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Belzutifan · Welireg, MK-6482

Small molecule · Inhibitor of hypoxia-inducible factor 2 alpha (EPAS1) · developed by Merck Sharp Dohme

Approved FDA, Aug 2021

MRK Developer

1 Registered trials

What is Belzutifan?

Belzutifan is a small-molecule inhibitor of hypoxia-inducible factor 2 alpha (HIF-2α). It blocks the interaction between HIF-2α and HIF-1β, reducing transcription of genes that promote cellular proliferation, angiogenesis, and tumor growth.

Summary written with AI from the sources listed at the end of this page.

At a glance

Also known as: Welireg, MK-6482, PT-2977, WELIREG
Drug type: Small molecule
Targets: hypoxia-inducible factor 2 alpha (EPAS1), hypoxia-inducible factor 1 beta (ARNT) (binding partner it blocks), von Hippel-Lindau protein (VHL) (biomarker)
Mechanism: Inhibitor of hypoxia-inducible factor 2 alpha (EPAS1)
Pathways: angiogenesis, cellular proliferation
Therapy area: Oncology
Developer: Merck Sharp Dohme (MRK)
FDA status: Approved as Welireg (August 13, 2021), NDA215383 · FDA label
UNII: 7K28NB895L

✅ FDA-approved uses

Von Hippel-Lindau disease with associated renal cell carcinoma, CNS hemangioblastomas, or pancreatic neuroendocrine tumors
Clear cell renal cell carcinoma, adjuvant treatment following nephrectomy
Advanced clear cell renal cell carcinoma following PD-1/PD-L1 inhibitor and VEGF-TKI
Pheochromocytoma or paraganglioma, locally advanced, unresectable, or metastatic

From the indications section of the FDA label (version of Jun 12, 2026). Read the full label for the exact wording, limitations and safety information.

🧪 Clinical trials

Trial	Phase	Condition	Status	Sponsor
NCT04924075	Phase 2	Pheochromocytoma/Paraganglioma	Recruiting	MRK

Trials of the companies BioRadar tracks, from ClinicalTrials.gov, most advanced phase first.

Conditions studied

Advanced Gastrointestinal Stromal TumorHIF-2α Mutated CancersPancreatic Neuroendocrine TumorPheochromocytoma/ParagangliomaVon Hippel-Lindau Disease

Other drugs acting on EPAS1

Casdatifan Phase 1/2 Imdatifan Phase 1/2 Zifcasiran Phase 1

More from Merck Sharp Dohme

BCG Live FDA approved Berahyaluronidase Alfa FDA approved Berahyaluronidase Alfa and Pembrolizumab FDA approved Enlicitide FDA approved Ensifentrine FDA approved Letermovir FDA approved Pembrolizumab FDA approved Probenecid FDA approved Alimatravir Phase 2 Bomedemstat Phase 2/3 Calderasib Phase 3 Favezelimab Phase 1/2

Sources

Updated Oct 3, 2026. Something wrong or missing? Report it on the MRK page.

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Data: FDA (Drugs@FDA, Purple Book, DailyMed), NIH (NCI Thesaurus, GSRS, RxNorm), ClinicalTrials.gov • Informational purposes only, not medical or investment advice. • All drugs A–Z