Roche announced results from a phase-I study with PLX4032 (R7204) a new, highly selective and promising treatment for patients with advanced melanoma whose cancer harbours the BRAF mutation (known as mutation-positive). Patients treated with PLX4032 lived for a median of at least six months without their disease getting worse and experienced shrinkage of their tumours; this included patients where the cancer had spread to the liver, lung and bone. Historically, metastatic melanoma patients live less than two months before their disease progresses.
PLX4032 works in a highly innovative way by selectively inhibiting the cancer-causing BRAF mutation, and is being developed in parallel with a companion diagnostic to identify mutation-positive patients. These data represent a significant development in the treatment of melanoma for which there are few treatment options.
Following these initial positive findings, Roche and its partner Plexxikon will evaluate the activity of PLX4032 in larger trials to support a potential registration program beginning later this year. If successful, it is expected to launch with a tissue based companion diagnostic test, representing another step forward in personalising cancer treatment. The two companies in their strong partnership are co-developing PLX4032 for potential use in a number of cancers harbouring the BRAF mutation. They are also co-developing the diagnostic test to select mutation-positive patients for clinical trials, and ultimately, for treatment with PLX4032.
"PLX4032 has shown both tumour shrinkage and delay in tumour progression in patients whose tumours harbour a BRAF mutation, as well as improved quality of life for symptomatic patients," stated Keith T Flaherty, assistant professor at the Abramson Cancer Center of the University of Pennsylvania and principal investigator for the PLX4032 phase-I clinical trial. "Seven years after BRAF mutations were first identified we have validation that this mutation is a cancer driver and therapeutic target. In addition to a new and important chapter in the story of targeted therapy development in cancer, we are especially excited for our melanoma patients for whom there are few treatment options."
PLX4032 works by targeting and destroying tumour cells carrying the BRAF mutation. BRAF is an important mediator of cell growth and division, but when mutated is known to cause 60 per cent of melanomas, the most deadly form of skin cancer, and approximately eight per cent of all solid tumours. PLX4032's potency and selectivity is expected to result in a treatment that is both effective and well tolerated.
Malignant melanoma is the most serious type of skin cancer, with about 160,000 new cases diagnosed worldwide each year. Melanoma is treatable if caught early but patients who develop metastatic disease are rarely cured with available treatments. Only a small proportion of people (<2 per cent) live more than two years once systemic metastases become evident.
Plexxikon is a leader in the structure-guided discovery and development of novel small molecule pharmaceuticals to treat human disease.