Immunotherapy Approved for Endometrial Cancer  

The FDA approved pembrolizumab for certain patients with advanced endometrial cancer with DNA repair defects 

The U.S. Food and Drug Administration (FDA) has approved pembrolizumab (Keytruda) for the treatment of adult patients with advanced endometrial cancer who had disease progression following prior systemic therapy and are not candidates for curative surgery or radiation, and whose tumors display microsatellite instability or mismatch repair deficiency. The FDA also approved a companion diagnostic device called VENTANA MMR RxDx Panel to identify patients with these molecular features who are eligible for treatment with pembrolizumab. 

Pembrolizumab is a checkpoint inhibitor that harnesses the body’s anticancer immune response by blocking an inhibitory protein called PD-1. 

The mismatch repair (MMR) pathway is a mechanism used by cells to repair damage to their DNA. Deficiency in MMR (dMMR) leads to a high number of mutations within particular DNA sequences known as microsatellites. Research has shown that tumors with dMMR and microsatellite instability, also called microsatellite instability high (MSI-H), are more sensitive to immune checkpoint inhibitors. 

The approval was based on the results of a phase II, multi-cohort clinical trial that assessed pembrolizumab in patients with multiple types of advanced solid tumors, including 90 patients with unresectable or metastatic MSI-H or dMMR endometrial cancer. Patients received pembrolizumab infusions every three weeks until unacceptable toxicity or disease progression for a maximum of 24 months.  

Among the 90 patients with advanced MSI-H/dMMR endometrial cancer, 46 percent responded to the therapy. The duration of response was at least 12 months in 68 percent of patients and at least 24 months in 44 percent of patients.  

Endometrial cancer is a type of uterine cancer that develops in the lining of the uterus. According to federal statistics, nearly 66,000 people are expected to be diagnosed with uterine cancer in the U.S. in 2022.   

The FDA decision was rendered on March 21, 2022.