Moderna Inc. MRNA stock is trading lower after it rallied around 170% on Wednesday on upbeat data from individualized cancer therapy for advanced skin cancer. At a pre-planned interim analysis, Merck & Co Inc.

A personalized mRNA cancer vaccine combined with the immunotherapy Keytruda succeeded in a late-stage trial for the deadly skin cancer melanoma, its makers said Wednesday, potentially opening up a new way of treating the disease.

Investors had been pessimistic about the probability of success for the personalized cancer vaccine intismeran autogene, so the Phase 3 win was a welcome surprise.

Moderna (MRNA) shares are paring back some of their recent gains on Thursday morning – but a Morgan Stanley analyst believes Merck MRK stock remains a buy following blockbuster cancer drug trial results.

Merck (NYSE: MRK), known as MSD outside of the United States and Canada, and Moderna, Inc. (NASDAQ: MRNA) today announced positive topline results from the Phase 3 INTerpath-001 trial evaluating adjuvant treatment with intismeran autogene (intismeran;

People given the experimental vaccine with standard treatment lived longer without their cancer returning, the companies reported this week.

Moderna MRNA stock fell 20%% to $138, compared with Wednesday’s close of $174.38. The decline followed a more than doubling of the shares on August 19 after Moderna and Merck announced positive results from the Phase 3 INTerpath-001 study of their personalized mRNA cancer vaccine, intismeran autogene.

Today, Aug. 19, 2026, Moderna's personalized cancer vaccine met its late-stage goal, with the company and Merck planning an FDA submission.