Rina-S ovarian cancer trial shows tumor shrinkage in nearly 46% of patients, with median response duration exceeding one year

When ovarian cancer becomes resistant to platinum-based chemotherapy, the challenge of subsequent treatment is not only to shrink tumors but also to determine how long that effect can last. On October 3, Genmab announced the latest results for its investigational drug rinatabart sesutecan (Rina-S): among 109 treated patients, 45.9% had a confirmed objective response, with a median duration of response of 12.1 months, providing new research findings for this group of patients who had already received multiple lines of treatment.

These data came from Part C of the Phase I/II RAINFOL-01 trial and were presented at the 2026 International Gynecologic Cancer Society (IGCS) Annual Meeting in Montreal, Canada. Reports from RTTNews and Nordic Life Science both noted that patients received Rina-S monotherapy at 120 mg/m² every three weeks. Eligible diseases included platinum-resistant high-grade serous ovarian cancer, primary peritoneal cancer, and fallopian tube cancer; 53% of patients had received three or four lines of treatment.

An objective response means that tumor shrinkage meets predefined criteria. Five patients achieved a complete response, but this does not mean they were cured. Duration of response is calculated among patients who respond; median progression-free survival among all treated patients was 9.5 months. This measures the time before disease progression or death and cannot be interpreted as an extension of overall survival.

Rina-S is an antibody-drug conjugate targeting folate receptor alpha (FRα), linking an antibody that recognizes the target to a drug payload that inhibits topoisomerase I. The company said antitumor activity was also observed in patients with low or undetectable FRα expression and in those previously treated with mirvetuximab. This suggests that there may be room to further explore the populations in which it could be used. However, the announcement did not provide complete sample sizes and response rates for each subgroup, so it cannot yet be concluded that patients with different levels of target expression benefit equally.

Beyond efficacy, the treatment burden also requires careful consideration. According to Genmab's announcement and RTTNews reporting, common treatment-emergent adverse events included nausea, fatigue, anemia, and neutropenia. Approximately one-third of patients experienced serious adverse events, and 5.5% discontinued treatment because of adverse events. The announcement did not classify all serious events as drug-related. The study observed no safety signals for ocular toxicity, peripheral neuropathy, interstitial lung disease, or stomatitis, but this does not mean these risks have been ruled out.

The current evidence still comes from an early-stage, open-label trial. This monotherapy cohort had no randomized control group and cannot directly establish that Rina-S is superior to other treatments. The company announcement and media reports on the same event also cannot replace scrutiny of the complete study data. Genmab is evaluating Rina-S in gynecologic cancers through four Phase III trials, including in platinum-resistant ovarian cancer. The key questions ahead are whether randomized trials can confirm an advantage in disease control and clarify the side effects and changes in quality of life that patients experience as a result.