Genmab's Rina-S Shows 50% Response Rate in Tough-to-Treat Endometrial Cancer—Phase 3 Trial Underway After FDA Breakthrough Designation
Rina-S Demonstrates Durable Anti-Tumor Activity in Heavily Pretreated Patients
Genmab has announced encouraging results for its investigational therapy, rinatabart sesutecan (Rina-S), targeting advanced endometrial cancer—a group where treatment options are often limited and prognosis poor. Updated data from the Phase 1/2 RAINFOL™-01 trial show that patients who had exhausted prior therapies saw a confirmed objective response rate (ORR) of 50%, including two complete responses, after treatment with Rina-S at the 100 mg/m2 dose every three weeks.
Responses Maintained and Unrelated to Tumor FRa Levels
Notably, the trial included women whose disease had already progressed on both platinum-based chemotherapy and immune checkpoint inhibitors—a particularly difficult-to-treat population. The observed responses with Rina-S occurred regardless of folate receptor alpha (FRa) expression levels, broadening its potential impact. At the one-year mark, nearly two-thirds (63.6%) of responders in the 100 mg/m2 cohort maintained their response and continued on treatment, suggesting durable benefit.
| Cohort Dose | Confirmed ORR | Complete Responses (CR) | Median Prior Therapies | % Maintaining Response at 1 Year |
|---|---|---|---|---|
| 100 mg/m2 (n=22) | 50.00% | 2 | 3 (range 1-8) | 63.64% |
| 120 mg/m2 (n=42) | 44.10% | 1 | 3 (range 1-8) | Not reported |
Safety Profile: No Ocular Toxicities, Low Rates of Discontinuation
The most common side effects observed were manageable, including low-grade blood cell reductions and gastrointestinal events. Importantly, there were no reported cases of ocular toxicity, neuropathy, or interstitial lung disease, which can complicate other treatments in this class. Grade 3 or higher side effects occurred in 36.4% of patients in the 100 mg/m2 group and 52.4% in the 120 mg/m2 group, but these rarely led to discontinuation or dose reduction.
Momentum Continues: FDA Breakthrough Therapy Designation and Next Steps
Building on these promising results, Rina-S has now earned a Breakthrough Therapy Designation from the U.S. FDA for advanced endometrial cancer following progression after platinum chemotherapy and PD-(L)1 therapy. Phase 3 studies are already underway, not just in endometrial cancer, but also in platinum-resistant ovarian cancer.
Key Takeaway: Rina-S Offers New Hope Where Few Options Exist
The strong response rate, durable benefits, and tolerable side effect profile put Genmab’s Rina-S in the spotlight as a potential game changer for a difficult-to-treat population. The fact that responses occur regardless of FRa status further widens its relevance. While long-term results are still pending and larger Phase 3 trials are needed, these findings offer real hope for patients and signal Genmab’s ongoing commitment to developing next-generation therapies in oncology.
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