The Phase III trial met its primary endpoint and showed that the combination therapy helped these patients live significantly longer without their disease worsening (progression-free survival; PFS) compared to Zelboraf alone.
About 495 patients have participated in the trial, whose primary endpoint is PFS, while secondary endpoints include overall survival, objective response rate, duration of response and other safety, pharmacokinetic and quality of life measures.
The company said that adverse events were consistent with those observed in a previous trial of the combination therapy.
Roche chief medical officer and head of Global Product Development Sandra Horning said these encouraging data support the potential combined use of cobimetinib with Zelboraf to block tumour growth longer than Zelboraf alone.
"We hope this combination therapy will lead to a new option for patients," Horning said.
In addition, the company intends to submit these data to the US Food and Drug Administration (FDA), European Medicines Agency (EMA) and other health authorities around the world for potential approval.
Cobimetinib, which is designed to selectively block the activity of MEK, binds to MEK while Zelboraf binds to mutant BRAF.
MEK is one of a series of proteins inside cells that make up a signaling pathway that helps regulate cell division and survival.
BRAF is another protein on the pathway, to interrupt abnormal signaling that can cause tumours to grow.