Moderna, Merck melanoma vaccine hits Phase 3 goals, shares surge 40%

Moderna and Merck said their personalized mRNA melanoma vaccine met Phase 3 goals, cutting recurrence and distant metastasis versus pembrolizumab (KEYTRUDA) alone in 1,137 patients.

"For many years, the idea of creating an mRNA treatment designed specifically for an individual patient's cancer was aspirational. We are now helping turn that vision into a reality," Stéphane Bancel, chief executive officer of Moderna, said.

The INTerpath-001 trial enrolled patients with completely resected stage IIB-IV melanoma, randomized 2:1 to receive intismeran (1 mg every three weeks for up to nine doses) plus KEYTRUDA (400 mg every six weeks for up to nine cycles) versus KEYTRUDA alone for about one year. The combination met the primary endpoint of recurrence-free survival and the key secondary endpoint of distant metastasis-free survival, with statistically significant and clinically meaningful improvements. Safety was consistent with previously reported studies, with no new signals observed.

Moderna shares rose as much as 40% in premarket trading, while Merck climbed 2%, according to Reuters. The result is the first positive Phase 3 readout for an individualized neoantigen therapy and for an mRNA-based cancer therapy, and the first to show a clinically meaningful improvement over KEYTRUDA alone in the adjuvant melanoma setting. The companies plan to present the data at an upcoming international medical meeting and engage with regulators on filing submissions.

The readout builds on five-year follow-up data from the Phase 2b KEYNOTE-942/mRNA-4157-P201 trial, presented at the 2026 ASCO Annual Meeting, which showed the combination reduced the risk of recurrence or death by 49% (HR=0.51; 95% CI, 0.294-0.887) and the risk of distant metastasis or death by 59% (HR=0.411; 95% CI, 0.200-0.843) versus KEYTRUDA alone.

Intismeran is designed from a patient's tumor sample to identify the unique mutational signature of their cancer. Each therapy consists of synthetic mRNA coding for up to 34 neoantigens, which train the immune system to recognize and attack residual cancer cells. Merck and Moderna have collaborated on the program for more than a decade.

"These first Phase 3 findings for intismeran in combination with KEYTRUDA as adjuvant therapy reinforce the promise of a more personalized approach to cancer treatment," Dr. Dean Y. Li, president of Merck Research Laboratories, said.

The INTerpath program now comprises nine Phase 2 and Phase 3 trials across melanoma, non-small cell lung cancer, bladder cancer and renal cell carcinoma, with additional studies in adjuvant pancreatic ductal adenocarcinoma, perioperative gastric carcinoma and perioperative NSCLC.

The result arrives after a string of positive analyst actions. Daiwa upgraded Merck to Outperform from Neutral on Aug. 17, and Wells Fargo issued a Buy rating the same day, citing pipeline success. Merck's premarket price of $143.52 marked a new 52-week high, above the prior ceiling of $137.98. Moderna shares had already climbed 113% this year through Tuesday's close.

Melanoma is the deadliest form of skin cancer, with about 112,000 new cases and more than 8,500 deaths expected in the U.S. in 2026, and more than 330,000 new cases worldwide in 2022. Most recurrences after surgery are metastatic rather than localized, a pattern that highlights the need for treatments that reduce recurrence risk.

The readout strengthens the commercial case for the intismeran platform across multiple tumor types. Bancel said the product could be approved as early as 2027, depending on regulatory review, with additional Phase 3 studies in non-small cell lung cancer still enrolling.

This article is for informational purposes only and does not constitute investment advice.