Details about the trial

The personalized vaccine, called intismeran autogene, treats melanoma, which is the deadliest form of skin cancer and can often recur even after a tumor is surgically removed. According to estimates from the National Cancer Institute, there will be over 100,000 new cases of melanoma this year.

The vaccine is designed to be used in combination with the immunotherapy treatment Keytruda as part of a two-pronged approach against cancer. The vaccine teaches the immune system to recognize mutations unique to a patient's tumor while Keytruda helps release a "brake" that cancer can use to hold back the immune system, allowing immune cells to more effectively target tumors.

In a Phase 2 trial, the combination of intismeran and Keytruda reduced the risk of recurrence or death by almost half over five years in patients with resected melanoma, compared with Keytruda alone. The patients with resected melanoma had previously had a tumor completely removed.

Moderna and Merck then tested the same combination in a Phase 3 trial with 1,137 patients.  The new trial also found that intismeran plus Keytruda reduced the risk of both recurrence and metastasis.

The drugmakers have not yet released the full study results, saying they will be shared at a future medical meeting.

According to the drugmakers, the safety profile of intismeran plus Keytruda "remains consistent " with previous reports, with rates of serious reactions similar to those seen in patients who received Keytruda alone. The most commonly reported side effects related to intismeran were fatigue, pain at the injection site, and chills.

"While we need to await the final results, this early report is certainly promising and builds on the encouraging results that have been observed across smaller studies over the past decade," said Catherine Wu, an oncologist at the Dana-Farber Cancer Institute. "It is highly conceivable that this treatment paradigm will be extendable to other cancers as well."

"This is exciting," said Antoni Ribas, a professor of medicine at the University of California, Los Angeles, referring to the trial results. "That hasn't happened ever, with any cancer vaccine."

"I think this is a really important achievement," said Jedd Wolchok, director of the Meyer Cancer Center at Weill Cornell Medicine. "It tells us what might have been considered science fiction 15 or 20 years ago — that we can produce a personalized vaccine based on sequencing from a tumor from a pathology specimen — could be used to delay progression of melanoma."

"These Phase 3 findings represent a pivotal moment for the field of cancer research," said Moderna CEO Stéphane Bancel. "For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. We are now helping turn that vision into a reality."

Currently, it's not clear when Moderna plans to apply for FDA approval of intismeran, but Moderna president Stephen Hoge said the company would move "as fast as possible."