• Veteran Pfizer researcher Andreas Maderna, Ph.D., joins the company

SOUTH SAN FRANCISCO, Calif., Jan. 29, 2019 –Sutro Biopharma, Inc. (NASDAQ: STRO) today announced the appointment of Andreas Maderna, Ph.D., as vice president of chemistry. Dr. Maderna has extensive experience building successful scientific teams and a strong background in medicinal chemistry.

“Dr. Maderna arrives at an important time for the company as we continue to fortify our leadership team and advance our cancer therapy pipeline,” said Sutro CEO Bill Newell. “His expertise and background in antibody-drug conjugates and immuno-oncology will be instrumental as we continue building our pipeline. Dr. Maderna will contribute significantly as we implement our strategy of transforming next-generation science into medicines.”

Dr. Maderna has more than 15 years of experience in medicinal chemistry. Prior to joining Sutro, Dr. Maderna was an associate research fellow in the oncology medicinal chemistry department at Pfizer. He led multiple chemistry design teams in hit-to-lead optimization campaigns. Prior to this role, Dr. Maderna worked as a laboratory head at Pfizer, where he led the payload discovery and development efforts to support Pfizer’s antibody-drug conjugate portfolio. His team developed new and highly potent payloads that resulted in multiple clinical candidates. For these contributions, Dr. Maderna received the 2015 Pfizer World Wide Research and Development Achievement Award.Dr. Maderna obtained his Ph.D. in chemistry from the University of Heidelberg, Germany.

“Antibody-drug conjugates have the ability to deliver highly potent molecules to target tissues and thereby hold great promise in the development of new effective cancer therapies,” said Dr. Maderna. “Sutro’s cell-free protein synthesis and site-specific conjugation technology is revolutionary in this field and allows, for the first time, a rapid and efficient evaluation process for these agents. I’m excited to join the Sutro team and to have the opportunity to contribute and help further develop this truly novel technology.”

About Sutro Biopharma

Sutro Biopharma, Inc., located in South San Francisco, is a clinical-stage drug discovery, development and manufacturing company. Using precise protein engineering and rational design, Sutro is advancing next-generation oncology therapeutics.

Sutro’s proprietary and integrated cell-free protein synthesis and site-specific conjugation platform, XpressCF+™, led to the discovery of STRO-001 and STRO-002, Sutro’s first two internally-developed antibody-drugconjugates, or ADCs. STRO-001 is a potentially first-in-class ADC targeting CD74, a protein highly expressed in multiple myeloma and non-Hodgkin’s lymphoma, and is currently in a Phase I study. Orphan Drug Designation was granted for multiple myeloma.  STRO-002 is a potentially best-in-class ADC targeting folate receptor alpha, a cell-surface protein highly expressed in gynecological cancers. The IND is currently open for enrollment and the first patient is expected to be dosed in the first quarter of 2019.

Sutro is dedicated to transforming the lives of cancer patients by creating medicines with improved therapeutic profiles for areas of unmet need.

To date, Sutro has designed cytokine-based immuno-oncology therapies, antibody-drug conjugates, and bispecific antibodies primarily directed at clinically-validated targets for which the current standard of care is suboptimal.

Sutro’s platform allows it to accelerate discovery and development of potential first-in-class and best-in-class molecules through rapid and systematic evaluation of protein structure-activity relationships to create optimized homogeneous product candidates.

In addition to developing its own oncology pipeline, Sutro is collaborating with select pharmaceutical and biotech companies to discover and develop novel, next-generation therapeutics. As the pace of clinical development accelerates, Sutro and its partners are developing therapeutics designed to more efficiently kill tumors without harming healthy cells.

Follow Sutro on Twitter, @Sutrobio, and at www.sutrobio.com to learn more about our passion for changing the future of oncology.

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, planned development activities and the potential benefits of the company’s product candidates and platform. 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, obtain regulatory approval of and ultimately commercialize its 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 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.

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