of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Termination of a Material Definitive Agreement. As previously disclosed, on April 2, 2021, the Company entered into an Open Market Sale AgreementSM (the “Sales Agreement”) with Jefferies LLC (the “Agent”), pursuant to which the Company could issue and sell, from time to time, shares of its common stock, par value $0.001 per share (the “Common Shares”), up to an aggregate offering price equal to the Maximum Program Amount (the “ATM Program”). On March 23, 2026, the Company and Agent mutually a…

Entry into a Material Definitive Agreement On February 9, 2026, Sutro Biopharma, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Leerink Partners LLC and TD Securities (USA) LLC, as representatives of the several underwriters named therein (the “Underwriters”), pursuant to which the Company agreed to issue and sell 7,868,383 shares of its common stock (the “Shares”) to the Underwriters (the “Offering”). The Shares will be sold at an offering pri…

Material Modification to the Rights of Security Holders The information set forth in

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Costs Associated with Exit or Disposal Activities On September 29, 2025, Sutro Biopharma, Inc. (the “Company”) announced further organizational restructuring to prioritize the advancement of its three preclinical ADC programs and its research and development collaborations. The restructuring is expected to extend the Company’s runway into at least mid-2027 resulting from cost savings associated with the restructuring and certain expected near-term milestone payments. Following further priorit…

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing. On June 20, 2025, Sutro Biopharma, Inc. (the “Company”) received written notice from The NASDAQ Stock Market, LLC (“NASDAQ”) indicating that the Company is not in compliance with the $1.00 minimum bid price requirement for continued listing on The NASDAQ Global Market, as set forth in Listing Rule 5450(a)(1). In accordance with Listing Rule 5810(c)(3)(A), the Company has a period of 180 calend…

Chief Financial Officer — Gregory K. Chow: The company appointed a new Chief Financial Officer from an external candidate.

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Director — John Freund, M.D.: Dr. John Freund decided not to stand for re-election to the Board of Directors.

Costs Associated with Exit or Disposal Activities On March 13, 2025, the Company announced the completion of a strategic portfolio review resulting in the prioritization of its three wholly-owned preclinical programs in its next-generation ADC pipeline, beginning with its potentially best-in-class exatecan ADC targeting Tissue Factor, STRO 004, expected to enter the clinic in the second half of 2025. As a result of the reprioritization, the Company announced plans to deprioritize additional i…

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “Securities Act”), except as expressly set forth by specific reference in such a filing.

CEO — William J. Newell: Mr. William J. Newell transitioned out of his role as CEO and was succeeded by Jane Chung.

Other Events. On December 10, 2024, Sutro Biopharma, Inc. (the “Company”) announced the selected dose from the dose-optimization portion (Part 1) of REFRαME-O1, the registration-directed trial of luveltamab tazevibulin (“luvelta”), a novel folate receptor-α (FolRα) targeting antibody drug conjugate (“ADC”), in platinum-resistant ovarian cancer (“PROC”). REFRαME-O1 (Part 1): REFRαME-O1 (Part 1) evaluated luvelta in patients with PROC with low, medium, and high FRα expression levels. This inclu…

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Director — Sukhi Jagpal: Appointment of Sukhi Jagpal as a Class III director and member of the Audit Committee.

of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “ Securities Act ”), except as expressly set forth by specific reference in such a filing.

Entry into a Material Definitive Agreement On April 2, 2024, Sutro Biopharma, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with BofA Securities, Inc., as representative of the several underwriters named therein (the “Underwriter”), pursuant to which the Company agreed to issue and sell 14,478,764 shares of its common stock (the “Shares”) to the Underwriter (the “Offering”). The Shares will be sold at an offering price of $5.18 per share. The Under…

Entry into a Material Definitive Agreement On March 29, 2024, Sutro Biopharma, Inc. (the “ Company ”) and Ipsen Pharma SAS (“ Ipsen ”) entered into an Exclusive License Agreement (the “ License Agreement ”) pursuant to which the Company will license to Ipsen, on an exclusive basis, the right to research, develop, manufacture and commercialize STRO-003. All capitalized terms herein have the definitions assigned to them in the License Agreement unless otherwise defined herein. In consideration…

The Company Share Issuance is being made in a private placement that is exempt from registration under Section 4(a)(2) of the Securities Act of 1933, as amended.

of this report, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (“ Exchange Act ”) , or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing. This Current Report on Form 8-K contains forward-looking statemen…