Last week the FDA approved a new ORAL therapy, Welireg (belzutifan) from Merck, for adult patients with von Hippel-Lindau (VHL) disease who require therapy for associated renal cell carcinoma (RCC), central nervous system (CNS) hemangioblastomas, or pancreatic neuroendocrine tumors (pNET), not requiring immediate surgery. Welireg is the first systemic treatment for cancers linked to VHL which affects about 10,000 Americans annually.
Welireg works by blocking a protein known as HIF-2 alpha which limits the expression of certain genes associated with cellular proliferation and tumor growth. Welireg is administered once daily until disease progression or unacceptable toxicity. There is a serious risk of embryo-fetal harm which led the FDA to require a black box warning.
Merck confirmed that it will launch Welireg at a wholesale price of $26,400 monthly. Details relating to access were not released. However, it is highly likely to be placed in limited distribution due to the relatively small patient population and need to monitor patients for serious side effects and adverse events.
FDA approves belzutifan for cancers associated with von Hippel-Lindau disease
On August 13, 2021, the Food and Drug Administration approved belzutifan (Welireg, Merck), a hypoxia-inducible factor inhibitor for adult patients with von Hippel-Lindau (VHL) disease who require therapy for associated renal cell carcinoma (RCC), central nervous system (CNS) hemangioblastomas, or pancreatic neuroendocrine tumors (pNET), not requiring immediate surgery.
Belzutifan was investigated in the ongoing Study 004 (NCT03401788), an open-label clinical trial in 61 patients with VHL-associated RCC (VHL-RCC) diagnosed based on a VHL germline alteration and with at least one measurable solid tumor localized to the kidney. Enrolled patients had other VHL-associated tumors, including CNS hemangioblastomas and pNET.
The primary efficacy endpoint was overall response rate (ORR) measured by radiology assessment, as assessed by an independent review committee using RECIST v1.1. Additional efficacy endpoints included duration of response (DoR), and time- to- response (TTR). An ORR of 49% (95% CI:36, 62) was reported in patients with VHL-associated RCC. All patients with VHL-RCC with a response were followed for a minimum of 18 months from the start of treatment. The median DoR was not reached; 56% of responders had DoR ≥ 12 months and a median TTR of 8 months. In patients with other VHL-associated non-RCC tumors, 24 patients with measurable CNS hemangioblastomas had an ORR of 63% and 12 patients with measurable pNET had an ORR of 83%. Median DoR was not reached, with 73% and 50% of patients having response durations ≥ 12 months for CNS hemangioblastomas and pNET, respectively.
The most common adverse reactions, including laboratory abnormalities, reported in ≥ 20% of patients who received belzutifan were decreased hemoglobin, anemia, fatigue, increased creatinine, headache, dizziness, increased glucose, and nausea. Anemia and hypoxia from belzutifan use can be severe. In Study 004, anemia occurred in 90% of patients and 7% had Grade 3 anemia. Patients should be transfused as clinically indicated. The use of erythropoiesis stimulating agents for treatment of anemia is not recommended in patients treated with belzutifan. In Study 004, hypoxia occurred in 1.6% of patients. Belzutifan can render some hormonal contraceptives ineffective, and belzutifan exposure during pregnancy can cause embryo-fetal harm.
The recommended belzutifan dosage is 120 mg administered orally once daily with or without food.