August 16, 2021
The U.S. FDA has approved Merck’s Welireg™ (belzutifan), the first hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor to become available in the United States. Welireg is indicated to treat adults who have von Hippel-Lindau (VHL) disease and require therapy for associated renal cell carcinoma, central nervous system hemangioblastomas, or pancreatic neuroendocrine tumors and do not require immediate surgery.
VHL disease is a rare genetic condition that affects approximately 10,000 people in the United States. It occurs when the VHL gene mutates in such a way that it cannot properly regulate cell growth and division. This leads to rapid cell proliferation, which in turn leads to tumors that can be either cancerous or benign.
In a clinical trial, patients treated with Welireg had an overall response rate ranging from 49% to 83%, depending on tumor type. Anywhere from 50% to 73% of patients had a response lasting at least 12 months, again depending on tumor type. Welireg works by reducing the transcription and expression of certain genes associated with cellular proliferation, development of new blood vessels, and tumor growth.
Recommended dosing is 120mg (three 40mg tablets) taken by mouth with or without food once each day. A black box warning cautions that exposure to Welireg during pregnancy can cause embryo-fetal harm. The black box warning also advises that the drug may render some hormonal contraceptives ineffective.
Welireg is expected to launch in September.