Sutro Biopharma Earns Milestone Payment from Cytokine Derivatives Collaboration with Merck

SOUTH SAN FRANCISCO, Calif., April 15, 2021 /PRNewswire/ -- 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 that Merck, known as MSD outside the United States and Canada, will make to Sutro a $15 million milestone payment for the initiation of an IND enabling toxicology study for the first program in its collaboration to develop novel cytokine derivative therapeutics for cancer and autoimmune disorders. In July 2018, Sutro entered into a collaboration with Merck to jointly discover and develop best-in-class immune-modulating cytokine derivatives for both oncology and autoimmune indications.

"The advancement of this first candidate into an IND enabling toxicology study represents an important preclinical milestone in our collaboration, led by Merck's deep understanding and leadership within immuno-oncology and Sutro's strength in precise protein design and optimization through its proprietary cell-free synthesis approaches," said Bill Newell, Chief Executive Officer of Sutro. "We are pleased with the continued progress in our collaboration with Merck and will continue our efforts towards developing novel therapeutics to improve outcomes and expand much-needed treatment options for cancer patients."

Under the terms of the 2018 Merck collaboration agreement, Sutro has been primarily responsible for preclinical research and development of cytokine derivatives utilizing Sutro's proprietary cell-free protein synthesis and site-specific conjugation platforms, XpressCF® and Xpress CF+™. Merck has exclusive worldwide rights to therapeutic candidates derived from the collaboration. In March 2020, Merck exercised its option to extend the first research term of the program by one year, which generated a payment of $5.0 million to Sutro.

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

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SOURCE Sutro Biopharma