Updated

An experimental drug has shown promise as a treatment for advanced melanoma, one of the deadliest of cancers, according to preliminary results from a small trial presented on Monday.

The oral drug, known as PLX4032, is being developed by privately-held Plexxikon Inc and Roche Holding AG.

The experimental compound is designed to block a genetic mutation in a cellular pathway, known as BRAF, that occurs in up to 60 percent of melanomas and about 8 percent of all solid tumors.

In a Phase 1 trial, nine of out of 16 melanoma patients with the mutation who were treated with clinically relevant doses had tumor shrinkage of at least 30 percent, said Dr. Keith Flaherty, assistant professor at the Abramson Cancer Center of the University of Pennsylvania and the trial's lead investigator.

Plexxikon said larger clinical trials to support a registration program for product approval are targeted to start later this year.

Dr. Flaherty, who presented the results at a meeting here of the American Society of Clinical Oncology, said future trials will only enroll patients who test positive for the mutation.

Other drugs in development which target BRAF pathway mutations include XL281 from Exelixis Inc and RAF265 from Novartis AG.