On March 15, 2025 Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), an oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), reported expanded data in a late-breaking oral presentation from the dose-optimization portion of the REFRαME-O1 trial with luveltamab tazevibulin (luvelta) in patients with platinum resistant ovarian cancer (PROC) at the Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer (Press release, Sutro Biopharma, MAR 15, 2025, View Source [SID1234651158]). The SGO Annual Meeting will take place from March 14-17, 2025 in Seattle, Washington.

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In this study, luvelta demonstrated encouraging antitumor activity in patients with late-stage ovarian cancer across all levels of Folate Receptor-α (FRα) expression of 25% or greater, including an improved overall response rate (ORR), a low discontinuation rate, and a consistent safety profile across dose levels. Based on these findings, Sutro selected the optimized dose of luvelta: 5.2 mg/kg + G-CSF for two cycles then continued on 4.3 mg/kg.

"These data demonstrate the potential for improved patient responses compared to standard chemotherapy in PROC, especially patients whose FRα expression falls within the range of at least 25% to less than 75% 2+, which remains an important unmet medical need," commented Dr. Jung Yun Lee, Professor, Gynecologic Oncologist, Yonsei Cancer Center and Severance Hospital, Yonsei University College of Medicine, Seoul, Republic of Korea.

Late-Breaking Oral Presentation Highlights:

At the selected optimized dose (5.2 mg/kg), luvelta achieved an ORR of 32%1 and a disease control rate (DCR) of 96% compared to an ORR of 13.8% and a DCR of 69% for the 4.3 mg/kg group.
The demonstrated clinical activity in the 5.2 mg/kg group was consistent in patients across all levels of FRα expression of 25% or greater, with an ORR of 30.8% and a DCR of 100% for positive staining (PS) 2+ ≥75% (eligible for approved FRα-targeting ADC) and an ORR of 33.3%1 and DCR of 91.7%1 for PS2+ < 75%.
Safety was consistent across dosing groups, with no new safety signals observed and neutropenia well-managed.
The majority of patients across both dose cohorts received prior bevacizumab.
The presentation will be accessible through the News & Events page of the Investor Relations section of the company’s website at www.sutrobio.com.

The Company recently announced that it is deprioritizing investment into the development of luvelta across all indications. Sutro continues to explore out-licensing opportunities to deliver the promise of luvelta’s benefit to patients with unmet need in platinum resistant ovarian cancer and beyond.

Immediately after data extraction, one additional patient experienced a confirmed PR and is included in the analysis.

About Luveltamab Tazevibulin

Luveltamab tazevibulin, abbreviated as "luvelta" and formerly known as STRO-002, is a FRα-targeting antibody-drug conjugate (ADC) designed to treat a broad range of patients with ovarian cancer, including those with lower FRα-expression who are not eligible for approved treatment options targeting FRα. Developed and manufactured with Sutro’s cell-free XpressCF platform, luvelta is a homogeneous ADC with four hemiasterlin cytotoxins per antibody, precisely positioned to efficiently deliver to the tumor while ensuring systemic stability after dosing. The U.S. Food and Drug Administration (FDA) has granted luvelta a Fast Track designation for Ovarian Cancer, as well as Orphan and Rare Pediatric Disease designations for CBF/GLIS2 Pediatric AML.