Welireg (Belzutifan)

What is a Generic Drug?

A generic drug is a copy of the brand-name drug with the same dosage, safety, strength, quality, consumption method, performance, and intended use. Before generics become available on the market, the generic company must prove it has the same active ingredients as the brand-name drug and works in the same way and in the same amount of time in the body.

The only differences between generics and their brand-name counterparts is that generics are less expensive and may look slightly different (eg. different shape or color), as trademarks laws prevent a generic from looking exactly like the brand-name drug.

Generics are less expensive because generic manufacturers don't have to invest large sums of money to develop a drug. When the brand-name patent expires, generic companies can manufacture a copy of the brand-name and sell it at a substantial discount.

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Prescription Required

  • Product Details


    Belzutifan is a prescription medication used to treat von Hippel-Lindau (VHL) disease, which is a disease that can produce tumors that lead to renal cell carcinoma (RCC), central nervous system hemangioblastomas, or pancreatic neuroendocrine tumors (pNET).

    Belzutifan belongs to a class of drugs known as hypoxia-inducible factor-2 alpha (HIF-2a) inhibitors. It works by blocking the activity of HIF-2a, a protein that promotes the growth of cancer cells by allowing them to adapt to low-oxygen conditions. By inhibiting HIF-2a, Belzutifan helps to suppress the growth and spread of tumors.


    Do not stop or change directions without speaking to your doctor first.

    The usual dosage is 120 mg by mouth once daily. Since Welireg is supplied as 40 mg tablets, three tablets should be taken daily.

    Fact Table




    US DailyMed


    No Data Available

    Legal status


    Chemical Name


    Elimination half-life

    14 hours

    Dosage (Strength)



    Consult Doctor



    Protein binding


    PubChem CID





    No Data Available

    ATC code






    Routes of administration

    By mouth


    The active ingredient in Welireg is belzutifan.


    Common drug-drug interactions may include:

    • Acetohexamide
    • Acarbose
    • Albiglutide
    • Alogliptin
    • Atogepant
    • Bexagliflozin
    • Canagliflozin
    • CarBAMazepine
    • Chlorpropamide
    • CloZAPine
    • CYP2C19 Inhibitors
    • CYP3A4 Inducers
    • Dapagliflozin
    • Dipeptidyl Peptidase-4 (DPP-4) Inhibitors
    • Dulaglutide
    • Empagliflozin
    • Ertugliflozin
    • Exenatide
    • First Generation Sulfonylureas
    • Gliclazide
    • Glimepiride
    • Glipizide
    • Glyburide (Glibenclamide)
    • Glucagon-Like Peptide-1 (GLP-1) Analogues
    • Hormonal Contraceptives
    • Incretin-Based Drugs
    • Linagliptin
    • Liraglutide
    • Lixisenatide
    • Metformin
    • Metiglinide Analogues
    • Miglitol
    • Nateglinide
    • NiMODipine
    • Pioglitazone
    • Pramlintide
    • Repaglinide
    • Rosiglitazone
    • Saxagliptin
    • Second Generation Sulfonylureas
    • Selpercatinib
    • Semaglutide
    • Sodium-Glucose Cotransporter-2 (SGLT2) Inhibitors
    • Sirolimus
    • Sitagliptin
    • Tacrolimus
    • Teplizumab
    • Thiazolidinediones
    • Tirzepatide
    • Tolazamide
    • Tolbutamide
    • Troglitazone
    • Ubrogepant


    Belzutifan may cause harm to unborn babies if used during pregnancy.

    Treatment with Welireg may cause anemia or hypoxia. Tell your doctor if you have trouble breathing at any point during therapy.

    Side Effects

    Common adverse reactions include:

    • Abdominal pain
    • Anemia
    • Arthralgia
    • Constipation
    • Cough
    • Decreased calcium
    • Decreased phosphate
    • Dehydration
    • Dizziness
    • Dyspnea
    • Edema
    • Fatigue
    • Flu-like symptoms
    • Headache
    • Hypertension
    • Hypoxia
    • Increased creatinine
    • Increased aspartate aminotransferase
    • Leukocytosis
    • Musculoskeletal pain
    • Myalgia
    • Nausea
    • Retinal detachment
    • Retinal vein occlusion
    • Upper respiratory tract infection
    • Visual impairment
    • Vomiting
    • Weight gain


    1. Welireg [package insert]. Whitehouse Station, NJ: Merck; 2021.

    IMPORTANT NOTE: The above information is intended to increase awareness of health information and does not suggest treatment or diagnosis. This information is not a substitute for individual medical attention and should not be construed to indicate that use of the drug is safe, appropriate, or effective for you. See your health care professional for medical advice and treatment.

    Product Code : 13772

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