A phase II study of retifanlimab, a humanized anti-PD-1 monoclonal antibody, in patients with solid tumors (POD1UM-203)

Background: POD1UM-203, an open-label, multicenter, phase II study, evaluated retifanlimab, a humanized monoclonal antibody targeting programmed cell death protein-1 (PD-1) in patients with selected solid tumors where immune checkpoint inhibitor therapies have previously shown efficacy. Patients and methods: Eligible patients (≥18 years) had measurable disease and included unresectable or metastatic melanoma, treatment-naive metastatic non-small-cell lung cancer (NSCLC) with high programmed death-ligand 1 (PD-L1) expression (tumor proportion score ≥50%), cisplatin-ineligible locally advanced/metastatic urothelial carcinoma (UC) with PD-L1 expression (combined positive score ≥10%), or treatment-naive locally advanced/metastatic clear-cell renal cell carcinoma (RCC). Retifanlimab 500 mg was administered intravenously every 4 weeks as a 30-min infusion. The primary endpoint was investigator-assessed overall response rate. Results: Overall, 121 patients (35 melanoma, 23 NSCLC, 29 UC, 34 RCC) were enrolled and treated. The overall response rate [95% confidence interval (CI)] was 40.0% (23.9-57.9) in the melanoma cohort, 34.8% (16.4-57.3) in the NSCLC cohort, 37.9% (20.7-57.7) in the UC cohort, and 23.5% (10.7-41.2) in the RCC cohort. Median duration of response was 11.5 months (95% CI 2.2-not reached) in the UC cohort, and was not reached in the other cohorts. Retifanlimab safety was consistent with previous experience for PD-(L)1 inhibitors. Conclusions: Retifanlimab demonstrated durable antitumor activity in patients with melanoma, NSCLC, UC, or RCC. The efficacy and safety of retifanlimab were as expected for a PD-(L)1 inhibitor. These data support further study of retifanlimab in solid tumors.