On August 26, 2025 Genmab A/S (Nasdaq: GMAB) reported that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation (BTD) to rinatabart sesutecan (Rina-S), an investigational folate receptor alpha (FRα)-directed, TOPO1-inhibitor antibody-drug conjugate (ADC), for the treatment of adult patients with recurrent or progressive endometrial cancer (EC) who have disease progression on or following prior treatment with a platinum-containing regimen and a PD-(L)1 therapy (Press release, Genmab, AUG 26, 2025, View Source [SID1234655479]). BTD aims to expedite the development and review of investigational medicines by the U.S. FDA for serious or life-threatening diseases in cases where preliminary clinical evidence shows that a therapy may provide substantial improvements over available therapies.

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The designation was supported by previously published results from the endometrial cancer monotherapy dose expansion B2 cohort of the multi-part, Phase 1/2 RAINFOL-01 trial (NCT05579366), evaluating the safety and efficacy of Rina-S in solid tumors. In the B2 cohort, 64 patients with heavily pretreated advanced or recurrent EC whose disease had progressed on or after an anti-PD-(L)1 and platinum-based chemotherapy were enrolled and treated with Rina-S. The results were presented at the 2025 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting.

"This Breakthrough Therapy Designation underscores the future potential of Rina-S as a treatment option for women diagnosed with advanced endometrial cancer, who face a poor prognosis after progressing on standard of care treatment," said Judith Klimovsky, M.D., Executive Vice President and Chief Development Officer of Genmab. "Rina-S reinforces Genmab’s determination to advance wholly owned antibody medicines in areas long overdue for innovation and our commitment to driving a strong clinical development program to help redefine what’s possible to treat gynecologic cancers."

Rina-S is advancing through late-stage development supported by a growing portfolio of clinical trials, including the ongoing Phase 1/2 RAINFOL-01 trial, the ongoing Phase 3 RAINFOL-02 trial (NCT06619236) in ovarian cancer, and several planned trials to evaluate Rina-S as a potential treatment option for a variety of tumor types, including a Phase 3 trial in endometrial cancer.

About the RAINFOLTM -01 Trial
RAINFOL-01 (NCT05579366) is an open-label, multicenter Phase 1/2 study, designed to evaluate the safety and efficacy of rinatabart sesutecan (Rina-S) Q3W at various doses in solid tumors that are known to express FRα. The study consists of multiple parts including Part A dose escalation; Part B tumor-specific monotherapy dose-expansion cohorts; Part C platinum-resistant ovarian cancer (PROC) cohort; Part D combination therapy cohorts; Part F a monotherapy endometrial cancer (EC) cohort; and Part K monotherapy QTc cohort in high-grade ovarian cancer.

About Endometrial Cancer
Endometrial cancer (EC) starts in the lining of the uterus, known as the endometriumii and ranks as the second most prevalent gynecologic cancer globally, with increasing incidence and mortality ratesiii,iv. Patients with advanced or recurrent EC have a relatively poor prognosis and treatment options are limited for those patients who have progressed following treatment with chemotherapy and immune checkpoint inhibitor. FRα is overexpressed on multiple tumors, including EC, making it a promising therapeutic target. Anti-tumor activity with Rina-S was observed across a broad range of FRα expression, and there are currently no approved FRα-directed therapies approved for the treatment of endometrial cancer.

About Rinatabart Sesutecan (Rina-S; GEN1184)
Rinatabart sesutecan (Rina-S; GEN1184) is an investigational ADC. It is composed of a novel human monoclonal antibody directed at folate receptor α (FRα), a novel hydrophilic protease-cleavable linker, and exatecan, a topoisomerase I inhibitor payload. The clinical trial program for Rina-S continues to expand including ovarian, endometrial and other cancers of unmet need.

The safety and efficacy of rinatabart sesutecan has not been established. Please visit www.clinicaltrials.gov for more information.