(AP) – Moderna shares more than doubled Wednesday after it announced initial results from a study of an experimental cancer treatment that would be the first of its kind if approved by regulators.

Moderna and Merck are developing a treatment using an mRNA-based cancer vaccine called intismeran that is designed to be tailored to individual patients based on unique mutations within their tumors. In current studies, they are pairing it with Keytruda, a immunotherapy drug made by Merck.

The study compared using intismeran and Keytruda together on melanoma patients against using Keytruda alone. The companies said patients who received the combination lived longer without cancer returning or metastasizing than patients who got Keytruda alone.

The companies did not say how long patients survived without cancer returning or whether patients lived longer overall. They said they plan to present the study results at an upcoming international medical meeting.

Moderna shares rose more than 120% to $140.12 a share. Merck shares rose about 11%.