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 28, 2023

SUTRO BIOPHARMA, INC.

(Exact name of registrant as specified in its charter)

111 Oyster Point Blvd,

South San Francisco, California, 94080

(Address of principal executive offices) (Zip Code)

(650) 881-6500

(Registrant’s telephone number, including area code)

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:

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 1.01 Entry into a Material Definitive Agreement.

On December 19, 2022, Sutro Biopharma, Inc. (the “Company”) entered into a letter agreement (the “Agreement”) with Vaxcyte, Inc. (“Vaxcyte”) under which the Company granted to Vaxcyte (i) authorization to enter into an agreement with an independent alternate contract manufacturing organization (“CMO”) to source cell-free extract solely for the products it licensed from the Company, allowing Vaxcyte to have direct oversight over financial and operational aspects of the relationship with the CMO, and (ii) a right, but not an obligation, to obtain certain exclusive rights to internally manufacture and/or source extract from certain CMOs and the right to independently develop and make improvements to extract for use in connection with the exploitation of certain vaccine compositions (the “Option”). Pursuant to the Agreement, the Company and Vaxcyte agreed to negotiate the terms and conditions of a form definitive agreement to be entered into in the event Vaxcyte exercises the Option (the “Form Definitive Agreement”) and, within five days after the Company and Vaxcyte mutually agreed in writing upon the Form Definitive Agreement, Vaxcyte agreed to pay the Company $5.0 million. On September 28, 2023, the Companies mutually agreed in writing upon the Form Definitive Agreement.

Pursuant to the Agreement, and effective immediately upon agreement to the Form Definitive Agreement, the Company and Vaxcyte entered into amendment No 3. (the “Amendment”) to that certain license agreement between the Company and Vaxcyte, dated August 1, 2014, and amended and restated on October 12, 2015, and amended again on May 9, 2018 and May 29, 2018 (the “License Agreement”). The Amendment amended certain terms of the License Agreement including with respect to (i) royalty reduction provisions applicable in the event of expiration of relevant patent claims, which would result in lower royalties payable by Vaxcyte under certain circumstances, (ii) the ownership, prosecution, maintenance and enforcement of certain intellectual property rights licensed or arising under the License Agreement, and (iii) the timing and form for financial reporting of royalty payment calculations.

The foregoing description of the Amendment is qualified in its entirety by reference to the Amendment, a copy of which will be filed as an exhibit to the Company’s Quarterly Report on Form 10-Q for the quarter ending September 30, 2023.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.