Combining the treatment for the most deadly form of skin cancer with a common anti-rheumatic drug could provide more effective results, new research has shown.

The findings showed that using "leflunomide" -- an immunosuppressive drug approved for treatment of rheumatoid arthritis -- in combination with another melanoma drug, selumetinib almost completely stopped the growth of a melanoma tumour in mice. "By combining therapies, it's possible to attack the disease from several angles, which makes it harder for the melanoma to develop resistance to any of the drugs," said Grant Wheeler from the University of East Anglia (UEA) in the UK. "Our research has shown that there could also be further benefits - by joining these two drugs together you may be able to enhance their effects, getting a treatment that is more than the sum of its parts," Wheeler said. 

Although only five per cent of skin cancer cases involve melanoma, it causes the majority of deaths from the disease. If caught early, melanoma is very treatable, but once the cancer has metastasised or spread, then treatment becomes more difficult. The research, published in the journal Oncotarget, tested leflunomide's effect against melanoma with selumetinib. When the team tested leflunomide in the lab, it was found to work on melanoma cells irrespective of the genetic signature of the cancer. 

This means that leflunomide has the potential to be used in all melanoma cases, not just for tumours harbouring BRAF mutations, the researchers said. However, when leflunomide was tested on melanoma cells jointly with selumetinib, the scientists found it was more effective than either drug on its own. In mice, the two drugs together almost completely halted the growth of the tumour over a 12 day period, which far outstripped the effect of either drug used in isolation, the researchers said.