mRNA-4157 plus pembrolizumab reduced recurrence or death risk 42% at two years in phase 3 resected melanoma trial
Phase 3 data confirm a statistically significant but attenuated benefit for personalized mRNA-4157 added to pembrolizumab in resected melanoma. The 42% risk reduction at two years is the first such result versus PD-1 alone, yet falls short of phase 2 magnitude. Manufacturing logistics and longer-term survival data will determine whether the approach advances to approval and broader use.
The randomized phase 3 trial enrolled patients with resected stage III/IV melanoma. Investigators sequenced each tumor, selected up to 34 neoantigens, and manufactured individualized mRNA-4157. Participants received the vaccine plus pembrolizumab or pembrolizumab plus placebo after surgery.
Two-year recurrence-free survival reached 82% in the combination arm and 70% in the control arm; distant-metastasis-free survival reached 88.5% versus 80%. The 42% and 38% risk reductions were smaller than the 49% and 59% reductions recorded in the preceding phase 2 study at five years.
The result establishes the first phase 3 evidence that a neoantigen mRNA vaccine improves outcomes over PD-1 monotherapy in the adjuvant setting. Manufacturing turnaround, neoantigen selection criteria, and durability of response remain the principal operational variables for scale-up.
Merck and Moderna have stated that overall-survival and additional tumor-type cohorts will read out in 2027-2028; regulatory filing is planned only after those data mature.
FDA: Oncology Drug Advisory Committee vote on mRNA-4157 by Q2 2028 if three-year OS hazard ratio <0.75
Sources (2)
- [1]Merck Research Laboratories Phase 3 Announcement(https://www.merck.com/news/moderna-merck-mrna-4157-phase3-melanoma-2026/)
- [2]ClinicalTrials.gov NCT03897881 Primary Completion Update(https://clinicaltrials.gov/study/NCT03897881)