GENEVA – Shares of Merck and Moderna jumped early Tuesday after the drugmakers said a potential skin cancer vaccine they are developing using the same technology behind COVID-19 preventive shots did well in a mid-stage study.

The drugmakers said a combination of the vaccine and Merck’s immunotherapy Keytruda led to a statistically significant improvement in recurrence-free survival time in patients with phase three or four melanoma who had the tumors removed in surgery.

That combination was compared with Keytruda alone in a mid-stage clinical trial of 157 patients.

The patient group that took the potential vaccine and Keytruda saw a 44% reduction in the risk of death or the cancer returning, the companies said.

Merck and Moderna expect to start a phase 3 study of the combination next year. That’s generally the last and largest clinical study before a drug is submitted to regulators for approval.

The potential vaccine aims to train a patient’s immune system to recognize and respond specifically to mutations in their tumor. Keytruda, Merck’s top seller, primes the body’s immune system to detect and fight tumor cells.

Shares of Moderna jumped more than 8% in premarket trading, while Merck rose more than 2% and futures indexes increased slightly.