An experimental cancer vaccine, combined with another drug, performed well in midstage testing against a deadly form of skin cancer in the first effort to show that a cancer vaccine using messenger RNA may be effective, two pharmaceutical companies announced Tuesday.

The therapy being tested by Moderna and Merck includes a vaccine created using mRNA technology, the same approach employed in the two most commonly used coronavirus vaccines. It was combined with Merck’s cancer immunotherapy drug pembrolizumab, marketed as Keytruda.

After surgery and as long as a year on the pair of drugs, melanoma patients in the trial saw a 44% reduced risk of recurrence or death when compared with patients who received Keytruda alone, according to an announcement from the two companies. The companies did not release the results of the study itself, but described the results as statistically significant.

“Today’s results are highly encouraging for the field of cancer treatment,” Stéphane Bancel, Moderna’s chief executive officer, said in a news release. “mRNA has been transformative for COVID-19, and now, for the first time ever, we have demonstrated the potential for mRNA to have an impact on outcomes in a randomized clinical trial in melanoma.”

He said full data would be shared with health authorities, including the Food and Drug Administration, and released at a medical conference. The phase 2b trial involved 157 patients with Stage 3 or 4 melanoma that had spread to a lymph node and who faced a high risk of recurrence. The patients were split randomly into two groups.

Positive results in a larger phase 3 trial would be required before the FDA would consider allowing the drug combination on the market. The companies said they hope to begin that trial next year.

In addition to using the breakthrough mRNA technology, Moderna’s proposed vaccine employs a “personalized” approach designed to prompt a patient’s immune system to attack the specific mutations of his or her tumors.

Merck’s drug Keytruda is a monoclonal antibody that helps the immune system detect and fight invading cancers.

“Serious adverse events” related to the treatment occurred in 14.4% of patients who received the drug combination and 10% of those who received Keytruda alone.

In 2018, 83,996 people were diagnosed with melanoma in the United States and 8,199 died, according to the Centers for Disease Control and Prevention. The five-year survival rates of the disease are estimated at 60.3% for Stage 3 and 16.2% for Stage 4, according to the companies.