Moderna-Merck mRNA-4157 Plus Pembrolizumab Cuts Melanoma Recurrence Risk in Phase 2 Update

The leaked ESMO presentation revealed updated efficacy from the randomized phase 2b trial of mRNA-4157 (V940) with pembrolizumab. Investigators measured relapse-free survival as the primary endpoint in 157 patients after complete resection. Absolute risk reduction reached 20 percentage points at two years, with distant-metastasis-free survival also favoring the combination arm. The mRNA platform encodes up to 34 neoantigens identified from each patient’s tumor, aiming to broaden T-cell responses beyond PD-1 blockade alone.

This builds on the 2023 NEJM publication of the same trial’s initial readout and aligns with patterns seen in other neoantigen vaccines where early relapse-free survival gains have not always translated to overall survival in larger studies. Regulatory strategy now hinges on the ongoing phase 3 trial (NCT05920941) that began enrolling in 2023; Merck and Moderna have indicated an interim analysis could occur in 2026 if event rates hold.

Context missed by initial coverage includes manufacturing scale-up challenges for individualized vaccines and competition from off-the-shelf approaches such as BioNTech’s BNT111. Payer reimbursement models remain untested for a therapy requiring tumor sequencing, neoantigen prediction, and on-demand manufacturing within weeks.

Next steps require the phase 3 trial to confirm the 44% relative reduction with at least 500 patients and mature overall-survival data before any accelerated approval pathway is considered.