Phase 2 trial of tremelimumab in patients with metastatic urothelial cancer previously treated with programmed death 1/programmed death ligand 1 blockade

IntroductionProgrammed death 1 (PD-1)/programmed death ligand 1 (PD-L1) blockade has changed the landscape of treatment for metastatic urothelial cancer, but single-agent cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) blockade in metastatic urothelial cancer has been underexplored. A prior phase 2 trial of tremelimumab in PD-1/PD-L1-blockade naive patients with metastatic urothelial cancer revealed activity comparable to that observed with PD-1/PD-L1 blockade raising the hypothesis that these classes of immune checkpoint inhibitors might be non-cross-resistant.MethodsThe current phase 2 trial treated patients with PD-1/PD-L1 blockade-resistant metastatic urothelial cancer with single-agent tremelimumab (750 mg intravenously every 28 days for up to 7 cycles). The primary end point was objective response rate.ResultsTwenty-six patients were enrolled and 24 patients were evaluable for response. The objective response rate was 8.3%, composed of a total of two partial responses that lasted 10.9 and 24.0 months. Stable disease was observed in another 20.8% of patients, with a median duration of stable disease of 5.4 months. Diarrhea occurred in 15 patients (58%), elevated hepatic transaminases occurred in seven patients (27%), and adrenal insufficiency occurred in two patients (8%); one patient died after experiencing immune-related hepatitis.ConclusionsHigh dose CTLA-4 blockade in patients with PD-1/PD-L1-resistant metastatic urothelial cancer has modest activity and is associated with treatment-related toxicity similar to prior reports. The current phase 2 trial sought to test that cytotoxic T-lymphocyte-associated protein 4 blockade demonstrates anticancer activity in patients with metastatic urothelial cancer and is non-cross-resistant with programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) blockade. Tremelimumab in patients with PD-1/PD-L1-resistant metastatic urothelial cancer demonstrated modest activity and is associated with treatment-related toxicity similar to prior reports.