A combination treatment from GlaxoSmithkline for melanoma, the deadliest form of skin cancer, has won priority review from U.S. regulators.

The move means the Food and Drug Administration will now decide whether to approve the dual use of Tafinlar, also known as dabrafenib, and Mekinist, or trametinib, by early January.

Both drugs are already approved for separate use but GSK believes they will have a longer-lasting effect if given together. Industry analysts also see a combination offering the greatest commercial potential.

Tafinlar, which is similar to Roche's rival medicine Zelboraf, is designed to work in patients with a mutation of a gene known as BRAF. So-called BRAF inhibitors have been remarkably effective in shrinking melanoma tumours but most patients eventually develop resistance to the drugs.

By combining Tafinlar with Mekinist, which works in a different way, the hope is that the cancer will be held at bay for longer.

GSK said that the FDA had set a target date of Jan. 8, 2014 for the review of the Mekinist supplement and Jan. 9 for the Tafinlar supplement.

If approved, the drug combination will be used to treat melanoma that cannot be removed by surgery or which has spread to other organs. The applications are based on data from a randomised study comparing combination therapy to Tafinlar given alone.

Melanoma is diagnosed in nearly 160,000 people worldwide each year. It can spread quickly to internal organs and average survival is six to nine months.