v3.25.1

Income Taxes (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2024
Income Tax Disclosure [Abstract] |
Components of Net Loss Before Income Taxes | The components of net loss before income taxes consisted of the following (in thousands):
| Year Ended December 31, |
| 2024 |  |  | 2023 |
United States | $ | (30,905 | ) |  | $ | (31,476 | )
International |  | (4,573 | ) |  |  | - |
Net loss before taxes | $ | (35,478 | ) |  | $ | (31,476 | )
Summary of Reconciliations of Income Tax | The benefit for income taxes differs from the amount of income tax determined by applying the applicable U.S. statutory federal income tax rate to pretax income as a result of the following differences (in thousands):
|  | Year Ended December 31, |
|  | 2024 |  |  | 2023 |
Income tax expense (benefit) at federal statutory rate |  | $ | (7,450 | ) |  | 21.0 | % |  | $ | (6,610 | ) |  | 21.0 | %
Increase/(decrease) in tax resulting from: |  |  |  |  |  |  |  |  |  |
State income taxes |  |  | — |  |  | 0.0 | % |  |  | — |  |  | 0.0 | %
Change in valuation allowance |  |  | 6,441 |  |  | -18.2 | % |  |  | 6,541 |  |  | -20.8 | %
Nondeductible R&D Expenses |  |  | 921 |  |  | -2.6 | % |  |  | — |  |  | 0.0 | %
Stock-based compensation expense |  |  | 90 |  |  | -0.2 | % |  |  | 60 |  |  | -0.2 | %
Other |  |  | (2 | ) |  | 0.0 | % |  |  | 9 |  |  | 0.0 | %
Total |  | $ | — |  |  | 0.0 | % |  | $ | — |  |  | 0.0 | %
Components of Net Deferred Tax Assets and Liabilities | The primary components of temporary differences which give rise to the Company’s net deferred tax assets and liabilities as of December 31, 2024 and 2023 are as follows (in thousands):
| Year Ended December 31, |
| 2024 |  |  | 2023 |
Deferred tax assets: |  |  |  |  |
Accrual to cash adjustment | $ | 499 |  |  | $ | 433 |
Start-up costs |  | 7,190 |  |  |  | 4,508 |
Patent costs |  | 40 |  |  |  | 40 |
Stock-based compensation expense |  | 1,432 |  |  |  | 1,627 |
Net operating loss |  | 7,638 |  |  |  | 6,515 |
Capitalized R&D |  | 6,813 |  |  |  | 4,940 |
Other deferred taxes |  | 21 |  |  |  | 11 |
R&D credits |  | 868 |  |  |  | 528 |
Total noncurrent deferred tax assets |  | 24,501 |  |  |  | 18,602 |
Valuation Allowance |  | (24,501 | ) |  |  | (18,602 | )
Net deferred tax assets after valuation allowance | $ | — |  |  | $ | — |
Summary of Net Operating Losses and Tax Credit Carryforwards | Net operating losses and tax credit carryforwards as of December 31, 2024 are as follows (in thousands):
|  | Amount |  |  | Expiration Years
Net operating losses, federal (Post December 31, 2017) |  | $ | 32,229 |  |  | Do Not Expire
Net operating losses, federal (Pre January 1, 2018) |  | $ | 11 |  |  | 2037
Net operating losses, state |  | $ | 11,602 |  |  | 2037
Net operating losses, foreign |  | $ | 192 |  |  | Indefinite
Tax credits, federal |  | $ | 752 |  |  | 2041
Tax credits, state |  | $ | 617 |  |  | Indefinite
Summary of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits | A reconciliation of the beginning and ending amount of unrecognized tax benefits for 2024 and 2023 is as following (in thousands):
| Year Ended December 31, |
| 2024 |  |  | 2023 |
Beginning Balance | $ | 251 |  |  | $ | 157 |
Additions based on tax positions related to the current year | $ | 160 |  |  | $ | 94 |
Ending Balance | $ | 411 |  |  | $ | 251 |

X
- Definition Summary Of Operating Loss And Tax Credit Carryforwards Table Text Block. + References No definition available. + Details
Name: | fbrx_SummaryOfOperatingLossAndTaxCreditCarryforwardsTableTextBlock
Namespace Prefix: | fbrx_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 231 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-231 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12A Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-12 + Details
Name: | us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of income before income tax between domestic and foreign jurisdictions. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(1)(Note 1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 + Details
Name: | us-gaap_ScheduleOfIncomeBeforeIncomeTaxDomesticAndForeignTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the change in unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 217 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482663/740-10-55-217 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 15A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-15A + Details
Name: | us-gaap_ScheduleOfUnrecognizedTaxBenefitsRollForwardTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration