Retifanlimab (PD-1) MAIC Suggests Lower Progression Risk vs Avelumab (PD-L1) in Metastatic MCC

Retifanlimab is an anti–PD-1 monoclonal antibody, while avelumab is an anti–PD-L1 antibody; this unanchored matching-adjusted indirect comparison (MAIC) contrasted individual patient data from Phase 2 POD1UM-201 (NCT03599713; data cutoff July 2024) against published aggregate data from Phase 2 JAVELIN Merkel 200 part B (NCT02155647) in metastatic Merkel cell carcinoma (effective sample size after weighting for retifanlimab ≈42, ~47% of the original). After adjustment for key prognostic variables, retifanlimab numerically favored avelumab for OS (HR 0.80; 95% CI 0.49–1.30) and ORR (OR 1.87; 95% CI 0.90–3.91) and showed a lower modeled risk of progression (HR 0.59; 95% CI 0.40–0.88), largely driven by early separation in the first ~2 months—directionally supportive given that 1L PD-(L)1 monotherapy benchmarks in MCC tend to land around ~50–60% ORR in prospective Phase 2 datasets (e.g., pembrolizumab first-line ORR ~58% in NCCN-cited KEYNOTE-017 data), but this analysis remains inherently fragile because it is unanchored and cross-trial.