Moderna and Merck mRNA vaccine cuts melanoma recurrence in late-stage trial

Moderna and Merck announced on Wednesday that their personalised mRNA cancer vaccine, Intismeran, reduced the risk of recurrence and distant spread of melanoma in a late-stage clinical trial. The companies said the treatment met both primary endpoints when used alongside the immunotherapy drug Keytruda.

The trial enrolled patients with high-risk melanoma who had undergone surgery to remove their tumours. Intismeran is designed for each patient by sequencing the tumour and encoding up to 34 neoantigens into a single mRNA construct, aiming to train the immune system to recognise and attack residual cancer cells.

Interim results were released in a press statement; detailed efficacy data, safety profiles and statistical analyses have not been made public. The companies said they plan to present full results at an upcoming medical meeting and are already in discussions with regulatory authorities.

Moderna President Stephen Hoge said that, if approved, thousands of patients in the United States with high-risk melanoma could have access to the vaccine as early as next year. The National Cancer Institute estimated more than 1.5 million people were living with melanoma in the US in 2023.

Karen Knudsen, CEO of the Parker Institute for Cancer Immunotherapy, described the outcome as an auspicious start that could signal a new phase for treating solid-tumour cancers with mRNA technology. Similar personalised vaccine approaches are being tested in lung, breast and pancreatic cancers.

The announcement marks the first positive Phase 3 result for an mRNA-based cancer vaccine. Previous evidence came from preclinical models and smaller clinical studies. Independent experts have cautioned that peer-reviewed publication and longer follow-up are needed to confirm the magnitude and durability of the benefit.

Moderna shares rose sharply after the news. The companies did not disclose the trial's hazard ratios, median follow-up time, or rates of adverse events in the interim release.

Regulatory timelines and pricing have not been announced. The treatment's personalised manufacturing process, which requires tumour sequencing and custom production for each patient, may affect accessibility and cost if the vaccine reaches the market.