Moderna Surges 177% After mRNA Melanoma Vaccine Succeeds in First-Ever Phase 3 Cancer Vaccine Trial

Moderna shares closed up 177% on Wednesday, their best single day on record, adding roughly $44 billion in market cap after the company and partner Merck announced positive topline results from the Phase 3 INTerpath-001 trial of intismeran autogene, a personalized mRNA-based individualized neoantigen therapy combined with Merck's immunotherapy Keytruda. The trial, which enrolled more than 1,100 patients with completely resected Stage IIB-IV melanoma, met both primary endpoints, significantly extending recurrence-free survival and distant metastasis-free survival compared with Keytruda alone. It marks the first positive Phase 3 result for any mRNA-based personalized cancer vaccine.

The trial was halted at its first interim analysis after the data crossed the efficacy threshold. Moderna CEO Stephane Bancel is targeting regulatory approval by 2027, and William Blair upgraded the stock to Outperform following the announcement. Merck shares closed up roughly 12% and hit all-time highs.

The news also triggered a broad biopharma rally, with Eli Lilly up 4%, Amgen up 3.7%, AbbVie up 2.6%, and Johnson and Johnson up 1%. Tempus AI and Personalis also gained on the view that their tumor-sequencing capabilities are central to designing this class of neoantigen vaccines. Reuters reported the breakthrough is expected to open a new avenue of treatment that doctors hope will extend to many tumor types beyond melanoma.