The FDA has granted accelerated approval to a treatment for patients whose cancers have a specific biomarker. This is the first time the agency has approved a cancer treatment based on a common biomarker rather than the location in the body where the tumor originated.
Pembrolizumab is indicated for the treatment of adult and pediatric patients with unresectable or metastatic solid tumors that have been identified as having a biomarker referred to as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). This indication covers patients with solid tumors that have progressed following prior treatment and who have no satisfactory alternative treatment options, and patients with colorectal cancer that has progressed following treatment with certain chemotherapy drugs.
"This is an important first for the cancer community," said Richard Pazdur, MD, Acting Director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research and Director of the FDA's Oncology Center of Excellence. "Until now, the FDA has approved cancer treatments based on where in the body the cancer started-for example, lung or breast cancers. We have now approved a drug based on a tumor's biomarker without regard to the tumor's original location."
MSI-H and dMMR tumors contain abnormalities that affect the proper repair of DNA inside the cell. Tumors with these biomarkers are most commonly found in colorectal, endometrial, and gastrointestinal cancers, but also less commonly appear in cancers arising in the breast, prostate, bladder, thyroid gland, and other places. Approximately 5 percent of patients with metastatic colorectal cancer have MSI-H or dMMR tumors.
Pembrolizumab was approved for this new indication using the Accelerated Approval pathway, under which the FDA may approve drugs for serious conditions where there is unmet medical need and a drug is shown to have certain effects that are reasonably likely to predict a clinical benefit to patients. Further study is required to verify and describe anticipated clinical benefits of pembrolizumab, and studies are currently being conducted in additional patients with MSI-H or dMMR tumors.
The safety and efficacy of pembrolizumab for this indication were studied in patients with MSI-H or dMMR solid tumors enrolled in one of five uncontrolled, single-arm clinical trials. In some trials, patients were required to have MSI-H or dMMR cancers, while in other trials, a subgroup of patients were identified as having MSI-H or dMMR cancers by testing tumor samples after treatment began.
A total of 15 cancer types were identified among 149 patients enrolled across these five clinical trials. The most common cancers were colorectal, endometrial, and other gastrointestinal cancers. The review of pembrolizumab for this indication was based on overall response rate and durability of response. Of the 149 patients who received pembrolizumab in the trials, 39.6 percent had a complete or partial response. For 78 percent of those patients, the response lasted for 6 months or more.
The FDA granted this application Priority Review designation, under which the FDA's goal is to take action on an application within 6 months where the agency determines that the drug, if approved, would significantly improve the safety or effectiveness of treating, diagnosing, or preventing a serious condition.