Moderna shares jump after Merck-partnered mRNA melanoma vaccine posts 5-year follow-up data

Moderna’s (MRNA) shares surged about 5.1% in the afternoon session on June 4, extending a run of positive momentum tied to oncology clinical updates, according to Yahoo Finance. The latest catalyst was a set of long-term findings, presented with partner Merck, supporting the durability of a personalized mRNA cancer vaccine used alongside Merck’s Keytruda immunotherapy in patients with high-risk melanoma after surgery.

The companies reported detailed results from a planned five-year follow-up analysis of a Phase 2b randomized study, KEYNOTE-942/mRNA-4157-P201, evaluating intismeran autogene (also known as mRNA-4157 or V940) combined with Keytruda (pembrolizumab) in patients with stage III/IV melanoma following complete resection. At a median follow-up of 60.3 months (range 50.5 to 76.4), the companies said the combination continued to reduce the risk of recurrence or death versus Keytruda alone, with a hazard ratio of 0.51, representing a 49% reduction.

They also highlighted improvement in distant metastasis-free survival, a key secondary endpoint, with a hazard ratio of 0.411, which corresponds to a 59% reduction in the risk of distant metastasis or death compared to Keytruda alone. Overall survival was described as an encouraging exploratory trend, but the reported hazard ratio (0.471) had a wide confidence interval and was based on a small number of events (n=14), a fact that underscores that the data are not yet definitive on survival.

On safety, the release said the regimen’s tolerability profile remained consistent with prior analyses. The most common adverse events attributed to the combination included fatigue (59.6%), injection site pain (59.6%), and chills (51.0%). The companies said most adverse events were Grade 1 or Grade 2, fatigue was the most common Grade 3 event at 4.8%, and there were no Grade 4 to 5 events attributed to the combination. They also reported immune-related adverse event rates of 45.2% for the combination arm versus 44% for Keytruda alone and said the combination did not intensify immune-related adverse events.

For investors, the focus is not just on whether the vaccine works in the first few years, but whether benefit holds up as patients move deeper into long-term follow-up. Intismeran autogene is an investigational mRNA-based individualized neoantigen therapy designed for each patient using the tumor’s unique mutational signature, with the mRNA encoding up to 34 neoantigens. Once administered, the mRNA is translated in the body and processed for immune presentation, aiming to train T-cell responses against the patient’s cancer-specific targets. In the KEYNOTE-942/mRNA-4157-P201 study, the release said 157 patients were randomized 2:1 after surgery, with intismeran dosed at 1 mg every three weeks for nine doses and Keytruda dosed at 200 mg every three weeks up to 18 cycles (about one year).

Still, the data leave open questions that could affect how long the market holds the optimism. While recurrence-free and distant metastasis-free survival benefits were presented with statistical measures, the overall survival announcement was explicitly labeled exploratory and involved limited events, with the confidence interval spanning 1. The companies also did not provide full details in the release on absolute recurrence or survival rates, and Phase 2b results typically require additional study to confirm clinical benefit for regulatory and practice decisions.

Looking ahead, both companies said they are enrolling other studies across tumor types, including Phase 2 randomized trials in resected bladder cancer and additional settings involving resectable NSCLC and metastatic melanoma. For Moderna shareholders, near-term watch items are additional follow-up reporting from ongoing randomized studies, and any new disclosures that clarify whether the durability seen at five years translates into longer-term survival benefit in larger datasets.