433 | ​ | ​ | 873
Total Liabilities | ​ |  | 24,098 | ​ | ​ | 16,285
​ | ​ | ​ | ​ | ​ | ​ | ​
Commitments and Contingencies (Note 13) | ​ |  | ​ | ​ |  | ​
Stockholders’ Equity: | ​ |  | ​ | ​ |  |
Preferred Stock; 10,000,000 authorized; none issued or outstanding at September 30, 2025 and December 31, 2024 | ​ | ​ | — | ​ | ​ | —
Common stock, $0.001 par value; 350,000,000 shares authorized, 10,333,572 issued and 10,304,762 outstanding at September 30, 2025 and 2,811,259 issued and 2,782,449 outstanding at December 31, 2024 | ​ |  | 9 | ​ | ​ | 3
Additional paid-in capital | ​ |  | 362,968 | ​ | ​ | 355,501
Treasury stock at cost, 28,809 shares at September 30, 2025 and at December 31, 2024 | ​ | ​ | (288) | ​ | ​ | (288)
Accumulated other comprehensive income (loss) | ​ | ​ | 763 | ​ | ​ | (1,178)
Accumulated deficit | ​ |  | (356,714) | ​ | ​ | (334,971)
Total Stockholders’ Equity | ​ |  | 6,738 | ​ | ​ | 19,067
​ | ​ | ​ | ​ | ​ | ​ | ​
Total Liabilities and Stockholders’ Equity | ​ | $ | 30,836 | ​ | $ | 35,352

​

See accompanying notes to unaudited condensed consolidated financial statements.

​

3

Table of Contents

Theriva Biologics, Inc. and Subsidiaries

Condensed Consolidated Statements of Operations and Comprehensive Loss

(In thousands, except share and per share amounts)

(Unaudited)

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | For the three months ended September 30, |  | For the nine months ended September 30,
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024
Operating Costs and Expenses: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
General and administrative | ​ | ​ | 1,889 | ​ | ​ | 2,302 | ​ | ​ | 14,516 | ​ | ​ | 5,702
Research and development | ​ |  | 2,551 | ​ | ​ | 2,734 | ​ | ​ | 7,472 | ​ | ​ | 9,145
In-process research and development impairment | ​ | ​ | — | ​ | ​ | 1,325 | ​ | ​ | — | ​ | ​ | 1,325
Goodwill impairment | ​ | ​ | — | ​ | ​ | 1,526 | ​ | ​ | — | ​ | ​ | 5,594
Total Operating Costs and Expenses | ​ |  | 4,440 | ​ | ​ | 7,887 | ​ | ​ | 21,988 | ​ | ​ | 21,766
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Loss from Operations | ​ |  | (4,440) | ​ | ​ | (7,887) | ​ | ​ | (21,988) | ​ | ​ | (21,766)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Other Income/Expense: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Foreign currency exchange (loss) gain | ​ | ​ | 14 | ​ | ​ | 3 | ​ | ​ | 30 | ​ | ​ | 1
Interest income, net | ​ |  | 65 | ​ | ​ | 158 | ​ | ​ | 215 | ​ | ​ | 559
Total Other Income | ​ |  | 79 | ​ | ​ | 161 | ​ | ​ | 245 | ​ | ​ | 560
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Net Loss | ​ | ​ | (4,361) | ​ | ​ | (7,726) | ​ | ​ | (21,743) | ​ | ​ | (21,206)
Income tax benefit | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | —
Net Loss Attributable to Common Stockholders | ​ | $ | (4,361) | ​ | $ | (7,726) | ​ | $ | (21,743) | ​ | $ | (21,206)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Net Loss Per Share - Basic and Dilutive | ​ | $ | (0.45) | ​ | $ | (6.81) | ​ | $ | (3.38) | ​ | $ | (24.47)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Weighted average number of shares outstanding during the period - Basic and Dilutive | ​ |  | 9,676,521 | ​ | ​ | 1,134,391 | ​ | ​ | 6,429,227 | ​ | ​ | 866,529
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Net Loss | ​ | ​ | (4,361) | ​ | ​ | (7,726) | ​ | ​ | (21,743) | ​ | ​ | (21,206)
Gain (loss) on foreign currency translation | ​ | ​ | (30) | ​ | ​ | 821 | ​ | ​ | 1,941 | ​ | ​ | 80
Total comprehensive loss | ​ | $ | (4,391) | ​ | $ | (6,905) | ​ | $ | (19,802) | ​ | $ | (21,126)

​

​

See accompanying notes to unaudited condensed consolidated financial statements.

​

4

Table of Contents

Theriva Biologics, Inc. and Subsidiaries

Condensed Consolidated Statements of Stockholder’s Equity

(In thousands, except share and par value amounts)

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Common Stock $0.001 Par Value | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Accumulated | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Additional | ​ | ​ | ​ | ​ | Other | ​ | ​ | ​ | ​ | Total
​ | ​ | ​ | ​ | ​ | ​ | ​ | Paid-in | ​ | Accumulated | ​ | Comprehensive | ​ | ​ | ​ | ​ | Stockholders’
​ |  | Shares |  | Amount |  | Capital |  | Deficit |  | income |  | Treasury Stock |  | Equity
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at December 31, 2024 | ​ | 2,811,259 | ​ | $ | 3 | ​ | $ | 355,501 | ​ | $ | (334,971) | ​ | $ | (1,178) | ​ | $ | (288) | ​ | $ | 19,067
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 100 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 100
Foreign currency exchange gains | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 654 | ​ | ​ | — | ​ | ​ | 654
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (4,324) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (4,324)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at March 31, 2025 | ​ | 2,811,259 |  | $ | 3 |  | $ | 355,601 |  | $ | (339,295) |  | $ | (524) | ​ | $ | (288) | ​ | $ | 15,497
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 173 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 173
Issuance of Common Stock and Warrants, net of issuance costs | ​ | 1,990,900 | ​ | ​ | 2 | ​ | ​ | 6,688 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 6,690
Conversion of Warrants to Common | ​ | 4,285,883 | ​ | ​ | 3 | ​ | ​ | 1 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 4
Foreign currency exchange gains | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,317 | ​ | ​ | — | ​ | ​ | 1,317
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (13,058) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (13,058)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at June 30, 2025 | ​ | 9,088,042 | ​ | $ | 8 | ​ | $ | 362,463 | ​ | $ | (352,353) | ​ | $ | 793 | ​ | $ | (288) | ​ | $ | 10,623
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 228 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 228
Stock issued under “at-the-market” offering | ​ | 706,810 | ​ | ​ | 1 | ​ | ​ | 278 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 279
Conversion of Warrants to Common | ​ | 538,720 | ​ | ​ | — | ​ | ​ | (1) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (1)
Foreign currency exchange gains | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (30) | ​ | ​ | — | ​ | ​ | (30)
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (4,361) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (4,361)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at September 30, 2025 | ​ | 10,333,572 | ​ | $ | 9 | ​ | $ | 362,968 | ​ | $ | (356,714) | ​ | $ | 763 | ​ | $ | (288) | ​ | $ | 6,738

​

5

Table of Contents

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Common Stock $0.001 Par Value | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Accumulated | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ |  | ​ | ​ | ​ | Additional | ​ | ​ | ​ | ​ | Other | ​ | ​ | ​ | ​ | Total
​ | ​ | ​ | ​ | ​ | ​ | ​ | Paid-in | ​ | Accumulated | ​ | Comprehensive | ​ | ​ | ​ | ​ | Stockholders’
​ |  | Shares |  | Amount |  | Capital |  | Deficit |  | income |  | Treasury Stock |  | Equity
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at December 31, 2023 | ​ | 715,028 | ​ | $ | 1 | ​ | $ | 346,536 | ​ | $ | (309,318) | ​ | $ | 32 | ​ | $ | (288) | ​ | $ | 36,963
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 160 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 160
Foreign currency exchange gains (losses) | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (569) | ​ | ​ | — | ​ | ​ | (569)
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (5,165) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (5,165)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at March 31, 2024 | ​ | 715,028 |  | $ | 1 |  | $ | 346,696 |  | $ | (314,483) |  | $ | (537) | ​ | $ | (288) | ​ | $ | 31,389
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 172 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 172
Stock issued under “at-the-market” offering | ​ | 174,282 | ​ | ​ | — | ​ | ​ | 1,839 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,839
Foreign currency exchange gains (losses) | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (172) | ​ | ​ | — | ​ | ​ | (172)
Series C Preferred Stock conversion to Common | ​ | 35,523 | ​ | ​ | — | ​ | ​ | 988 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 988
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (8,316) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (8,316)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at June 30, 2024 | ​ | 924,833 | ​ | $ | 1 | ​ | $ | 349,695 | ​ | $ | (322,799) | ​ | $ | (709) | ​ | $ | (288) | ​ | $ | 25,900
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Stock-based compensation | ​ | — | ​ | ​ | — | ​ | ​ | 177 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 177
Stock issued under “at-the-market” offering | ​ | 395,000 | ​ | ​ | 1 | ​ | ​ | 1,763 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,764
Issuance of Common Stock and Warrants, net of issuance costs | ​ | 918,600 | ​ | ​ | 1 | ​ | ​ | 1,952 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,953
Foreign currency exchange gains (losses) | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 821 | ​ | ​ | — | ​ | ​ | 821
Series C Preferred Stock conversion to Common | ​ | 36,609 | ​ | ​ | — | ​ | ​ | 1,018 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,018
Series D Preferred Stock conversion to Common | ​ | 26,230 | ​ | ​ | — | ​ | ​ | 728 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 728
Conversion of Pre-Funded Warrants to Common | ​ | 345,000 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | —
Net loss | ​ | — | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (7,726) | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (7,726)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance at September 30, 2024 | ​ | 2,646,272 | ​ | $ | 3 | ​ | $ | 355,333 | ​ | $ | (330,525) | ​ | $ | 112 | ​ | $ | (288) | ​ | $ | 24,635

​

See accompanying notes to unaudited condensed consolidated financial statements.

​

​

6

Table of Contents

Theriva Biologics, Inc. and Subsidiaries

Condensed Consolidated Statements of Cash Flows

(In thousands)

(Unaudited)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the Nine Months Ended September 30,
​ |  | 2025 |  | 2024
Cash Flows From Operating Activities: |  | ​ |  |  | ​ |
Net loss | ​ | $ | (21,743) | ​ | $ | (21,206)
Adjustments to reconcile net loss to net cash used in operating activities: | ​ |  | ​ | ​ |  | ​
Stock-based compensation | ​ |  | 501 | ​ | ​ | 509
In-process research and development impairment | ​ | ​ | — | ​ | ​ | 1,325
Goodwill impairment | ​ |  | — | ​ |  | 5,594
Change in fair value of contingent consideration | ​ |  | 9,806 | ​ | ​ | 514
Non-cash lease expense | ​ | ​ | 383 | ​ | ​ | 335
Depreciation | ​ |  | 81 | ​ | ​ | 110
Deferred research and development tax credit | ​ | ​ | (1,306) | ​ | ​ | (669)
Changes in operating assets and liabilities: | ​ |  | ​ | ​ |  | ​
Prepaid expenses and other current assets | ​ |  | 866 | ​ | ​ | 1,124
Accounts payable | ​ |  | (140) | ​ | ​ | (21)
Accrued expenses | ​ |  | (1,386) | ​ | ​ | 725
Accrued employee benefits | ​ |  | (436) | ​ | ​ | (229)
Operating lease liability | ​ |  | (413) | ​ | ​ | (357)
Net Cash Used In Operating Activities | ​ |  | (13,787) | ​ | ​ | (12,246)
​ | ​ | ​ | ​ | ​ | ​ | ​
Cash Flows from Investing Activities | ​ |  | ​ | ​ |  | ​
Purchase of property and equipment | ​ | ​ | (35) | ​ | ​ | (1)
Net Cash Used in Investing Activities | ​ | ​ | (35) | ​ | ​ | (1)
​ | ​ | ​ | ​ | ​ | ​ | ​
Cash Flows from Financing Activities | ​ |  | ​ | ​ |  | ​
Tax credit receivable | ​ | ​ | 1,839 | ​ | ​ | —
Proceeds from issuance of common stock | ​ | ​ | 6,690 | ​ | ​ | 1,953
Proceeds from issuance of common stock for warrant exercises | ​ | ​ | 4 | ​ | ​ | —
Payment of loans payable | ​ | ​ | (69) | ​ | ​ | (67)
Proceeds from issuance ATM offering, net of issuance costs | ​ | ​ | 279 | ​ | ​ | 3,603
Payment of contingent consideration | ​ | ​ | (500) | ​ | ​ | —
Proceeds from long term debt | ​ | ​ | 1,492 | ​ | ​ | —
Net Cash provided by Financing Activities | ​ | ​ | 9,735 | ​ | ​ | 5,489
​ | ​ | ​ | ​ | ​ | ​ | ​
Effects of exchange rate changes on cash and cash equivalents | ​ | ​ | (44) | ​ | ​ | (9)
Net increase (decrease) in cash and cash equivalents and restricted cash | ​ | ​ | (4,131) | ​ | ​ | (6,767)
Cash, cash equivalents and restricted cash at the beginning of this period | ​ |  | 11,705 | ​ | ​ | 23,279
Cash, cash equivalents and restricted cash at the end of this period | ​ | $ | 7,574 | ​ | $ | 16,512
​ | ​ | ​ | ​ | ​ | ​ | ​
Reconciliation of cash, cash equivalents, and restricted cash reported in the consolidated balance sheet | ​ | ​ | ​ | ​ | ​ | ​
Cash and cash equivalents | ​ | $ | 7,528 | ​ | $ | 16,409
Restricted cash included in other long-term assets | ​ | ​ | 46 | ​ | ​ | 103
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows | ​ | $ | 7,574 | ​ | $ | 16,512
​ | ​ | ​ | ​ | ​ | ​ | ​

​

See accompanying notes to unaudited condensed consolidated financial statements.

​

​

7

Table of Contents

​

Synthetic Biologics, Inc. and Subsidiaries

Notes to Condensed Consolidated Financial Statements

(Unaudited)

1. Organization, Nature of Operations and Basis of Presentation

Description of Business

Theriva Biologics, Inc. (the “Company” or “Theriva Biologics”) is a diversified clinical-stage company developing therapeutics in areas of high unmet need. As a result of the acquisition in March 2022 of Theriva Biologics S.L. (“VCN”, formerly known as VCN Biosciences, S.L.) (the “Acquisition”), described in more detail below, the Company transitioned its strategic focus to oncology through the development of VCN’s new oncolytic adenovirus platform designed for intravenous and intravitreal delivery to trigger tumor cell death, to improve access of co-administered cancer therapies to the tumor, and to promote a robust and sustained anti-tumor response by the patient’s immune system. Prior to the Acquisition, the Company’s focus was on developing therapeutics designed to treat gastrointestinal (GI) diseases in areas which included its clinical development candidates: (1) SYN-004 (ribaxamase) which is designed to degrade certain commonly used intravenous (IV) beta-lactam antibiotics within the GI tract to prevent microbiome damage thereby preventing overgrowth and infection by pathogenic organisms such as Clostridioides difficile infection (CDI), and vancomycin resistant Enterococci (VRE), and reducing the incidence and severity of acute graft-versus-host-disease (aGVHD) in allogeneic hematopoietic cell transplant (HCT) recipients, and (2) SYN-020, a recombinant oral formulation of the enzyme intestinal alkaline phosphatase (IAP) produced under cGMP conditions and intended to treat both local GI and systemic diseases.

Basis of Presentation

The accompanying condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, they do not include all the information and notes required by Accounting Principles Generally Accepted in the United States of America (“U.S. GAAP”) for complete financial statements. The accompanying condensed consolidated financial statements include all adjustments, comprised of normal recurring adjustments, considered necessary by management to fairly state the Company’s results of operations, financial position, and cash flows. The operating results for the interim periods are not necessarily indicative of results that may be expected for any other interim period or for the full year. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 filed on March 6, 2025 (the “2024 Form 10-K”).

On August 15, 2024, the Board of Directors of the Company approved a reverse stock split of the Company’s authorized, issued and outstanding shares of common stock, par value $0.001 per share (the “Common Stock”), at a ratio of one (1) share of Common Stock for every twenty - five (25) shares of Common Stock (the “Reverse Stock Split”). The Reverse Stock Split was effective on August 26, 2024 (the “Effective Time).

As a result of the Reverse Stock Split, each twenty-five (25) pre-split shares of Common Stock outstanding was automatically combined into one (1) new share of Common Stock without any action on the part of the holders, and the number of outstanding shares of Common Stock was reduced from 25,131,230 shares to 1,005,249 shares (subject to rounding of fractional shares) and the number of authorized shares of Common Stock was reduced from 350,000,000 share to 14,000,000 shares and then increased to 350,000,000 after obtaining approval of the Company’s stockholders at the 2024 annual meeting of stockholders. Stockholders who otherwise were entitled to receive fractional shares because they held a number of pre-reverse stock split shares of the Company’s Common Stock not evenly divisible by 25, received, in lieu of a fractional share, that number of shares rounded up to the nearest whole share. The Reverse Stock Split did not alter the par value of the Company’s Common Stock or modify any voting rights or other terms of the Common Stock. In addition, pursuant to their terms, a proportionate adjustment was made to the per share conversion exercise price and number of shares issuable under all of the Company’s outstanding shares of convertible preferred stock and stock options and warrants to purchase shares of Common Stock, and the number of shares authorized and reserved for issuance pursuant to the Company’s equity incentive plans was reduced proportionately.

​

8

Table of Contents

1. Organization, Nature of Operations and Basis of Presentation (continued)

All affected share amounts and exercise/conversion prices in the condensed consolidated financial statements and footnotes below have been adjusted retrospectively for the Reverse Stock Split.

The condensed consolidated financial statements are prepared in conformity with U.S. GAAP, which requires the use of estimates, judgments and assumptions that affect the amounts of assets and liabilities at the reporting date and the amounts of revenue and expenses in the periods presented. The Company believes that the accounting estimates employed are appropriate and the resulting balances are reasonable; however, due to the inherent uncertainties in making estimates, actual results may differ from the original estimates, requiring adjustments to these balances in future periods. As of September 30, 2025, the Company has one operating segment (which includes the legacy Company business and the VCN business) and therefore one reporting segment.

​

2. Going Concern

The accompanying consolidated financial statements have been prepared assuming the Company will continue as a going concern. The Company continues to incur losses and, as of September 30, 2025, the Company had an accumulated deficit of approximately $357 million. Since inception, the Company has financed its activities principally from the proceeds from the issuance of equity securities.

The Company’s ability to continue as a going concern is dependent upon the Company’s ability to raise additional debt and equity capital or secure a potential license or strategic relationship that can help fund its clinical development activities. There can be no assurance that such capital will be available in sufficient amounts or on terms acceptable to the Company. These factors raise substantial doubt about the Company’s ability to continue as a going concern. The accompanying consolidated financial statements do not include any adjustments relating to the recoverability of the recorded assets or the classification of liabilities that may be necessary should the Company be unable to continue as a going concern.

The Company continues to experience operating losses and faces significant uncertainties related to its business model, market conditions, and strategic initiatives. These factors raise substantial doubt about the Company’s ability to continue as a going concern beyond the next twelve months without additional capital,or other strategic actions. In order to address the Company’s capital needs, including its planned clinical trials, the Company is actively pursuing additional equity or debt financing in the form of either a private placement or a public offering as well as partnerships and other collaborations. The Company has been in ongoing discussions with strategic institutional investors and investment banks with respect to such possible offerings. Such additional financing opportunities might not be available to the Company when and if needed, on acceptable terms or at all. If the Company is unable to obtain additional financing in sufficient amounts or on acceptable terms under such circumstances, the Company’s operating results and prospects will be adversely affected.

On September 28, 2025, the Board of Directors of the Company approved a plan to resize and restructure the Company (the “Plan”) for purposes of focusing its attention on business development and licensing activities and the Company’s upcoming meetings with the U.S. Food and Drug Administration and the European Medicines Agency for planned clinical trials in patients with metastatic pancreatic ductal adenocarcinoma (“PDAC”) and retinoblastoma. The Company’s lead product candidate, VCN-01, a clinical stage oncolytic human adenovirus that is modified for tumor-selective replication and to express an enzyme, PH20 or hyaluronidase, has been evaluated in a Phase 2b clinical study for the treatment of pancreatic cancer (“VIRAGE”), and has recently been used to treat patients in a Phase 1 clinical study for the treatment of retinoblastoma.

Pursuant to the Plan, on September 30, 2025, the Company implemented a workforce reduction of approximately seven employees or 32% of the current global Company workforce. The goal of this reduction is to direct the Company’s resources towards business development and licensing activities and clinical trial planning and preparation for potential pivotal trials of VCN-01 in patients with PDAC and retinoblastoma, which it believes will represent its best opportunity for success. The Company expects to substantially complete the employee reduction immediately and estimates that it will incur a total of approximately $520,000 in charges in connection with the workforce reduction, which was accrued for as of September 30, 2025. These charges consist primarily of cash severance and benefits over a three-month period, in connection with the workforce reduction. The Plan is expected to save approximately $1.8 million in compensation and benefits annually, and together with additional anticipated operating cost reductions the Company expects that it will extend its cash runway into the first quarter of 2027.

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2. Going Concern (continued)

The estimates of the charges and expenditures that the Company expects to incur in connection with the workforce reduction, and the timing thereof, are subject to a number of assumptions, including local law requirements in various jurisdictions, and actual amounts may differ materially from estimates. The Company may also incur other charges or cash expenditures not currently contemplated due to unanticipated events that may occur.

At September 30, 2025, the Company had cash and cash equivalents of approximately $7.5 million. Based upon the Company’s current business plans, management believes that the Company’s current cash on hand of $15.5 million in early November 2025 will be sufficient to fully execute its plans through the fourth quarter of 2026 and into the first quarter of 2027. Commencement of planned future clinical trials is subject to the Company’s successful pursuit of opportunities that will allow it to establish the clinical infrastructure and financial resources necessary to successfully initiate and complete its plan. The Company anticipates its current cash will allow it to cover overhead costs, exploratory VCN-01 manufacturing scale-up activities, regulatory activities and preparation for proposed VCN-01 clinical trials in PDAC and retinoblastoma, and limited preclinical research efforts. The Company will be required to obtain additional funding in order to continue the development of its current product candidates within the anticipated time periods (including initiation of its planned future clinical trials), if at all, and to continue to fund operations at the current cash expenditure levels. Currently, the Company does not have commitments from any third parties to provide it with capital. Potential sources of financing include strategic relationships, public or private sales of equity (including through its Amended and Restated At The Market Issuance Sales Agreement, dated February 9, 2021, as amended by Amendment No. 1 thereto, dated May 3, 2021, as further amended by Amendment No. 2 thereto, dated May 2, 2024 (the “ATM Sales Agreement”)) or debt and other sources. The Company cannot assure that it will meet the requirements for use of the ATM Sales Agreement or that additional funding will be available on favorable terms at all. If the Company fails to obtain additional funding for its clinical trials, whether through the sale of securities or a partner or collaborator, and otherwise when needed, it will not be able to execute its business plan as planned and will be forced to cease certain development activities (including initiation of planned clinical trials) until funding is received and its business will suffer, which would have a material adverse effect on its financial position, results of operations and cash flows.

​

The actual amount of funds the Company will need to operate is subject to many factors, some of which are beyond its control. These factors include the following:

| ● | the progress of its research activities;

| ● | the number and scope of its research programs;

| ● | the ability to recruit patients for clinical studies in a timely manner;

| ● | the progress of its preclinical and clinical development activities;

| ● | the progress of the development efforts of parties with whom the Company has entered into research and development agreements and amount of funding received from partners and collaborators;

| ● | its ability to maintain current research and development licensing arrangements and to establish new research and development and licensing arrangements;

| ● | the Company’s ability to achieve its milestones under licensing arrangements;

| ● | the costs associated with manufacturing-related services to produce material for use in its clinical trials;

| ● | the costs involved in prosecuting and enforcing patent claims and other intellectual property rights; and

| ● | the costs and timing of regulatory approvals.

​

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2. Going Concern (continued)

The Company has based its estimates of funding requirements on assumptions that may prove to be wrong. The Company may need to obtain additional funds sooner or in greater amounts than it currently anticipates.

If the Company raises funds by selling additional shares of Common Stock or other securities convertible into Common Stock, the ownership interest of the existing stockholders will be diluted. If the Company is not able to obtain financing when needed, it may be unable to carry out its business plan. As a result, the Company may have to significantly limit its operations and its business, financial condition and results of operations would be materially harmed.

​

3. Summary of Significant Accounting Policies

There have been no new or material changes to the significant accounting policies discussed in the Company’s audited financial statements and the notes thereto included in the 2024 Form 10-K.

Segment information

The Company’s chief operating decision maker (“CODM”) is the Company’s Chief Executive Officer. The CODM is assisted in his responsibilities of making decisions regarding resource allocation and performance assessment by the leadership team, consisting of the General Director, Europe and Head of Corporate and Product Development.

The Company views its operations and manages its business as one operating segment, focused on the discovery and development of oncolytic viruses intended to overcome the protective barrier surrounding solid tumors and selectively kill tumor cells. The segment-level financial statement information is the same as the financial information presented in the statement of operations and comprehensive loss. The Company monitors its cash and cash equivalents as reported on the Company’s Balance Sheets to determine funding for its research and development.

As the Company does not currently generate revenue, the CODM assesses Company performance through the achievement of pre-clinical and clinical research goals. In addition to the Company’s Statement of Operations and Comprehensive Loss, the CODM is regularly provided with budgeted and forecasted expense information which is used to determine the Company’s liquidity needs and cash allocation. The measure of segment assets is reported on the balance sheet as total assets.

IPR&D

IPR&D assets represent the fair value assigned to technologies that the Company acquired, which at the time of acquisition have not reached technological feasibility and have no alternative future use. IPR&D assets are considered to have indefinite-lives until the completion or abandonment of the associated research and development projects. If and when development is complete, which generally occurs upon regulatory approval and the ability to commercialize products associated with the IPR&D assets, these assets are then deemed to have definite lives and are amortized based on their estimated useful lives at that point in time. If development is terminated or abandoned, the Company may have a full or partial impairment charge related to the IPR&D assets, calculated as the excess of carrying value of the IPR&D assets over fair value.

During the period that the assets are considered indefinite-lived, they are tested for impairment on an annual basis on October 1, or more frequently if the Company becomes aware of any events occurring or changes in circumstances that could indicate an impairment. The impairment test consists of a comparison of the estimated fair value of the IPR&D with its carrying amount. If the carrying amount exceeds the fair value, an impairment charge is recognized in an amount equal to that excess. The key assumptions used to value IPR&D include estimates of future cash flows and to the discount rate applicable to the future cash flow periods.

No impairment charges were recorded during the three and nine months ended September 30, 2025. For the three and nine months ending September 30, 2024, the Company concluded that the in-process R&D with a carrying value of $19.8 million was impaired and was written down to its estimated fair value of $18.6 million and an impairment charge of $1.3 million was recorded.

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3. Summary of Significant Accounting Policies (continued)

Contingent Consideration

Consideration paid in a business combination may include potential future payments that are contingent upon the acquired business achieving certain milestones in the future (“contingent consideration”). Contingent consideration liabilities are measured at their estimated fair value as of the date of acquisition, with subsequent changes in fair value recorded in the consolidated statements of operations. The Company estimates the fair value of the contingent consideration as of the acquisition date using the estimated future cash outflows based on the probability of meeting future milestones. Payments for amounts not in excess of original fair values established at acquisition date (including measurement period adjustments), and not paid within a period considered to be close to the transaction date, are reflected as financing activities in the statement of cash flows. Subsequent to the date of acquisition, the Company reassesses the actual consideration earned and the probability-weighted future earn-out payments at each balance sheet date. The discounted cash flow is the method used to value the contingent consideration which includes inputs of not readily observable market data, which are level 3 inputs. Any adjustment to the contingent consideration liability will be recorded in the consolidated statements of operations. Contingent consideration liabilities expected to be settled within 12 months after the balance sheet date are presented in current liabilities, with the non-current portion recorded under long-term liabilities in the consolidated balance sheets. See Fair Value of Financial Instruments below.

Long-Lived Assets Impairment

Long-lived assets include property, equipment, and right of use assets. Management reviews the Company’s long-lived assets for impairment annually or whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be fully recoverable. The judgments made related to the expected useful lives of long-lived assets, definitions of lease terms and the Company’s ability to realize undiscounted cash flows in excess of the carrying amounts of these assets are affected by factors such as the ongoing maintenance and improvements of the assets, changes in economic conditions, changes in usage or operating performance and other factors. The Company determines the extent to which an asset may be impaired based upon its expectation of the asset’s future usability as well as whether there is reasonable assurance that the future cash flows associated with the asset will be in excess of its carrying amount. If the total of the expected undiscounted future cash flows is less than the carrying amount of the asset, a loss is recognized for the difference between the fair value and the carrying value of the asset. No impairment charges were recorded during the three and nine months ended September 30, 2025 and 2024.

Research and Development Tax Credits

The Company, through its Theriva S.L. subsidiary, participates in a Research and Development incentive program sponsored by the Spanish government. The program provides for reimbursement of certain expenses incurred in research and development efforts the Company incurs in Spain. The program provides for certain limits on the types and amounts of expenses and requires participants to complete a certification and apply for the refund annually. Subsequent to the period in which expenses are incurred, the program requires participants to maintain certain workforce levels and research and development expenditures over a 24-month period. The Company accounts for the reimbursement as a tax credit receivable related to amounts that had been approved by the Spanish government and a corresponding deferred research and development tax credit as it was determined that amounts became probable of being received upon the receipt of the approval. Additionally, the Company has elected to account for the tax credit as a contra-expense as this most appropriately reflects the nature of the transaction and will reduce future research and development expenditures as the Company continues to incur expenses in the upcoming 24-month period.

​

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3. Summary of Significant Accounting Policies – (continued)

Recent Accounting Pronouncements and Developments

On November 2024, the FASB issued ASU 2024-03 - Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses. The ASU requires more detailed disclosures about the types of expenses in commonly presented expense captions such as cost of sales, selling, general and administrative expenses and research and development expenses. This includes separate footnote disclosure for expenses such as purchases of inventory, employee compensation, depreciation, and intangible asset amortization. Public business entities are required to apply the guidance prospectively and may apply it retrospectively. The ASU’s amendments are effective for public business entities for annual periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Public business entities are required to apply the guidance prospectively and may apply it retrospectively. The Company is currently evaluating the effect of adopting this ASU.

In December 2023, the FASB issued final guidance in ASU No. 2023-09, Income Taxes (ASC 740): Improvements to Income Tax Disclosures requiring entities to provide additional information in the rate reconciliation and disclosures about income taxes paid. For public business entities, the guidance is effective for annual periods beginning after December 15, 2024. The Company is not early adopting this ASU, and therefore, this ASU is not adopted in the current period. The Company does not expect this ASU to have a material impact on the consolidated financial statements.

​

4. Intangibles

As a result of the Acquisition of VCN, the Company has an intangible asset, in-process research and development (“IPR&D”). The IPR&D is deemed to have indefinite lives and therefore not amortized. During the three months ended June 30, 2025, the Company announced in a press release that it had met the primary survival and safety endpoints in its VIRAGE Phase 2b clinical trial evaluating the Company’s lead product candidate VCN-01. As a result, the Company deemed this to be a change in circumstances that could indicate impairment. The Company updated its key assumptions used to value IPR&D including estimates of future cash flows and the discount rate applicable to the future cash flow periods. The Company determined that there was no impairment to the valuation of the IPR&D asset.

The following table provides the Company’s in-process R&D as of September 30, 2025.

​

​ | ​ | ​ | ​
​ |  | In-process
​ | ​ | R&D (in thousands)
Balance at December 31, 2024 | ​ | $ | 17,358
Effects of exchange rates | ​ | ​ | 2,256
Balance at September 30, 2025 | ​ | $ | 19,614

​

There were no impairment charges recorded during the three months ended September 30, 2025. During the three and nine months ending September 30, 2024, the Company experienced a sustained decline in the quoted market price of the Company’s Common Stock and the Company deemed this to be a triggering event for impairment. The Company performed an interim impairment analysis using both the replacement cost method and the “Income approach” that requires significant judgments, including primarily the estimation of future development costs, the probability of success in various phases of its development programs, potential post-launch cash flows and a risk-adjusted weighted average cost of capital. For the three and nine months ending September 30, 2024, the Company concluded that the in-process R&D with a carrying value of $19.8 million was impaired and was written down to its estimated fair value of $18.6 million and an impairment charge of $1.3 million was recorded.

​

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5. Fair Value of Financial Instruments

Fair Value of Financial Instruments

Accounting Standards Codification (“ASC”) 820, Fair Value Measurement, defines fair value as the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is determined based upon assumptions that market participants would use in pricing an asset or liability. Fair value measurements are classified on a three-tier hierarchy as follows:

| ● | Level 1 inputs: Quoted prices (unadjusted) for identical assets or liabilities in active markets;

| ● | Level 2 inputs: Inputs, other than quoted prices, that are observable either directly or indirectly; and

| ● | Level 3 inputs: Unobservable inputs for which there is little or no market data, which require the reporting entity to develop its own assumptions.

In many cases, a valuation technique used to measure fair value includes inputs from multiple levels of the fair value hierarchy described above. The lowest level of significant input determines the placement of the entire fair value measurement in the hierarchy.

The carrying amounts of the Company’s short-term financial instruments, including cash and cash equivalents, accounts payable and accrued liabilities, approximate fair value due to the relatively short period to maturity for these level 1 instruments.

As a result of the acquisition of VCN the Company acquired interest-free or below-market interest rate loans extended by Spanish government. Additionally, the Company received an unsecured loan of €1.3 million (approximately $1.4 million) as a lump sum payment on January 17, 2025 which bears interest at a rate of 4.015% from the National Knowledge Transfer Program of the Spanish government’s Ministry of Science, Innovation & Universities (See Note 12). The carrying value of the loans payable approximate fair value and are classified under level 2.

Pursuant to the terms of the VCN purchase agreement, the Company agreed to pay up to $70.2 million in additional consideration upon the achievement of certain milestones, including regulatory filings of which to date $6.8 million has been paid. In September 2022, the Company received approval from the FDA to proceed with the Phase 2 clinical trial of VCN - 01 in metastatic pancreatic ductal adenocarcinoma (mPDAC). Due to this approval the Company paid Grifols Innovation and New Technologies Limited (“Grifols”), $3.0 million in the fourth quarter 2022. In August 2023, the Company initiated patient dosing in the U.S. in its Phase 2 clinical trial of VCN-01 in mPDAC. As a result, payment was made subsequent to September 30, 2023 in the amount of $3.25 million. During the three months ended June 30, 2025, the Company met the primary survival and safety endpoints in its VIRAGE Phase 2b clinical trial evaluating the Company’s lead product candidate VCN-01. As a result of achieving the primary survival and safety endpoints in the Phase 2b clinical trial, the Company is obligated to pay Grifols $6 million. On August 5, 2025, the Company and Grifols agreed to deferring the $6 million milestone payment into three payments; $500,000 was paid in August 2025, $500,000 will be paid by the end of December 2025, and the remaining $5 million payment will be deferred until a licensing or business development transaction is secured. The discounted cash flow method used to value this contingent consideration includes inputs of not readily observable market data, which are Level 3 inputs. The fair value of the contingent consideration was $10.8 million as of September 30, 2025 and is all reflected as non-current contingent consideration liability. During the three months ended September 30, 2025 and 2024, the Company recognized in operating expense a $633,000 increase and $587,000 increase, respectfully, fair value adjustment to contingent consideration. During the nine months ended September 30, 2025 and 2024, the Company recognized in operating expense a $9.8 million increase and $514,000 increase, respectfully, fair value adjustment to contingent consideration. There were no transfers in or out of the level 3 liabilities during the three and nine months ended September 30, 2025 and 2024, with the exception of the reclassification of $6.0 million related to the milestone that was met during the quarter ending June 30, 2025 and reclassified to accrued expenses.

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5. Fair Value of Financial Instruments – (continued)

The following table summarizes the change in the fair value as determined by Level 3 inputs for the contingent consideration liabilities as of September 30, 2025 and December 31, 2024:

​

​ | ​ | ​ | ​
​ |  | (in thousands)
Balance at December 31, 2024 | ​ | $ | 6,973
Change in fair value | ​ |  | 9,806
Reclassification of amounts to accrued expenses due to milestone being achieved | ​ |  | (5,986)
Balance at September 30, 2025 | ​ | $ | 10,793
​ | ​ | ​ | ​
Contingent consideration, current portion | ​ | $ | —
Contingent consideration, net of current portion | ​ |  | 10,793
Balance at September 30, 2025 | ​ | $ | 10,793

​

​ | ​ | ​ | ​
​ |  | (in thousands)
Balance at December 31, 2023 | ​ | $ | 6,274
Change in fair value | ​ |  | 699
Balance at December 31, 2024 | ​ | $ | 6,973
​ | ​ | ​ | ​
Contingent consideration, current portion | ​ | $ | —
Contingent consideration, net of current portion | ​ |  | 6,973
Balance at December 31, 2024 | ​ | $ | 6,973

​

The fair value of financial instruments measured on a recurring basis is as follows:

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | As of September 30, 2025
Description |  | Total |  | Level 1 |  | Level 2 |  | Level 3
Liabilities: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Contingent consideration | ​ | $ | 10,793 |  | $ | — |  | $ | — | ​ | $ | 10,793
Total liabilities | ​ | $ | 10,793 |  | $ | — |  | $ | — | ​ | $ | 10,793

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | As of December 31, 2024
Description |  | Total |  | Level 1 |  | Level 2 |  | Level 3
Liabilities: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Contingent consideration | ​ | $ | 6,973 |  | $ | — |  | $ | — | ​ | $ | 6,973
Total liabilities | ​ | $ | 6,973 |  | $ | — |  | $ | — | ​ | $ | 6,973

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5. Fair Value of Financial Instruments – (continued)

The recurring Level 3 fair value measurements of contingent consideration for which a liability is recorded include the following significant unobservable inputs:

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | As of September 30, 2025
​ | ​ | Valuation | ​ | Significant | ​ | Weighted Average
​ |  | Methodology |  | Unobservable Input |  | (range, if applicable)
Contingent Consideration |  | Discounted Cash Flows |  | Milestone dates |  | 2026-2031
​ |  | ​ | ​ | ​ | ​ | ​
​ |  |  |  | Discount rate |  | 11.7% to 11.9%
​ |  |  |  | Weighted Average Discount rate |  | 11.7%
​ |  |  |  | Probability of Occurrence (periodic for each Milestone) |  | 11.7% to 92.0%
​ |  |  |  | Probability of occurrence (cumulative through each Milestone) |  | 5.3% to 48.8%

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | As of December 31, 2024
​ | ​ | Valuation | ​ | Significant | ​ | Weighted Average
​ |  | Methodology |  | Unobservable Input |  | (range, if applicable)
Contingent Consideration |  | Discounted Cash Flows |  | Milestone dates |  | 2026-2028
​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Discount rate | ​ | 11.6% to 11.8%
​ | ​ | ​ | ​ | Weighted Average Discount rate | ​ | 11.7%
​ | ​ | ​ | ​ | Probability of Occurrence (periodic for each Milestone) | ​ | 11.7% to 92.0%
​ |  | ​ |  | Probability of occurrence (cumulative through each Milestone) | ​ | 5.3% to 48.8%

​

​

6. Research and Development Tax Credits

The Company, through its Theriva S.L. subsidiary, participates in a Research and Development program sponsored by the Spanish government. The program provides for reimbursement of certain expenses incurred in research and development efforts Theriva S.L. incurs in Spain. The reimbursements can be through either tax credits or direct refunds. The program provides for certain limits on the types and amounts of expenses for which reimbursement may be sought and requires participants to complete a certification and apply for the refund annually. Subsequent to the period in which expenses are incurred, the program requires participants to maintain certain workforce levels and research and development expenditures over a 24-month period.

In the quarter ended June 30, 2023, the Company completed the certification and applied for direct reimbursement, as opposed to a tax credit, for its qualifying research and development expenses incurred in the year ended December 31, 2022. The Company received approvals from the Spanish government in September and October 2023. During the quarter ended June 30, 2024, the Company completed the certification and applied for direct reimbursement for its qualifying research and development expenses incurred in the year ended December 31, 2023. The Company received approvals from the Spanish government in December 2024.

The Company evaluated the program and concluded that it qualified to be accounted for as government assistance. Accordingly, the Company, as allowed by U.S. GAAP, elected to account for the grant by analogizing to the guidance provided by International Accounting Standards (“IAS”) 20, Accounting for Government Grants and Disclosure of Government Assistance. Accordingly, the Company recognized a tax credit receivable of $3.2 million related to amounts that had been approved by the Spanish government and a corresponding deferred research and development tax credit current portion of $1.6 million and a deferred research and development tax credit non-current portion of $762,000 as it was determined that amounts became probable of being received upon the receipt of the approval. Additionally, the Company has elected to account for the tax credit as a contra-expense as this most appropriately reflects the nature of the transaction and will reduce future research and development expenditures as the Company continues to incur expenses in the upcoming 24-month period. During the three months ending September 30, 2025 and 2024, the Company recorded $442,000 and $221,000, respectively, as a reduction in research and development expense. During the nine months ending September 30, 2025 and 2024, the Company recorded $1.3 million and $669,000, respectively, as a reduction in research and development expense. In February 2025, the Company received $1.7 million for the 2023 Research and Development rebate program sponsored by the Spanish government.

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7. Selected Balance Sheet Information

​

Prepaid expenses and other current assets (in thousands)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | September 30, | ​ | December 31,
​ |  | 2025 |  | 2024
Prepaid consulting, subscriptions and other expenses | ​ | $ | 251 | ​ | $ | 235
Prepaid manufacturing expenses | ​ | ​ | 216 | ​ | ​ | 375
VAT receivable | ​ | ​ | 103 | ​ | ​ | 95
Prepaid insurance | ​ | ​ | 84 | ​ | ​ | 374
Prepaid clinical research organizations | ​ | ​ | — | ​ | ​ | 365
​ | ​ | ​ | ​ | ​ | ​ | ​
Total | ​ | $ | 654 | ​ | $ | 1,444

​

Prepaid clinical research organizations (CROs) expense is classified as a current asset. The Company makes payments to the CROs based on agreed upon terms that include payments in advance of study services.

​

Property and equipment, net (in thousands)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, | ​ | December 31,
​ |  | 2025 |  | 2024
Computers and office equipment | ​ | $ | 689 | ​ | $ | 708
Other property, plant and equipment | ​ | ​ | 443 | ​ | ​ | 392
Leasehold improvements | ​ |  | 94 | ​ |  | 94
Software | ​ |  | 11 | ​ |  | 11
​ | ​ |  | 1,237 | ​ |  | 1,205
Less: accumulated depreciation and amortization | ​ |  | (988) | ​ |  | (935)
​ | ​ | ​ | ​ | ​ | ​ | ​
Total | ​ | $ | 249 | ​ | $ | 270

​

Accrued expenses (in thousands)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, | ​ | December 31,
​ |  | 2025 |  | 2024
Milestone due to Grifols | ​ | $ | 5,500 | ​ | $ | —
Accrued clinical consulting services | ​ | ​ | 1,732 | ​ | ​ | 2,390
Accrued vendor payments | ​ |  | 433 | ​ |  | 206
Accrued manufacturing costs | ​ | ​ | 20 | ​ | ​ | 772
​ | ​ | ​ | ​ | ​ | ​ | ​
Total | ​ | $ | 7,685 | ​ | $ | 3,368

​

Accrued employee benefits (in thousands)

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, | ​ | December 31,
​ |  | 2025 |  | 2024
Accrued compensation expense | ​ | $ | 616 | ​ | $ | 187
Accrued vacation expense | ​ | ​ | 131 | ​ | ​ | 87
Accrued bonus expense | ​ |  | — | ​ |  | 870
​ | ​ | ​ | ​ | ​ | ​ | ​
Total | ​ | $ | 747 | ​ | $ | 1,144

​

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8. Stock-Based Compensation

Stock Incentive Plans

On November 2, 2010, the Board of Directors and stockholders adopted the 2010 Stock Incentive Plan (“2010 Stock Plan”) for the issuance of up to 343 shares of Common Stock to be granted through incentive stock options, nonqualified stock options, stock appreciation rights, dividend equivalent rights, restricted stock, restricted stock units and other stock-based awards to officers, other employees, directors and consultants of the Company and its subsidiaries. From time to time the number of shares authorized for awards was increased such that 16,000 were authorized as of September 5, 2019. The exercise price of stock options under the 2010 Stock Plan was determined by the compensation committee of the Board of Directors and could be equal to or greater than the fair market value of the Company’s Common Stock on the date the option was granted. Options become exercisable over various periods from the date of grant and expire between five and ten years after the grant date. As of September 30, 2025, there were 7,566 options issued and outstanding under the 2010 Stock Plan. There are no shares available to be issued under this plan. Only options were issued under the plan.

On September 17, 2020, the stockholders approved and adopted the 2020 Stock Incentive Plan (“2020 Stock Plan”) for the issuance of up to 16,000 shares of Common Stock to be granted through incentive stock options, nonqualified stock options, stock appreciation rights, dividend equivalent rights, restricted stock, restricted stock units and other stock-based awards to officers, other employees, directors and consultants of the Company and its subsidiaries. The number of shares authorized for awards under the 2020 Stock Plan was increased such that 4,500,000 shares were authorized as of September 30, 2025. As of September 30, 2025, there were 1,108,535 options issued and outstanding under the 2020 Stock Plan. Only options have been issued under the plan.

In the event of an employee’s termination, the Company will cease to recognize compensation expense for that employee. Stock option forfeitures are recognized as incurred. The fair value of the stock-based payment is recognized over the stated vesting period.

The Company has applied fair value accounting for all stock-based payment awards since inception. The fair value of each option granted is estimated on the date of grant using the Black-Scholes option pricing model. The assumptions used for the nine months ended September 30, 2025 are as follows:

​

​ | ​ | ​ | ​ | ​
​ | ​ | 2025 |
Exercise price | ​ | $ | 1.41 | ​
Expected dividends | ​ |  | — | %
Expected volatility | ​ |  | 107.4 | %
Risk free interest rate | ​ |  | 3.74 | %
Expected life of option (years) | ​ |  | 4.23 | ​

​

There were no options granted during the nine months ended September 30, 2024.

Expected dividends—The Company has never declared or paid dividends on its Common Stock and has no plans to do so in the foreseeable future.

Expected volatility—Volatility is a measure of the amount by which a financial variable such as a share price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. The expected volatility assumption is derived from the historical volatility of the Company’s Common Stock over a period approximately equal to the expected term.

Risk-free interest rate—The assumed risk-free rate used is a zero coupon U.S. Treasury security with a maturity that approximates the expected term of the option.

Expected life of the option—The period of time that the options granted are expected to remain unexercised. Options granted during the prior year have a maximum term of seven years. The Company estimates the expected life of the option term based on the weighted average life between the dates that options become fully vested and the maximum life of options granted.

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8. Stock-Based Compensation – (continued)

The Company records stock-based compensation based upon the stated vesting provisions in the related agreements. The vesting provisions for these agreements have various terms as follows:

| ● | immediate vesting,

| ● | in full on the one-year anniversary date of the grant date,

| ● | half vesting immediately and the remaining over three years,

| ● | quarterly over three years,

| ● | annually over three years,

| ● | one-third immediate vesting and the remaining annually over two years,

| ● | one-half immediate vesting and the remaining over nine months,

| ● | one-quarter immediate vesting and the remaining over three years,

| ● | one-quarter immediate vesting and the remaining over 33 months,

| ● | monthly over one year, and

| ● | monthly over three years.

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8. Stock-Based Compensation – (continued)

A summary of stock option activity for the nine months ended September 30, 2025 and the year ended December 31, 2024 is as follows:

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted |  | Weighted Average |  | Aggregate
​ | ​ | ​ | ​ | Average Exercise | ​ | Remaining | ​ | Intrinsic
​ |  | Options |  | Price |  | Contractual Life |  | Value
Balance - December 31, 2023 |  | 175,049 | ​ | $ | 45.55 |  | 7.70 years | ​ | $ | —
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Granted |  | 420 | ​ | ​ | 5.25 |  | ​ | ​ |  | ​
Expired |  | (435) | ​ | ​ | 3,498.79 |  | ​ | ​ |  | ​
Forfeited |  | — | ​ | ​ | — |  | ​ | ​ |  | ​
Balance - December 31, 2024 | ​ | 175,034 | ​ | ​ | 36.88 | ​ | 6.72 years | ​ | ​ | —
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Granted | ​ | 951,500 | ​ | ​ | 1.41 | ​ | ​ | ​ | ​ | ​
Expired | ​ | (104) | ​ | ​ | 18,900 | ​ | ​ | ​ | ​ | ​
Forfeited | ​ | (10,329) | ​ | ​ | 14.72 | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance - September 30, 2025 -outstanding |  | 1,116,101 | ​ | $ | 5.09 |  | 6.36 years | ​ | $ | —
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Balance - September 30, 2025 -exercisable |  | 436,513 | ​ | $ | 10.05 |  | 3.80 years | ​ | $ | —
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Grant date fair value of options granted – nine months ended September 30, 2025 | ​ | ​ | ​ | $ | 1,011,295 |  |  | ​ |  |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Weighted average grant date fair value – nine months ended September 30, 2025 | ​ | ​ | ​ | $ | 1.06 |  |  | ​ |  |

​

Stock-based compensation expense included in general and administrative expenses and research and development expenses relating to stock options issued to employees for the three months ended September 30, 2025 and 2024 was $184,000 and $123,000, respectively. Stock-based compensation expense included in general and administrative expenses and research and development expenses relating to stock options issued to consultants for the three months ended September 30, 2025 and 2024 was $44,000 and $54,000, respectively. Stock-based compensation expense included in general and administrative expenses and research and development expenses relating to stock options issued to employees for the nine months ended September 30, 2025 and 2024 was $407,000 and $347,000, respectively. Stock-based compensation expense included in general and administrative expenses and research and development expenses relating to stock options issued to consultants for the nine months ended September 30, 2025 and 2024 was $94,000 and $161,000, respectively.

As of September 30, 2025, total unrecognized stock-based compensation expense related to stock options was $847,000, which is expected to be expensed through November 2027.

The FASB’s guidance for stock-based payments requires cash flows from excess tax benefits to be classified as a part of cash flows from operating activities. Excess tax benefits are realized tax benefits from tax deductions for exercised options in excess of the deferred tax asset attributable to stock compensation costs for such options. The Company did not record any excess tax benefits during the three and nine months ended September 30, 2025 and 2024.

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9. Stock Warrants

On May 8, 2025 the Company consummated a public offering (the “May 2025 Offering”) of an aggregate of (i) 1,990,900 shares (the “Shares”) of Common Stock, (ii) pre-funded warrants (“Pre-Funded Warrants”) to purchase up to 4,827,280 shares of Common Stock (the “Pre-Funded Warrant Shares”), and (iii) Common Stock purchase warrants (“Common Warrants”) to purchase up to 6,818,180 shares of Common Stock (the “Common Warrant Shares”). Each Share and associated Common Warrant to purchase one (1) Common Warrant Share was sold at a combined public offering price of $1.10. Each Pre-Funded Warrant and associated Common Warrant to purchase one (1) Common Warrant Share was sold at a combined public offering price of $1.099. The Company received aggregate gross proceeds from the May 2025 Offering of approximately $7.5 million, before deducting placement agent fees and other offering expenses. The Company intends to use the proceeds of the May 2025 Offering primarily for working capital and general corporate purposes, including for research and development and manufacturing scale-up and may use a portion of the proceeds to invest in or acquire other products, businesses or technologies. Each Pre-Funded Warrant was immediately exercisable for one (1) Pre-Funded Warrant Share at an exercise price of $0.001 per share and will remain exercisable until such Pre-Funded Warrant is exercised in full. Each Common Warrant has an exercise price of $1.10 per Common Warrant Share, is immediately exercisable, and expires five (5) years from its issuance date. The exercise price of the Common Warrants and the Pre-Funded Warrants and number of shares of Common Stock issuable upon exercise will be adjusted in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events. In the event of a fundamental transaction, as described in each of the Common Warrants and the Pre-Funded Warrants, the holders of such warrants will be entitled to receive upon exercise of their respective warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised their warrants immediately prior to such fundamental transaction. In addition, in certain circumstances, upon a fundamental transaction, a holder of Common Warrants will have the right to require us to repurchase its Common Warrants at the Black Scholes Value; provided, however, that, if the fundamental transaction is not within the Company’s control, including not approved by the Company’s board of directors, then the holder shall only be entitled to receive the same type or form of consideration (and in the same proportion), at the Black Scholes Value of the unexercised portion of the Common Warrant, that is being offered and paid to the holders of Common Stock in connection with the fundamental transaction. The Common Warrants may be exercised on a cashless basis if at the time of exercise thereof there is no effective registration statement registering, or the prospectus contained therein is not available for, the issuance of the Common Warrant Shares to the holder. The Pre-Funded Warrants may be exercised on a cashless basis at any time.

A holder of the Common Warrants and the Pre-Funded Warrants (together with its affiliates) may not exercise any portion of the Common Warrant or Pre-Funded Warrant to the extent that the holder would own more than 4.99% (or 9.99%, at the election of the holder) of the outstanding shares of Common Stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to the Company, the holder may increase the amount of beneficial ownership of outstanding shares after exercising the holder’s Common Warrants or Pre-Funded Warrants up to 9.99% of the number of the Company’s shares of Common Stock outstanding immediately after giving effect to the exercise. The Company has concluded that the Common Warrants and Pre-Funded Warrants are required to be equity classified. The Common Warrants were valued on the date of grant using Black Scholes model. During the nine months ended September 30, 2025, there were no exercises of Common Warrants issued in the May 2025 Offering and 4,827,280 Pre-Funded Warrants issued in the May 2025 Offering were exercised.

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9. Stock Warrants (continued)

On September 27, 2024, the Company consummated a public offering (the “September 2024 Offering”) of an aggregate of (i) 918,600 shares (the “Shares”) of Common Stock, (ii) pre-funded warrants (“Pre-Funded Warrants”) to purchase up to 510,000 shares of Common Stock (the “Pre-Funded Warrant Shares”), and (iii) Common Stock purchase warrants (“Common Warrants”) to purchase up to 1,428,600 shares of Common Stock (the “Common Warrant Shares”). Each Share and associated Common Warrant to purchase one (1) Common Warrant Share was sold at a combined public offering price of $1.75. Each Pre-Funded Warrant and associated Common Warrant to purchase one (1) Common Warrant Share was sold at a combined public offering price of $1.7499. The Company received aggregate gross proceeds from the September 2024 Offering of approximately $2.5 million, before deducting placement agent fees and other offering expenses. The Company intends to use the proceeds of the September 2024 Offering primarily for working capital and general corporate purposes, including research and development and manufacturing scale-up and may use a portion of the proceeds to invest in or acquire other products, businesses or technologies. Each Pre-Funded Warrant was immediately exercisable for one (1) Pre-Funded Warrant Shares at an exercise price of $0.0001 per share and was to remain exercisable until the Pre-Funded Warrants are exercised in full. Each Common Warrant has an exercise price of $2.00 per share, is immediately exercisable for one (1) Common Warrant Share, and expires five (5) years from its issuance date. The Shares, Pre-Funded Warrants and accompanying Common Warrants were issued separately. The exercise price of the Common Warrants and the Pre-Funded Warrants and number of shares of Common Stock issuable upon exercise will adjust in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events. The Common Warrants may be exercised on a cashless basis if at the time of exercise thereof there is no effective registration statement registering, or the prospectus contained therein is not available for, the issuance of the Common Warrant Shares to the holder. The Pre-Funded Warrants could be exercised on a cashless basis at any time. A holder of the Common Warrants and the Pre-Funded Warrants (together with its affiliates) may not exercise any portion of the Common Warrant or Pre-Funded Warrant to the extent that the holder would own more than 4.99% (or 9.99%, at the election of the holder) of the outstanding shares of Common Stock immediately after exercise, except that upon at least 61 days’ prior notice from the holder to the Company, the holder may increase the amount of beneficial ownership of outstanding shares after exercising the holder’s Common Warrants or Pre-Funded Warrants up to 9.99% of the number of the Company’s shares of Common Stock outstanding immediately after giving effect to the exercise. The Company has concluded that the Common Warrants and Pre-Funded Warrants are required to be equity classified. The Common Warrants were valued on the date of grant using Black Scholes model. During the three and nine months ended September 30, 2025 and 2024, there were no exercises of Common Warrants issued in the September 2024 Offering and as of September 30, 2025, 510,000 Pre-Funded Warrants issued in the September 2024 Offering were exercised.

​

A summary of all warrant activity for the Company for the year ended December 31, 2024 and nine months ended September 30, 2025 is as follows:

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted Average
​ |  | Number of |  | Weighted Average |  | Remaining
​ | ​ | Warrants | ​ | Exercise Price |  | Contractual Life
Balance at December 31, 2023 |  | — | ​ | $ | — | ​ | —
Granted | ​ | 1,938,600 | ​ | ​ | 1.47 | ​ | 4.74 years
Exercised | ​ | (510,000) | ​ | ​ | 0.0001 | ​ | —
Forfeited | ​ | — | ​ | ​ | — | ​ | —
Balance at December 31, 2024 | ​ | 1,428,600 | ​ | ​ | 2.0 | ​ | 4.74 years
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Granted | ​ | 11,645,460 | ​ | ​ | 0.64 | ​ | 4.61
Exercised | ​ | (4,827,280) | ​ | ​ | 0.001 | ​ | —
Forfeited | ​ | — | ​ | ​ | — | ​ | —
Balance at September 30, 2025 | ​ | 8,246,780 | ​ | ​ | 1.26 | ​ | 4.50

​

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10. Net Loss per Share

Basic net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding. Diluted net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding including the effect of common share equivalents. Diluted net loss per share assumes the issuance of potential dilutive common shares outstanding for the period and adjusts for any changes in income and the repurchase of common shares that would have occurred from the assumed issuance, unless such effect is anti-dilutive. Net loss attributable to common stockholders for the three and nine months ended September 30, 2025 was $4.4 million and $21.7 million, respectively. Net loss attributable to common stockholders for the three and nine months ended September 30, 2024 was $7.7 million and $21.2 million, respectively. The number of options and warrants for the purchase of Common Stock that were excluded from the computations of net loss per common share for the three and nine months ended September 30, 2025 were 1,116,101 and 8,246,780, respectively, and for the three and nine months ended September 30, 2024 were 175,207 and 1,428,600, respectively, because their effect is anti-dilutive.

​

11. Common and Preferred Stock

Series C and D Preferred Stock

On July 29, 2022, the Company closed a private placement offering pursuant to the terms of a Securities Purchase Agreement dated as of July 28, 2022 entered into with MSD Credit Opportunity Master Fund, L.P.(the “Securities Purchase Agreement”), pursuant to which the Company issued and sold 275,000 shares of the Company’s Series C Convertible Preferred Stock, par value $0.001 per share (the “Series C Preferred Stock”), and 100,000 shares of the Company’s Series D Convertible Preferred Stock, par value $0.001 per share, (the “Series D Preferred Stock,” and together with the Series C Preferred Stock, the “Preferred Stock”), at an offering price of $8.00 per share, for gross proceeds of approximately $3.0 million in the aggregate, before the deduction of discounts, fees and offering expenses. The shares of Preferred Stock were convertible, at a conversion price (the “Conversion Price”) of $1.22 per share (subject in certain circumstances to adjustments), into an aggregate of 2,459,016 shares of the Company’s Common Stock, at the option of the holders of the Preferred Stock and, in certain circumstances, by the Company. The Securities Purchase Agreement contains customary representations, warranties and agreements by the Company and customary conditions to closing.

The Company included certain proposals at its 2022 annual meeting of stockholders, including (i) an amendment to the Company’s Articles of Incorporation, as amended (the “Charter”), to change the name of the Company to “Theriva Biologics, Inc.” (the “Name Change”), (ii) an amendment to the Articles of Incorporation, as amended to increase the number of authorized shares of Common Stock from 20,000,000 to 350,000,000 (the “Authorized Common Stock Increase”) and (iii) to adjourn any meeting of stockholders called for the purpose of voting on the Authorized Common Stock Increase (collectively, the “Stockholder Items”). The purchaser of the Preferred Stock agreed in the Purchase Agreement to (i) not transfer, offer, sell, contract to sell, hypothecate, pledge or otherwise dispose of the shares of the Preferred Stock until the earlier of the date that the authorized Common Stock Increase being proposed at the 2022 annual meeting of stockholders was effected or October 26, 2022 and (ii) vote the shares of the Series C Preferred Stock purchased in the Offering in favor of the Stockholder Items. The authorized increase was effected prior to October 26, 2022.

Pursuant to the Securities Purchase Agreement, the Company filed certificates of designation (the “Certificates of Designation”) with the Secretary of the State of Nevada designating the rights, preferences and limitations of the shares of Series C Preferred Stock and Series D Preferred Stock. The Certificate of Designation for the Series C Preferred Stock provides, in particular, that the Series C Preferred Stock will have no voting rights other than the right to vote as a class on the Stockholder Items (as defined therein) and the right to cast votes on an as converted to Common Stock basis on the Stockholder Items. The Certificate of Designation for the Series D Preferred Stock provides, in particular, that the Series D Preferred Stock will have no voting rights other than the right to vote as a class on the Stockholder Items and the right to cast 20,000 votes per share of Series D Preferred Stock on the Stockholder Items and to vote the shares of the Series D Preferred Stock purchased in the Offering in the same proportion as shares of Common Stock and any other shares of capital stock of the Company that are entitled to vote thereon (excluding any shares of Common Stock that are not voted) on the Stockholder Items.

The holders of Preferred Stock were entitled to dividends, on an as-if converted basis, equal to dividends actually paid, if any, on shares of Common Stock. The Conversion Price may be adjusted pursuant to the Certificates of Designation for stock dividends and stock splits, subsequent rights offering, pro rata distributions of dividends or the occurrence of a fundamental transaction (as defined in the applicable Certificate of Designation).

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11. Common and Preferred Stock (continued)

The Series C Preferred Stock and Series D Preferred Stock were classified as temporary equity as a result of the deemed liquidation provision. Transaction expenses paid to third parties will be charged to temporary equity and will not be accreted as deemed dividends until redemption becomes probable.

During the year ending December 31, 2024, the Company issued 72,132 shares of its Common Stock upon the conversion effected by the holder of the Series C Preferred Stock of 275,000 shares of its Series C Preferred Stock at a conversion price of $30.50 per share. As a result of the conversions during the year ending December 31, 2024, the Company reduced the Series C Preferred Stock $2.0 million and Additional Paid in Capital $2.0 million. There are no shares of Series C Preferred Stock outstanding as of September 30, 2025.

During the year ending December 31, 2024, the Company issued 26,230 shares of its Common Stock upon the conversion effected by the holder of the Series D Preferred Stock of 100,000 shares of its Series D Preferred Stock at a conversion price of $30.50 per share. As a result of the conversion during the year ending December 31, 2024 the Company reduced the Series D Preferred Stock by $728,000 and Additional Paid in Capital by $728,000. There are no shares of Series D Preferred Stock outstanding as of September 30, 2025.

At Market Issuance Sales Agreement

On May 2, 2024, the Company and A.G.P./Alliance Global Partners (“AGP”) entered into the ATM Sales Agreement, pursuant to which the Company may offer and sell, from time to time, at its option, shares of the Common Stock through A.G.P, as sales agent, in an “at the market offering” as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended (the “Securities Act”). Sales in the “at the market offering” may occur under the Company’s current effective registration statement on Form S-3 (File No. 333-255726) utilizing a prior prospectus and related prospectus supplements thereto or a newly filed registration statement on Form S-3 which was filed on May 2, 2024 (File No. 333-279077) and declared effective on September 25, 2024. In addition, on May 1, 2024, the Company and B. Riley Securities, Inc. mutually agreed to enter into a notice of termination whereby B. Riley Securities, Inc. would no longer be a party to the ATM Sales Agreement. During the three and nine months ended September 30, 2025, the Company sold through the ATM Sales Agreement approximately 706,810 shares of the Company’s Common Stock and received net proceeds of approximately $279,000. During the three and nine months ended September 30, 2024, the Company sold through the ATM Sales Agreement approximately 395,000 and 569,000, respectively, shares of the Company’s Common Stock and received net proceeds of approximately $1.8 million and $3.6 million, respectively.

​

12. Loans Payable

As a result of the Acquisition of VCN, the Company acquired interest-free or below-market interest rate loans (0%-1%) extended by Spanish governmental institutions of Ministerio de Ciencia, Innovacion y Universidades (RETOS loan) and ACC10 Generalitat de Catalunya (NEBT loan). The maturities of these loans are between 2024 and 2028. As a result of the Acquisition, the Company maintains a restricted cash collateral account of $46,000 relating to the RETOS loan, which is reflected as a non-current asset on the balance sheet.

During September 2024, the Company announced that its THERICEL project had been awarded €2.28 million (approximately $2.54 million) from the National Knowledge Transfer Program of the Spanish government’s Ministry of Science, Innovation & Universities to support a collaboration between the Company and the Universitat Autònoma de Barcelona (“UAB”) to advance the Company’s THERICEL suspension cell platform for the clinical manufacture of adenovirus- and adeno-associated virus (“AAV”) therapies. Under the award, the Company (via its wholly owned subsidiary, Theriva Biologics SL) received an unsecured loan (the “Loan”) of €1.3 million (approximately $1.4 million) as a lump sum payment on January 17, 2025 which bears interest at a rate of 4.015% and is to be repaid over 7 years commencing three years from the date of award.

​

​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, 2025 |  | September 30, 2025 | ​ | December 31, 2024 |  | December 31, 2024
​ | ​ | Current | ​ | Non-current |  | Current | ​ | Non-current
​ |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
NEBT Loan | ​ | ​ | 9 | ​ | $ | 9 | ​ | ​ | 7 | ​ | $ | 16
RETOS 2015 | ​ | ​ | 48 | ​ | ​ | 37 | ​ | ​ | 54 | ​ | ​ | 76
THERICEL Loan | ​ | ​ | — | ​ | ​ | 1,608 | ​ | ​ | — | ​ | ​ | —
​ | ​ | $ | 57 | ​ | $ | 1,654 | ​ | $ | 61 | ​ | $ | 92

​

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12. Loans Payable (continued)

A maturity analysis of the debt as of September 30, 2025 is as follows (amounts in thousands of dollars):

​ | ​ | ​ | ​
2026 |  | $ | 57
2027 |  | ​ | 35
2028 |  | ​ | 11
2029 |  | ​ | 69
2030 | ​ | ​ | 232
Thereafter | ​ | ​ | 1,307
Total |  | $ | 1,711

​

​

13. Commitments and Contingencies

The Company’s existing leases as of September 30, 2025 for its U.S. and Spanish facilities are classified as operating leases. During the quarter ended June 30, 2021, the Company renewed its Rockville, MD facility lease by entering into a Second Lease Amendment which extends the lease term for 63 months beginning on September 1, 2022 and ending on December 31, 2027 at stated rental rates and including a 3-month rent abatement. The Second Amendment also has options for a Tenant Improvement Allowance and a Second Extension Term. The Second Extension Term is offered at market rates and there is no economic incentive for the lessee, therefore the Company has determined that it is not part of the original lease term.

The Company also leases research and office facilities in Parets del Vallès, Barcelona, Spain for its 100 percent owned Theriva S.L. subsidiary. The lease that was in existence from December 2021 to December 2022 was a short term agreement with a 90-day termination notice provision that can be exercised by either party. On the closing date of the Acquisition, a sublease was executed for Theriva S.L. to lease research and office facilities at a new location in Parets del Valles (Barcelona) from the former owner of Theriva S.L. This lease was executed for an initial term to begin in January 2023 until October 2026, with an option to renew for an additional five years. On January 15, 2023, Theriva S.L. moved into the facilities and the new lease commenced and the prior lease terminated.

Operating lease costs are presented as part of general and administrative expenses in the condensed consolidated statements of operations, and were approximately $164,000 and $493,000, respectively, for the three and nine months ended September 30, 2025, and $158,000 and $474,000 the three and nine months ended September 30, 2024, respectively. For the Barcelona lease, the day one non-cash addition of right of use assets due to adoption of ASC 842 was $937,000.

A maturity analysis of the Company’s operating leases as of September 30, 2025 is as follows (amounts in thousands of dollars):

​

​ | ​ | ​ | ​
Future undiscounted cash flow for the years ending December 31, |  | ​ |
​ | ​ | ​ | ​
2025 | ​ | ​ | 175
2026 | ​ | ​ | 606
2027 | ​ | ​ | 368
Total | ​ | ​ | 1,149
​ | ​ | ​ | ​
Discount factor | ​ | ​ | (98)
Operating lease liability | ​ | ​ | 1,051
Operating lease liability – current | ​ | ​ | (618)
Operating lease liability – long term | ​ | $ | 433

​

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13. Commitments and Contingencies (continued)

Risks and Uncertainties

The uncertain financial markets, disruptions in supply chains, mobility restraints, and changing priorities as well as volatile asset values could impact the Company’s business in the future. The Company and its third-party contract manufacturers, contract research organizations, and clinical sites may also face disruptions in procuring items that are essential to the Company’s research and development activities, including, for example, medical and laboratory supplies used in its clinical trials or preclinical studies, in each case, that are sourced from abroad or for which there are shortages. In addition, tariffs imposed on or by countries where the Company conducts its research and development or where the Company obtains supplies could impact the prices it pays for goods and services. Further, although the Company has not experienced any material adverse effects on business due to increasing inflation, it has raised operating costs for many businesses and, in the future, could impact demand or pricing manufacturing of its drug candidates or services providers, foreign exchange rates or employee wages. The Company is actively monitoring the effects that these disruptions and increasing inflation could have on its operations.

As of the date of this filing, the U.S. federal government is experiencing a partial shutdown. While the SEC’s EDGAR system remains operational and the Company continues to meet its filing obligations under the Securities Exchange Act of 1934, as amended, the shutdown has resulted in limited availability of the SEC staff to review filings, issue comments, or declare registration statements effective. This may delay regulatory review processes and affect the timing of certain capital markets transactions. The Company has evaluated the potential impact of the shutdown on its financial reporting and operations and has determined that, as of the reporting date, there are no material changes to accounting policies, estimates, or internal controls attributable to the shutdown. The Company will continue to monitor developments and assess any future implications.

Through the Acquisition, the Company has operations in Spain related to conducting research and development, manufacturing, and clinical trials in Western European countries. The invasion of Ukraine by Russia, the war in the Middle East, and the retaliatory measures that have been taken, or could be taken in the future, by the United States, NATO, and other countries have created global security concerns that could result in a regional conflict and otherwise have a lasting impact on regional and global economies, any or all of which could disrupt the Company’s supply chain, and despite the fact that it currently does not plan any clinical trials in Eastern Europe or the Middle East, may adversely impact the cost and conduct of R&D, manufacturing, and international clinical trials of its product candidates.

14. Related Party

On December 14, 2023, the Company approved the retention of MaryAnn Shallcross, the wife of Steven Shallcross, as Director of Clinical Operations, for compensation of $152,000, a bonus of $70,000 and the grant of an option to purchase 3,000 shares of Common Stock having a value of $30,000. During the year ended December 31, 2023, the Company had $145,000 in compensation expense related to Mrs. Shallcross. On December 13, 2024, the Company approved the compensation of MaryAnn Shallcross of $157,000 and a bonus of $45,000. During the three and nine months ended September 30, 2025, the Company had $39,000 and $117,000 in compensation expense, respectively, related to Ms. Shallcross. During the nine months ended September 30 2025, the Company approved the grant of an option to purchase 25,000 shares of Common Stock having a value of $27,000. Ms. Shallcross was one of the seven employees whose employment was terminated in connection with the Company’s workforce reduction.

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15. Subsequent Events

The Company has evaluated events that occurred through November 12, 2025, the date that the financial statements were issued, and determined that there have been no events that have occurred that would require adjustments to its disclosures in the financial statements except for the transaction described below.

On October 16, 2025, the Company entered into a warrant inducement agreement (the “Inducement Agreement”) with certain holders named therein (the “Holders”) of existing Common Stock Purchase Warrants to purchase up to an aggregate of 8,092,280 shares of the Company’s Common Stock, consisting of (i) Common Stock Purchase Warrants to purchase up to an aggregate of 1,345,000 shares of Common Stock issued on September 27, 2024 (the “September Warrants”) and (ii) Common Stock Purchase Warrants to purchase up to an aggregate of 6,747,280 shares of Common Stock issued on May 8, 2025 (the “May Warrants” and, together with the September Warrants, the “Existing Warrants”). Pursuant to the Inducement Agreement, on October 17, 2025, the Holders exercised for cash the Existing Warrants at a reduced exercise price of $0.54 per share and, in consideration therefor, the Company issued to the Holders new Common Stock Purchase Warrants (the “New Warrants”) to purchase an aggregate of 16,184,560 shares of Common Stock, equal to 200% of the number of shares of Common Stock underlying the Existing Warrants, at an exercise price of $0.54 per share, which New Warrants are exercisable for a term of five (5) years from the date of the approval from the stockholders of the Company of the full exercise of the New Warrants and the issuance of all of the shares of Common Stock issuable upon the exercise thereof.

The Company received aggregate gross proceeds of approximately $4.4 million for the exercise of the Existing Warrants, before deducting placement agent fees and other expenses payable by the Company. The Company expects to use the net proceeds from the Warrant Exercise for working capital. AGP served as the Company’s exclusive financial advisor in connection with the warrant exercise and other transactions described in the Inducement Agreement. Pursuant to the terms of an engagement letter, dated October 16, 2025, by and between the Company and AGP, the Company agreed to pay to AGP a cash fee equal to 7.0% of the aggregate gross proceeds received from the Holder upon exercise of the Existing Warrants and reimbursement of certain expenses.

On October 24, 2025, the Company filed a prospectus supplement to its Registration Statement on Form S-3, as amended (File No. 333-279077), which Form S-3 was declared effective by the SEC on September 25, 2024 (the “Shelf Registration Statement”), relating to the offer and sale of up to $4,019,597 of shares of the Company’s Common Stock from time to time through or directly to A.G.P./Alliance Global Partners (the “Sales Agent”) pursuant to the terms of the ATM Sales Agreement.

On October 29, 2025, the Company filed a prospectus supplement to its Shelf Registration Statement, relating to the offer and sale of up to $2,894,225 of shares of the Company’s Common Stock, from time to time through or directly to A.G.P./Alliance Global Partners (the “Sales Agent”) pursuant to ATM Sales Agreement.

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ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS.

The following discussion should be read in conjunction with our unaudited condensed consolidated financial statements and notes thereto included in this Quarterly Report on Form 10-Q, and our audited consolidated financial statements and notes thereto for the year ended December 31, 2024 included in our 2024 Form 10-K. This discussion contains forward-looking statements reflecting our current expectations that involve risks and uncertainties. See “Note Regarding Forward-Looking Statements” for a discussion of the uncertainties, risks and assumptions associated with these statements. Our actual results and the timing of events could differ materially from those expressed or implied by the forward-looking statements due to important factors and risks including, but not limited to, those set forth below under “Risk Factors” and elsewhere herein, and those identified under Part I, Item 1A of our 2024 Form 10-K.

Overview

We are a diversified clinical-stage company developing therapeutics designed to treat cancer and related diseases in areas of high unmet need. As a result of the acquisition in March 2022 of Theriva Biologics, S.L. (“VCN”, formerly named VCN Biosciences, S.L.), described in more detail below (the “Acquisition”), we transitioned our strategic focus to oncology through the development of VCN’s new oncolytic adenovirus platform designed for intravenous and intravitreal delivery to trigger tumor cell death, to improve access of co-administered cancer therapies to the tumor, and to promote a robust and sustained anti-tumor response by the patient’s immune system. Our lead product candidate, VCN-01, a clinical stage oncolytic human adenovirus that is modified for tumor-selective replication and to express an enzyme, PH20 hyaluronidase, that has been evaluated in a Phase 2b clinical study for the treatment of pancreatic cancer (“VIRAGE”), and has recently been used to treat patients in a Phase 1 clinical study for the treatment of retinoblastoma, and Phase 1 clinical studies for the treatment of other solid tumors including head and neck squamous cell carcinoma.

Prior to the Acquisition, our focus was on developing therapeutics designed to treat gastrointestinal (GI) diseases which included our clinical development candidates: (1) SYN-004 (ribaxamase) which is designed to degrade certain commonly used intravenous (IV) beta-lactam antibiotics within the GI tract to prevent microbiome damage, thereby preventing overgrowth and infection by pathogenic organisms such as Clostridioides difficile infection (CDI) and vancomycin resistant Enterococci (VRE), and reducing the incidence and severity of acute graft-versus-host-disease (aGVHD) in allogeneic hematopoietic cell transplant (HCT) recipients, and (2) SYN-020, a recombinant oral formulation of the enzyme intestinal alkaline phosphatase (IAP) produced under cGMP conditions and intended to treat both local GI and systemic diseases. As part of our strategic transformation into an oncology focused company, we are exploring value creation options for our SYN-004 and SYN-020 assets, including out-licensing or partnering.

Financial Developments

On June 20, 2025, we filed a prospectus supplement (the “Prospectus Supplement”) to our Registration Statement on Form S-3(the “Form S-3”), as amended (File No. 333-279077), which Form S-3 was declared effective by the Securities and Exchange Commission (the “SEC”) on September 25, 2024 (the “Registration Statement”), relating to the offer and sale of up to $2,534,352 of shares of our common stock, par value $0.001 per share (the “Common Stock”), from time to time through or directly to A.G.P./Alliance Global Partners (the “Sales Agent”) pursuant to the terms of that certain Amended and Restated At Market Issuance Sales Agreement, dated February 9, 2021, as amended by Amendment No. 1 thereto, dated May 3, 2021, as further amended by Amendment No. 2 thereto, dated May 2, 2024 (the “ATM Sales Agreement”). Sales of Common Stock, if any, under the Prospectus Supplement will be made by any method permitted that is deemed an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act. The Sales Agent is not required to sell any specific amount, but will act as our Sales Agent using commercially reasonable efforts consistent with its normal trading and sales practices. The Sales Agent will be entitled to compensation at a commission rate equal to up to 3.0% of the gross sales price per share of Common Stock sold. During the three and nine months ended September 30, 2025, we sold approximately 706,810, shares of our Common Stock pursuant to the ATM Sales Agreement and received net proceeds of approximately $279,000. During October 2025, we sold approximately 5,016,586 shares of our Common Stock pursuant to the ATM Sales Agreement and received net proceeds of approximately $2.2 million. On October 24, 2025, we filed prospectus supplement no. 2 to the Form S-3, relating to the offer and sale of up to $4,019,597 of shares of our Common Stock pursuant to the ATM Sales Agreement, pursuant to which we have sold 10,326,015 of shares of Common Stock and received net proceeds of approximately $3.9 million as of the date of the filing of this Quarterly Report on Form 10-Q.

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On September 28, 2025, the Board of Directors approved a plan to resize and restructure the company for purposes of focusing its attention on business development and licensing activities, clinical trial planning, exploratory VCN-01 manufacturing scale-up, limited preclinical activities related to VCN-01 and VCN-12 (the first candidate from our VCN-X discovery program), and our upcoming interactions with the U.S. Food and Drug Administration and the European Medicines Agency for proposed pivotal clinical trials of VCN-01 in patients with mPDAC and retinoblastoma (the “Plan”). Pursuant to the Plan, on September 30, 2025, we implemented a workforce reduction of approximately seven employees or 32% of the current global Company workforce. The goal of this reduction is to direct our resources towards the activities detailed above in the Plan, which it believes will represent its best opportunity for success. We expect to substantially complete the employee reduction immediately and estimate that it will incur a total of approximately $520,000 in charges in connection with the workforce reduction, which was accrued for as of September 30, 2025. These charges consist primarily of cash severance and benefits over a three-month period, in connection with the workforce reduction. The Plan is expected to save approximately $1.8 million in compensation and benefits annually, and together with additional anticipated operating cost reductions and capital raised pursuant to the ATM Sales Agreement, we expect that it will extend our cash runway into the first quarter of 2027.

On October 16, 2025, we entered into a warrant inducement agreement (the “Inducement Agreement”) with certain holders named therein (the “Holders”) of existing Common Stock Purchase Warrants to purchase up to an aggregate of 8,092,280 shares of Common Stock, consisting of (i) Common Stock Purchase Warrants to purchase up to an aggregate of 1,345,000 shares of Common Stock issued on September 27, 2024 (the “September Warrants”) and (ii) Common Stock Purchase Warrants to purchase up to an aggregate of 6,747,280 shares of Common Stock issued on May 8, 2025 (the “May Warrants” and, together with the September Warrants, the “Existing Warrants”). Pursuant to the Inducement Agreement, on October 17, 2025, the Holders exercised for cash the Existing Warrants at a reduced exercise price of $0.54 per share and, in consideration therefor, we issued to the Holders new Common Stock Purchase Warrants (the “New Warrants”) to purchase an aggregate of 16,184,560 shares of Common Stock, equal to 200% of the number of shares of Common Stock underlying the Existing Warrants, at an exercise price of $0.54 per share, which New Warrants are exercisable for a term of five (5) years from the date of the approval from our stockholders of the full exercise of the New Warrants and the issuance of all of the shares of Common Stock issuable upon the exercise thereof.

We received aggregate gross proceeds of approximately $4.4 million for the exercise of the Existing Warrants, before deducting placement agent fees and other expenses payable by us. We expect to use the net proceeds from the Warrant Exercise for working capital. AGP served as our exclusive financial advisor in connection with the warrant exercise and other transactions described in the Inducement Agreement. Pursuant to the terms of an engagement letter, dated October 16, 2025, by and between us and AGP, we agreed to pay to AGP a cash fee equal to 7.0% of the aggregate gross proceeds received from the Holders upon exercise of the Existing Warrants and reimbursement of certain expenses.

On August 29, 2025, we held our 2025 Annual Meeting of Stockholders (the “Annual Meeting”). At the Annual Meeting, our stockholders (i) elected Jeffrey J. Kraws, John Monahan, Steven A. Shallcross and Jeffery Wolf as directors; (ii) ratified the appointment of BDO USA P.C. as our independent registered public accounting firm for the year ending December 31, 2025; (iii) approved an amendment (“Amendment No. 2”) to our 2020 Stock Incentive Plan (the “2020 Stock Incentive Plan”) to (a) increase the number of shares of Common Stock that we will have authority to grant under the 2020 Stock Incentive Plan from 2,500,000 shares of Common Stock to 4,500,000 shares of Common Stock and (iii) approved, on an advisory basis, the compensation of our named executive officers.

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Our Current Product Pipeline

​

​

*Based on management’s current beliefs and expectations

aGVHD acute graft-versus host disease. allo-HCT allogeneic hematopoietic cell transplant. CSR clinical study report. HNSCC head and neck squamous cell carcinoma. IV intravenous. IVit intravitreal. For other abbreviations see the text.

¹Additional products with preclinical proof-of-concept include SYN-006 (carbapenemase) to prevent aGVHD, CDI, and microbiome damage in patients treated with carbapenem antibiotics and SYN-007 (ribaxamase) DR to prevent antibiotic associated diarrhea with oral β-lactam antibiotics.

²Depending on funding/partnership. SYN-004 may enter a U.S. Food and Drug Administration (“FDA”)-agreed Phase 3 clinical trial for the treatment of CDI.

Recent Clinical Developments

On October 8, 2025, preclinical data for VCN-12, a next generation oncolytic adenovirus developed as part of the VCN-X discovery program, was presented by Dr. Ramon Alemany at the 32nd Annual Congress of the European Society of Gene & Cell Therapy. VCN-12 uses the same virus capsid as our lead clinical candidate VCN-01 (zabilugene almadenorepvec), but includes modifications intended to (i) increase stroma degradation by replacing human hyaluronidase PH20 with the more active bee hyaluronidase; and (ii) increase tumor cell lysis by expressing the pore forming protein parasporin-2 to enable both cytotoxic and immunogenic cell death. Parasporin-2 expression is expected to destroy both infected and surrounding uninfected tumor cells and stimulate a strong overall antitumor immune response and reduce viral immunodominance. Data presented by Dr. Alemany support the proposed VCN-12 mechanisms of action. VCN-12 showed increased cell killing compared to VCN-01 in a variety of cancer cell models in vitro. VCN-12 also displayed higher levels of hyaluronidase activity. In animal studies, intravenous VCN-12 had a similar toxicity profile to VCN-01 in immunodeficient mice bearing human tumor xenografts. Intratumoral VCN-12 significantly reduced tumor growth compared to VCN-01 in immunocompetent hamsters bearing HP-1 pancreatic tumors. The antitumor effect of VCN-12 was observed in both the injected tumors and second tumors-implanted 4-days later but not injected. Complete tumor regression of the first tumor was observed in two of nine hamsters and the second implanted tumor did not grow in these animals. VCN-12 appeared to stimulate a persistent immune response that prevented the establishment of tumors in these two complete responders when they were implanted with HP-1 cells 43 days after VCN-12 treatment. Further preclinical studies are planned to elaborate these initial findings. In addition to the scheduled presentation on VCN-12, a recently-published pre-ESGCT meeting monograph details the results of a preclinical study conducted by investigators at the University of Navarra evaluating the intracranial administration of VCN-01 for the potential treatment of brain tumors. The authors highlight the urgent need to develop new and improved therapies for brain cancers and conclude that their findings “provide a strong rationale for its [VCN-01] further development as a therapeutic option for patients with brain tumors” (Palacios-Alonso D et al. (2025) Toxicity and Biodistribution of the Oncolytic Virus VCN-01 Following Intracranial Injection in Syrian Hamsters. Hum Gene Ther. 36(17-18):1237-1247. (doi: 10.1177/10430342251372091).

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On October 20, 2025, expanded mPDAC data from the VIRAGE Phase 2b trial (NCT05673811) was presented at the European Society for Medical Oncology (ESMO 2025) Annual Congress. An abstract separate poster presentation on the same day describing previously reported data for SYN-004 (ribaxamase) in allogeneic hematopoietic transplant recipients was presented at Infectious Diseases Week (IDWeek) 2025 Annual Meeting. Results from the VIRAGE Phase 2b trial included in the abstract for the presentation titled “VIRAGE trial: randomized Phase IIb, open-label, study of Nab-Paclitaxel and Gemcitabine with/without intravenous VCN-01 in Patients with Metastatic Pancreatic Cancer (mPDAC )” are set forth below:

112 patients were randomized. Patients in the modified intent to treat (mITT) population received at least 1 dose of gemcitabine/nab-paclitaxel (GA) standard of care chemotherapy (GA, Arm I) or VCN-01 (Arm II). Patients in the full analysis set (FAS) population received at least 1 dose of gemcitabine/nab-paclitaxel standard of care chemotherapy (GA; Arm I) or VCN-01 followed by at least 1 dose of GA (Arm II).

​

​ |  | mITT |  | FAS
​ | ​ | Arm I (48) | ​ | Arm II (53) | ​ | HR (95% CI) | ​ | Arm I (48) | ​ | Arm II (48) |  | HR (95% CI)
OS mo. | ​ | 8.6 | ​ | 10.6 | ​ | 0.69 (0.42-1.12) P=0.196 | ​ | 8.6 | ​ | 10.8 | ​ | 0.57 (0.34-0.96) P=0.055
PS mo. | ​ | 4.6 | ​ | 5.6 | ​ | 0.63 (0.4-1.0) P=0.047 | ​ | 4.6 | ​ | 7.0 | ​ | 0.55 (0.34-0.88) P=0.011
DoR mo. | ​ | 5.4 | ​ | 11.2 | ​ | 0.22 (0.08-0.62) P=0.004 | ​ | 5.4 | ​ | 11.2 | ​ | 0.22 (0.08-0.62) P=0.004
ORR | ​ | 31.3% |  | 35.8% |  | ​ | ​ | 31.3% | ​ | 39.6% | ​ | ​
Definitions -mo. (Months). OS (overall survival). PS or PFS (progression free survival). DoR (duration of response). ORR (objective response rate). HR (hazard ratio). CI (confidence interval).

​

Compared to patients who started GA cycle 4 alone (Arm I), patients who received 2 VCN-01 doses and started GA cycle 4 (Arm II) showed greater improvement in OS (14.8 vs 11.6 months; HR 0.44; 95% CI 0.21 - 0.92; P=0.046) and PFS (11.2 vs 7.4 months; HR 0.48; 95% CI 0.25 - 0.91; P=0.017). VCN-01 administration was well tolerated. All VCN- 01-related serious adverse events (n=13) were resolved, the most common being flu-like symptoms (13,2%), transaminase increase (5.7%) and drug-induced liver injury (3.8%). Viral genome analysis confirmed the bioactivity of the second VCN-01 dose.

This study met its primary endpoints. Patients receiving VCN-01 + GA had improved OS, PFS and DoR compared to GA standard of care.

Our Current Oncology-Focused Pipeline

Oncolytic Viruses

Our oncology platform is based on oncolytic virotherapy (“OV therapy”), which exploits the ability of certain viruses to kill tumor cells and trigger an anti-tumor immune response. This novel class of anticancer agents has unique mechanisms of action compared to other cancer drugs. Oncolytic viruses (“OV”) exploit the fact that cancer cells contain mutations that cause them to lose growth control and form tumors. Once inside a tumor cell, oncolytic viruses exploit the tumor cell machinery to generate thousands of additional copies of the virus, which then kill the tumor cell and spread to neighboring cells, causing a chain reaction of cell killing. This infection and tumor cell killing by OVs also alerts the immune system, which can then attack the virus infected tumor cells to help destroy the tumor in some instances.

Our OV product candidates are engineered to efficiently infect and selectively replicate to a high extent in tumor cells versus normal host cells, which enables intravenous delivery. By contrast, many other OVs in clinical development today are administered by direct injection into the tumor. Intravenous delivery has the potential to expand the therapeutic effect of OVs because the virus can infect both the primary tumor and tumor metastases throughout the body.

Our first product candidate VCN-01, is a clinical stage oncolytic human adenovirus that is modified to express an enzyme, PH20 hyaluronidase, that is designed to degrade hyaluronan in the tumor stroma, which helps the virus and other molecules to penetrate and spread throughout the tumor. VCN-01 can be used alone or in combination with other cancer therapies, such as chemotherapy and

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immunotherapy, for difficult to treat cancers. An expanding intellectual property portfolio supports our oncology programs, and because our products are characterized as biologics with Orphan Drug designation in our target indications, if approved by the FDA they will be further protected by data and/or market exclusivity.

VCN-01 has been administered to 142 patients across multiple Phase 1 clinical trials and the Phase 2b VIRAGE trial, including patients with pancreatic cancer, head and neck squamous cell carcinoma, ovarian carcinoma, colorectal cancer, and retinoblastoma.

Current clinical update

We have recently completed patient treatment and follow-up in a Phase 2b clinical trial of intravenous VCN-01 with nab-paclitaxel plus gemcitabine in patients with mPDAC and the clinical study report (CSR) has been completed. Similarly, CSRs have been completed for the Phase 1 investigator sponsored trials evaluating (i) intravitreal VCN-01 in patients with retinoblastoma; and (ii) intravenous VCN-01 in combination with durvalumab in subjects with recurrent/ metastatic squamous cell carcinoma of the head and neck (mSCCHN). A protocol amendment has been submitted in an additional investigator sponsored Phase 1 trial evaluating the intravenous administration of VCN-01 in patients prior to surgical resection of high-grade brain tumors and on July 8, 2025 we were notified by the investigator that the protocol amendment had been approved by the Medicines and Healthcare products Regulatory Agency (MHRA) from UK.

Phase 1 Clinical Trials in PDAC

The safety, tolerability, and potential dosing regimens for VCN-01 in patients with PDAC or colorectal cancer were evaluated in Phase 1 clinical trials evaluating intratumoral (n=8; NCT02045589) and intravenous (n= 42; NCT02045602) VCN-01 either alone or in combination with gemcitabine ± nab-paclitaxel (published in J. Immunother. Cancer 2021 Nov;9(11):e003254 and J. Immunother. Cancer 2022 Mar;10(3):e003255, respectively). Intravenous VCN-01 was found to have an acceptable tolerability profile in PDAC and colorectal cancer patients and demonstrated compelling biochemical and clinical outcomes that enabled the advancement of VCN-01 into the Phase 2 clinical trial in patients with metastatic PDAC.

Phase 2 Trial of intravenous VCN-01 with nab-paclitaxel plus gemcitabine in patients with PDAC

In January 2023, we dosed the first patients in VIRAGE, the Phase 2b randomized, open-label, multicenter clinical trial of systemically administered VCN-01 in combination with standard-of-care (SoC) chemotherapy (gemcitabine/nab-paclitaxel) as a first line therapy for patients with newly-diagnosed metastatic pancreatic ductal adenocarcinoma. The study is being conducted at approximately 17 sites in the US and EU. Two doses of VCN-01 are included in the treatment arm: the 1st dose is administered on day 1, then one week later 3 cycles of gemcitabine and nab-paclitaxel as standard of care is administered. The second VCN-01 dose is administered 7 days before the 4th cycle of chemotherapy (approximately 90 days after the first VCN-01 dose), followed by additional cycles of gemcitabine/nab-paclitaxel chemotherapy.

Patient dosing was initiated in the U.S. in July 2023 and on September 23, 2024, we announced that we achieved our target patient enrollment of 92 evaluable patients in the VIRAGE Phase 2b clinical trial. Thirty - six patients received their second doses of intravenous VCN-01, which were well tolerated and demonstrated the expected VCN-01 adverse event profile. Topline data for the VIRAGE Phase 2b clinical trial was announced Q2 2025.

On January 30, 2024, the accumulated clinical data from patients enrolled across 6 sites open in the U.S. and 9 sites open in Spain were reviewed by an Independent Data Monitoring Committee (IDMC). According to the IDMC’s assessment, the ongoing Phase 2b trial continued without any changes to the protocol. No safety concerns were raised based on the evaluation of data presented at the IDMC meeting. Intravenous VCN-01 has been well tolerated and demonstrated a safety profile consistent with prior clinical trials. Importantly, no additional toxicities were observed in patients receiving a second dose of VCN-01, providing the first clinical evidence of the feasibility of repeated systemic dosing.

On May 10, 2024, we presented data demonstrating enhanced anti-tumor effects in human pancreatic cancer xenograft-bearing mice treated with lead product candidate VCN-01 and liposomal irinotecan. These data support the potential synergy of VCN-01 and first-line pancreatic cancer chemotherapy regimens.

On May 23, 2024, we announced that the FDA granted Fast Track Designation (FTD) to lead clinical candidate VCN-01 in combination with gemcitabine and nab-paclitaxel to improve progression-free survival and overall survival in patients with metastatic pancreatic adenocarcinoma.

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On June 1, 2024, we presented the design of VIRAGE trial in a poster at the American Society of Clinical Oncology (ASCO) Annual Meeting 2024 Congress held and in Chicago (Illinois) from May 31- June 4, 2024. The poster discussed the objectives, endpoints and key inclusion and exclusion criteria included in the trial protocol, together with the treatment schedule for each arm of the study.

On December 5, 2024 we announced the outcomes of a Type D meeting with the FDA to obtain guidance on the design of a potential Phase 3 clinical study of VCN-01 in combination with standard-of-care chemotherapy for the treatment of mPDAC. FDA advised that the optimal path forward for the VCN-01 PDAC program is to conduct a stand-alone Phase 3 study of VCN-01 with gemcitabine/nab-paclitaxel. The FDA provided general agreement with our proposed design for a Phase 3 clinical study and indicated that inclusion of additional standard-of-care chemotherapy for mPDAC was not necessary as it would complicate the study design and analysis. The FDA meeting also highlighted the FDA’s preferences regarding certain statistical elements of confirmatory clinical studies, including methods for sample size estimation and the study population(s) used for data analysis.

On February 4, 2025, we received Scientific Advice from the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) on the design of a potential Phase 3 clinical study of VCN-01 in combination with standard-of-care chemotherapy for the treatment of mPDAC. Consistent with feedback from the FDA, CHMP advised that a marketing authorization application (MAA) for VCN-01 in mPDAC could be supported by positive results from a randomized, controlled, stand-alone Phase 3 study comparing VCN-01 combined with gemcitabine/nab-paclitaxel to gemcitabine/nab-paclitaxel standard-of-care alone. The Scientific Advice also included CHMP suggestions regarding the study populations, inclusion/exclusion criteria, randomization and blinding, priority endpoints, and proposed statistical strategies for data analysis. An additional comment from the EMA Committee for Orphan Medicinal Products (COMP) noted that the potential benefit of VCN-01 with gemcitabine/nab-paclitaxel in a Phase 3 trial will be compared with the therapeutic effects of the other approved standard-of-care chemotherapies (FOLFIRINOX, NALIRIFOX) when considering maintenance of the Orphan Medicinal Product status of VCN-01 at the time of an MAA.

On March 31, 2025, we announced that a second Independent Data Monitoring Committee (IDMC) review of data from the VIRAGE Phase 2b clinical trial in newly-diagnosed mPDAC found that VCN-01 was well tolerated in combination with standard-of-care chemotherapy (gemcitabine/nab-paclitaxel) and the adverse event (AE) profile was as expected for the patient population and the medications being studied. The VCN-01 AE profile was consistent with that observed in prior clinical trials. The most common VCN-01 related AEs (pyrexia, flu-like illness, vomiting, nausea, and elevated transaminases) were transient and reversible. These AEs were observed to be less frequent and of reduced CTCAE grade after the second VCN-01 dose (administered on day 92) compared to the first VCN-01 dose (administered on day 1). The IDMC noted that the overall type and number of AEs in the VCN-01 treatment group was as expected for the pancreatic cancer population, the duration of treatment, and the administration of an oncolytic virus.

On May 7, 2025, we announced positive topline outcomes from the VIRAGE Phase 2b clinical trial evaluating our lead product candidate VCN-01 (zabilugene almadenorepvec) plus standard-of-care (SoC) chemotherapy gemcitabine/nab-paclitaxel as a first line therapy for patients with mPDAC for whom gemcitabine/nab-paclitaxel is the recommended first-line treatment option. Topline outcomes are detailed above under “Recent Clinical Developments”.

On October 20, 2025, expanded mPDAC data from the VIRAGE Phase 2b trial (NCT05673811) were presented at ESMO 2025.

Retinoblastoma

Phase 1 Trial of intravitreal VCN-01 in patients with retinoblastoma

During the third quarter of 2017, VCN entered into a Clinical Trial Agreement with Hospital Sant Joan de Déu (Barcelona, Spain) to conduct an investigator sponsored Phase 1 clinical study evaluating the safety and tolerability of two intravitreal injections of VCN-01 in patients with intraocular retinoblastoma refractory to systemic, intra-arterial or intravitreal chemotherapy, or radiotherapy, in whom enucleation was the only recommended treatment (NCT03284268). Patients received two intravitreal injections of VCN-01, 14 days apart, at a dose of either 2 x 109 vp/eye (n=1) or 2 x 1010 vp/eye (n=8). The clinical database for the study has now been locked and the clinical study report is being prepared.

On April 23, 2024, we announced positive topline data from this study, with agreement by the study Monitoring Committee that the study had a positive outcome. Per the terms of the clinical trial agreement, the determination by the study Monitoring Committee that the study had a positive outcome means we received an exclusive, worldwide technology license, and related patents from Hospital Sant Joan de Déu for the treatment of pediatric patients with advanced retinoblastoma and we will pay to Hospital Sant Joan de Déu the

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amount of three hundred twenty thousand, two hundred and sixty five Euros (€320,265) or approximately $334,000, upon receipt by us of the final clinical study report.

A pre-Investigational New Drug (“IND”) meeting with the FDA was held on December 19, 2023 to discuss the path forward for VCN-01 as an adjunct to chemotherapy in pediatric patients with advanced retinoblastoma. The FDA provided some guidance on the potential endpoints and patient population for an advanced clinical trial and encouraged submission of a formal protocol under a US IND in order to provide more detailed commentary.

On July 30, 2024, we received notice from the FDA that we had been granted Rare Pediatric Drug Designation (RPDD) for VCN-01 for the treatment of retinoblastoma. The FDA grants RPDD for rare diseases (fewer than 200,000 affected persons in the United States) that are serious and life-threatening and primarily affect children ages 18 years or younger. If a Biologics License Application for VCN-01 for the treatment of retinoblastoma is approved by the FDA by September 30, 2026, we may be eligible to receive a Priority Review Voucher. Previously, the FDA granted orphan drug designation to VCN-01 for treatment of retinoblastoma.

On October 11, 2024, the European Commission adopted the European Medicines Agency (EMA) recommendation to grant Orphan Medicinal Product Designation to VCN-01 for the treatment of retinoblastoma.

On May 27, 2025, we announced the presentation of the final data from an investigator-sponsored Phase 1 study of VCN-01 (zabilugene almadenorepvec) in refractory retinoblastoma patients in a poster presented by Dr. Jaume Català-Mora, Pediatric Ophthalmologist, Sant Joan de Déu-Barcelona Children’s Hospital at the 2025 American Society of Clinical Oncology (ASCO) annual meeting. Topline outcomes are detailed above under “Recent Clinical Developments” section.

Phase 1 Trial of intravenous VCN-01 in Combination with Durvalumab in Subjects with Recurrent/ Metastatic SCCHN

In February 2019, VCN entered into a Clinical Trial Agreement with Catalan Institute of Oncology (ICO) (Spain) to conduct an investigator sponsored Phase 1 clinical study to evaluate the safety, tolerability and RP2D of a single intravenous injection of VCN-01 combined with durvalumab in two administration regimens: VCN-01 concomitantly with durvalumab, or sequentially with durvalumab starting two weeks after VCN-01 administration (NCT03799744). The study is also designed to evaluate whether VCN-01 treatment can re-sensitize PD-(l)-1 refractory tumors to subsequent anti-PD-L1 therapy. Durvalumab is a human monoclonal antibody (mAb) of the immunoglobulin G (IgG) 1 kappa subclass that inhibits binding of PD-L1. It is marketed as IMFINZI® by AstraZeneca/MedImmune, who supplied the product for its use in the clinical study. This Phase I trial is a multicenter, open label, dose escalation study in patients with histologically confirmed head and neck squamous cell carcinoma from specific sites: oral cavity, oropharynx, larynx or hypopharynx that is recurrent/metastatic (R/M) and not amenable to curative therapy by surgery or radiation. In addition, all patients should have undergone prior exposure to anti-PD-(L) 1 and progressed. Patients are entered at each dose level, according to a planned dose escalation schedule. The treatment is a single intravenous VCN-01 dose combined with concomitant intravenous durvalumab (MEDI4736) 1500 mg Q4W (Arm I) or durvalumab starting two weeks after VCN-01 administration (“sequential schedule”; Arm II). Patient recruitment into Arm I and Arm II was performed concurrently. Intravenous VCN-01 was administered to each patient only once during the trial at the VCN-01 dose level to which they were randomized. Durvalumab was administered Q4W until disease progression, unacceptable toxicity, withdrawal of consent, or another discontinuation criterion. Patient recruitment into the study was completed in February 2022 with a total of 18 patients enrolled. On September 5, 2022 we announced a presentation of initial data from this study in a poster at the European Society for Medical Oncology (ESMO) Congress. The poster reported that treatment with VCN-01 was well tolerated when administered with durvalumab in the sequential schedule and the most common treatment-related adverse events were dose-dependent and reversible pyrexia, flu-like symptoms and increases in liver transaminases. Sustained blood levels of VCN-01 viral genomes and increased serum hyaluronidase levels were maintained for over six weeks and analysis of tumor samples showed an increase in CD8 T cells (a marker of tumor inflammation); upregulation of PD-L1; and downregulation of matrix-related pathways after VCN-01 administration. The study has been completed and the clinical study report has been completed.

On October 16, 2023, we presented additional data from this study in a poster at the European Society for Medical Oncology (ESMO) 2023 Congress held virtually and in Madrid, Spain from October 20-24, 2023. Key data and conclusions featured in the ESMO presentation include:

| ● | 20 patients were enrolled with a median of 4 prior lines of therapy, from which six in the concomitant (CS) (single dose of VCN-01 in combination with durvalumab on day 1) and 12 in the sequential (SS) (single dose of VCN-01 on day -14 and durvalumab on day 1) were evaluable for response.

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| ● | In the CS cohort at the 3.3×1012 viral particles (vp) dose, overall survival (OS) was 10.4 months.

| ● | In the SS cohort at the 3.3×1012vp dose OS was 15.5 months, whereas in the SS cohort at the 1×1013 vp dose OS was 17.3 months.

| ● | 11 patients (61.1%) were alive >12 months (2 in CS; 5 in SS at 3.3×1012vp, 4 in SS at 1×1013 vp).

| ● | In spite of the advanced stage of the disease, and a global objective response rate for the trial of 5.5%, most of the patients appeared to benefit from subsequent treatment, with 2 patients showing complete responses to palliative chemotherapy and at least one patient still alive 4 years after entering the study.

| ● | Biological activity: Patients showed VCN-01 replication and increased serum hyaluronidase levels were maintained for over six weeks.

| ● | Observed an increase in CD8 T cells, a marker of tumor inflammation and an upregulation of PD-L1 in tumors.

| ● | Increase of PDL1- combined positive score (CPS; 16/21; p=0.013) and CD8 T-cells (12/21; p=0.007) from baseline were found in tumor biopsies.

| ● | There was a statistically significant correlation between OS observed in patients and CPS on day 8 (p=0.005).

Phase 1 Trial evaluating the safety and feasibility of huCART-meso cells when given in combination with VCN-01

In July 2021, VCN entered into a Clinical Trial Agreement with the University of Pennsylvania (Philadelphia) to conduct an investigator sponsored Phase 1 clinical study to evaluate the safety, tolerability and feasibility of intravenous administration of VCN-01 in combination with lentiviral transduced huCART-meso cells (developed by the laboratory of Dr. Carl June) in patients with histologically confirmed unresectable or metastatic pancreatic adenocarcinoma and serous epithelial ovarian cancer (NCT05057715). This is a Phase I study evaluating the combination of VCN-01 when given in combination with huCART-meso cells in a dose-escalation design in two cohorts (N = 3-6), where patients receive VCN-01 as a single IV infusion (at 3.3x1012 or 1x1013 vp) on Day 0, followed by a single dose of 5x107 huCART-meso cells on Day 14 via IV infusion. huCART-meso cells are modified T-cells targeting the mesothelin antigen, which is frequently expressed in multiple tumor types, particularly in pancreatic and ovarian cancers. Dr. June’s previous clinical studies have shown that huCART-meso cells encounter significant challenges in the tumor microenvironment, including immunosuppressive cells and soluble factors as well as metabolic restrictions. Initial VCN-01 clinical data from the studies described above suggest that administration of VCN-01 may increase tumor immunogenicity and improve access of the huCART-meso cells to tumor cells. This Phase I study will evaluate the safety and tolerability of the VCN-01 huCART-meso cell combination and test the hypothesis that administration of VCN-01 may enhance the potential antitumor effects of the co-administered huCART-meso cells.

On July 8, 2022, we were notified that the first patient to be dosed with VCN-01 had passed the safety evaluation period in this study. On June 22, 2023, at their Cellicon Valley conference, and again at the Society for Immunotherapy of Cancer (SITC) meeting in San Diego, CA on November 3, 2023, and the International Oncolytic Virotherapy Conference (IOVC2023) in Calgary on November 13 2023, University of Pennsylvania investigators presented preliminary clinical safety and pharmacokinetic data from this study highlighting the feasibility of administering VCN-01 in sequence with huCART-meso cells in pancreatic and ovarian cancer patients. VCN-01 persistence was suggestive of tumor infection and active replication. The peak and duration of huCART-meso T cells in the peripheral blood as well as duration of stable disease in evaluable patients showed encouraging trends.

On October 16, 2024, at the 2024 Advancing Gene Therapy and Cell Therapies for Cancer conference by the American Society for Gene and Cell Therapy in Philadelphia, University of Pennsylvania investigators presented results from the Phase 1 trial of huCART-meso cells administered in combination with VCN-01 in patients with pancreatic and serous epithelial ovarian cancer. Safety was in line with expectations from monotherapy studies and 3.3x1012 was defined as the dose for further development. The Cmax of huCART-meso cells showed some signs of enhancement in patients previously infused with VCN-01. 66.6% (4 out of 6) patients with measurable disease receiving huCART-meso after VCN-01 showed tumor shrinkage, indicating a promising trend in disease stabilization in patients receiving huCART-meso and VCN-01 compared to either agent alone.

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On November 19, 2024 we were notified by the investigators that they would not continue with the present clinical trial, instead preferring to focus on advancement of a next-generation mesothelin-specific CAR-T. This new CAR-T could potentially be evaluated in combination with VCN-01 in a future clinical trial.

Phase 1 Trial evaluating the intravenous administration of VCN-01 in patients prior to surgical resection of high-grade brain tumors

In the second quarter of 2021, VCN entered into a Clinical Trial Agreement with the University of Leeds (UK) to sponsor a proof-of-concept Phase 1 clinical study to evaluate whether intravenously administered VCN-01 can cross the blood-brain barrier and infect the target brain tumor. This is an open-label, non-randomized, single center study of VCN-01 given intravenously at a dose of 1x1013 virus particles to patients prior to planned surgery for recurrent high-grade primary or metastatic brain tumors. We believe that the intravenous delivery of anti-cancer therapy to brain tumors, if effective, may enable the treatment of systemically disseminated brain metastases and may allow for reduction in the need to use neurosurgery to administer the drugs. This study aims to assess the presence of VCN-01 within the resected surgical specimen after systemic VCN-01 delivery and determine the safety of intravenous VCN-01 in patients with recurrent high-grade glioma or brain metastases. By confirming the presence of VCN-01 in high grade brain tumors following intravenous delivery, this study may pave the way for larger trials to study VCN-01 efficacy, both as a monotherapy and in combination with PD-1/PD-L1 blockade. This trial has already received approval from Medicines & Healthcare Products Regulatory Agency (MHRA) from UK Government.

On January 9, 2023, we issued a press release announcing that the first patient was dosed in this study and recruitment is on-going.

On May 12, 2025, a protocol amendment was submitted for this trial to MHRA (UK Regulatory Authorities) and on July 8, 2025 we were notified by the investigator that the protocol amendment had been approved.

Our Current Gastrointestinal (GI) and Microbiome-Focused Pipeline

Our SYN-004 (ribaxamase) and SYN-020 clinical programs are focused on the gastrointestinal tract (GI) and the gut microbiome, which is home to billions of microbial species and composed of a natural balance of both “good” beneficial species and potentially “bad” pathogenic species. When the natural balance or normal function of these microbial species is disrupted, a person’s health can be compromised. All of our programs are supported by our growing intellectual property portfolio. We are maintaining and building our patent portfolio through filing new patent applications; prosecuting existing applications; and licensing and acquiring new patents and patent applications.

SYN-004 (ribaxamase) — Prevention of antibiotic-mediated microbiome damage, thereby preventing overgrowth and infection by pathogenic organisms such as Clostridioides difficile infection (CDI) and vancomycin resistant Enterococci (VRE), and reducing the incidence and severity of acute graft-versus-host disease (aGVHD) in allogeneic HCT recipients

SYN-004 (ribaxamase) is a proprietary oral capsule prophylactic therapy designed to degrade certain IV beta-lactam antibiotics excreted into the GI tract and thereby maintain the natural balance of the gut microbiome. Preventing beta-lactam damage to the gut microbiome has a range of potential therapeutic outcomes, including prevention of CDI, suppression of the overgrowth of pathogenic species (particularly antimicrobial-resistant organisms) and potentially reducing the incidence and/or severity of aGVHD in allogeneic hematopoietic cell transplant (HCT) patients. SYN-004 (ribaxamase) 75 mg capsules are intended to be administered orally while patients are administered certain IV beta-lactam antibiotics. The capsule dosage form is designed to release the SYN-004 (ribaxamase) enzyme into proximal small intestine, where it has been shown to degrade beta-lactam antibiotics in the GI tract without altering systemic antibiotic levels. Beta-lactam antibiotics are a mainstay in hospital infection management and include the commonly used penicillin and cephalosporin classes of antibiotics.

Clostridioides difficile Infection

Clostridioides difficile (formerly known as Clostridium difficile and often called C. difficile or CDI) is a leading type of hospital acquired infection and is frequently associated with IV beta-lactam antibiotic treatment. The Centers for Disease Control and Prevention (CDC) identified C. difficile as an “urgent public health threat,” particularly given its resistance to many drugs used to treat other infections. CDI is a major unintended risk associated with the prophylactic or therapeutic use of IV antibiotics, which may adversely alter the natural balance of microflora that normally protect the GI tract, leading to C. difficile overgrowth and infection. Other risk factors for CDI include hospitalization, prolonged length of stay (estimated at 7 days), underlying illness, and immune-compromising conditions including the administration of chemotherapy and advanced age.

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Phase 1b/2a Clinical Study in Allogeneic HCT Recipients

In August 2019, we entered into a Clinical Trial Agreement (CTA) with the Washington University School of Medicine (Washington University) to conduct a Phase 1b/2a clinical trial of SYN-004 (ribaxamase). Under the terms of this agreement, we serve as the sponsor of the study and supply SYN-004 (ribaxamase). Dr. Erik R. Dubberke, Professor of Medicine and Clinical Director, Transplant Infectious Diseases at Washington University and a member of the SYN-004 (ribaxamase) steering committee serves as the principal investigator of the clinical trial in collaboration with his Washington University colleague Dr. Mark A. Schroeder, Associate Professor of Medicine, Division of Oncology, Bone Marrow Transplantation and Leukemia.

The Phase 1b/2a clinical trial was a single center, randomized, double-blinded, placebo-controlled clinical trial of oral SYN-004 (ribaxamase) in up to 36 evaluable adult allogeneic HCT recipients. The goal of this study is to evaluate the safety, tolerability and potential absorption into the systemic circulation (if any) of oral SYN-004 (ribaxamase; 150 mg four times daily) administered to allogeneic HCT recipients who receive an IV carbapenem or beta-lactam antibiotic to treat fever. Study participants were enrolled into three sequential cohorts administered a different study-assigned IV antibiotic. Each cohort seeks to complete eight evaluable participants treated with SYN-004 (ribaxamase) and four evaluable participants treated with placebo. Safety and pharmacokinetic data for each cohort will be reviewed by an independent Data and Safety Monitoring Committee, which will make a recommendation on whether to proceed to the next IV antibiotic cohort. The study will also evaluate potential protective effects of SYN-004 on the gut microbiome as well as generate preliminary information on potential therapeutic benefits and patient outcomes of SYN-004 in allogeneic HCT recipients.

To date, we have completed 2 of 3 cohorts (Cohorts 1 and 2) in this study. On September 27, 2022, we issued a press release announcing positive outcomes from the Data and Safety Monitoring Committee (“DSMC”) review of results from the first Cohort and their recommendation that the study may proceed to enroll Cohort 2 in which study drug (SYN-004 or Placebo) is administered in combination with the IV beta-lactam antibiotic piperacillin/tazobactam.

On February 16, 2023 and April 13, 2023, we announced the presentation of safety and pharmacokinetic data from Cohort 1 of the Phase 1b/2a Clinical Trial of SYN-004 (ribaxamase) in allogeneic hematopoietic cell transplant recipients at the 2023 Tandem Meetings: Transplantation & Cellular Therapy Meetings of ASTCT and CIBMTR and at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID), respectively.

On October 3, 2024, we announced a positive outcome from the DSMC review of results from the second Cohort of our Phase 1b/2a randomized, double - blinded, placebo - controlled clinical trial of SYN - 004 (ribaxamase) in allogeneic hematopoietic cell transplant (“HCT”) recipients for the prevention of acute graft - versus - host - disease. Based on a review of the safety and pharmacokinetic data, the DSMC recommended that the study may proceed to enroll Cohort 3 in which study drug (SYN - 004 or Placebo) will be administered in combination with the IV beta - lactam antibiotic cefepime. Based upon our current available funding and our focus on our clinical development of VCN - 01 we do not anticipate that enrollment for the third cohort will commence unless we obtain grant funding, or find a licensee or partner to fund the SYN - 004 development program.

On April 10, 2025, we announced the presentation of the previously disclosed blinded safety and pharmacokinetic (PK) data from the ongoing Phase 1b/2a randomized, double - blinded, placebo - controlled clinical trial of SYN - 004 (ribaxamase) in allogeneic hematopoietic cell transplant (HCT) recipients for the prevention of acute graft - versus - host - disease (aGVHD) at the Congress of the European Society of  Clinical Microbiology and Infectious Diseases (ESCMID Global), taking place in Vienna, Austria from April 11 - 15, 2025. This data was featured in an ePoster Flash Session oral presentation.

SYN-020 — Oral Intestinal Alkaline Phosphatase (IAP)

SYN-020 is a quality-controlled, recombinant version of bovine Intestinal Alkaline Phosphatase (IAP) produced under cGMP conditions and formulated for oral delivery. The published literature indicates that IAP functions to diminish GI and systemic inflammation, tighten the gut barrier to diminish “leaky gut,” diminish fat absorption, and promote a healthy microbiome. Despite its broad therapeutic potential, a key hurdle to commercialization has been the high cost of IAP manufacture which is commercially available for as much as $10,000 per gram. We believe we have developed technologies to traverse this hurdle and now have the ability to produce more than 3 grams per liter of SYN-020 and anticipate a cost of roughly a few hundred dollars per gram at commercial scale. Based on the known mechanisms as well as our own supporting animal model data, we intended to initially develop SYN-020 to mitigate the intestinal damage caused by radiation therapy that is routinely used to treat pelvic cancers. While we believe SYN-020 may play a pivotal role in addressing acute and long-term complications associated with radiation exposure to the GI tract, we have also begun planning for

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potential development of SYN-020 in large market indications with significant unmet medical needs. Such indications include celiac disease, non-alcoholic fatty liver disease (“NAFLD”), and indications to treat and prevent metabolic and inflammatory disorders associated with aging.

On June 30, 2020, we submitted an IND application to the FDA in support of an initial indication for the treatment of radiation enteropathy secondary to pelvic cancer therapy. On July 30, 2020, we announced that we received a study-may-proceed letter from the FDA to conduct a Phase 1a single-ascending-dose (“SAD”) study in healthy volunteers designed to evaluate SYN-020 for safety, tolerability and pharmacokinetic parameters (NCT04815993). On June 29, 2021, we announced that enrollment, patient dosing and observation had been completed in the Phase 1, open-label, SAD study of SYN-020. The SAD study enrolled 6 healthy adult volunteers into each of four cohorts with SYN-020 given orally as single doses ranging from 5 mg to 150 mg. The data demonstrated that SYN-020 maintained a favorable safety profile, was well tolerated at all dose levels, and no adverse events were attributed to the study drug. No serious adverse events were reported.

During the third quarter of 2021 we initiated a Phase 1 clinical study evaluating multiple ascending doses (“MAD”) of SYN-020 (NCT05045833). The placebo-controlled, blinded study enrolled 32 healthy adult volunteers into four cohorts with SYN-020 administered orally in doses ranging from 5 mg to 75 mg twice daily for 14 days with a follow-up evaluation at day 35. Each cohort included six subjects who received SYN-020 and two who received placebo. On May 10, 2022, we announced positive safety data from the Phase 1 MAD study demonstrating that SYN-020 maintained a favorable safety profile and was well-tolerated across all dose levels. There were a few treatment-related adverse events, and all were mild (grade 1) and resolved without medical intervention. The most common adverse event, constipation, occurred in three out of 24 subjects in the treatment arm and in one out of eight subjects in the placebo arm. No adverse event led to discontinuation of the study drug and there were no serious adverse events. Additionally, fecal SYN-020 analyses verified intestinal bioavailability while plasma levels of SYN-020 were below the limit of quantitation in all samples at all timepoints verifying that SYN-020 was not absorbed into the systemic circulation.

During the second quarter of 2020, we announced that we entered into an agreement with Massachusetts General Hospital (“MGH”) granting us an option for an exclusive license to intellectual property and technology related to the use of IAP to maintain GI and microbiome health, diminish systemic inflammation, and treat age-related diseases, which option was later amended to include liver fibrosis in select diseases, including NAFLD. The option expired unexercised on July 1, 2024.

The Phase 1 data from our SAD and MAD studies are intended to support the development of SYN-020 in multiple clinical indications including radiation enteritis, NAFLD, celiac disease, and diseases associated with aging. With our transition to an oncology focused company, we are exploring strategic opportunities to enable advancement of this potentially valuable asset.

As part of our strategic transformation into an oncology focused company, we are exploring value creation options for our SYN - 004 and SYN - 020 assets, including out - licensing or partnering.

VCN-01 + Topoisomerase Inhibitors

On May 10, 2024, we presented non-clinical describing enhanced anti-tumor effects in human pancreatic cancer xenograft-bearing mice treated with lead product candidate VCN-01 and liposomal irinotecan in a poster at the 27th American Society of Gene and Cell Therapy (ASGCT) 2024 Congress held in Baltimore (Maryland) from May 7-11, 2024. These data support the potential synergy of VCN-01 and additional first-line pancreatic cancer chemotherapy regimens FOLFIRINOX and NALIRIFOX. Key findings reported in the poster include:

| ● | The combination of VCN-01 + topoisomerase I (topo1) inhibitors, such as liposomal irinotecan, has a tolerable toxicity profile and may improve efficacy in the treatment of human pancreatic cancer.

| ● | Viral protein expression was increased in human pancreatic cancer cell lines when they were exposed to topo1 inhibiting chemotherapeutics, irinotecan, its active metabolite, SN-38, and topotecan.

| ● | Synergy of VCN-01 plus liposomal irinotecan was observed in animals bearing subcutaneous human pancreatic tumors.

| o | In human pancreatic mouse xenograft models, treatment with VCN-01 at a dose of 4x1010 vp or liposomal irinotecan alone (at both the 10 mg/kg and 5 mg/kg doses) resulted in significant tumor growth inhibition compared to saline.

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| o | Combination therapy with VCN-01 + liposomal irinotecan at either dose displayed significantly reduced tumor growth compared to each treatment alone.

| o | qPCR analyses performed on tumors collected at end of study confirmed the presence of viral genomes, indicating ongoing transcriptional activity of VCN-01, which is consistent with viral replication for several days after administration.

VCN-X Next Generation OVs and Albumin Shield™ Technology

In parallel with VCN-01 clinical development, we are developing next-generation oncolytic adenoviruses (termed VCN-X) with novel therapeutic payloads and structural modifications designed to increase tumor cell killing and improve systemic virus pharmacokinetics. Preclinical proof-of-concept has been established with VCN-11, which has been engineered to contain all the features of VCN-01 as well as an additional modification to include an albumin binding domain (ABD) in the virus capsid. The virus capsid is the target for neutralizing antibodies (NAbs) that are generated by the host immune system to destroy circulating viruses. The presence of an ABD, however, blocks the binding of most neutralizing antibodies, which allows the virus to reach the tumor following intravenous administration. This “Albumin Shield” works because human blood contains a large amount of albumin to coat the ABD-containing virus. Importantly, this coating of albumin appears to be displaced after the virus reaches tumor cells to infect them. In pre-clinical mouse studies to test the functionality of the “Albumin Shield”, mice pre-immunized with virus are able to completely neutralize an unmodified OV because they have a large concentration of neutralizing antibodies in their blood. By contrast, viruses such as VCN-11 that contain the ABD are not neutralized and retain their ability to infect and destroy tumor cells. We believe the results with VCN-11 support the application of the Albumin Shield technology in our VCN-X program to advance treatments for tumors in which rapid multi-dosing may be beneficial.

In March 2021, preclinical data obtained with VCN-11 was published (J Control Release. 2021 Apr 10;332:517-528), showing that the ABD-containing virus induced 450 times more cytotoxicity in tumor cells than in normal cells. Hyaluronidase production was confirmed by measuring the activity of the PH20 enzyme with a hyaluronic acid-degradation assay, and by measuring PH20 activity in VCN-11 infected tumors in vivo. The ABD-containing virus evaded NAbs from different sources and tumor levels of virus were demonstrated in the presence of high levels of NAbs in vivo, whereas the control virus without ABD was neutralized. VCN-11 showed a low toxicity profile in athymic nude mice and Syrian hamsters, allowing treatments with high doses and fractionated administrations without major toxicities (up to 1.2x1011vp/mouse and 7.5x1011vp/hamster). ALT levels were increased on day 3 within an acceptable range that returned to normal levels by day 9. Fractionated intravenous administration of the ABD-containing virus (splitting the dose into two portions administered 4 h apart) appeared to improve virus circulation kinetics and increase tumor levels. Antitumor efficacy was observed in the presence of NAbs against Ad5 and the ABD-containing virus.

In May 2022, we presented data at the 25th Annual Meeting of the American Society of Gene & Cell Therapy (ASGCT). The presentation included preclinical results showcasing the potential of the Albumin Shield Technology to effectively target tumors after intravenous re-administration, even in the presence of high level NAbs, with no major toxicities observed. Our internal VCN-X discovery programs are currently evaluating new oncolytic viruses that contain the Albumin Shield technology and may expand the potential efficacy of Theriva’s oncolytic viruses.

In October 2025, Dr. Ramón Alemany, co-founder of VCN (now Theriva Biologics S.L.) and Head of the Immunotherapy and Virotherapy Group at the ProCURE Program of the Catalan Institute of Oncology (ICO) and the Oncobell Program of the Biomedical Research Institute of Bellvitge (IDIBELL) in Barcelona, presented new mechanistic and preclinical data for VCN-12, a next generation oncolytic adenovirus selected from our VCN-X discovery program at the 32nd Annual Congress of the European Society of Gene & Cell Therapy (ESGCT) in Seville, Spain. VCN-12 is derived from lead clinical product VCN-01 (zabilugene almadenorepvec) and is armed with additional transgenes designed to improve tumor cell lysis, enhance stroma degradation, and augment the antitumor immune response.

THERICEL suspension cell lines for viral manufacturing

The THERICEL program is advancing a proprietary A549 suspension cell line for use in the manufacture of viral therapeutics. These cells are entering feasibility studies to support significant scale - up and potential Phase 3 GMP manufacture of VCN-01 for use in clinical trials. The use of the THERICEL suspension cells is expected to increase the efficiency and significantly reduce the cost of manufacture for VCN - 01 and other viral therapies.

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We also have a Spanish government funded collaboration with the Universitat Autònoma de Barcelona to adapt the THERICEL suspension cell platform for the clinical manufacture of adeno - associated virus (“AAV”) therapies. If successful, adaptation of the THERICEL platform to AAV manufacture provides an opportunity for potential commercial collaborations in the manufacture of a range of gene therapy products.

Intellectual Property

All of our programs are supported by growing patent estates. In total, Theriva Biologics has over 135 U.S. and foreign patents and over 50 U.S. and foreign patents pending. VCN, through assignment or exclusive licenses, controls over 50 U.S. and foreign patents and over 15 U.S. and foreign patents pending.

The SYN-004 (ribaxamase) program is supported by intellectual property (“IP”) that is assigned to Theriva Biologics, namely U.S. and foreign patents (in most major markets, e.g. Europe (including Germany, Great Britain and France), Japan, China and Canada, among others) and U.S. and foreign patents pending (in most major markets, e.g. Europe (including Germany, Great Britain and France), Japan, China and Canada, among others). For instance, U.S. Patent Nos. 8,894,994 and 9,587,234, which include claims to compositions of matter and pharmaceutical compositions of beta-lactamases, including SYN-004 (ribaxamase), have patent terms to at least 2031. Further, U.S. Patent 9,301,995 and 9,301,996, both of which will expire in at least 2031, cover various uses of beta-lactamases, including SYN-004 (ribaxamase), in protecting the microbiome, and U.S. Patent Nos. 9,290,754, 9,376,673, 9,404,103, 9,464,280, and 9,695,409 which will expire in at least 2035, covers further beta-lactamase compositions of matter related to SYN-004 (ribaxamase).

The SYN-020 (oral intestinal alkaline phosphatase (IAP)) program is supported by IP that is assigned to Theriva Biologics, namely U.S. and foreign patents and patent applications (in many major markets, e.g. Europe, China, Japan, Korea, Canada, and Australia). These patents and patent applications, which cover various formulations, medical uses and manufacture of SYN-020, are expected to expire in 2038-2040, without taking potential patent term extensions or patent term adjustment into account.

The VCN-01 and Albumin Shield programs are supported by U.S. and foreign patents and patent applications that are assigned to VCN or exclusively licensed from Fundació Privada Institut d’Investigacio Biomedica de Bellvitge (IDIBELL), Institut Catala d’Oncologia (ICO), and Hospital Sant Joan de Déu in Barcelona. The patents and patent applications include U.S. patents and foreign patents (in most major markets, e.g. Europe, China, Japan, Korea, Canada, Israel, Mexico, Russia, and Australia) and U.S. and foreign patents pending (in most major markets, e.g. Europe, China, Korea, Canada, Mexico, and India). The patents and patent applications cover compositions of matter and pharmaceutical compositions of oncolytic adenoviruses and various medical uses of the same. For instance, U.S. Patent No. 10,316,065, which expires in 2030 without taking potential patent term extensions or patent term adjustment into account, provides composition of matter and pharmaceutical composition coverage for a genus of engineered oncolytic adenovirus suitable for the treatment of solid tumors. Other patents and patent applications, if granted, will provide protection to 2037 without taking potential patent term extensions or patent term adjustment into account.

Our goal is to (i) obtain, maintain, and enforce patent protection for our products, formulations, processes, methods, and other proprietary technologies, (ii) preserve our trade secrets, and (iii) operate without infringing on the proprietary rights of other parties worldwide. We seek, where appropriate, the broadest intellectual property protection for product candidates, proprietary information, and proprietary technology through a combination of contractual arrangements and patents.

Critical Accounting Estimates

The preparation of our consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) requires the use of estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses in the periods presented. We believe that the accounting estimates employed are appropriate and resulting balances are reasonable; however, due to inherent uncertainties in making estimates, actual results may differ from the original estimates, requiring adjustments to these balances in future periods.

There are accounting policies, each of which requires significant judgments and estimates on the part of management, that we believe are significant to the presentation of our consolidated financial statements. The most significant accounting estimates relate to goodwill and IPR&D, research and development costs, and contingent consideration.

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Goodwill and IPR&D

We classify intangible assets into two categories: (1) intangible assets with indefinite lives not subject to amortization and (2) goodwill. Intangible assets that are deemed to have indefinite lives, including goodwill, are reviewed for impairment annually, or more frequently if events or changes in circumstances indicate that the asset might be impaired. The impairment test for indefinite-lived intangibles, other than goodwill, consists of a comparison of the fair value of the intangible asset with their carrying amount. If the carrying amount exceeds the fair value, an impairment charge is recognized in an amount equal to that excess. Indefinite-lived intangible assets, such as goodwill, are not amortized. We test the carrying amounts of goodwill for recoverability on an annual basis or when events or changes in circumstances indicate evidence a potential impairment exists, using a fair value-based test. If a reporting unit’s carrying value exceeds its fair value, then we will record a goodwill impairment charge for the excess amount.

IPR&D assets are considered to be indefinite-lived until the completion or abandonment of the associated research and development projects. IPR&D assets represent the fair value assigned to technologies that we acquire, which at the time of acquisition have not reached technological feasibility and have no alternative future use. IPR&D is capitalized at its fair value as an indefinite-lived intangible asset, and any development costs incurred after the acquisition are expensed as incurred. During the period that the assets are considered indefinite-lived, they are tested for impairment on an annual basis, or more frequently if we become aware of any events occurring or changes in circumstances that indicate that the fair value of the IPR&D assets are less than their carrying amounts. If and when development is complete, which generally occurs upon regulatory approval and the ability to commercialize products associated with the IPR&D assets, these assets are then deemed definite-lived and are amortized based on their estimated useful lives at that point in time. If development is terminated or abandoned, we may have a full or partial impairment charge related to the IPR&D assets, calculated as the excess of carrying value of the IPR&D assets over fair value.

Goodwill represents the excess of the purchase price paid when we acquired VCN in March 2022, over the fair values of the acquired tangible or intangible assets and assumed liabilities. We conduct an impairment test of goodwill on an annual basis as of October 1 of each year and will also conduct tests if events occur or circumstances change that would, more likely than not, reduce our fair value below our net equity value.

Contingent Consideration

Consideration paid in a business combination may include potential future payments that are contingent upon the acquired business achieving certain milestones in the future (“contingent consideration”). Contingent consideration liabilities are measured at their estimated fair value as of the date of acquisition, with subsequent changes in fair value recorded in the consolidated statements of operations. We estimate the fair value of the contingent consideration as of the acquisition date using the estimated future cash outflows based on the probability of meeting future milestones. The milestone payments will be made upon the achievement of clinical and commercialization milestones. Subsequent to the date of acquisition, we reassess the actual consideration earned and the probability-weighted future earn-out payments at each balance sheet date. Any adjustment to the contingent consideration liability will be recorded in the consolidated statements of operations. Contingent consideration liabilities expected to be settled within 12 months after the balance sheet date are presented in current liabilities, with the non-current portion recorded under long term liabilities in the consolidated balance sheets.

Research and Development Costs

We expense research and development costs associated with developmental products not yet approved by the FDA to research and development expense as incurred. Research and development costs consist primarily of license fees (including upfront payments), milestone payments, manufacturing costs, salaries, stock-based compensation and related employee costs, fees paid to consultants and outside service providers for laboratory development, legal expenses resulting from intellectual property prosecution and other expenses relating to the design, development, testing and enhancement of our product candidates. Research and development expenses include external CRO services. We make payments to the CROs based on agreed upon terms and may include payments in advance of study services. We review and accrue CRO expenses based on services performed and rely on estimates of those costs applicable to the stage of completion of study as provided by the CRO. Accrued CRO costs are subject to revisions as such studies progress to completion. At September 30, 2025 and 2024, we have accrued CRO expenses of $1.7 million and $2.4 million, respectively, that are included in accrued expenses. As of September 30, 2025 and 2024, we have prepaid CRO costs of zero and $0.4 million, respectively, that are included in prepaid expenses.

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Results of Operations

Three Months Ended September 30, 2025 and 2024

General and Administrative Expenses

General and administrative expenses decreased to $1.9 million for the three months ended September 30, 2025, from $2.3 million for the three months ended September 30, 2024. This decrease of 18% is primarily comprised of the decrease in compensation costs offset by the increase in the fair value of the contingent consideration and increased investor relations expense. The charge related to stock-based compensation expense was $118,000 for the three months ended September 30, 2025, compared to $118,000 for the three months September 30, 2024. We expect general and administrative expenses to decrease due to the workforce reduction implemented on September 30, 2025.

Research and Development Expenses

Research and development expenses decreased to $2.6 million for the three months ended September 30, 2025, from approximately $2.7 million for the three months ended September 30, 2024. This decrease of 7% is primarily the result of lower clinical trial expenses related to the completion of our VIRAGE Phase 2b clinical trial of VCN-01 in PDAC, lower indirect cost related to compensation and lower clinical trial expenses related to our Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients, offset by higher patent expenses related to SYN-020. We anticipate research and development expense to decrease subsequent to the completion of our VIRAGE Phase 2b clinical trial of VCN-01 as we focus on regulatory interactions around potential pivotal clinical trials of VCN-01 in PDAC and retinoblastoma, continue exploratory VCN-01 manufacturing scale-up activities, and continue supporting our other preclinical and discovery initiatives. The charge related to stock-based compensation expense was $110,000 for the three months ended September 30, 2025, compared to $59,000 related to stock-based compensation expense for the three months ended September 30, 2024.

The following table sets forth our research and development expenses directly related to our product candidates for the three months ended September 30, 2025 and 2024. These direct expenses were external costs associated with preclinical studies and clinical trials. Indirect research and development expenses related to employee costs, facilities, stock-based compensation and research and development support services that are not directly allocated to specific product candidates.

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​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | September 30, | ​ | September 30,
Therapeutic Areas |  | 2025 |  | 2024
VCN-01 | ​ | $ | 1,372 | ​ | $ | 1,418
Ribaxamase | ​ | ​ | 60 | ​ | ​ | 177
SYN-020 | ​ | ​ | 77 | ​ | ​ | 41
Other therapeutic areas | ​ |  | 134 | ​ | ​ | 72
​ | ​ | ​ | ​ | ​ | ​ | ​
Total direct costs | ​ |  | 1,643 | ​ | ​ | 1,708
Total indirect costs | ​ |  | 909 | ​ | ​ | 1,026
​ | ​ | ​ | ​ | ​ | ​ | ​
Total Research and Development | ​ | $ | 2,552 | ​ | $ | 2,734

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IPRD and Goodwill Impairment

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During the three months ended September 30, 2024, we experienced a sustained decline in the quoted market price of our Common Stock and we deemed this to be a triggering event for impairment. We performed an interim impairment analysis using the “Income approach” that requires significant judgments, including primarily the estimation of future development costs, the probability of success in various phases of our development programs, potential post-launch cash flows and a risk-adjusted weighted average cost of capital. We concluded that the in-process R&D with a carrying value of $19.8 million was written down to its estimated fair value of $18.6 million and an impairment charge of $1.3 million was recorded, and goodwill with a carrying value of $1.5 million was written down to its estimated fair value of zero and an impairment charge of $1.5 million was recorded during the quarter. The decrease in the valuation was primarily driven by an increase in the discount rate which was impacted by an increase in the company specific risk premium, and not by material changes to the clinical and administrative operations of the business. There were no impairment indicators present during the three months ended Septemebr 30, 2025.

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Other Income/Expense

Other income was $79,000 for the three months ended September 30, 2025 compared to other income of $161,000 for the three months ended September 30, 2024. Other income for the three months ended September 30, 2025 is primarily comprised of interest income of $65,000 and an exchange gain of $14,000. Other income for the three months ended September 30, 2024 is primarily comprised of interest income of $158,000 and exchange gain of $3,000.

Net Loss

Our net loss for the three months ended September 30, 2025 was $4.4 million, or ($0.45) per common share, compared to $7.7 million, or ($6.81) per common share for the three months ended September 30, 2024.

Nine Months Ended September 30, 2025 and 2024

General and Administrative Expenses

General and administrative expenses increased to $14.5 million for the nine months ended September 30, 2025, from $5.7 million for the nine months ended September 30, 2024. This increase of 155% is primarily comprised of the increase in fair value of the contingent consideration adjustment of $9.2 million due to the VIRAGE Phase 2b clinical trial of VCN-01 in PDAC achieving its primary survival and safety endpoints offset by decrease in compensation costs. The charge related to stock-based compensation expense was $269,000 for the nine months ended September 30, 2025, compared to $335,000 for the nine months ended September 30, 2024. We expect general and administrative expenses to decrease due to the workforce reduction implemented on September 30, 2025.

Research and Development Expenses

Research and development expenses decreased to $7.5 million for the nine months ended September 30, 2025, from approximately $9.1 million for the nine months ended September 30, 2024. This decrease of 18% is primarily the result of lower clinical trial expenses related to the completion of our VIRAGE Phase 2b clinical trial of VCN-01 in PDAC, lower clinical trial expenses related to our Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients and lower indirect cost related to compensation, offset by higher patent expenses related to SYN-020. We anticipate research and development expense to decrease subsequent to the completion of our VIRAGE Phase 2b clinical trial of VCN-01 as we focus on regulatory interactions around potential pivotal clinical trials of VCN-01 in PDAC and retinoblastoma, continue exploratory VCN-01 manufacturing scale-up activities, and continue supporting our other preclinical and discovery initiatives. The charge related to stock-based compensation expense was $232,000 for the nine months ended September 30, 2025, compared to $175,000 related to stock-based compensation expense for the nine months ended September 30, 2024.

The following table sets forth our research and development expenses directly related to our product candidates for the nine months ended September 30, 2025 and 2024. These direct expenses were external costs associated with preclinical studies and clinical trials. Indirect research and development expenses related to employee costs, facilities, stock-based compensation and research and development support services that are not directly allocated to specific product candidates.

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​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | September 30, |  | September 30,
Therapeutic Areas | ​ | 2025 | ​ | 2024
VCN-01 | ​ | $ | 4,097 | ​ | $ | 4,657
Ribaxamase | ​ |  | 227 | ​ |  | 719
SYN-020 | ​ |  | 227 | ​ |  | 109
Other therapeutic areas | ​ |  | 339 | ​ |  | 288
​ | ​ | ​ | ​ | ​ | ​ | ​
Total direct costs | ​ |  | 4,890 | ​ |  | 5,773
Total indirect costs | ​ |  | 2,582 | ​ |  | 3,372
​ | ​ | ​ | ​ | ​ | ​ | ​
Total Research and Development | ​ | $ | 7,472 | ​ | $ | 9,145

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IPRD and Goodwill Impairment

During the nine months ended September 30, 2024, we experienced a sustained decline in the quoted market price of our Common Stock and we deemed this to be a triggering event for impairment. We performed an interim impairment analysis using the “Income approach” that requires significant judgments, including primarily the estimation of future development costs, the probability of success in various phases of its development programs, potential post-launch cash flows and a risk-adjusted weighted average cost of capital. We concluded that the in-process R&D with a carrying value of $19.8 million was written down to its estimated fair value of $18.6 million and an impairment charge of $1.3 million was recorded, and goodwill with a carrying value of $5.6 million was written down to its estimated fair value of zero and an impairment charge of $5.6 million was recorded during the nine months ended September 30, 2024. The decrease in the valuation was primarily driven by an increase in the discount rate which was impacted by an increase in the company specific risk premium, and not by material changes to the clinical and administrative operations of the business. There were no impairment indicators present during the nine months ended Septemebr 30, 2025.

Other Income/Expense

Other income was $245,000 for the nine months ended September 30, 2025 compared to other income of $560,000 for the nine months ended September 30, 2024. Other income for the nine months ended September 30, 2025 is primarily comprised of interest income of $215,000 and an exchange gain of $30,000. Other income for the nine months ended September 30, 2024 is primarily comprised of interest income of $559,000 and exchange gain of $1,000.

Net Loss Attributable to Common Stockholders

Our net loss attributable to common stockholders was approximately $21.7 million, or ($3.38) per basic and diluted common share for the nine months ended September 30, 2025, compared to a net loss of approximately $21.2 million, or ($24.47) per basic common share and diluted common share for the nine months ended September 30, 2024.

Liquidity and Capital Resources

As of September 30, 2025, we had a significant accumulated deficit, and with the exception of the three months ended June 30, 2010 and the three months ended December 31, 2017, we have experienced significant losses and incurred negative cash flows since inception. We have incurred an accumulated deficit of $356.7 million as of September 30, 2025, and expect to continue to incur losses in the foreseeable future with the recognition of revenue being contingent on successful phase 3 clinical trials and requisite approvals by the FDA or foreign equivalents.

Our cash and cash equivalents totaled $7.5 million as of September 30, 2025, a decrease of $4.1 million from December 31, 2024. However, subsequent to September 30, 2025, our cash position increased to $15.5 million as a result of our receipt of $6.1 in net proceeds from sales made pursuant to the ATM Sales Agreement and $4.0 million in net proceeds in connection with the warrant inducement consummated in October 2025. During the year ended December 31, 2024 and nine months ended September 30, 2025, the primary use of cash was for working capital requirements and operating activities which resulted in a net loss of $25.6 million and $21.7 million.

We believe our cash position of $15.5 million as of early November 2025, will allow us to fund our operations into the first quarter of 2027. However, despite this liquidity position, we continue to experience operating losses and face significant uncertainties related to our business model, market conditions, clinical trial outcomes, FDA review timelines and strategic initiatives. These factors raise substantial doubt about our ability to continue as a going concern beyond the next twelve months without additional capital or other strategic actions. Management has developed plans intended to mitigate these uncertainties, including pursuing strategic collaborations, securing additional financing, and prioritizing key development programs. While management believes these plans are probable of being successfully implemented, there can be no assurance that such actions will be sufficient to alleviate the going concern uncertainty.

Based on our current plans, our cash and cash equivalents will be sufficient to cover overhead costs, close out of the VIRAGE Phase 2b clinical trial, exploratory VCN-01 manufacturing scale-up activities, regulatory interactions regarding proposed VCN-01 clinical trials in PDAC and retinoblastoma, and preclinical studies supporting VCN-01 and VCN-12, the first candidate from our VCN-X discovery program. The cash is also sufficient to fund our committed obligations under the terms of the VCN share purchase agreement (the “VCN Purchase Agreement”) related to the Acquisition, but will not be sufficient for additional trials of VCN-01, SYN-020 or SYN-004, or to complete the last cohort of the Phase 1b/2a clinical trial of SYN-004, which are expected to require significant cash expenditures. Following the completion of our ongoing Phase 1 and Phase 2b clinical trials for VCN-01, and preclinical studies supporting VCN-01

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and our discovery initiatives, we will need to obtain additional funds for future clinical trials. We anticipate that our future clinical trials will be much larger in size and require larger cash expenditures than the aforementioned clinical programs. We do not have any committed sources of financing for future clinical trials at this time, and it is uncertain whether additional funding will be available when we need it on terms that will be acceptable to us, or at all. Management believes its plan, which is focused on the advancement of VCN-01, will allow us to meet our financial obligations, further advance key products, and maintain our planned operations. Based upon our current available funding and our focus on our clinical development of VCN-01 we do not anticipate that we will fund the last cohort of the Phase 1b/2a clinical trial of SYN-004 and enrollment in this cohort will not commence unless we obtain grant funding, or find a licensee or partner for the SYN-004 development program. However, the amount of additional capital needed by us will also depend upon the costs to advance our VCN-01 clinical programs. If necessary, we may attempt to utilize the ATM Sales Agreement or seek to raise additional capital in other financing transactions, neither of which is guaranteed. Use of the ATM Sales Agreement is limited by certain restrictions and management’s plan does not rely on additional capital from any sources. If we are not able to obtain additional capital (which is not assured at this time), our long-term business plan may not be accomplished, and we may be forced to cease certain development activities. More specifically, the completion of any later stage clinical trial will require significant financing or a significant partnership.

Historically, we have financed our operations primarily through public and private sales of our securities, and we expect to continue to seek and obtain additional capital in a similar manner. During the year ended December 31, 2024, our only source of cash was from sales of our Common Stock through the ATM Sales Agreement pursuant to which we sold 569,000 shares of our Common Stock for net proceeds of $3.6 million and from the sale of our securities in our public offering of 918,600 shares of Common Stock in combination with accompanying warrants to purchase an aggregate of 1,428,600 shares of the Common Stock for gross proceeds of $2.5 million (net proceeds of $2.0 million, after deducting underwriting discounts and estimated expenses). During the three and nine months ended September 30, 2025, we sold approximately 706,810 shares of our Common Stock pursuant to the ATM Sales Agreement and received net proceeds of approximately $279,000. During October 2025, we sold through the Sales Agreement approximately 15,342,601 shares of our Common Stock pursuant to the ATM Sales Agreement and received net proceeds of approximately $6.1 million. During the nine months ended September 30, 2025, the primary source of cash was from the $1.7 million received for the Research and Development rebate program, $1.4 million for the THERICEL project loan from the National Knowledge Transfer Program of the Spanish government’s Ministry of Science and, in May 2025, we closed our May 2025 Offering of 6,818,180 shares of Common Stock (or Pre-Funded Warrants in lieu thereof) in combination with accompanying Common Warrants to purchase an aggregate of 6,818,180 shares of the Common Stock for gross proceeds of $7.5 million (net proceeds of $6.9 million, after deducting underwriting discounts and estimated expenses).

Pursuant to the terms of the VCN Purchase Agreement, we were required to pay up to $70.2 million in additional consideration upon the achievement of certain milestones, including regulatory filings of which to date $6.8 million has been paid. In September 2022, we received approval from the FDA to proceed with the Phase 2 clinical trial of VCN-01 in metastatic pancreatic ductal adenocarcinoma (mPDAC). Due to this approval we paid Grifols Innovation and New Technologies Limited (“Grifols”), $3.0 million in the fourth quarter 2022. In August 2023, we initiated patient dosing in the U.S. in our Phase 2 clinical trial of VCN-01 in mPDAC. As a result, payment was made subsequent to September 30, 2023 in the amount of $3.25 million. During the three months ended June 30, 2025, we met the primary survival and safety endpoints in our VIRAGE Phase 2b clinical trial evaluating our lead product candidate VCN-01. As a result of achieving the primary survival and safety endpoints in the Phase 2b clinical trial, we are obligated to pay Grifols $6 million. On August 5, 2025, we and Grifols agreed to deferring the $6 million milestone payment into three payments; $500,000 was paid in August 2025, $500,000 will be paid by the end of December 2025, and the remaining $5 million payment will be deferred until a licensing or business development transaction is secured.

There can be no assurance that we will be able to continue to raise funds through the sale of shares of Common Stock through the ATM Sales Agreement or other equity financings. If we raise funds by selling additional shares of Common Stock or other securities convertible into Common Stock, the ownership interest of our existing stockholders will be diluted. If we are not able to obtain funding for future clinical trials when needed, we will be unable to carry out our business plan and we will be forced to delay the initiation of future clinical trials until such time as we obtain adequate financing and may need to abandon some of our development programs, cease operations, liquidate our assets or reorganize the Company, or a combination of the foregoing.

We have spent, and expect to continue to spend, a substantial amount of funds in connection with implementing our business strategy, including our planned product development efforts, preparation for our planned clinical trials, performance of clinical trials and our research and discovery efforts. We will be required to obtain additional funding in order to continue the development of certain product candidates within the anticipated time periods (including initiation of planned clinical trials), if at all, and to continue to fund operations at the current cash expenditure levels. We do anticipate that our current cash of approximately $15.5 million as of early November 2025

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will allow us to fund our operations into the first quarter of 2027, including overhead costs, close out of the VIRAGE Phase 2b clinical trial; exploratory VCN-01 manufacturing scale-up activities, regulatory interactions regarding proposed VCN-01 clinical trials in PDAC and retinoblastoma, and preclinical studies supporting VCN-01 and VCN-12, the first candidate from our VCN-X discovery program. The cash is also sufficient to fund our committed obligations under the terms of the VCN Purchase Agreement related to the Acquisition. Our ability to continue as a going concern is dependent upon our ability to obtain additional equity or debt financing, attain further operating efficiencies, reduce expenditures, and, ultimately, to generate revenue. Our notes to the consolidated financial statements contain an explanatory paragraph referring to our recurring and continuing losses from operations and expressing substantial doubt in our ability to continue as a going concern without additional capital becoming available. We cannot provide any assurance that we will be able to obtain the required funding to achieve our current business plan, obtain the required regulatory approvals for our product candidates or complete additional corporate partnering or acquisition transactions in order to commercialize such product candidates once regulatory approval is received. If we fail to obtain additional funding for our clinical trials, whether through the sale of securities or a partner or collaborator, and otherwise when needed, we will not be able to execute our business plan as planned and will be forced to cease certain development activities (including initiation of planned clinical trials) until funding is received and our business will suffer, which would have a material adverse effect on our financial position, results of operations and cash flows.

Our ability to continue as a going concern is dependent upon our ability to raise additional capital. Our cash and cash equivalents will not be sufficient to initiate or complete future registrational studies for VCN-01, any potential future trials of SYN-004 including Phase 3 clinical programs of SYN-004 (ribaxamase) for prevention of CDI or the Phase 1b/2a clinical study of SYN-004 (ribaxamase) in allogeneic HCT recipients, or later-stage clinical trials of SYN-020. Therefore, we do not intend to commence future new studies of VCN-01, SYN-004 (ribaxamase) or SYN-020 until we are confident that we have funding necessary to complete such trials. We are actively pursuing additional equity or debt financing, in the form of either a private placement or a public offering and have been in ongoing discussions with strategic institutional investors and investment banks with respect to such possible offerings. However, we do not currently have commitments from any third parties to provide us with capital. Potential sources of financing that we are pursuing include strategic relationships, licensing arrangements, public or private sales of our equity (including through the ATM Sales Agreement) or debt and other sources. Such additional financing opportunities might not be available to us when and if needed, on acceptable terms or at all. We cannot assure that we will meet the requirements for use of the ATM Sales Agreement especially in light of the fact that we are currently limited by rules of the Securities and Exchange Commission (the “SEC”) as to the number of shares of Common Stock that we can sell pursuant to the ATM Sales Agreement due to the market value of our Common Stock held by non-affiliates. Even if we meet the requirements for use of the ATM Sales Agreement, there can be no assurance that we will be able to raise funds through the sale of shares of Common Stock through the ATM Sales Agreement. Additionally, we may seek to access the public or private equity markets when conditions are favorable due to our long-term capital requirements. If we are unable to obtain additional capital (which is not assured at this time), our long-term business plan may not be accomplished and we may be forced to cease certain development activities. More specifically, the completion of future Phase 3 and/or registrational clinical studies will require significant financing or a significant partnership. If we raise funds by selling additional shares of Common Stock or other securities convertible into Common Stock, the ownership interest of our existing stockholders will be diluted. If we are not able to obtain funding for future clinical trials when needed, we will be unable to carry out our business plan and we will be forced to delay the initiation of future clinical trials until such time as we obtain adequate financing and our operating results and prospects will be adversely affected.

Cash Flows

The following table summarizes our cash flows for the periods presented:

​

​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | Nine Months Ended September 30,
​ | ​ | 2025 | ​ | 2024
Cash used in operating activities | ​ | $ | (13,787) | ​ | $ | (12,246)
Cash used in investing activities | ​ |  | (35) | ​ |  | (1)
Cash provided by financing activities | ​ |  | 9,735 | ​ |  | 5,489
Effects of exchange rate changes on cash and cash equivalents | ​ | ​ | (44) | ​ | ​ | (9)
Net (decrease) in cash | ​ |  | (4,131) | ​ |  | (6,767)
Cash and cash equivalents, beginning of period | ​ |  | 11,705 | ​ |  | 23,279
Cash and cash equivalents, end of period | ​ | $ | 7,574 | ​ | $ | 16,512

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Cash Used in Operating Activities

Net cash used in operating activities was $13.8 million and $12.2 million during the nine months ended September 30, 2025 and 2024, respectively, which was primarily due to the use of funds in our operations related to the development of VCN-01 our product candidate.

Cash Used in Investing Activities

Cash used in investing activities during the nine months ended September 30, 2025 and 2024 was $35,000 and $1,000, respectively, for equipment purchases.

Cash Provided By Financing Activities

Cash provided by financing activities during the nine months ended September 30, 2025 included $1.8 million received for the research and development tax credit, $1.5 million in loan proceeds from the THERICEL project loan, $6.7 million in net proceeds from the sale of Common Stock and at the market offering proceeds of $279,000 from sales of 706,810 shares of our Common Stock pursuant to the ATM Sales Agreement offset by payments of loans in the amount of $69,000 and payment of contingent consideration of $500,000. Cash provided by financing activities during the nine months ended September 30, 2024 included at the market offering proceeds of $3.6 million from sales of 569,000 shares of our Common Stock offset by payments related to loans extended by certain Spanish institutions of $67,000 and net proceeds of $2.0 million from the sale of our securities in our public offering of 918,600 shares of Common Stock in combination with accompanying warrants to purchase an aggregate of 1,428,600 shares.

Off-Balance Sheet Arrangements

During the three months ended September 30, 2025, we did not have, and we do not currently have, any off-balance sheet arrangements, as defined under SEC rules.

Contractual Obligations

Leases

At the inception of a contract we determine if the arrangement is, or contains, a lease. Right of use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term.

We have made certain accounting policy elections whereby we (i) do not recognize ROU assets or lease liabilities for short-term leases (those with original terms of 12-months or less) and (ii) combine lease and non-lease elements of our operating leases. As of September 30, 2025, we did not have any material finance leases.

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ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK.

We are a smaller reporting company as defined by Rule 12b-2 of the Exchange Act and are not required to provide the information required under this item.

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ITEM 4. CONTROLS AND PROCEDURES.

(a) Evaluation of Disclosure Controls and Procedures

Our management, with the participation of our Chief Executive Officer, who also serves as our Chief Financial Officer, evaluated the effectiveness of our disclosure controls and procedures as of September 30, 2025. The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act, means controls and other procedures of a company that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the rules and forms of the SEC. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is accumulated and communicated to the Company’s management, including its principal executive and principal financial officers, or persons performing similar functions, as appropriate to allow timely decisions regarding required disclosure. We have adopted and maintain disclosure controls and procedures (as defined Rules 13a-15(e) and 15d-15(e) under the Exchange Act) that are designed to provide reasonable assurance that information required to be disclosed in the reports filed under the Exchange Act, such as this Quarterly Report on Form 10-Q, is collected, recorded, processed, summarized and reported within the time periods specified in the rules of the SEC. The Company’s disclosure controls and procedures are also designed to ensure that such information is accumulated and communicated to management to allow timely decisions regarding required disclosure. Management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures. Our Chief Executive Officer, who also serves as our Chief Financial Officer, concluded that, as of the end of the period covered by this report, our disclosure controls and procedures were effective.

(b) Changes in Internal Control over Financial Reporting

There have not been any changes in our internal controls over financial reporting during the three months ended September 30, 2025 that materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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PART II–OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS.

From time to time we may become involved in legal proceedings or be subject to claims arising in the ordinary course of our business. We are not presently a party to any legal proceedings that, if determined adversely to us, would individually or taken together have a material adverse effect on our business, operating results, financial condition or cash flows. Regardless of the outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors.

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ITEM 1A. RISK FACTORS.

The following information updates, and should be read in conjunction with, the information disclosed in Part I, Item 1A, “Risk Factors,” contained in our 2024 Form 10-K. Except as disclosed below, there have been no material changes from the risk factors disclosed in our 2024 Form 10-K.

Our auditor’s report on our consolidated financial statements contains an explanatory paragraph regarding our ability to continue as a going concern.

Our consolidated unaudited financial statements as of September 30, 2025 have been prepared under the assumption that we will continue as a going concern for the next twelve months. Our management concluded that our recurring losses from operations and the fact that as of September 30, 2025 we have an accumulated deficit of approximately $356.7 and working capital of $(1.1 million) raise substantial doubt about our ability to continue as a going concern for the next twelve months after issuance of our financial statements. In addition, in connection with the filing of our 2024 Form 10-K our independent registered public accounting firm issued a report that included an explanatory paragraph referring to our recurring losses from operations (anticipated continued losses in the future) and net capital deficiency that, as of the date of such report, raised substantial doubt in our ability to continue as a going concern without additional capital becoming available. As of September 30, 2025, we had cash and cash equivalents of approximately $7.5 million and as of early November 2025, we had cash and cash equivalents of $15.5 million. At December 31, 2024, we had an accumulated deficit of $335 million and working capital of $8.7 million. As of December 31, 2024, we had cash and cash equivalents of approximately $11.6 million consisting of cash and investments in highly liquid U.S. money market funds. Our ability to continue as a going concern is dependent upon our ability to obtain additional equity or debt financing, attain further operating efficiencies, reduce expenditures, and, ultimately, to generate revenue. Our consolidated unaudited financial statements as of September 30, 2025 do not include any adjustments that might result from the outcome of this uncertainty. Based upon the Company’s current business plans, we expect that our current cash will be able to fund operations into the first quarter of 2027.

We will need to raise additional capital to operate our business and our failure to obtain funding when needed may force us to delay, reduce or eliminate certain of our development programs or commercialization efforts.

During the nine months ended September 30, 2025, our operating activities used net cash of approximately $13.8 million and our cash and cash equivalents were approximately $7.5 million as of September 30, 2025. With the exception of the three months ended June 30, 2010 and the three months ended December 31, 2017, we have experienced significant losses since inception and have a significant accumulated deficit. As of September 30, 2025, our accumulated deficit totaled approximately $356.7 million on a consolidated basis. Pursuant to the VCN Purchase Agreement, we have agreed to use reasonable efforts to commercialize VCN-01 and we agreed as a post- closing covenant to commit to fund VCN’s research and development programs, including but not limited to VCN-01 PDAC phase 2 clinical trial, VCN-01 retinoblastoma trial and necessary general and administrative expenses within a budgetary plan of approximately $27. 8 million over three years. If we are required to make the $5 million milestone payment to Grifols, it will significantly deplete our cash and cash equivalents, which could materially and adversely affect our liquidity and limit our ability to fund operations or meet other financial obligations. We expect to incur additional operating losses in the future and therefore expect our cumulative losses to increase. With the exception of the quarter ended June 30, 2010, and limited laboratory revenues from Adeona Clinical Laboratory, which we sold in March 2012, we have generated very minimal revenues. We do not expect to derive revenue from any source in the near future until we or our potential partners successfully commercialize our products. We expect our expenses to increase in connection with our anticipated activities, particularly as we continue research and development, initiate and conduct clinical trials, and seek marketing approval for our product candidates. Until such time as we receive approval from the FDA and other regulatory authorities for our product candidates, we will not be permitted to sell our products and therefore will not have product revenues from the sale of products. For the foreseeable future we will have to fund all of our operations and capital expenditures from equity and debt offerings, cash on hand, licensing and collaboration fees and grants, if any.

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We will need to raise additional capital to fund our operations and meet our current timelines and we cannot be certain that funding will be available on acceptable terms on a timely basis, or at all. The amount of government funding available for grants is dependent upon governmental budgets over which we have no control and which change with new administrations. Based on our current plans, we expect that our current cash will be able to fund operations into the first quarter of 2027 but will not be sufficient to fund our operations for the next twelve months and will only be sufficient to cover overhead costs, close out of the VIRAGE Phase 2b clinical trial; exploratory VCN-01 manufacturing scale-up activities, regulatory interactions regarding proposed VCN-01 clinical trials in PDAC and retinoblastoma, preclinical studies supporting VCN-01 and VCN-12, the first candidate from our VCN-X discovery program. The cash is also sufficient to fund our committed obligations under the terms of the VCN Purchase Agreement related to the Acquisition, but may not be sufficient for additional trials of VCN-01, SYN-020 or SYN-004, or to complete the last cohort of the Phase 1a/2a clinical trial of SYN-004, which are expected to require significant cash expenditures. In addition, based on the significant anticipated cost of a Phase 3 clinical program in a broad indication for SYN-004, we expect it will not be feasible for us to initiate and complete this trial at this time without a partner given the capital constraints tied to our current market cap and share price. We intend to focus our capital on our VCN-01 clinical trials and do not intend to provide further funding for our development of SYN-004 internally but intend to out-license or partner further development of SYN-004. Further development of VCN’s product candidates will require additional funding. To the extent that we raise additional funds by issuing equity securities, our stockholders may experience significant dilution. Any debt financing, if available, may involve restrictive covenants that may impact our ability to conduct our business and also have a dilutive effect on our stockholders. A failure otherwise to secure additional funds when needed in the future whether through an equity or debt financing or a sufficient amount of capital without a strategic partnership could result in us being unable to complete planned preclinical and clinical trials or obtain approval of our product candidates from the FDA and other regulatory authorities. In addition, we could be forced to delay, discontinue or curtail product development, forgo sales and marketing efforts, and forgo licensing in attractive business opportunities, cease operations, liquidate our assets or reorganize the Company, or a combination of the foregoing. Our ability to raise capital through the sale of securities may be limited by the rules of the SEC and NYSE American that place limits on the number and dollar amount of securities that may be sold. There can be no assurances that we will be able to raise the funds needed, especially in light of the fact that our ability to sell securities registered on our registration statement on Form S-3 will be limited until such time the market value of our voting securities held by non-affiliates is $75 million or more. We also may be required to seek collaborators for our product candidates at an earlier stage than otherwise would be desirable and on terms that are less favorable than might otherwise be available.

Changes to trade policy, including tariff and customs regulations, or failure to comply with such regulations may have an adverse effect on our reputation, business, financial condition and results of operations.

Changes in U.S. or international social, political, regulatory and economic conditions or in laws and policies governing trade, manufacturing, development and investment in the countries where we currently conduct our business could adversely affect our business, reputation, financial condition and results of operations. Changes or proposed changes in U.S. or other countries’ trade policies may result in restrictions and economic disincentives on international trade. The U.S. government has recently imposed, or is currently considering imposing, tariffs on certain trade partners, including China, where we have engaged a vendor. Tariffs, economic sanctions and other changes in U.S. trade policy have in the past and could in the future trigger retaliatory actions by affected countries, and certain foreign governments have instituted or are considering imposing retaliatory measures on certain U.S. goods. Further, any emerging protectionist or nationalist trends (whether regulatory- or consumer-driven) either in the United States or in other countries could affect the trade environment. Our business, like many other corporations, would be impacted by changes to the trade policies of the United States and foreign countries (including governmental action related to tariffs, international trade agreements, or economic sanctions). Such changes have the potential to adversely impact the U.S. economy or certain sectors thereof, the global economy, and our industry, and as a result, could have a material adverse effect on our business, financial condition and results of operations.

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The shutdown of the U.S. federal government may adversely affect our business.

A prolonged or recurring shutdown of the U.S. federal government may adversely affect our business operations and regulatory compliance. During such shutdowns, while the SEC’s EDGAR system remains operational, the unavailability of SEC staff to review filings, issue comments, or declare registration statements effective may delay our ability to complete public offerings, respond to comment letters, or obtain timely regulatory approvals. These delays could impact our access to capital markets, hinder strategic transactions, and create uncertainty around our disclosure obligations. Additionally, the lack of interpretive guidance or exemptive relief during a shutdown may increase legal and compliance risks. We continue to monitor developments and adjust our regulatory strategies accordingly, but there can be no assurance that future shutdowns will not materially affect our operations or financial condition.

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Inadequate funding for the FDA, the SEC and other government agencies, including from government shutdowns, or other disruptions to these agencies’ staffing and operations, could hinder their ability to hire and retain key leadership and other personnel, prevent new products and services from being developed or commercialized in a timely manner or otherwise prevent those agencies from performing normal business functions on which the operation of our business may rely, which could negatively impact our business.

Currently, federal agencies in the United States are operating under a federal government shutdown due to the expiration of the continuing resolution that expired on September 30, 2025. The duration of the current government shutdown is unknown. In addition, the current U.S. administration is focused on reducing costs of the federal government generally, including significantly reducing the number of government employees. Without appropriation of additional funding to federal agencies, our business operations related to our product development activities for the U.S. market could be impacted. The ability of the FDA to review and approve new products can be affected by a variety of factors, including government budget and funding levels, the ability to hire and retain key personnel and accept the payment of user fees, and statutory, regulatory and policy changes. Average review times at the agency have fluctuated in recent years as a result. In addition, government funding of the SEC and other government agencies on which our operations may rely is subject to the political process, which is inherently fluid and unpredictable.

Our business depends on timely interactions with the FDA, including the review of regulatory submissions, scheduling of formal meetings, and oversight of clinical trials. Disruptions at the FDA and other federal agencies, including substantial leadership departures, personnel cuts, policy changes and those related to the federal government shutdown, may result in reduced staffing or suspension of non-essential FDA operations, which could delay or cancel meetings with the FDA, including our upcoming meetings with the FDA for planned clinical trials in patients with mPDAC and retinoblastoma, hinder regulatory guidance, cause delays in the implementation or enforcement of regulatory requirements in a timely fashion or at all, and postpone the review of IND applications, New Drug Applications (NDAs), and Biologics License Applications (BLAs). These disruptions may also affect the initiation, conduct, and monitoring of clinical trials, particularly those requiring FDA authorization or ongoing regulatory engagement. Interruptions in FDA activities could materially delay our development timelines, increase operational costs, and adversely impact our ability to complete our ongoing and planned clinical trials and to advance product candidates toward approval and commercialization. Any such delays or uncertainties may have a significant negative effect on our business, financial condition, and results of operations.

If the current U.S. federal government shutdown is prolonged or if the FDA, National Institutes of Health (“NIH”), SEC or the United States Patent and Trademark Office (“USPTO”) experiences significant decreases in funding or personnel, it could significantly impact the ability of the FDA to issue licenses needed for conduct of our clinical trials, the NIH to conduct research or provide grants, and the abilities of the FDA and the USPTO to timely review and process our regulatory submissions, which could have a material adverse effect on our business. Further, future government shutdowns could impact our ability to access the public markets and obtain necessary capital in order to properly capitalize and continue our operations.

Certain of our clinical trials are dependent on federal grant funding. A lapse in appropriations resulting in a government shutdown could materially disrupt the timing and availability of these funds. During such shutdowns, federal agencies may suspend the processing of new grant applications, delay reimbursements, or pause disbursements for existing awards. These interruptions could adversely affect our ability to commence enrollment for the third cohort of our Phase 1b/2a randomized, double-blinded, placebo-controlled clinical trial of SYN-004 (ribaxamase) in allogeneic hematopoietic cell transplant (“HCT”) recipients for the prevention of acute graft-versus-host-disease because we cannot fund the SYN-004 development program unless we receive grant funding. If federal funding continues to be delayed, reduced or canceled, we may need to seek alternative sources of financing, scale back research efforts, or defer planned initiatives, any of which could have a material adverse effect on our financial condition and results of operations.

There is substantial uncertainty as to whether and how the new administration will seek to modify or revise the requirements and policies of the FDA and other regulatory agencies with jurisdiction over our product candidates and any products for which we obtain approval. Additionally, the new administration could also issue or promulgate executive orders, regulations, policies or guidance that adversely affect us or create a more challenging or costly environment to pursue the development of new therapeutic candidates.

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ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS.

(a) | Unregistered Sales of Equity Securities

We did not sell any equity securities during the quarter ended September 30, 2025 in transactions that were not registered under the Securities Act other than as previously disclosed in our filings with the SEC.

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(b) | Use of Proceeds

Not applicable.

(c) | Issuer Purchases of Equity Securities

Not applicable.

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ITEM 3. DEFAULTS UPON SENIOR SECURITIES.

Not applicable.

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ITEM 4. MINE SAFETY DISCLOSURES.

Not applicable.

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ITEM 5. OTHER INFORMATION.

During the three months ended September 30, 2025, no director or officer of the Company adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K.

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ITEM 6. EXHIBITS.

The exhibits filed or furnished as part of this Quarterly Report on Form 10-Q are set forth on the Exhibit Index, which Exhibit Index is incorporated herein by reference.

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EXHIBIT INDEX

​ | ​ | ​
Exhibit Number |  | Exhibit Title
3.1 | ​ | Certificate of Incorporation, as amended (Incorporated by reference to (i) Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed October 16, 2008, File No. 001-12584, (ii) Exhibit 3.1 of the Registrant’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2001 filed August 14, 2001, File No. 001-12584; and (iii) Exhibits 3.1, 4.1 and 4.2 of the Registrant’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 1998 filed August 14, 1998, File No. 001-12584.)
​ | ​ | ​
3.2 | ​ | Articles of Merger (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed October 19, 2009, File No. 001-12584.)
​ | ​ | ​
3.3 | ​ | Certificate of Merger filed with the Secretary of State of Delaware (Incorporated by reference to Exhibit 3.2 of the Registrant’s Current Report on Form 8-K filed October 19, 2009, File No. 001-12584.)
​ | ​ | ​
3.4 | ​ | Articles of Incorporation filed with the Nevada Secretary of State (Incorporated by reference to Exhibit 3.3 of the Registrant’s Current Report on Form 8-K filed October 19, 2009, File No. 001-12584.)
​ | ​ | ​
3.5 | ​ | Certificate of Amendment to Articles of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed February 16, 2012, File No. 001-12584.)
​ | ​ | ​
3.6 | ​ | Certificate of Amendment to Articles of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed May 18, 2015, File No. 001-12584.)
​ | ​ | ​
3.7 | ​ | Certificate of Amendment to Articles of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed September 8, 2017, File No. 001-12584.)
​ | ​ | ​
3.8 | ​ | Certificate of Designations for Series A Preferred Stock to Certificate of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed September 12, 2017, File No. 001-12584.)
​ | ​ | ​
3.9 | ​ | Certificate of Change Pursuant to NRS 78. 209 (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed August 13, 2018, File No. 001-12584.)
​ | ​ | ​
3.10 | ​ | Certificate of Amendment to Articles of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed September 26, 2018, File No. 001-12584.)
​ | ​ | ​
3.11 | ​ | Certificate of Designations for Series B Preferred Stock to Certificate of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed October 15, 2018, File No. 001-12584.)
​ | ​ | ​
3.12 | ​ | Certificate of Amendment to Certificate of Designation for Series B Preferred Stock to Certificate of Incorporation (Incorporated by reference to Exhibit 3.2 of the Registrant’s Current Report on Form 8-K filed October 15, 2018, File No. 001-12584.)
​ | ​ | ​
3.13 | ​ | Certificate of Amendment to the Certificate of Designation for the Series A Convertible Preferred Stock (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K/A filed on February 1, 2021 File No. 001-12584.)
​ | ​ | ​
3.14 | ​ | Certificate of Designation for Series C Preferred Stock to Certificate of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed July 29, 2022, File No. 001-12584.)
​ | ​ | ​

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3.15 | ​ | Certificate of Designation for Series D Preferred Stock to Certificate of Incorporation (Incorporated by reference to Exhibit 3.2 of the Registrant’s Current Report on Form 8-K filed July 29,2022, File No. 001-12584.)
​ | ​ | ​
3.16 | ​ | Second Amended and Restated Bylaws (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed August 11, 2023, File No. 001-12584.)
​ | ​ | ​
3.17 | ​ | Certificate of Change filed with the Secretary of State of the State of Nevada on August 22, 2024 (effective as of August 26, 2024) (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed August 26, 2024, File No. 001-12584.)
​ | ​ | ​
3.18 | ​ | Certificate of Change to the Articles of Incorporation (Incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K filed November 1, 2024, File No. 001-12584.)
​ | ​ | ​
4.1 | ​ | Form of New Warrant (Incorporated by reference to Exhibit 4.1 of the Registrant’s Current Report on Form 8-K filed October 17, 2025, File No. 001-12584.)
​ | ​ | ​
10.1 | ​ | Amendment No. 3 to the Theriva Biologics, Inc. 2020 Stock Incentive Plan (Incorporated by reference to Exhibit 10.1 of the Registrant’s Current Report on Form 8-K filed September 4, 2025, File No. 001-12584.)
​ | ​ | ​
10.2 | ​ | Form of Warrant Inducement Agreement (Incorporated by reference to Exhibit 10.1 of the Registrant’s Current Report on Form 8-K filed October 17, 2025, File No. 001-12584.)
​ | ​ | ​
31.1 | ​ | Certification of Principal Executive Officer and Principal Financial Officer pursuant to Rule 13a-14(a)/15d-14(a)*
​ | ​ | ​
32.1 | ​ | Certification of Principal Executive Officer and Principal Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002*
​ | ​ | ​
101.INS | ​ | Inline XBRL Instance Document*
​ | ​ | ​
101.SCH | ​ | Inline XBRL Taxonomy Extension Schema*
​ | ​ | ​
101.CAL | ​ | Inline XBRL Taxonomy Extension Calculation Linkbase*
​ | ​ | ​
101.DEF | ​ | Inline XBRL Taxonomy Extension Definition Linkbase*
​ | ​ | ​
101.LAB | ​ | Inline XBRL Taxonomy Extension Label Linkbase*
​ | ​ | ​
101.PRE | ​ | Inline XBRL Taxonomy Extension Presentation Linkbase*
​ | ​ | ​
104 | ​ | Cover Page Interactive Data File (formatted in XBRL in Exhibit 101)

*Filed or furnished herewith.

# | Management contract or compensatory plan or arrangement required to be identified pursuant to Item 15(a)(3) of this report

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

​ | THERIVA BIOLOGICS, INC.
​ | ​ | ​
​ | By: | /s/ Steven A. Shallcross
​ | ​ | Steven A. Shallcross
​ | ​ | Chief Executive Officer, Chief Financial Officer
​ | ​ | (Principal Executive Officer, Principal Financial Officer and Principal Accounting Officer)
​ | ​ | ​
​ | ​ | Date: November 12, 2025

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