Dr Lee on the Antitumor Activity of Rinatabart Sesutecan in FRα+ Platinum-Resistant Ovarian Cancer

“There were…a total of 4 CRs, 2 of which are pending confirmation. With the longer duration of follow-up… the median DOR has still not yet been reached. We’re very, very encouraged by the findings so far.”

Elizabeth Lee, MD, a gynecologic oncologist and the gynecologic oncology program's liaison to the Center for Cancer Therapeutics Innovation at Dana-Farber Cancer Institute, discusses results from the dose-expansion cohort B1 of the phase 2 RAINFOLTM-01 trial (NCT05579366) evaluating the novel folate receptor alpha (FRα)–targeted antibody-drug conjugate rinatabart sesutecan (Rina-S; PRO1184) for the treatment of patients with FRα-expressing high-grade serous or endometrioid platinum-resistant ovarian cancer.

Updated results presented during the 2025 SGO Annual Meeting on Women’s Cancer demonstrated clinical activity and tolerability with Rina-S across 2 dose cohorts in patients with advanced gynecologic malignancies, Lee began. At a median follow-up of 46.4 months (range, 6.6–65.3) for the 100 mg/m² cohort (n = 22) and 48.1 months (range, 10.9–65.9) for the 120 mg/m² cohort (n = 20), the confirmed objective response rates (ORRs) were 22.7% (95% CI, 7.8%–45.4%) and 55.6% (95% CI, 30.8%–78.5%), respectively. Across both cohorts, 4 CRs were observed, 2 of which were pending confirmation at the time of analysis, Lee noted. The disease control rates were 86.4% (95% CI, 65.1%–97.1%) and 88.9% (95% CI, 65.3%–98.6%) in the respective cohorts.

Notably, Rina-administered at 120 mg/m² elicited early, deep, and durable responses at the 120 mg/m² dose regardless of FRα expression levels. The median duration of response (DOR) was not reached (NR; 95% CI, 16.3 months–NR) in the 100 mg/m² group and NR (95% CI, 40.14 months–NR) in the 120 mg/m² group.

Treatment was generally well tolerated, with manageable treatment-emergent adverse effects and no new safety signals. Across cohorts, 4 CRs were observed, 2 of which were pending confirmation at the time of analysis. The prolonged follow-up and sustained DOR support continued investigation of Rina-S in this setting, Lee concluded.