An experimental mRNA vaccine has shown promise to treat melanoma -- the most deadly form of skin cancer.

The mRNA vaccine developed by Moderna and administered along with Merck’s cancer drug Keytruda can slash the death rate or recurrence of melanoma after three years by 49 per cent compared to Keytruda alone, the companies said in a statement.

The drug combination also reduced the risk of distant metastasis (spread to other parts of the body) or death by 62 per cent.

The most common side effects of the vaccine were fatigue, injection site pain and chills, the results showed.

Melanoma, the most serious form of skin cancer, is characterised by the uncontrolled growth of pigment-producing cells. The rates of melanoma have been rising over the past few decades, with nearly 325,000 new cases diagnosed worldwide in 2020.

The vaccine could win regulatory approvals and launch in some countries as early as 2025, Moderna CEO Stephane Bancel was quoted as saying on CNBC’s “Squawk Box” on 14 Dec.

The companies are also studying the vaccine in patients at earlier stages of melanoma, he noted.

“We believe that the earlier you go in disease, the stronger the immune system of a patient is, meaning our individualised treatment should work even better,” Bancel said.

The vaccine, which uses the same mRNA technology as Moderna’s COVID vaccine, is custom-built based on an analysis of a patient’s tumours after surgical removal. The shot is designed to train the immune system to recognise and attack specific mutations in cancer cells.

Keytruda, on the other hand, is an immunotherapy that works by increasing the ability of the body's immune system to help detect and fight tumour cells.

Together, the two drugmakers have started testing the vaccine with Keytruda against non-small cell lung cancer.