Moderna-Merck melanoma vaccine cuts relapse risk by 42% but shares dip
A combined vaccine and Keytruda regimen reduced the relative risk of disease recurrence or death by 42% in advanced melanoma, meeting expectations, while the companies' stocks fell after the announcement.
Moderna and Merck reported that their personalized cancer vaccine, intismeran autogene, when added to Merck's immunotherapy Keytruda, lowered the relative risk of disease recurrence or death by 42% compared with Keytruda alone in an adjuvant trial of resected advanced melanoma. The data, presented ahead of the European Society for Medical Oncology meeting, met Wall Street forecasts of a 40%-50% risk reduction.
"The findings represent a highly compelling efficacy profile and substantially clear the physician-defined bar for a practice-changing dataset in adjuvant melanoma," wrote TD Cowen analyst Tyler Van Buren.
"While approval seems likely, commercial success is far less certain," noted RBC Capital Markets analyst Trung Huynh.
The trial, which followed patients for a median of 24.6 months, also showed a 38% reduction in the risk of distant metastasis. Safety outcomes were comparable between groups, although fever and injection-site pain were more common with the vaccine; 7% of vaccine recipients discontinued treatment due to adverse events versus 5% in the control arm.
Despite the positive efficacy, Moderna's shares dropped nearly 25% and Merck's fell about 1% in immediate trading, a reaction analysts described as a typical "sell-the-news" move. Researchers highlighted the result as a potential advance for a cancer type where one-third of patients experience relapse or death within five years despite existing therapies.
The vaccine uses individualized neoantigen therapy, sequencing each patient's tumor to identify up to 34 unique protein markers and delivering mRNA that prompts T-cell responses. Moderna and Merck plan further trials in lung, bladder and kidney cancers, with interim kidney-cancer data expected later this year or early 2027.