SOUTH SAN FRANCISCO, Calif., April 8, 2022 – Sutro Biopharma, Inc. (“Sutro” or the “Company”) (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 therapeutics, today announced new nonclinical data for its folate receptor alpha (FolRα) targeting antibody-drug conjugate (ADC) STRO-002, in an e-poster session, at the American Association for Cancer Research (AACR) Annual Meeting 2022, being held virtually and in New Orleans from April 8-13, 2022.

STRO-002 is an ADC designed to target FolRα, which is currently in Phase 1 clinical trials for the treatment of ovarian and endometrial cancers. In the e-poster session presented at AACR, studies in vitro demonstrate STRO-002’s ability to induce hallmarks of immunogenic cell death. Studies in vivo show that pre-administration of STRO-002 to FolRα-expressing tumor cells confers anti-tumor immunity as demonstrated by both rejection of the primary tumor and significant protection after a tumor re-challenge. Further, in vivo induction of immunogenic cell death extended to a complementary anti-tumor mechanism in combination with a checkpoint inhibitor (avelumab) in re-challenged animals. Additionally, when STRO-002 was administered in combination with an anti-VEGF antibody (bevacizumab), the tumor growth was significantly inhibited.

Nonclinical studies using endometrial and non-small cell lung cancer (NSCLC) patient derived xenograft models with diverse levels of FolRα expression demonstrated robust STRO-002 activity, with the degree of efficacy correlating with FolRα levels. Similar activity was also seen in cells with moderate to low levels of FolRα expression. In the NSCLC model, a STRO-002 dose of 10 mg/ml resulted in significant and long-term responses.

“These nonclinical data provide insight into STRO-002’s immunogenic cell death properties and reveal its potential to elicit host immune system engagement and potentiate efficacy in a targeted and dependent manner,” said Trevor Hallam, Ph.D., President of Research and Chief Scientific Officer at Sutro. “The potent cytotoxic and immune stimulatory properties of STRO-002 through immunogenic cell death may also enhance activity in indications that are thought to have lower levels of FolRα such as in non-small cell lung cancer and endometrial cancers.”

The data is being presented as an e-poster at the AACR Annual Meeting, with details as follows:

Abstract:        #5591
Session:          OPO.IMO2.01 – Preclinical Immunotherapy
Title:                Anti-FolRα ADC STRO-002 induces immunogenic cell death (ICD) to enhance anti-tumor activity
Presenter:     Kristin Bedard, Ph.D., Vice President of Discovery at Sutro Biopharma

The poster is accessible through the Clinical/Scientific Presentation and Publication Highlights page of the News section of the company’s website at www.sutrobio.com.

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 under investigation in a Phase 1 clinical trial for patients with advanced B-cell malignancies and was granted Orphan Drug Designation by the FDA for multiple myeloma. STRO-002, a folate receptor alpha (FolRα)-targeting ADC, is currently being investigated in a Phase 1 clinical trial for patients with ovarian and endometrial cancers and was granted Fast Track designation by the FDA for ovarian cancer. A third product candidate, CC-99712, a 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. A fourth product candidate, M1231, a MUC1-EGFR, bispecific ADC, which is part of Sutro’s collaboration with Merck KGaA, Darmstadt, Germany, known as EMD Serono in the U.S. and Canada (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. These four product candidates 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 ADCs, bispecific antibodies, cytokine-based immuno-oncology therapies, and vaccines directed at precedented targets in clinical indications where 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 biotechnology companies to discover and develop novel, next-generation therapeutics.

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 or nonclinical results, potential benefits of STRO-002 and the Company’s other product candidates and platform, potential future milestone and royalty payments, and potential market opportunities for STRO-002 and the Company’s other 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 and the Company’s ability to successfully leverage Fast Track designation, the market size for the Company’s product candidates to be smaller than anticipated, 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 Contact

Annie J. Chang
Sutro Biopharma
(650) 801-5728
ajchang@sutrobio.com

Media Contact

Maggie Beller
Russo Partners
(646) 942-5631
Maggie.beller@russopartnersllc.com