Genmab's Rina-S Posts 45.9% Response Rate in Platinum-Resistant Ovarian Cancer; Shares Rise

Genmab's rinatabart sesutecan (Rina-S) produced a confirmed objective response rate of 45.9%, including five complete responses, in 109 patients with platinum-resistant ovarian cancer in Part C of the Phase 1/2 RAINFOL-01 trial. Median duration of response was 12.1 months, with 51% of responders still responding at one year, and median progression-free survival was 9.5 months. The results, at the 120 mg/m2 dose every three weeks, were presented on Saturday, October 3, in a late-breaking session at the IGCS 2026 Congress in Montreal.

The population was heavily pretreated: 53% had three or four prior lines of therapy, and a third had already received AbbVie's Elahere, the approved folate-receptor-alpha drug in this setting. Rina-S showed activity regardless of folate-receptor-alpha expression level, which could widen its addressable population relative to Elahere. Serious adverse events occurred in about a third of patients and 5.5% discontinued for adverse events. Barclays said the results "strengthen the case for Rina-S ahead of Phase 3 data" and compare favorably with Elahere, though that is a cross-trial comparison between single-arm studies.

GMAB shares rose 3.54% on Monday, the first trading session after the weekend release, after gaining more than 4% in early trading. The data also support Genmab's $1.8 billion acquisition of ProfoundBio, which brought Rina-S into the company. Rina-S is already in four Phase 3 trials, including RAINFOL-02 in platinum-resistant ovarian cancer and RAINFOL-03 in endometrial cancer. What to watch: timing of the first Phase 3 readout, whether the response rate holds in a randomized setting, and how regulators weigh the activity in low and non-expressing tumors.