– Luvelta demonstrated encouraging preliminary anti-tumor activity (29% response rate) in late-stage patients with recurrent/relapsed endometrial cancer with tumor proportion score (TPS) >25% FolRα expression –

– Safety profile was consistent with prior data in patients with platinum-resistant ovarian cancer –

SOUTH SAN FRANCISCO, Calif., October 22, 2023 – 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 initial results from a Phase 1 dose-expansion study of luveltamab tazevibulin (luvelta), a novel Folate receptor alpha (FolRα)-targeting ADC, in patients with endometrial cancer, in a mini oral presentation at the 2023 European Society For Medical Oncology (ESMO) Congress in Madrid, Spain.

Initial data from the Phase 1 dose-expansion study of luvelta were presented by Bhavana Pothurri, M.D., Professor, Department of Obstetrics and Gynecology at NYU Grossman School of Medicine and Director, Gynecologic Oncology Research at NYU Langone, Perlmutter Cancer Center.

Advanced endometrial cancer is the only gynecologic malignancy with increasing incidence and mortality in both the US and Europe¹. Estimated incidence in the EU: 92,746 pts with 23,047 deaths (2022)² and in the US: 66,000 pts with 13,030 deaths (2023)³.

“We are pleased to have the opportunity to present these encouraging early data at ESMO this year,” said Anne Borgman, M.D., Sutro’s Chief Medical Officer. “The late-stage endometrial cancer treatment landscape is still evolving.  With checkpoint inhibitors moving to first line, single agent chemotherapy with response rates in the 15% range⁴ may once again be the default therapy for patients whose tumors recur. We are optimistic that luvelta may be able to address this tremendous unmet need with a new targeted treatment option, given endometrial cancer expresses FolRα, along with the manageable tolerability profile and preliminary anti-tumor activity seen in the trial.”

FolRα is a validated anti-tumor target in ovarian cancer that is overexpressed in endometrial cancer compared with normal tissue⁵. As presented in June 2023 at the American Society of Clinical Oncology, luvelta has already demonstrated compelling preliminary efficacy and safety in patients with a broad range of FolRα-expressing recurrent epithelial ovarian cancers (EOC) in a Phase 1 dose escalation/expansion study.

ESMO Presentation Highlights:

• 17 patients were enrolled and initial data were presented on 16 patients with at least one post baseline scan
• Luvelta demonstrated encouraging preliminary anti-tumor activity in patients with FolRα-expressing endometrial cancer
  • In patients with TPS >25% FolRα expression (n=7):
    • Confirmed partial response (PR) was seen in 29% (2/7)
    • Disease Control Rate (DCR) was 86% (6/7)
  • In patients with TPS ≥1% FolRα expression (n=16):
    • Confirmed PR was seen in 19% (3/16)
    • DCR was 69% (11/16)
  • Consistent with previous reported luvelta safety results, the most common adverse event was neutropenia; no new safety signals were observed

The Presentation will be accessible through the News & Events page of the Investor Relations section of the company’s website at www.sutrobio.com. 

*1: Siegel RL, et al. CA Cancer J Clin. 2023;73(1):17–48.

*2: European Cancer Information System (ECIS). https://ecis.jrc.ec.europa.eu. Accessed 11 Oct 2023.

*3: American Cancer Society Cancer Statistics 2023. https://www.cancer.org. Accessed 08 Sep 2023.

*4: Makker V, et al. N Engl J Med. 2022;386(5):437–448.

*5: Despierre E, et al. Gynecol Oncol. 2013;130:192–199.

About Sutro Biopharma

Sutro Biopharma, Inc., is a clinical-stage company relentlessly focused on the discovery and development of precisely designed cancer therapeutics, transforming what science can do for patients. Sutro’s fit-for-purpose technology, including cell-free XpressCF®, provides the opportunity for broader patient benefit and an improved patient experience. Sutro has multiple clinical stage candidates, including luveltamab tazevibulin, or luvelta, a registrational-stage folate receptor alpha (FolRα)-targeting ADC in clinical studies. A robust pipeline, coupled with high-value collaborations and industry partnerships, validates our continuous product innovation. Sutro is headquartered in South San Francisco. 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, anticipated preclinical and clinical development activities, timing of announcements of clinical results, trial initiation, and regulatory filings, potential benefits of luvelta and the Company’s other product candidates and platform, potential future milestone and royalty payments, and potential market opportunities for luvelta 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.

Contact

Emily White
Sutro Biopharma
(650) 823-7681
ewhite@sutrobio.com