Nivolumab and Ipilimumab Combination Treatment in Advanced Ovarian and Endometrial Clear Cell Cancers

Importance Gynecological clear cell cancers (CCCs) are aggressive malignant neoplasms with low response rate to chemotherapy. The treatment of patients with metastatic disease remains an area of significant unmet need. Objective To evaluate the efficacy of combined anti–programmed cell death 1 protein (PD-1)/cytotoxic T-lymphocyte–associated protein 4 (CTLA-4) blockade using nivolumab and ipilimumab in advanced gynecological CCCs. Design, Setting, and Participants The MoST-CIRCUIT prospective multicenter phase 2 nonrandomized clinical trial included patients with advanced selected rare cancers. Patients with advanced clear cell ovarian cancer (CCOC)/clear cell endometrial cancer (CCEC) with a maximum of 1 course of prior systemic therapy were enrolled from August 2021 to February 2024 across 17 Australian and New Zealand sites. Interventions Patients received nivolumab, 3 mg/kg, and ipilimumab, 1 mg/kg, every 3 weeks for 4 doses followed by nivolumab, 480 mg, every 4 weeks for 96 weeks until disease progression or the development of unacceptable toxic effects. Main Outcomes and Measures Coprimary end points were objective response rate (ORR) and 6-month progression-free survival (PFS) as assessed by RECIST version 1.1 criteria, with the secondary end points being median overall survival, PFS, and treatment-related toxic effects. Results Of 28 included patients, the median (range) age was 55 (34-77) years. A total of 24 had CCOC and 4 had CCEC; 19 (68%) had a previous course of therapy. Overall ORR was 54% (95% CI, 35-71), with 3 (12%) with complete response and 12 (42%) with partial response; the ORR was 55% (95% CI, 35-73) in the CCOC group and 50% (95% CI, 9-91) in the CCEC group. The median duration of response has not been reached, with all responses ongoing. The 6-month PFS was 58% (95% CI, 39-74), and the median overall survival has not been reached. A total of 9 patients (35%) experienced a grade 3 or 4 immune-related adverse event, and a grade 5 myocarditis occurred in 1 patient. Conclusions and Relevance In this nonrandomized clinical trial, immunotherapy using combined anti–PD-1/CTLA-4 blockade demonstrated encouraging activity with a high rate of durable responses in patients with advanced gynecological CCCs. This regimen should be further investigated in this patient population with unmet medical need. Trial Registration ClinicalTrials.gov Identifier: NCT04969887