Sutro Biopharma Inc美股招股说明书(2026-04-01版)

We have entered into a Sales Agreement, or Sales Agreement, with TD Securities (USA) LLC, or TD Cowen. In accordance with the termsof the Sales Agreement, pursuant to this prospectus supplement, we may offer and sell shares of our common stock having an aggregateoffering price of up to $100.0million from time to time through TD Cowen acting as our agent or principal. Our common stock is traded on The Nasdaq Global Market under the symbol “STRO.” The last reported sales price of our common stockon The Nasdaq Global Market on March31, 2026 was $24.91 per share. Sales of our common stock, if any, under this prospectus supplement will be made in negotiated transactions, including block trades orblock sales, or by any method deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Actof 1933, as amended, or the Securities Act, including without limitation sales made through Nasdaq or any other existing trading market forthe common stock, or by any method permitted by law. TD Cowen is not required to sell any specific number or dollar amount ofsecurities, but will act as a sales agent using commercially reasonable efforts consistent with its normal trading and sales practices, onmutually agreed terms between TD Cowen and us. There is no arrangement for funds to be received in any escrow, trust or similararrangement. The compensation to TD Cowen for sales of common stock sold pursuant to the Sales Agreement will be up to 3.0% of the aggregategross proceeds of any shares of common stock sold under the Sales Agreement. In connection with the sale of the common stock on ourbehalf, TD Cowen will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of TD Cowen willbe deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to TD Cowenwith respect to certain liabilities, including liabilities under the Securities Act or the Securities Exchange Act of 1934, as amended, or theExchange Act. See “Plan of Distribution” beginning on page S-15 regarding the compensation to be paid to TD Cowen. Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties referencedunder the heading “Risk Factors” on page S-8 of this prospectus supplement as well as those contained in any related freewriting prospectus or prospectus supplement we prepare or authorize in connection with this offering, and in the otherdocuments that are incorporated by reference into this prospectus supplement. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is a criminaloffense. TD Cowen Table of Contents TABLE OF CONTENTS PROSPECTUS SUPPLEMENT ABOUT THIS PROSPECTUS SUPPLEMENTWHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCEPROSPECTUS SUPPLEMENT SUMMARYTHE OFFERINGRISK FACTORSCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSDIVIDEND POLICYDILUTIONPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTS PROSPECTUS ABOUT THIS PROSPECTUSPROSPECTUS SUMMARYRISK FACTORSCAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION OF INFORMATION BY REFERENCEUSE OF PROCEEDSPLAN OF DISTRIBUTION Table of Contents ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement is part of a registration statement that we filed with the Securities and Exchange Commission, or theSEC, using a “shelf” registration process. Under this shelf registration process, we may from time to time sell shares of our common stock,preferred stock or debt securities, subscription rights to purchase our common stock, preferred stock or debt securities and/or unitsconsisting of some or all of these securities, in any combination, having an aggregate offering price of up to $300.0million. Under thisprospectus supplement, we may from time to time sell shares of our common stock having an aggregate offering price of up to$100.0million, at prices and on terms to be determined by market conditions at the time of the offering. The $100.0million of shares ofcommon stock that may be sold under this prospectus supplement are included in the $300.0million of securities that may be sold underour shelf registration statement. This prospectus supplement describes the terms of this offering of common stock and also adds to and updates informationcontained in the documents incorporated by reference into this prospectus. To the extent there is a conflict between the informationcontained in this prospectus supplement, on the one hand, and the information contained in any document incorporated by reference intothis prospectus supplement that was filed with the SEC before the date of this prospectus supplement, on the other hand, you should relyon the information in t