On March 17, 2025 Genmab A/S (Nasdaq: GMAB) reported updated data from cohort B1 of the Phase 1/2 RAINFOL-01 study of rinatabart sesutecan (Rina-S), an investigational folate receptor-alpha (FRα)-targeted, TOPO1 antibody-drug conjugate (ADC) that showed Rina-S 120 mg/m2 every 3 weeks (Q3W) resulted in a confirmed objective response rate (ORR) of 55.6% (95% CI: 30.8-78.5) in heavily pre-treated ovarian cancer (OC) patients regardless of FRα expression levels (Press release, Genmab, MAR 17, 2025, View Source [SID1234651181]). 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.

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"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 1/2 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 RAINFOLTM -01 Trial
RAINFOL-01 (NCT05579366) is an open-label, multicenter Phase 1/2 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 (ESMO) (Free ESMO Whitepaper) Congress 2024 (ESMO) (Free ESMO Whitepaper).

About Ovarian Cancer
Ovarian cancer is a major global health issue, with over 320,000 new cases diagnosed annually worldwide.i It ranks as the eighth most common cancer and the eighth leading cause of cancer-related deaths among women globally.ii The disease is often diagnosed at an advanced stage due to its subtle and non-specific symptoms, such as abdominal bloating, pelvic pain and difficulty eating.iii Standard of care for platinum resistant ovarian cancer typically involves single agent chemotherapy (pegylated liposomal doxorubicin (PLD), topotecan, gemcitabine or paclitaxel).iv Approximately 70-90% of women with advanced-stage ovarian cancer worldwide experience a recurrence after initial treatment.v Ovarian cancer has a low five-year survival rate, which varies significantly by region, but generally hovers around 30-50%.vi,vii

About Rinatabart Sesutecan (Rina-S; GEN1184)
Rinatabart sesutecan (Rina-S; GEN1184) is a FRα-targeted, TOPO1 ADC, currently being evaluated for the potential treatment of ovarian cancer and other FRα-expressing cancers. A Phase 3 trial (RAINFOL-02, NCT06619236) evaluating Rina-S in patients with platinum resistant ovarian cancer compared to treatment of investigator’s choice is ongoing. In January 2024, the U.S. Food and Drug Administration granted Fast Track designation to Rina-S for the treatment of patients with FRα-expressing high-grade serous or endometrioid platinum-resistant ovarian cancer.

Please visit www.clinicaltrials.gov for more information.