Belzutifan — Drug Monograph

Brand names: Welireg

Drug class: HIF-2α Inhibitor

Mechanism of Action

Belzutifan is a first-in-class, oral, selective inhibitor of hypoxia-inducible factor-2α (HIF-2α), a transcription factor that drives expression of pro-tumorigenic genes including VEGF, PDGF, and EPO. In VHL-deficient tumors (including clear cell RCC), loss of VHL protein allows HIF-2α to accumulate and constitutively activate these pathways. Belzutifan binds directly to HIF-2α, preventing its heterodimerization with HIF-1β and blocking downstream transcription of hypoxia-response genes. Unlike VEGF-TKIs that act downstream of HIF-2α, belzutifan targets the upstream driver, offering a…

FDA Indications

• Renal cell carcinoma (RCC) associated with von Hippel-Lindau (VHL) disease — adults (FDA approved August 2021, Study 004/MK-6482-004)
• Advanced renal cell carcinoma (RCC) — adults after ≥2 prior therapies including a PD-1 or PD-L1 inhibitor and a VEGF-TKI (FDA approved December 2023, LITESPARK-005; ORR 22%, median DOR 19.3 months)
• Adjuvant treatment of adults with clear cell RCC (ccRCC) at intermediate-high or high risk of recurrence following nephrectomy — in combination with pembrolizumab (FDA approved June 12, 2026, LITESPARK-022; 28% reduction in risk of recurrence vs pembrolizumab + placebo, HR 0.72, p=0.0003)

Common Side Effects

• Anemia (very common, ~90%; dose reduction required in ~25%)
• Fatigue
• Dizziness
• Headache
• Nausea
• Dyspnea
• Weight gain
• Peripheral edema

Clinical Pearl

Belzutifan is the first HIF-2α inhibitor approved in oncology, targeting the transcriptional driver of VHL-deficient clear cell RCC directly — upstream of all VEGF-TKIs. Anemia is the dominant and near-universal toxicity, driven by EPO suppression (HIF-2α regulates EPO transcription); it is manageable with dose reduction and, if needed, ESA support, but requires proactive monitoring from cycle 1. For VHL disease, belzutifan offers a systemic oral option for multiple simultaneous tumor…

Related Therapies & Mechanisms

• Axitinib (Inlyta) — RCC
• Bevacizumab (Avastin) — RCC
• Cabozantinib (Cabometyx) — RCC
• Everolimus (Afinitor) — RCC