An experimental drug from Roche helped people with an advanced form of skin cancer live longer without their disease worsening when used in combination with another treatment, the Swiss drugmaker said on Monday.

Cobimetinib, which is being developed in collaboration with Exelixis Inc, is designed to be used with another Roche drug called Zelboraf for patients with tumors that have a mutation in a gene known as BRAF that allows melanoma cells to grow, NewsMax Health reported.

About half of all melanomas have the genetic aberration the drugs target.

Results of a Phase III study involving 495 patients previously untreated for advanced melanoma found those taking both drugs lived significantly longer without their disease worsening compared to those taking Zelboraf alone.

Melanoma globally afflicts more than 232,000 new people each year. While generally curable if caught early, it is one of the deadliest cancers in its advanced stages and there are few treatment options.

Cobimetinib works by blocking the activity of a protein called MEK, while Zelboraf - which is already approved in more than 80 countries - binds to the mutant protein BRAF.

Roche is also investigating Cobimetinib in combination with other experimental medicines, including an immunotherapy for the treatment of non-small cell lung cancer and colorectal cancer.