New data give Agenus' combo drug another boost, this time in ovarian cancer

A year and a half after Agenus withdrew its accelerated approval request for cervical cancer drug balstilimab, the biotech has provided new combo data in ovarian cancer.

In an ongoing phase 1b study, Agenus found a 33% overall response rate in 24 patients with platinum-resistant or refractory ovarian cancer treated with CTLA-4 antibody botensilimab and PD-1 antibody balstilimab, according to data shared today at the Society of Gynecologic Oncology 2023 Annual Meeting on Women’s Cancer in Tampa, Florida.

Other PD-(L)1 and CTLA-4 combinations in comparable patient populations have reported response rates between 3% and 10%, the company said.

The study is testing botensilimab alone and in combination with balstilimab among patients with multiple types of solid tumors. In January, Agenus shared combo data showing an overall response rate of 23% and disease control rate of 76% for 70 patients with refractory metastatic microsatellite stable colorectal cancer (MSS-CRC).

In the newest data drop, 24 patients with ovarian cancer received either 1 or 2 milligrams of botensilimab every six weeks and 3 milligrams of balstilimab every two weeks. The majority of enrolled patients—79% percent—had high-grade serous ovarian cancer, a form of disease generally thought to be unresponsive to immunotherapy. Patients were heavily pretreated, having received a median of four previous lines of therapy.

“The combination of botensilimab and balstilimab in platinum-resistant ovarian cancer holds promise for a substantial improvement in efficacy compared to existing therapies, which typically only yield single-digit response rates,” Bruno Bockorny, M.D., of Harvard Medical School and Beth Israel Deaconess Medical Center and principal investigator for the trial, said in a March 27 release. “The remarkable efficacy and manageable tolerability profile of this combination suggest a transformative potential for ovarian cancer patients.”

Meanwhile, the Massachusetts-based biotech is also conducting phase 2 trials for the combo in MSS-CRC, melanoma and pancreatic cancers. The company plans to launch a phase 3 study among MSS-CRC patients by the end of this year.  

The data could represent changing of the tides for balstilimab after Agenus pulled its application for an accelerated approval back in October 2021. The move came after Merck’s blockbuster Keytruda received a full FDA approval in the same indication.

The biotech said that the filing was voluntarily withdrawn, but, according to a source with knowledge of the decision, the FDA recommended that the request be retracted.

Even though Agenus dropped its solo balstilimab trial, the combo studies have continued. The company is also testing balstilimab alongside its anti-CTLA-4 zalifrelimab in a phase 2 cervical cancer trial.