Moderna and Merck are reporting sustained long-term gains from their experimental cancer vaccine approach, with new five-year follow-up data showing continued protection against melanoma recurrence in a closely watched Phase 2b trial.

 

The companies said detailed results from the KEYNOTE-942/mRNA-4157-P201 study—evaluating intismeran autogene (mRNA-4157/V940) combined with KEYTRUDA (pembrolizumab) in patients with high-risk stage III/IV melanoma after surgery—will be presented at the 2026 ASCO Annual Meeting.

 

With a median follow-up of 60.3 months, the combination therapy continued to outperform KEYTRUDA alone on key measures of disease control. The treatment reduced the risk of recurrence or death by 49% and cut the risk of distant metastasis or death by 59%.

 

An exploratory overall survival signal also leaned in favor of the combination, though the companies noted the result remains preliminary.

 

“With each year of continued follow-up of our Phase 2b study, we gain a more complete picture of the durability of intismeran autogene in combination with KEYTRUDA. 

 

"Now, with a median follow-up of five years, the sustained recurrence-free survival and distant metastasis-free survival demonstrate the potential long-term benefit of intismeran autogene in combination with KEYTRUDA in melanoma patients at high risk of recurrence,” said David Berman, Chief Development Officer of Moderna. 

 

“These findings add to our confidence in the potentially transformative impact of this novel, personalized approach to cancer care made possible by mRNA technology.”

 

Merck echoed the optimism, highlighting the durability of benefit in a population at particularly high risk after surgery.

 

“The risk of disease recurrence remains high for patients with stage III/IV melanoma following surgery, so we are encouraged by these long-term findings showing that intismeran autogene in combination with KEYTRUDA provided sustained and durable reductions in the risk of recurrence,” said Majorie Green, Senior Vice President and Head of Oncology, Global Clinical Development, Merck Research Laboratories. 

 

“These data further reinforce the potential of this individualized approach to address critical gaps in the adjuvant setting and reflect our continued commitment to advancing innovative therapies for patients.”

 

Safety findings were consistent with earlier reports, with no new signals emerging over extended follow-up. The most common side effects linked to intismeran autogene included fatigue (59.6%), injection site pain (59.6%), and chills (51.0%). Most events were mild to moderate, with Grade 1 (31.7%) and Grade 2 (51.9%) reactions predominating. Grade 3 fatigue was observed in 4.8% of patients, and no Grade 4 or 5 events were reported.

 

Immune-related adverse events occurred at similar rates in both arms—45.2% in the combination group and 44% with KEYTRUDA alone—suggesting no added immune toxicity from the personalized mRNA therapy.

 

The latest results reinforce a consistent pattern of reduced recurrence and metastasis risk over time and strengthening the case for long-term benefit from the combination approach in high-risk melanoma patients.