Moderna stock drops 25% after leak of early data on Merck‑partnered cancer vaccine

Moderna's shares fell up to 25% on Thursday after a leak of early data on its Merck‑partnered cancer vaccine. The full Phase 3 results released later that day showed positive outcomes that met Wall Street forecasts. The personalized shot, called intismeran autogene, was tested together with Merck's immunotherapy Keytruda. In melanoma patients, the combination cut the chance of disease returning or death by 42% compared with Keytruda alone. It also lowered the chance of cancer spreading to distant sites or death by 38% versus the immunotherapy by itself. The detailed findings are scheduled for presentation at the European Society for Medical Oncology meeting this weekend. Investors view the vaccine as a possible breakthrough that could be adapted to other cancers, offering Moderna a new revenue stream beyond its Covid‑19, flu and RSV shots. The high hopes for the product have already driven the company's stock up more than 530% year‑to‑date by Thursday afternoon. The market reaction highlights the weight investors place on innovative oncology assets for Moderna's future growth.

Context

Personalized cancer vaccines aim to train the immune system to target a patient’s unique tumor markers. Success in melanoma could encourage similar approaches for other tumor types, potentially expanding Moderna’s role in cancer treatment.