Merck and Moderna say mRNA melanoma vaccine hits goals in late-stage trial

Julie Steenhuysen · Thomson Reuters

· Posted: Aug 19, 2026 11:31 AM EDT | Last Updated: 9 minutes ago

Merck and Moderna said on Wednesday a study of a personalized mRNA vaccine combined with the immunotherapy drug ‌Keytruda reduced skin cancer recurrence and spread compared with Keytruda alone, the first positive late-stage trial results for an mRNA cancer vaccine.

The trial is ongoing, but interim results found the treatment, known as Intismeran, met both ​its primary target of reducing cancer recurrence and ⁠its secondary goal ⁠of keeping cancers from ‌spreading to other parts of the body.

In a statement emailed to CBC News, Melanoma Canada CEO Falyn Katz called the results "incredibly encouraging" while noting the preliminary nature of the information.

"This personalized mRNA therapy could offer patients at high risk of recurrence or metastasis a powerful new way to prevent melanoma from returning or spreading," Katz wrote. "We look forward to seeing the full data and what this innovative treatment could mean for patients in Canada."

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The treatment combines Merck's Keytruda with a made-to-order mRNA vaccine from Moderna that is based on an analysis of mutations ⁠found in the patients' own tumours.

The trial enrolled 1,137 high-risk patients with Stage IIB-IV melanoma that had been surgically ‌removed.

Volunteers were randomized to receive up to nine doses of Keytruda plus the personalized vaccine or Keytruda alone for about one year. The companies said no ​new safety signals have emerged in the trial.

In January, the companies announced ⁠results of a mid-stage trial of the treatment showing that ⁠it reduced the risk of recurrence or death by ⁠49 per cent ⁠after five years.

The ​companies said they will present their results at an upcoming medical ​meeting and share ⁠them with regulators.

Shares of Moderna were up over 150 per cent in mid-morning trading, while Merck had risen over 10 per cent.

According to the Canadian Cancer Society, around 11,300 people in Canada are likely to be diagnosed with melanoma this year, and an estimated 1,250 people will die from it. Melanoma Canada says melanoma is one of the most common types of cancer found among Canadians aged 15 to 29 and 30 to 49.

In 2023, there were more than 1.5 million people in the U.S. living with melanoma, according to the U.S. National Cancer ⁠Institute.