Pembrolizumab is a checkpoint inhibitor, a drug that essentially unmasks tumor cells so the immune system can attack and destroy them. Specifically, pembrolizumab is a PD-L1 inhibitor; it inhibits the interaction of PD-L1, a protein on tumor cells and PD-1, a protein on T-cells. Checkpoint inhibitors “turn off the off switch, which has the net effect of turning the immune system back on,” said David Brizel, MD, Leonard Prosnitz Professor of Radiation Oncology at Duke University in Durham, N.C.
The idea of unleashing the immune system against cancer cells is not new. What is new is the hope that these medications are offering hope to patients who would otherwise have no options. Maura Gillison, MD, PhD, professor of medicine and Jeg Coughlin Chair of Cancer Research at The Ohio State University Comprehensive Cancer Center in Columbus, has seen remission following checkpoint inhibitor treatment in some of her patients.
Checkpoint inhibitors “fulfill the promise of the immunotherapy that we’ve had for decades,” said Robert Ferris, MD, PhD, professor of otolaryngology and co-leader of the Cancer Immunology Program University at the Pittsburgh Cancer Institute. “Early clinical trial data suggests that checkpoint inhibitors can provide long-term, durable regression or stability. That durability has been the ‘holy grail’ for many years.”