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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 3, 2025

SEPTERNA, INC.

(Exact name of Registrant as Specified in Its Charter)

Delaware |  | 001-42382 |  | 84-3891440
(State or Other Jurisdiction of Incorporation) |  | (Commission File Number) |  | (IRS Employer Identification No.)
Septerna, Inc. |  |
250 East Grand Avenue |  |
South San Francisco, CA |  | 94080
(Address of Principal Executive Offices) |  | (Zip Code)

Registrant’s Telephone Number, Including Area Code: (650) 338-3533

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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, $0.001 par value per share |  | SEPN |  | The Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company☒

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.☐

Item 7.01. | Regulation FD Disclosure.

On September 3, 2025, Septerna, Inc. updated its corporate presentation for use in meetings with investors, analysts and others. A copy of the updated corporate presentation is furnished as Exhibit 99.1 to this Current Report on Form 8-K, which is incorporated herein by reference.

The information furnished under this Item 7.01, including Exhibit 99.1 attached hereto, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 9.01. | Financial Statements and Exhibits.

(d) Exhibits

99.1 |  | Corporate Presentation of Septerna, Inc., dated September 2025, furnished herewith.
104 |  | Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURE

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 hereunto duly authorized.

|  |  |  |  |  | Septerna, Inc.
Date: September 3, 2025 |  |  |  | By: |  | /s/ Jeffrey Finer, M.D., Ph.D.
|  |  |  |  |  | Jeffrey Finer, M.D., Ph.D. Chief Executive Officer