The drug leflunomide, currently licensed to treat rheumatoid arthritis, was found to inhibit the growth of malignant melanoma in mice.
Dr Richard White of the Children's Hospital, Boston, US, and his team believe a new treatment for malignant melanoma in humans could be just five years away.
Co-author Grant Wheeler from the University of East Anglia (UEA) said: 'This is a really exciting discovery - making use of an existing drug specifically to target melanoma.'
He added: 'We are very optimistic that this research will lead to novel treatments for melanoma tumours which, working alongside other therapies, will help to stop them progressing.'
More than 10,000 cases of melanoma are diagnosed in the UK each year. About 2,000 people a year in the UK die from malignant melanoma because the cancer has returned after being removed surgically.
Authors of the study attempted to identify tumour-suppressing components by testing 2,000 different chemicals on the development of pigment cells in tadpoles.
Analysis revealed that a particularly effective chemical was similar in composition to leflunomide. Researchers then transplanted melanoma cells into mice and attempted to treat tumour growth using leflunomide with PLX4720 - a new melanoma therapy undergoing clinical trials.
They found the effect of these two drugs together was greater than either drug alone.
Tumour growth was dramatically slowed and in 40 per cent of animals led to almost complete regression.
The next step is for clinical trials. As leflunomide is already licensed to treat arthritis, this process should be faster than usual.
As a result, a new treatment for melanoma could be available within about five years, the UEA team said.