Yesterday, the U.S. Food and Drug Administration (FDA) announced the highly anticipated approval of the cancer immunotherapeutic pembrolizumab (Keytruda) for the treatment of certain patients with metastatic melanoma, the most deadly form of skin cancer.
Pembrolizumab is the first in a new class of cancer immunotherapeutics called PD-1 inhibitors to be approved by the FDA. While the FDA decision came earlier than initially expected, the excitement surrounding it has been palpable for a while because pembrolizumab, as well as other PD-1 inhibitors, has been yielding dramatic and durable responses for patients with metastatic melanoma. In fact, many patients are continuing to benefit from pembrolizumab more than one year after starting treatment.
As I discussed in an earlier blog post, “Cancer Immunotherapy: Breaking Through to the Standard of Care,” PD-1 inhibitors work by releasing the PD-1 brake on cancer-fighting immune cells called T cells. Once the PD-1 brake is released, the T cells are able to carry out their natural function and can destroy cancer cells.
Louis M. Weiner, MD, director of the Georgetown Lombardi Comprehensive Cancer Center and a spokesman for the American Association for Cancer Research, told the New York Times: “This is really opening up a whole new avenue of effective therapies previously not available. It allows us to see a time when we can treat many dreaded cancers without resorting to cytotoxic chemotherapy.”
The patients who will benefit from yesterday’s FDA approval are those with metastatic melanoma that does not respond, or has stopped responding, to another cancer immunotherapeutic, ipilimumab (Yervoy). Ipilimumab targets another T-cell brake, CTLA4. A substantial number of patients with metastatic melanoma are still benefiting from ipilimumab more than five years after starting treatment, and it is hoped that pembrolizumab and other PD-1 inhibitors will have a similar impact so that significant inroads can be made against metastatic melanoma – a disease that has an overall five-year survival rate of only 16 percent.
Metastatic melanoma is a cancer diagnosis projected to be received by more than 3,000 U.S. residents in 2014 alone. With PD-1 inhibitors also showing tremendous promise in clinical trials as a potential treatment for other types of cancer, in particular non-small cell lung cancer – a disease that more than 180,000 individuals in the United States are expected to be diagnosed with in 2014 – it is hoped that additional FDA approvals for this groundbreaking class of drugs lie in the near future.
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