An estimated 70,000 new cases of metastatic melanoma are diagnosed each year in the United States, and of those 8,000 will die of the disease. About 50 percent of these men and women (or 35,000 a year) have a mutated protein called a BRAF mutation, which in most cases allows melanoma to eventually build up a resistance to many drug therapies.
In the new study led by UCLA Jonsson Comprehensive Cancer Center member Dr. Antoni Ribas and colleague Dr. Siwen Hu-Lieskovan, UCLA scientists combined targeted therapies utilizing a BRAF inhibitor (dabrafenib) and MEK inhibitor (trametinib) with immunotherapy. The three together are shown to be more effective treatments by sensitizing the patients’ own immune system to enhance immunotherapy, and reduce the probability of the melanoma eventually developing resistance.
This is a significant advance compared to previous drug combination findings, in which a combined BRAF inhibitor (vemurafenib) with immunotherapy (ipilimumab) caused serious liver toxicity in some patients, and the targeted therapies (BRAF and/or MEK inhibitors) became less effective and reactivated cancer cell growth.
“The two drug combination of BRAF and MEK inhibitors works synergistically and decreases the side effects of the BRAF inhibitor or normal cells. We reasoned that this combo would allow us to synergize with immunotherapy without increasing toxicities,” said Ribas, a professor of hematology and oncology. “We have made incredible progress in the last three years of treating advanced melanoma, with six new drug therapies approved by the FDA. Half are immunotherapies and the other half are BRAF or MEK inhibitors. The next step is to figure out how to rationally combine them and merge their benefits in the clinic.”
“The triple combination of targeted therapies BRAF (dabrafinib) and MEK (trametinib) inhibitors with immunotherapy (tumor antigen-specific adoptive cell transfer or anti-PD1 antibody) makes immune therapy more effective at killing cancerous tumors and causes less toxicity ” said Hu-Lieskovan, a UCLA clinical instructor of hematology and oncology. “We’re trying to take advantage of the high response rate of the targeted therapy and durability of the immune therapy to induce a response that lasts in the majority of patients.”
Ribas and Hu-Lieskovan have opened two clinical trials to test the effectiveness of the triple combination therapy in advanced melanoma patients. The first reported findings will be presented at the American Society of Clinical Oncology (ASCO) annual meeting in May 2015.
The study will be available online March 18th in the journal Science Translational Medicine.