Updated Data from RAINFOL-01 Study

With a median on-study follow-up of 48 weeks, 1 out of 10 patients experienced disease progression and the median duration of response (mDOR) was not reached (95% CI: 40.14-NR). The data are from the dose expansion cohort of the multi-part study evaluating the safety and efficacy of Rina-S as a single agent in solid tumors that are known to express FRα and were presented at the 2025 Society of Gynecologic Oncology Annual Meeting on Women’s Cancer (SGO) in Seattle, Washington.

“The antitumor activity observed in the dose expansion cohort continues to demonstrate the potential for a much-needed treatment option for patients with PROC, who have historically had poor prognosis. I am hopeful that further exploration of Rina-S will lead to advancements in the treatment landscape.” said Elizabeth Lee, M.D., a medical oncologist in the gynecologic oncology program at Dana-Farber. 

The B1 cohort is a dose expansion study in patients with histologically or cytologically confirmed advanced OC (epithelial ovarian cancer, primary peritoneal cancer or fallopian tube cancer). Rina-S 120 mg/m² Q3W at a median on-study follow-up of 48 weeks showed encouraging antitumor activity; the confirmed ORR was 55.6% (95% CI: 30.8-78.5), the disease control rate (DCR) was 88.9% (95% CI: 65.3-98.6), and the median duration of response (mDOR) was not reached (95% CI: 40.14-NR). In the 18 patients evaluable for response treated with 120 mg/m² Q3W, complete responses were observed in 4 patients (2 confirmed; 2 unconfirmed) and 8 patients experienced confirmed partial responses (44.4%). Most responses with Rina-S 120 mg/m² were observed early (at week 6). Only one patient in the 120 mg/m² treatment arm was not evaluable. In the Rina-S 100 mg/m² Q3W treatment arm (N=22), at a median on study follow-up of 46 weeks, the confirmed ORR was 22.7% (95% CI: 7.8-45.4), the DCR was 86.4% (95% CI: 65.1-97.1), and the mDOR was not reached (95% CI, 16.3-NR). Partial responses were observed in 4 patients (18.2%) and 1 patient (4.5%) experienced a complete response. Rina-S 120 mg/m² has been selected for further evaluation in the RAINFOL-01 and Phase 3 RAINFOL-02 trials for patients with platinum resistant ovarian cancer (PROC).

In this Phase 1/II study, common treatment-emergent adverse events (TEAEs) included anemia, nausea, neutropenia, leukopenia, fatigue, thrombocytopenia, vomiting, diarrhea, alopecia, and hypokalemia. Dose reductions and treatment discontinuations were infrequent and no new safety signals were observed.

“The updated results reinforce the potential of Rina-S and further validate our development approach in advanced ovarian cancer,” said Judith Klimovsky, M.D., Executive Vice President and Chief Development Officer of Genmab. “We are excited to keep moving forward with the ongoing Phase 3 trial, to evaluate the potential of Rina-S as a treatment option for patients facing this challenging disease.”

The safety and efficacy of rinatabart sesutecan has not been established for these investigational uses.

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

Part B of the trial includes the B1 cohort, a dose expansion study in patients with histologically or cytologically confirmed advanced OC (epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer). Patients were randomized 1:1 to 100 mg/m² and 120 mg/m² dose cohorts. Median age was 62.5 and 64.5 years in the 100 mg/m² and 120 mg/m² cohorts, respectively. Study participants were previously treated with a median of 3 prior lines of therapy (range 1-4). Patients received prior treatment with bevacizumab (90.9% in the 100 mg/m² group and 90.0% in the 120 mg/m² group respectively), PARP inhibitors (68.2%; 65%), and mirvetuximab soravtansin (18.2%; 19%). Initial results from Part B of this trial were presented during a mini-oral session at the European Society of Medical Oncology Congress 2024 (ESMO).