As a result of an immunotherapy breakthrough that was led by UCLA researcher, the Food and Drug Administration (FDA) announced that on December 18 it had approved Keytruda (pembrolizumab) as standard of care for the treatment of metastatic melanoma. The drug works by counteracting immune system inhibition; thus, allowing its T cells to attack cancer cells. Co-developed by UCLA Jonsson Comprehensive Cancer researcher Antoni Ribas, MD, PhD, Keytruda paves the way for a totally new method of melanoma treatment.
In 2014, Keytruda received accelerated FDA approval for metastatic melanoma. Until recently, pembrolizumab was only given to patients who were no longer responding to ipilimumab, which is the current standard first-line therapy for melanoma victimes. Ipilimumab works similarly to pembrolizumab by binding to another immune molecule, called CTLA-4, which also blocks T cell activity.
The FDA approval is based on the results of a recent study by Dr. Ribas and colleagues from 16 nations; it reported that pembrolizumab, compared to ipilimumab, has less severe side-effects, improved tumor responses, enhanced the duration of responses, and extended the patient’s life. Dr. Ribas noted, “We are delighted that we found that pembrolizumab is superior to ipilimumab as first-line therapy by improving responses and survival. With today’s approval by the FDA, physicians will be able to identify patients who are candidates for receiving pembrolizumab as first-line therapy.”
As a component of a phase III clinical trial, the researchers enrolled 834 patients with metastatic melanoma who were randomly assigned to pembrolizumab or ipilimumab. They assessed treatment responses by two criteria: progression-free survival (PFS, or the length of time before a patient’s cancer worsens) and overall survival. In addition, the researchers evaluated the patients’ overall response rate to treatment and safety.
After six months of treatment, 45% of the subjects taking pembrolizumab, compared to 26% receiving ipilimumab, responded to therapy’ this marked a 42% improvement in progression free survival for patients on pembrolizumab. Overall survival at one year for patients who received pembrolizumab was 74% in one study group and 68% in another, compared to 58% for the subjects who received ipilimumab; this marked a 34% improvement. Furthermore, the tumor response rate was 33% for pembrolizumab and 12% for ipilimumab. Adverse side effects were also less for patients receiving pembrolizumab (12%), compared to ipilimumab (20%).