On December 10, 2024 Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), reported the selected dose from the dose-optimization portion (Part 1) of REFRαME-O1, the registration-directed trial of luveltamab tazevibulin (luvelta) in platinum-resistant ovarian cancer (PROC), following a meeting with the U.S. Food and Drug Administration (FDA) (Press release, Sutro Biopharma, DEC 10, 2024, View Source [SID1234648998]).

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"The topline results confirm luvelta’s favorable safety and efficacy profile at the starting dose of 5.2 mg/kg, further supporting our confidence that it can improve clinical outcomes compared to chemotherapy in our ongoing registrational trial," said Anne Borgman, M.D., Sutro’s Chief Medical Officer. "Consistent response rates were observed in patients across all levels of FRα expression of 25% or greater, reconfirming luvelta’s potential to expand the benefit of a targeted treatment to 8 out of 10 PROC patients."

REFRαME-O1 (Part 1)

REFRαME-O1 (Part 1) evaluated luvelta in patients with PROC with low, medium, and high FRα expression levels. This includes patients with ≥25% Tumor Proportion Score (TPS), defined as at least 25% of tumor cells expressing FRα, at any staining intensity. In the dose-optimization (Part 1), patients were randomized 1:1 to a 5.2 mg/kg with prophylactic pegfilgrastim (G-CSF) for 2 cycles followed by 4.3 mg/kg for subsequent cycles (5.2 mg/kg group), or a 4.3 mg/kg dose of luvelta for all cycles (4.3 mg/kg group). We plan to present additional data at future medical meetings.

Topline Results from Evaluable Patients (5.2 mg/kg group; N = 25):

Achieved an objective response rate (ORR) of 32%, which includes one partial response that confirmed post data extraction1
Disease control rate of 96%
Approximately half of the patients treated were ineligible for an approved FRα-targeting ADC
88% of patients received prior bevacizumab
Grade 3 or higher neutropenia occurred in 32% of patients, no febrile neutropenia
"The clinical results from Part 1 of REFRαME-O1 provide compelling evidence that luvelta has the potential to be both first in class and best in class for patients who have low to medium expression of FRα. FRα is a validated target, and luvelta has the opportunity to reach more patients in need," commented Bradley Monk, M.D., Florida Cancer Specialists and Research Institute; Director GOG Partners.

"The topline safety profile of luvelta from Part 1 is encouraging. Neutropenia rates were low, highlighting successful management guidelines. Furthermore, the lack of serious ocular damage, pancytopenia, or Interstitial Lung Disease provide further confidence in our ability to treat a broad group of women with PROC with a focus on their overall wellbeing," stated Wendel Naumann, M.D., Professor, Levine Cancer, Atrium Health/Wake Forest University, Charlotte, NC.

REFRαME-O1 (Part 2) Registrational Trial

REFRαME-O1 (Part 2) is an ongoing global registrational trial for patients with PROC, evaluating a 5.2 mg/kg dose with prophylactic pegfilgrastim (G-CSF) for the first two cycles followed by a 4.3 mg/kg dose for subsequent cycles. Part 2 will enroll approximately 500 patients, randomized 1:1 to luvelta or investigators’ choice of chemotherapy. Luvelta is positioned for an Accelerated Approval application in mid-2027.

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. REFRαME-O1, a Phase 2/3 registration-directed study for patients with platinum-resistant ovarian cancer is ongoing. The Company has another ongoing registration-directed trial, REFRαME-P1, for patients with CBF/GLIS acute myeloid leukemia, a rare subtype of pediatric cancer, as well as additional ongoing trials in patients with endometrial cancer, non-small cell lung cancer, and in combination with bevacizumab in patients with ovarian cancer. 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/GLIS Pediatric AML.