SOUTH SAN FRANCISCO, Calif., March. 22, 2021 – Sutro Biopharma, Inc. (NASDAQ: STRO), a clinical-stage drug discovery, development and manufacturing company focused on the application of precise protein engineering and rational design to create next-generation cancer and autoimmune therapeutics, today announced the strengthening of key leadership roles including the promotion of David Pauling, J.D., M.A., to General Counsel, the promotion of Robert Kiss, Ph.D., to Senior Vice President, Process and Analytical Development, and the appointment of Ana Oaknin Benzaquen, M.D., Ph.D., to Sutro’s Clinical Advisory Board.

Promotion of David Pauling to General Counsel

“Sutro’s ability to develop multiple programs and to collaborate with various industry partners is reflective of the sound legal guidance that David has provided over the past ten years,” said Bill Newell, Sutro’s Chief Executive Officer. “David’s astute judgement and contribution, particularly on maintaining a strong IP position on our proprietary and integrated cell-free protein synthesis platform, XpressCF®, and on the programs from the platform, have been invaluable to the growth of Sutro as an integrated biopharma company. Sutro is committed to the highest level of integrity and compliance and with David’s continued legal leadership, we will continue to work diligently on bringing therapies for patients with unmet medical needs.”

In his expanded role as Sutro’s General Counsel, Mr. Pauling is responsible for all aspects of legal operations, including governance, compliance, disclosure, intellectual property, and agreements. Mr. Pauling joined Sutro in 2011 and has since held positions of increasing responsibility, including Intellectual Property Counsel, Associate General and Senior Intellectual Property Counsel, and most recently Executive Director of Legal Affairs. Prior to joining Sutro, Mr. Pauling practiced law at Jones Day and at Penne & Edmonds, LLP. Mr. Pauling received his J.D. from Santa Clara University School of Law (magna cum laude), and an M.A. in Molecular Biology and a B.S. in Biochemistry and Molecular Biology from the University of California, Santa Cruz.

Promotion of Bob Kiss to SVP, Process and Analytical Development

“Since joining Sutro, Bob’s leadership of the process development and analytical teams has contributed to 4 successful IND filings for Sutro’s and partner products,” said Shabbir Anik, Ph.D., Sutro’s Chief Technical Operations Officer. “The development of fit-to-purpose processes for the manufacture of GMP level therapeutics at our industry-leading cell-free protein synthesis facility in San Carlos, CA, is a strategic advantage for our clinical programs and for our partners. Bob’s expertise and experience in biologics product development and his rigorous scientific approach has allowed us to optimize the advantages of our cell-free platform for protein production, and to fulfill our commitment for rapid entry into the clinic for our own product candidate pipeline of novel therapeutics as well as for industry partners.”

As part of this promotion, Dr. Kiss is wholly responsible for the end-to-end industrialization of Sutro’s proprietary and integrated cell-free protein synthesis platform, XpressCF®, encompassing process scalability, technology transfers to CMO’s, and CMC strategies to ensure successful global regulatory filings. Dr. Kiss joined Sutro in 2017 as Vice President of Process and Analytical Development, after working at Genentech for nearly 24 years, where his last role was of Distinguished Engineer and Senior Director of Late-Stage Cell Culture process development. While at Genentech, he was directly involved in the development and initial licensure of the cell culture processes for Rituxan®, Herceptin®, Perjeta®, Tecentriq®, and Ocrevus™, the design and startup of the Vacaville manufacturing sites, and the transfer of multiple cell culture processes to Genentech/Roche and partner sites around the world. Dr. Kiss received a B.S. in chemical engineering from UC Davis and his M.S. and Ph.D. in chemical engineering from The Massachusetts Institute of Technology. He is a Fellow in the American Institute of Medical and Biological Engineering and was elected to the National Academy of Engineering in 2019. He was named a Distinguished Engineering Alumni by UC Davis in 2019 and is a licensed engineer in the state of California.

Appointment of Ana Oaknin Benzaquen to Clinical Advisory Board

“We are honored and delighted to appoint Ana to Sutro’s Clinical Advisory Board as her global clinical expertise will bring a unique perspective to our group of accomplished and diverse practitioners,” said Arturo Molina, M.D., Sutro’s Chief Medical Officer. “Her breadth of clinical trial expertise, specifically studying gynecological tumors will provide valuable insight to advancing STRO-002 as we expand our trial globally. Her authority and influence within the industry including with major cancer organizations such as ASCO and ESMO will be an asset to Sutro as we continue to develop therapies for cancer patients.”

Dr. Oaknin is the Head of the Gynecological Tumor Unit and full-time Senior Attending Physician at Medical Oncology Department at the Vall d’Hebron University Hospital in Barcelona, as well as the Principal Clinical Investigator of the Gynecological Malignancies Group at the Vall d’Hebrón Institute of Oncology. She also leads the Gynecological Cancer program at the Baselga Institute of Oncology. Dr. Oaknin received her Degree in Medicine and Surgery from the Universidad Complutense of Madrid and her Ph.D. from the Universidad Autonoma de Barcelona. She is the Principal Investigator on several clinical trials in ovarian, cervical, and endometrial cancer and has authored over 100 publications and presentations. Dr. Oaknin is an executive board member and Co-Chair of the GEICO Group (Spanish Ovarian Cancer Research Group) and an active member of the American Society of Clinical Oncology (ASCO), European Society of Medical Oncology (ESMO), and the Spanish Association of Medical Oncology (SEOM).

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 platform XpressCF^® and site-specific conjugation platform XpressCF+™ led to the discovery of STRO-001 and STRO-002, Sutro’s first two internally-developed ADCs. STRO-001 is a CD74-targeting ADC currently being investigated in a Phase 1 clinical trial of patients with advanced B-cell malignancies, including multiple myeloma and non-Hodgkin lymphoma. STRO-001 was granted Orphan Drug Designation by the FDA for multiple myeloma in October 2018. STRO-002 is a folate receptor alpha (FolRα)-targeting ADC, currently being investigated in a Phase 1 clinical trial of patients with ovarian and endometrial cancers. A third product candidate, CC-99712 (BCMA-targeting ADC), which is part of Sutro’s collaboration with Bristol Myers Squibb (formerly Celgene Corporation), is enrolling patients for its Phase 1 clinical trial of patients with multiple myeloma and has received Orphan Drug Designation from the FDA for multiple myeloma. A fourth product candidate, M1231, (MUC1-EGFR, first-in-class bispecific ADC), which is part of Sutro’s collaboration with Merck KGaA, EMD Serono (EMD Serono) is enrolling patients for its Phase 1 clinical trial of patients with metastatic solid tumors, non-small cell lung cancer (NSCLC) and esophageal squamous cell carcinoma. The four product candidates above being evaluated in clinical trials resulted from Sutro’s XpressCF^® and XpressCF+™ technology platforms. Bristol Myers Squibb and EMD Serono have worldwide development and commercialization rights for CC-99712 and M1231, respectively, for which Sutro is entitled to milestone or contingent payments and tiered royalties.

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’s platform has led to cytokine-based immuno-oncology therapies, ADCs, vaccines and bispecific antibodies directed at precedented targets in clinical indications where the current standard of care is suboptimal.

The 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, anticipated preclinical and clinical development activities, timing of announcements of clinical results, potential benefits of the company’s product candidates and platform and potential market opportunities for the company’s product candidates. 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 impact of the COVID-19 pandemic on the Company’s business, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to 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, the value of the Company’s holdings of Vaxcyte common stock, 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 Contacts

Annie J. Chang

Sutro Biopharma

(650) 801-5728

ajchang@sutrobio.com

Media Contacts

Maggie Beller

Russo Partners

(646) 942-5631

Maggie.beller@russopartnersllc.com