A supplemental new drug application (sNDA) seeking approval of WELIREG (belzutifan), Merck’s oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor, for the treatment of adult and pediatric patients (12 years and older) with advanced, unresectable, or metastatic pheochromocytoma and paraganglioma (PPGL), has been accepted for priority review by the U.S. Food and Drug Administration (FDA).

The sNDA is based on objective response rate (ORR) and duration of response (DOR) data from the Phase 2 LITESPARK-015 trial. The FDA has set a Prescription Drug User Fee Act (PDUFA), or target action, date of May 26, 2025.

“Pheochromocytoma and paraganglioma are rare tumors that form in and around the adrenal glands, and currently, there are no approved therapies available in the U.S. for patients with this rare disease,” said Dr. Marjorie Green, senior vice president and head of oncology, global clinical development, Merck Research Laboratories. “Today’s U.S. filing acceptance demonstrates our commitment to advancing novel therapies, such as WELIREG, to help treat patients with certain rare oncologic diseases. We look forward to working with the FDA to potentially provide this critical option to these patients who urgently need new innovative therapies.”

WELIREG is the first and only HIF-2α inhibitor therapy approved in the U.S. for the treatment of adult patients with von Hippel-Lindau (VHL) disease who require therapy for associated renal cell carcinoma (RCC), central nervous system hemangioblastomas, or pancreatic neuroendocrine tumors (pNETs) not requiring immediate surgery, based on results from the Phase 2 LITESPARK-004 trial. WELIREG is also approved for certain adult patients with VHL disease-associated tumors in China and 16 additional countries around the world.

WELIREG is also approved in the U.S. and Canada for the treatment of adult patients with advanced RCC following a PD-1/PD-L1 inhibitor and a vascular endothelial growth factor tyrosine kinase inhibitor (VEGF-TKI), based on results from the Phase 3 LITESPARK-005 trial.

Merck is investigating WELIREG in rare oncologic diseases, RCC and other tumor types through a broad clinical development program, including in Phase 2 and 3 trials evaluating WELIREG as monotherapy and in combination with other medicines.