Cabozantinib plus Pembrolizumab as First-line Therapy for Cisplatin-ineligible Advanced Urothelial Carcinoma: The PemCab Trial.

Background and objective: Pembrolizumab monotherapy is approved for patients with platinum-ineligible metastatic urothelial carcinoma (mUC). Cabozantinib is a multireceptor tyrosine kinase inhibitor with activity against MET and VEGFR2 and is approved as monotherapy or in combination with a PD-1 inhibitor for other malignancies. The objective was to determine the safety and efficacy of pembrolizumab + cabozantinib as first-line treatment for patients with mUC.

Methods: In this open-label, single-arm, multicenter, phase 2 study, patients received pembrolizumab 200 mg every 3 wk + cabozantinib 40 mg daily. Key inclusion criteria were locally advanced UC or mUC, Eastern Cooperative Oncology Group performance status 0-2, ineligible for or refused cisplatin, and no prior PD-1/L1 inhibitor. The primary endpoint was the objective response rate (ORR). Secondary endpoints included progression-free survival (PFS) and overall survival (OS). According to the statistical plan, in a cohort of 35 evaluable participants, the lower bound of the 95% confidence interval (CI) would extend no more than 26% from the ORR observed, and in a scenario with ≥17 objective responses, the CI would exclude 32%.

Key findings and limitations: Responses were observed in 16 of 35 evaluable patients, with an ORR of 46% (95% CI 31-62%). Median PFS and OS were 8 mo (95% CI 5-13) and 17 mo (95% CI 13-not reached), respectively. The most common treatment-emergent adverse events (any grade) were diarrhea (58%), fatigue (56%), pruritus (39%), nausea (36%), palmar-plantar erythrodysesthesia (36%), and a decrease in appetite (33%).

Conclusions and clinical implications: This phase 2 trial of pembrolizumab + cabozantinib demonstrated a manageable toxicity profile and promising efficacy as a first-line therapy combination for cisplatin-ineligible patients with mUC.