Organization	12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Description of the Business Septerna, Inc. (“Septerna” or the “Company”) is a biotechnology company pioneering a new era of G protein-coupled receptor (“GPCR”) oral small molecule drug discovery powered by its proprietary Native Complex PlatformTM. The Company’s industrial-scale platform aims to unlock the full potential of GPCR therapies and has led to the discovery and development of its deep pipeline of product candidates focused on treating patients in three therapeutic areas: endocrinology, immunology and inflammation, and metabolic diseases. The Company’s proprietary Native Complex Platform™ replicates the natural structure, function, and dynamics of GPCRs outside of cells at an industrial scale for, as the Company believes, the first time. The Company’s foundational technologies enable it to isolate, purify, and reconstitute full-length, properly folded GPCR proteins within ternary complexes with ligands and transducer proteins in a lipid bilayer that mimics the cell membrane. The Company then applies state-of-the-art discovery tools and technologies to these defined and tunable protein complexes to structurally design, screen for, and optimize potential product candidates. Leveraging its platform, the Company has transformed GPCR oral small molecule drug discovery to an industrialized and iterative structure-based drug design approach to expand the landscape of druggable GPCR targets with novel oral small molecule medicines for patients. The Company’s Native Complex Platform™ is designed to enable it to target certain GPCRs for the first time, uncover novel binding pockets for validated receptors, and pursue a wide spectrum of pharmacologies, including agonists, antagonists, and allosteric modulators, to affect GPCR signaling in different ways to achieve desired therapeutic effects. The Company was incorporated in Delaware in December 2019, under the name GPCR NewCo, Inc. In June 2021, the Company changed its name to Septerna, Inc. The Company is headquartered in South San Francisco, California. Reverse Stock Split On October 18, 2024, the Company effected a 1-for-8.6103 reverse stock split of its issued and outstanding shares of common stock. Upon the effectiveness of the reverse stock split, (i) all shares of outstanding common stock were adjusted; (ii) the conversion ratio of the convertible preferred stock was adjusted; (iii) the number of shares of common stock for which each outstanding option to purchase common stock is exercisable were adjusted; and (iv) the exercise price of each outstanding option to purchase common stock was adjusted. All of the outstanding common stock (including shares of common stock subject to the Company’s options and as converted for the outstanding convertible preferred stock), share prices, exercise prices and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock and preferred stock were not adjusted as a result of the reverse stock split. The number of authorized shares did not change. Initial Public Offering In October 2024, the Company completed its initial public offering (“IPO”), pursuant to which it issued and sold an aggregate of 18.4 million shares of its common stock at the IPO price of $18.00 per share, including 2.4 million shares that were issued to the underwriters pursuant to the full exercise of their option to purchase additional shares, resulting in net proceeds of $302.8 million, after deducting underwriting discounts and commissions of $23.2 million, and other offering expenses payable by the Company of $5.2 million. Immediately prior to the closing of the IPO, the Company’s then outstanding convertible preferred stock automatically converted into 22,839,774 shares of common stock. Following the closing of the IPO, no shares of convertible preferred stock were authorized or outstanding. In connection with the completion of the IPO, on October 28, 2024, the Company’s certificate of incorporation was amended and restated to (i) authorize 500.0 million shares of common stock, par value $0.001 per share, which eliminates all references to the previously existing series of convertible preferred stock; and (ii) authorize 10.0 million shares of undesignated preferred stock, par value $0.001 per share, that may be issued from time to time by the Company’s board of directors in one or more series. Liquidity and Capital Resources The accompanying financial statements have been prepared assuming the Company will continue as a going concern, which assumes that the Company will realize its assets and satisfies its liabilities in the normal course of business. The Company is subject to risks inherent in operating an early-stage biotechnology business. These risks include, but are not limited to, dependence on the development of marketable products, the ability to attract, retain, and motivate qualified personnel, rapid technological changes and the rapidly evolving nature of the biotechnology industry. The Company has incurred significant losses and negative cash flows from operations since its inception and expects to incur losses as a result of its continued research and development activities. To date, none of the Company’s product candidates have been approved by the U.S. Food and Drug Administration (the “FDA”) for commercial sale and, therefore, the Company has not generated any revenue from product sales. The Company historically financed its operations primarily through the issuances of convertible promissory notes and convertible preferred stock, and most recently, through sale of its common stock in an IPO. For the year ended December 31, 2024, the Company incurred net loss of $71.8 million. The Company had an accumulated deficit of $118.4 million as of December 31, 2024. The Company believes its cash, cash equivalents, marketable securities, and marketable securities, non-current of $420.8 million as of December 31, 2024 will be sufficient to fund its operations for, at least, 12 months from the date of issuance of the financial statements. The Company expects to continue to generate operating losses for the foreseeable future. The Company will need additional financing to support its continuing operations and pursue its growth strategy. It expects to finance its operations through equity offerings, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may not be able to obtain funding on acceptable terms, or at all. Any failure to raise capital as and when needed would compromise the Company’s ability to execute on its business plan and may cause the Company to significantly delay, scale back or discontinue the research and development of some of its programs or curtail any efforts to expand its product pipelines and will materially harm its business, financial position and results of operations.

Organization

12 Months Ended

Dec. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

1. Organization

Description of the Business

Septerna, Inc. (“Septerna” or the “Company”) is a biotechnology company pioneering a new era of G protein-coupled receptor (“GPCR”) oral small molecule drug discovery powered by its proprietary Native Complex PlatformTM. The Company’s industrial-scale platform aims to unlock the full potential of GPCR therapies and has led to the discovery and development of its deep pipeline of product candidates focused on treating patients in three therapeutic areas: endocrinology, immunology and inflammation, and metabolic diseases.

The Company’s proprietary Native Complex Platform™ replicates the natural structure, function, and dynamics of GPCRs outside of cells at an industrial scale for, as the Company believes, the first time. The Company’s foundational technologies enable it to isolate, purify, and reconstitute full-length, properly folded GPCR proteins within ternary complexes with ligands and transducer proteins in a lipid bilayer that mimics the cell membrane. The Company then applies state-of-the-art discovery tools and technologies to these defined and tunable protein complexes to structurally design, screen for, and optimize potential product candidates. Leveraging its platform, the Company has transformed GPCR oral small molecule drug discovery to an industrialized and iterative structure-based drug design approach to expand the landscape of druggable GPCR targets with novel oral small molecule medicines for patients. The Company’s Native Complex Platform™ is designed to enable it to target certain GPCRs for the first time, uncover novel binding pockets for validated receptors, and pursue a wide spectrum of pharmacologies, including agonists, antagonists, and allosteric modulators, to affect GPCR signaling in different ways to achieve desired therapeutic effects.

The Company was incorporated in Delaware in December 2019, under the name GPCR NewCo, Inc. In June 2021, the Company changed its name to Septerna, Inc. The Company is headquartered in South San Francisco, California.

Reverse Stock Split

On October 18, 2024, the Company effected a 1-for-8.6103 reverse stock split of its issued and outstanding shares of common stock. Upon the effectiveness of the reverse stock split, (i) all shares of outstanding common stock were adjusted; (ii) the conversion ratio of the convertible preferred stock was adjusted; (iii) the number of shares of common stock for which each outstanding option to purchase common stock is exercisable were adjusted; and (iv) the exercise price of each outstanding option to purchase common stock was adjusted. All of the outstanding common stock (including shares of common stock subject to the Company’s options and as converted for the outstanding convertible preferred stock), share prices, exercise prices and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock and preferred stock were not adjusted as a result of the reverse stock split. The number of authorized shares did not change.

Initial Public Offering

In October 2024, the Company completed its initial public offering (“IPO”), pursuant to which it issued and sold an aggregate of 18.4 million shares of its common stock at the IPO price of $18.00 per share, including 2.4 million shares that were issued to the underwriters pursuant to the full exercise of their option to purchase additional shares, resulting in net proceeds of $302.8 million, after deducting underwriting discounts and commissions of $23.2 million, and other offering expenses payable by the Company of $5.2 million. Immediately prior to the closing of the IPO, the Company’s then outstanding convertible preferred stock automatically converted into 22,839,774 shares of common stock.

Following the closing of the IPO, no shares of convertible preferred stock were authorized or outstanding. In connection with the completion of the IPO, on October 28, 2024, the Company’s certificate of incorporation was amended and restated to (i) authorize 500.0 million shares of common stock, par value $0.001 per share, which eliminates all references to the previously existing series of convertible preferred stock; and (ii) authorize 10.0 million shares of undesignated preferred stock, par value $0.001 per share, that may be issued from time to time by the Company’s board of directors in one or more series.

Liquidity and Capital Resources

The accompanying financial statements have been prepared assuming the Company will continue as a going concern, which assumes that the Company will realize its assets and satisfies its liabilities in the normal course of business. The Company is subject to risks inherent in operating an early-stage biotechnology business. These risks include, but are not limited to, dependence on the development of marketable products, the ability to attract, retain, and motivate qualified personnel, rapid technological changes and the rapidly evolving nature of the biotechnology industry.

The Company has incurred significant losses and negative cash flows from operations since its inception and expects to incur losses as a result of its continued research and development activities. To date, none of the Company’s product candidates have been approved by the U.S. Food and Drug Administration (the “FDA”) for commercial sale and, therefore, the Company has not generated any revenue from product sales.

The Company historically financed its operations primarily through the issuances of convertible promissory notes and convertible preferred stock, and most recently, through sale of its common stock in an IPO.

For the year ended December 31, 2024, the Company incurred net loss of $71.8 million. The Company had an accumulated deficit of $118.4 million as of December 31, 2024. The Company believes its cash, cash equivalents, marketable securities, and marketable securities, non-current of $420.8 million as of December 31, 2024 will be sufficient to fund its operations for, at least, 12 months from the date of issuance of the financial statements.

The Company expects to continue to generate operating losses for the foreseeable future. The Company will need additional financing to support its continuing operations and pursue its growth strategy. It expects to finance its operations through equity offerings, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may not be able to obtain funding on acceptable terms, or at all. Any failure to raise capital as and when needed would compromise the Company’s ability to execute on its business plan and may cause the Company to significantly delay, scale back or discontinue the research and development of some of its programs or curtail any efforts to expand its product pipelines and will materially harm its business, financial position and results of operations.