Keytruda (pembrolizumab), Merck & Co.’s immunotherapy drug, emerges as the first cancer medication approved by the U.S. Food and Drug Administration (FDA) based on the patient’s particular genetic feature or biomarker, no matter where the tumor originated in the body.
The bold move is seen as a major progress in precision medicine, a field where these biomarkers, not the kind of cancer, may steer the cancer therapy forward. In the future, genetic data may clue in on which patients will most certainly benefit from certain treatments.
How Keytruda Works
“This is an important first for the cancer community,” said Dr. Richard Pazdur, director of oncology products at the FDA’s Center for Drug Evaluation and Research, in a statement.
Prior to this development, the FDA has approved cancer therapies based on where the cancer began, such as in the lungs or breast, Pazdur added.
The accelerated FDA approval was intended for solid tumor cancers no longer fit for surgeries or have metastasized or spread in those identified with a biomarker known as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). Certain tumors with these traits most commonly appear in endometrial, colorectal, and gastrointestinal cancers but could also be seen in breast, prostate, pancreas, bladder, and thyroid cancers.
Keytruda works by targeting the cellular pathway called PD-1 or PD-L1, which are proteins located on the body’s immune cells and certain cancer cells. It inhibits this pathway that tumors use to avoid being detected by cancer-scouring cells.
At present, there are five PD-1 or PD-L1 inhibitor drugs for different types of cancer.
Across the five clinical trials conducted to determine Keytruda’s safety and efficacy, there were 15 cancer types identified in 149 patients enrolled. Of these participants, 39.6 percent exhibited a partial or complete response, and for 78 percent of those patients, the response lasted six or so months.
Historic FDA Approval: Prospects And Consequences
“This was one of those eureka trials where it didn’t take a lot of patients to see this was going to be something major,” said Dr. Drew Pardoll, Johns Hopkins Bloomberg-Kimmel Institute director and lead investigator of the trial leading to Keytruda’s approval.
According to Pardoll, around 4 percent of advanced cancer cases, or up to 20,000 U.S. cases every year, have the genetic features involved in the FDA approval. Testing for these specific gene defects cost $300 to $600.
This recent approval positions Merck at the center of immune system-focused cancer therapies. Last year, Keytruda’s survival as first treatment option for advanced NSCLC or non-small cell lung cancer was extended.
The drug was formerly approved for the treatment of advanced NSCLC, advanced melanoma, classical Hodgkin lymphoma, and head and neck cancers.
It was also recently approved for bladder cancer and awaits FDA approval for gastric cancer.
Common side effects include fatigue, itchy skin, diarrhea, rash, decreased appetite, fever, cough, dyspnea or difficulty breathing, nausea, muscle and joint pain, and constipation. Patients experiencing severe reactions are advised to stop taking it, while pregnant or breastfeeding women should avoid Keytruda to prevent harm to developing or newborn baby.
