How Does Rina-S Work in Patients With Pretreated Endometrial Cancer?

Rinatabart sesutecan (Rina-S) demonstrated a 100% disease control rate at the 100-mg/m² dose for patients with heavily pretreated endometrial cancer, according to Elizabeth Lee, MD.

In an interview with Oncology Nursing News, Lee, who works in gynecologic oncology at Dana-Farber Cancer Institute in Boston, Massachusetts, discussed findings from the phase 1/2 RAINFOL-01 trial (NCT05579366). As an investigator for the trial, she noted that the study included patients who had received a median of 3 prior lines of therapy, with some having received up to 8.

Results presented at the 2025 ESMO Congress focused on a dose-expansion cohort where patients were randomized to receive either 100 mg/m² or 120 mg/m² of Rina-S. While the 120-mg/m² dose showed a confirmed objective response rate (ORR) of approximately 80%, the 100-mg/m² dose achieved a 50% ORR and 100% disease control rate. Based on the balance of efficacy and toxicities, the 100-mg/m² dose was selected for ongoing investigation in RAINFOL-01 and an upcoming randomized phase 3 trial. These responses occurred regardless of FRα expression, marking a significant development for this patient population.

Transcript

What was presented by [Noelle Cloven, MD] at the 2025 ESMO Congress looked at a specific group of women with endometrial cancer who were enrolled in RAINFOL-01 in the dose-expansion portion. Within this cohort of patients who were enrolled, they were randomized to receive 2 different dose levels of Rina-S. This was still in the portion of the trial where we were trying to find the optimal dosing of Rina-S, balancing both the benefits as well as the toxicities that we see with Rina-S.

Sixty-four patients with endometrial cancer were enrolled, and they were required to have had prior chemotherapy as well as immunotherapy. In the case of these patients who were heavily pretreated, they had received a median of 3 prior lines of therapy, but it ranged all the way up to patients who have received 7 to 8 prior lines of therapy, which is quite remarkable. There was a substantial portion of patients who received pelvic radiotherapy, or other forms of radiation therapy as well.

The responses that we’re seeing were very encouraging, and this did seem to split out a bit between the group receiving 100 mg/m² vs those receiving 120 mg/m². In those patients who had received 100 mg/m², the confirmed ORR was 50%. This included 2 patients who had confirmed complete responses.

Overall, looking at disease control rate—the patients had complete response, a partial response, or durable, stable disease—this was 100% of the patients receiving 100 mg/m². This is intriguing and encouraging for patients with endometrial cancer. Those receiving 120 mg/m² did similarly, with a very high confirmed ORR around 80%.

Looking at benefit, the confirmed ORR, which were regardless of FRa expression, and looking at the toxicities that we see, the balance of all of this was at the 100-mg/m² dose, which was chosen to move forward in a larger group of patients that are still enrolling to the RAINFOL-01 study. This is a part of RAINFOL-01 is still enrolling patients with endometrial cancer, as well as being brought over into further investigation and a randomized phase 3 trial for patients with endometrial cancer.

This transcript has been edited for clarity and conciseness.