Retifanlimab Versus Avelumab for Metastatic Merkel Cell Carcinoma: Comparative Analysis Insights

A team of researchers from Italy conducted the study and published their findings in Advances in Therapy.

Both retifanlimab and avelumab are classified as monoclonal immune checkpoint inhibitor (ICI) antibodies, and investigators highlighted that both medications are approved for the treatment of metastatic or locally advanced recurrent MCC.

They explained that the goal of their research was to assess clinical outcomes of both ICIs via a MAIC analysis of data from the phase 2 POD1UM-201 trial and part B of the phase 2 JAVELIN Merkel 200 trial.

Patient data from each trial were used in the analysis, with data from POD1UM-201 informing the retifanlimab group and aggregate data from JAVELIN Merkel 200 informing the avelumab treatment group. Investigators also underscored that the data cutoff of POD1UM-201 was July 2024.

Furthermore, prognostic factors, such as Eastern Cooperative Oncology Group (ECOG) performance status, PD-L1 status, disease characteristics, and age were identified from published studies and used to account for “adjustment in the base case.”

Investigators also performed “scenario analyses,” which included “additional covariates.” They reported that an “unanchored” MAIC was performed for the outcomes of overall response rate (ORR), progression-free survival (PFS), and overall survival (OS).

Forty-two patients were included in the retifanlimab group “after weighing characteristics.” The results demonstrated that the weighted hazard ratio (HR) “numerically favored retifanlimab versus avelumab for OS (0.800 [0.492, 1.303]) and was statistically significant for PFS (0.590 [0.396, 0.881]).”

Investigators emphasized that the results for PFS were primarily due to “separation during the first 2 months of treatment.” The ORR findings also revealed that the weighted odds ratio (OR) was superior for retifanlimab (ORR 1.871 [0.896, 3.908]) versus avelumab and that scenario analyses “generally confirmed base case analyses.”

In reflecting on the statistically significant difference in PFS, and the numerical differences in OS and ORR, across study groups, investigators explained that the findings reiterated “clinical evidence supporting retifanlimab for the treatment of metastatic MCC.

“This indirect comparison of two separate trials suggests that patients treated with retifanlimab lived significantly longer with no disease progression versus avelumab,” they concluded. “These findings are subject to residual confounding and should be interpreted with caution.”