Phase II study of the safety and efficacy of the anti-PD-1 antibody balstilimab in patients with recurrent and/or metastatic cervical cancer

Objective: This phase II clinical trial evaluated the safety and antitumor activity of balstilimab, an anti-PD-1 antibody, in patients with previously-treated, recurrent/metastatic cervical cancer. Methods: Eligible patients were 18 years or older with recurrent and/or metastatic cervical cancer and who had relapsed after a prior platinum-based treatment regimen for advanced disease. Balstilimab was administered intravenously at 3 mg/kg once every two weeks, for up to 24 months. The primary endpoint was objective response rate (ORR, RECIST v1.1) as assessed by an independent review committee. Results: At data cutoff, 161 women (median age, 53 years [range 25–81]) were enrolled and treated with balstilimab. Of these, 140 had measurable disease at baseline and one prior line of platinum-based therapy in the metastatic, persistent, or recurrent setting; these patients were included in the efficacy analyses. The ORR was 15% (95% CI, 10.0%–21.8%) and included 5 patients with a complete response and 16 with a partial response. The median duration of response was 15.4 months. In patients with PD-L1-positive tumors the ORR was 20%, however patients with PD-L1-negative tumors also responded to balstilimab (ORR, 7.9%). Responses were not restricted to tumors of squamous cell histology, and an ORR of 12.5% was seen in the subset of patients with cervical adenocarcinoma. The disease control rate was 49.3% (95% CI, 41.1%–57.5%). Immune-mediated enterocolitis (3.1%) and diarrhea (1.9%) were the most common grade 3 or higher treatment-related adverse events. Conclusion: Balstilimab demonstrated meaningful and durable clinical activity, with manageable safety, in patients with previously-treated, recurrent/metastatic cervical cancer.