Genmab (NASDAQ:GMAB) has released new findings regarding its cancer therapy Rina-S, currently under investigation for endometrial cancer treatment. This development follows encouraging early results in ovarian cancer trials that prompted Genmab’s acquisition of ProfoundBio last year.
Rina-S is an antibody-drug conjugate designed to target the folate receptor alpha (FRα). The latest data comes from a dose expansion group within the phase II RAINFOL-01 trial, involving patients with advanced or treatment-resistant endometrial cancer.
The study evaluated two dosing regimens: 100 mg/m² and 120 mg/m². Surprisingly, the lower dose demonstrated a higher objective response rate (ORR) of 50%, compared to 38% for the higher dose. This contrasts with previous ovarian cancer data showing a clear dose-response relationship favoring the higher dose. Genmab speculates that variations in body mass index (BMI) between the two cohorts may account for this discrepancy.
Given these results, Genmab intends to move forward with the 100 mg/m² dose. The 50% ORR at this lower dose compares favorably against the current standard single-agent chemotherapy, which typically achieves an ORR near 16%.
Analysts at RBC noted that Rina-S’s ORR also stands out positively compared to rival treatments in development, such as Dato-DXd, which reported a 28% ORR in data shared at last year’s ESMO conference.
On the safety front, cytopenia—particularly neutropenia—was a frequent adverse event, with about 77% of patients experiencing grade 3 or higher severity. Most cases were manageable with granulocyte-colony stimulating factor (GCSF). However, two deaths occurred at the higher dose level, including one drug-related sepsis case, likely influencing Genmab’s choice to favor the lower dose for ongoing trials.
Genmab has already initiated a phase III trial of Rina-S as a second-line therapy for platinum-resistant ovarian cancer and plans to start a phase III study in platinum-sensitive ovarian cancer maintenance by year-end. Encouraged by the endometrial cancer data, the company also aims to launch a phase III trial in second-line endometrial cancer treatment within the same timeframe.
Further expansion plans include testing Rina-S in other tumor types, notably non-small cell lung cancer (NSCLC). A phase II study focusing on EGFR-mutated NSCLC is expected to begin before the end of the year.
RBC analysts concluded, “We see Rina-S as having blockbuster potential in both platinum-resistant ovarian cancer and endometrial cancer. These data strengthen that outlook. We project sales reaching $1.3 billion by 2033, with a risk-adjusted success probability of 65%.”