Sutro Biopharma Regains Compliance with Nasdaq Minimum Bid Price Requirement

Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today announced it has regained compliance with the Nasdaq Stock Market (Nasdaq) continued listing standard for minimum share price under Rule 5450(a)(1) of the Nasdaq Listing Qualifications.

On December 17, 2025, the Company received confirmation from the Listing Qualifications Department of Nasdaq that as of December 16, 2025 the Company’s common stock has maintained an average closing share price of at least $1.00 following the Company’s 1:10 reverse stock split that became effective on December 3, 2025. The Company’s shares are no longer considered to be below the minimum bid price requirement of Rule 5450(a)(1), and as a result the Company has regained compliance with the Nasdaq continued listing standard.

About Sutro Biopharma

Sutro Biopharma, Inc. is advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro’s cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what’s possible in cancer therapy. The Company’s pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies. For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, Sutro’s future stock price, the effects of the reverse stock split on stockholders, continued compliance with Nasdaq listing standards and Sutro’s ability to remain listed on the Nasdaq Global Market. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, and the Company’s commercial collaborations with third parties and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof.

Investor Contact: Emily White Sutro Biopharma (650) 823-7681 [email protected]

Media Contact: Amy Bonanno Lyra Strategic Advisory [email protected]