Belzutifan

HIF-2α (hypoxia-inducible factor 2 alpha): A protein inside cells that acts like a switch, turning on genes that help tumors grow and form new blood vessels when oxygen is low or VHL protein is missing.

VHL disease: Von Hippel-Lindau disease — a rare inherited condition caused by a faulty VHL gene that leads to tumors growing in the kidneys, brain, spinal cord, and other organs.

VHL protein: A protein produced by the VHL gene that normally keeps HIF-2α in check; when it's missing or faulty, HIF-2α builds up and drives tumor growth.

renal cell carcinoma (RCC): Kidney cancer — a tumor that starts in the cells lining the kidney's tiny filtering tubes.

clear cell renal cell carcinoma (ccRCC): The most common subtype of kidney cancer, named for the pale or clear appearance of its cells under a microscope.

hemangioblastoma: A noncancerous but serious tumor made up of blood vessel cells, most often found in the brain or spinal cord in people with VHL disease.

pancreatic neuroendocrine tumor (pNET): A tumor that starts in hormone-producing cells of the pancreas; can be associated with VHL disease.

pheochromocytoma: A rare tumor of the adrenal gland (located above the kidney) that can release stress hormones and cause dangerous spikes in blood pressure.

paraganglioma: A rare tumor similar to pheochromocytoma but growing outside the adrenal gland, usually near nerve tissue in the abdomen or chest.

PPGL: Abbreviation for pheochromocytoma and paraganglioma — two related rare tumor types treated by Welireg.

adjuvant treatment: Treatment given after the main therapy (such as surgery) to lower the risk of cancer coming back.

nephrectomy: Surgical removal of all or part of a kidney.

pembrolizumab: An immunotherapy drug (a PD-1 inhibitor) that helps the immune system recognize and attack cancer cells; used in combination with Welireg for certain kidney cancer patients.

PD-1 inhibitor: A type of immunotherapy that blocks the PD-1 protein, freeing the immune system to attack cancer cells more effectively.

PD-L1 inhibitor: A type of immunotherapy that blocks PD-L1, a protein cancer cells use to hide from the immune system.

VEGF-TKI (vascular endothelial growth factor tyrosine kinase inhibitor): A targeted cancer drug that blocks signals that tumors use to grow new blood vessels, starving the tumor of nutrients.

anemia: A condition where the blood has fewer red blood cells than normal, often causing fatigue, paleness, and shortness of breath.

hemoglobin: The protein in red blood cells that carries oxygen throughout the body; low levels indicate anemia.

hypoxia: Dangerously low oxygen levels in the body, which can cause shortness of breath, confusion, or organ damage.

erythropoietin (EPO): A hormone made mainly by the kidneys that tells the bone marrow to produce more red blood cells.

erythropoiesis-stimulating agents (ESAs): Drugs that mimic EPO to stimulate the bone marrow to make more red blood cells; used to treat anemia in some conditions.

QT interval prolongation: A change in the heart's electrical cycle (visible on an ECG) that can in some cases lead to abnormal heart rhythms.

CYP3A4: A liver enzyme that breaks down many medications; drugs that affect this enzyme can change how other medicines are processed in the body.

CYP2C19: A liver enzyme involved in breaking down belzutifan and some other medications; people with a less active version process drugs more slowly.

UGT2B17: A liver enzyme that helps break down belzutifan; people with reduced UGT2B17 activity may have higher drug levels in their blood.

poor metabolizer: A person whose genetic makeup causes them to break down a drug more slowly than average, leading to higher drug levels and potentially more side effects.

half-life: The time it takes for the concentration of a drug in the body to fall by half; belzutifan's half-life is about 14 hours.

steady state: The point during regular dosing when the amount of drug entering the body equals the amount leaving, keeping levels stable; belzutifan reaches this in about 3 days.

ALT (alanine aminotransferase): A liver enzyme measured in blood tests; elevated levels can signal liver stress or injury.

AST (aspartate aminotransferase): Another liver enzyme used in blood tests to check for liver or muscle damage.

alkaline phosphatase: An enzyme found in the liver and bones; elevated levels in a blood test can indicate liver or bone problems.

lymphocytes: A type of white blood cell that plays a key role in the immune system; low counts can increase infection risk.

thrombocytopenia: An abnormally low platelet count in the blood, which can increase the risk of bleeding.

embryo-fetal toxicity: Harm caused to a developing embryo or fetus by a drug taken during pregnancy, ranging from birth defects to pregnancy loss.

non-hormonal contraception: Birth control methods that do not use hormones, such as a copper IUD or condoms; recommended with Welireg because it can make hormonal methods fail.

hormonal contraceptive: A birth control method that uses hormones (estrogen or progestin) to prevent pregnancy, such as the pill, patch, ring, or hormonal IUD.

hepatic impairment: Reduced liver function, which can affect how drugs are broken down; may require dose monitoring adjustments.

eGFR (estimated glomerular filtration rate): A blood test result that estimates how well the kidneys are filtering waste; lower values mean worse kidney function.

angiogenesis: The growth of new blood vessels; tumors promote this process to get the nutrients they need to grow, and blocking it is one way targeted therapies work.

dyspnea: The medical term for shortness of breath or difficulty breathing.

Active ingredient: The part of a medicine that produces its intended effect on the body.

adjuvant: Extra treatment given after the main treatment to lower the chance that the cancer comes back.

Adverse Reactions: Unwanted or harmful effects that people experienced while taking a medicine, listed on its official label.

ALT: A liver enzyme (alanine aminotransferase) checked by a blood test; raised levels can signal that the liver is irritated or damaged.

antidote: A treatment that reverses or counteracts the effects of a specific medicine or poison.

anxiety: A feeling of worry, nervousness, or unease, sometimes along with a racing heart or restlessness.

AST: A liver enzyme (aspartate aminotransferase) measured in a blood test; higher levels may point to liver or sometimes muscle injury.

contraception: Methods used to prevent pregnancy, such as birth control pills, condoms, or an intrauterine device.

Dosage and Administration: The label section explaining how much of a medicine to use and how to take or give it.

eGFR: Estimated glomerular filtration rate, a blood-test-based estimate of how well the kidneys filter; lower numbers mean weaker function.

fertility: The natural ability to become pregnant or to father a child.

fetal harm: Injury or damage to a developing baby while it is growing inside the womb.

Indications and Usage: The label section stating which medical conditions the FDA has officially approved the medicine to treat, prevent, or manage.

inhibitor: A substance that blocks an enzyme or transporter, which can raise the levels of drugs it normally handles.

monotherapy: Treatment using a single medicine by itself.

NDC: A unique number that identifies a specific medicine, its maker, strength, and package size.

nursing infant: A baby who is being fed breast milk.

oxygen saturation: A measurement, shown as a percentage, of how much oxygen the red blood cells are carrying.

Warnings and Precautions: The label section describing serious risks to know about and safety steps to follow while using a medicine.