WAILEA, HAWAII – "The past 2 years have been a really exciting time for those of us who have spent the last several decades" in the field of melanoma, said Dr. Allan C. Halpern, chief of the dermatology service at Memorial Sloan Kettering Cancer Center, New York.
"We are in a whole new place with a very promising future for turning stage IV melanoma into maybe a chronic disease for many patients, instead of a death sentence. For some patients, we’re already seeing what may be cures," he said at the Hawaii Dermatology Seminar sponsored by the Global Academy for Medical Education/Skin Disease Education Foundation.
Bruce Jancin/IMNG Medical Media
Dr. Allan C. Halpern
The greatest enthusiasm in the field now involves combining a pathway-targeted agent, such as vemurafenib, with an immunologic checkpoint blocker, such as ipilimumab. The vemurafenib knocks down 60%-70% of metastatic melanomas temporarily and the ipilimumab promotes durable responses.
But there’s a formidable economic obstacle to this approach: The strongest drug combinations often put big pharmaceutical companies in the uncomfortable position of having to cooperate with their competitors in expensive research projects. "A lot of the drug companies, to their credit, are finding ways to make it work," Dr. Halpern said.
Dr. Halpern detailed the therapeutic history that has revolutionized the treatment of metastatic melanoma.
Prior to 2011 there were only two Food and Drug Administration–approved therapies for metastatic melanoma, dacarbazine and high-dose interleukin II. Both were unimpressive. The therapeutic dry spell has ended, he said. "There are for the first time in melanoma, instead of no hopeful drugs, a slew of hopeful drugs."
Targeted therapeutic approaches, the result of laboratory insights into the molecular pathways to melanoma and the key genetic mutations involved, led to the development of vemurafenib, a selective, first-in-class BRAF inhibitor approved in 2011.
"Vemurafenib is an astounding drug. When you give it to a BRAF-mutated cell, it essentially turns off the cell’s metabolic activity." When given to patients whose tumors test positive for the BRAF mutation, "it’s dramatically effective in 60%-70%." But the response does not persist. "After about 6-18 months, the tumor develops resistance to the drug. It’s like somebody hit a switch to turn the tumor back on. The tumor comes roaring back, in the same places for the most part," Dr. Halpern said.
As a result of this limited success, ongoing clinical trials are aimed at determining whether dual pathway blockade using combination therapy will provide more durable responses. Trials are underway with the oral BRAF inhibitor dabrafenib plus the oral MEK 1/2 pathway inhibitor trametinib. Other dual pathway combinations are also under study in melanoma.
The prospects are even more promising, according to Dr. Halpern, for immunologic checkpoint blockade, which is based upon the concept that some cancers progress because the immune system turns off prematurely and stops battling the malignancy. Ipilimumab is one such agent. An anti-CTLA-4 antibody, ipilimumab enhances T-cell activation and proliferation and has earned FDA approval as single-agent therapy in advanced melanoma.
Tumors often don’t begin to shrink until after 3-4 months, but the response is impressively durable in the roughly 30% of patients who respond to immunologic checkpoint blockade.
"These people look like they might be cured," said Dr. Halpern.
Another important immunologic checkpoint molecule is PD-1. The anti-PD-1 agent known as MDX-1106 appears to be nearly as effective as ipilimumab, but with less toxicity. The early impression from ongoing clinical trials is that dual immunologic checkpoint blockade using anti-CTLA-4 therapy along with an anti-PD-1 drug provides synergistic anti-tumor activity.
Dr. Halpern reported serving as a consultant to Canfield Scientific, DermTech, SciBase, Quintiles, and Lucid.
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