Septerna, Inc.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

(a) Unregistered Sales of Equity Securities

None.

(b) Use of Proceeds from our IPO

On October 24, 2024, our Registration Statement on Form S-1 (File No. 333-282469), as amended, relating to our IPO was declared effective by the Securities and Exchange Commission (the “SEC”) (the “Registration Statement”). Pursuant to the Registration Statement, we registered the offer and sale of 18,400,000 shares of our common stock. On October 28, 2024, we closed our IPO, pursuant to which we issued and sold 18.4 million shares of common stock at the public offering price of $18.00 per share, which included 2.4 million shares of our common stock issued and sold on October 30, 2024 to the underwriters pursuant to the full exercise of their option to purchase additional shares of our common stock, at the public offering price of $18.00 per share. Pursuant to the IPO, we received gross proceeds of $331.2 million, which resulted in net proceeds to us of $302.8 million, after deducting underwriting discounts and commissions and other offering costs payable by us of $28.4 million. J.P. Morgan Securities LLC, TD Securities (USA) LLC, Cantor Fitzgerald & Co. and Wells Fargo Securities, LLC acted as joint book-running managers for the IPO.

The net proceeds from our IPO have been invested according to our approved investment policy in a mix of money market funds and high-quality, fixed income securities. Our planned use of the net proceeds from the IPO as described in our final prospectus filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “Securities Act”) on October 25, 2024 has changed due to the discontinuation of the development of our prior lead product candidate, SEP-786. As a result, we currently expect to use our cash, cash equivalents and marketable securities, which include the net proceeds from the IPO, to advance a next-generation oral small molecule PTH1R agonist from our PTH1R program into clinical development, advance SEP-631 into clinical development, continue to advance the other programs in our pipeline, and the remainder to fund working capital and other general corporate purposes. Except for the reallocation of SEP-786 funds discussed above, there has been no material changes in the planned use of proceeds from our IPO as described in our final prospectus filed with the SEC pursuant to Rule 424(b)(4) under the Securities Act on October 25, 2024.

(c) Issuer Repurchases of Equity Securities

The following table provides stock repurchase activity during each of the months of the three months ended September 30, 2025:

(1) Represents shares of unvested common stock that were repurchased by us from former employees upon termination of employment in accordance with the terms of the employees’ stock option agreements. We purchased the shares from the former employees at the respective original exercise prices.