Pharmaceutical companies Moderna and Merck announced on Wednesday that their personalised mRNA cancer treatment, intismeran autogene, has succeeded in a large-scale phase 3 clinical trial — the first time an mRNA-based cancer therapy has achieved a positive result at this stage. The trial, known as INTerpath-001, enrolled 1,137 patients with surgically removed stage IIB to IV melanoma — a form of skin cancer known for its high mutation rate and tendency to recur — who had received no prior systemic treatment. Patients were split in a two-to-one ratio: the majority received intismeran autogene in combination with pembrolizumab, the immunotherapy Merck markets as Keytruda, while the remainder received Keytruda alone, the current standard of care. The combination met both its primary endpoint of recurrence-free survival and a secondary endpoint of distant metastasis-free survival.

The treatment works by analysing each patient's removed tumour to identify the specific genetic mutations unique to their cancer. That information is used to design a tailored mRNA therapy — administered in up to nine doses — that instructs the immune system to recognise and attack those cancer cells if they return. Despite being widely described as a vaccine, the therapy is not a preventive measure; it is a treatment for people who have already had cancer. The companies reported no new side effects beyond those already associated with Keytruda. Moderna's president, Stephen Hoge, described reactions similar to those seen with flu or COVID-19 shots.

The companies have not yet released the full numerical data, describing the improvement over Keytruda alone only as