Moderna Inc said on Wednesday its experimental personalized mRNA skin cancer vaccine in combination with Merck & Co Inc's drug Keytruda has received breakthrough therapy designation from U.S. regulators as an additional treatment for high risk patients.

Shares of Moderna rise 2.5% to $164 after the market.

The breakthrough tag is granted by the U.S. Food and Drug Administration (FDA) based on data from a mid-stage study of the drug that showed the therapy reduced risk of skin cancer's recurrence or death by 44% compared with Keytruda alone.

The FDA's breakthrough therapy designation is granted to expedite the development and review of drugs that are intended to treat a serious condition.

The companies said they plans to initiate a late-stage study in adjuvant treatment of melanoma in 2023.