The Food and Drug Administration (FDA) has approved the cancer-fighting drug pembrolizumab (Keytruda) as a single agent to treat advanced endometrial carcinoma that is microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) in patients whose disease has progressed following prior systemic therapy in any setting and who are not candidates for curative surgery or radiation. The FDA also approved a special diagnostic test, the Ventana MMR RxDx Panel, for use in selecting patients who are appropriate for pembrolizumab treatment. Pembrolizumab was previously approved to treat a variety of cancers, including melanoma, non-small cell lung cancer; head and neck squamous cell cancer; classical Hodgkin lymphoma; MSI-H or dMMR solid tumors; and MSI-H or dMMR colorectal cancer, among others.

Pembrolizumab is a programmed death receptor-1-blocking monoclonal antibody that inhibits T-cell proliferation and cytokine production, as well as releasing an antitumor immune response. It is administered intravenously.

The efficacy of pembrolizumab for treating advanced MSI-H or dMMR endometrial carcinoma was determined in a multicenter, nonrandomized, open-label, multicohort trial of 90 patients. The major efficacy outcomes were the objective response rate, which was 46%, and the duration of response, which was not reached with 44% of patients having a duration of >= 24 months.

This new indication for pembrolizumab has not changed the warnings and precautions or the adverse effects listed on the product's labeling. The warnings are for immune-mediated complications and include severe and fatal immune-mediated adverse effects, such as pneumonitis; colitis; hepatotoxicity and hepatitis; endocrinopathies, including thyroid disorders and type 1 diabetes, possibly presenting with diabetic ketoacidosis; nephritis with renal dysfunction, and dermatologic adverse effects. Additionally, the labeling warns of infusion-related reactions, complications of allogeneic hematopoietic stem cell transplantation, increased mortality in those with multiple myeloma who add pembrolizumab to their thalidomide analogue and dexamethasone treatment, and embryo-fetal toxicity. The most common adverse effects are fatigue, musculoskeletal pain, rash, diarrhea, pyrexia, cough, decreased appetite, pruritis, dyspnea, constipation, pain, abdominal pain, nausea, and hypothyroidism.

Nurses should confirm that patients prescribed pembrolizumab have been identified with the companion diagnostic test. Patients who may be developing an immune-mediated complication should be fully assessed. All serious adverse effects should be reported to the FDA's MedWatch reporting system at http://www.accessdata.fda.gov/scripts/medwatch/index.cfm.

For complete prescribing information for pembrolizumab, see http://www.accessdata.fda.gov/drugsatfda_docs/label/2022/125514s110lbl.pdf.