FDA approves belzutifan for pheochromocytoma or paraganglioma
Dear Pheo Para Community,
On May 14, 2025, the US Food and Drug Administration (FDA) approved belzutifan for adults and children over 12 years of age, who have pheochromocytoma (pheo) or paraganglioma (para) that has spread to nearby tissues, metastasized, not able to be removed surgically, or unable to be cured through other treatment options. This FDA approval is very exciting news for our community because belzutifan is the first and only approved oral treatment for pheo para in the US.
Belzutifan is produced by Merck, known as MSD outside of the United States and Canada, under the brand name Welireg and has previously been approved by the FDA to treat patients with a number of conditions associated with von Hippel-Lindau disease (e.g., renal cell carcinoma, central nervous system hemangioblastoma, pancreatic neuroendocrine tumors) and adult patients with advanced renal cell carcinoma with a clear cell component.
How it works.
Belzutifan is a “hypoxia-inducible factor 2 alpha (HIF-2a) inhibitor”. As such, it functions to block the activity of HIF-2a, a protein, that is important in determining how cells adapt to low levels of oxygen (hypoxia). In low oxygen conditions or with specific diseases/tumors, this protein may become overactive and result in undesirable effects such as tumor growth and excessive red blood cell production. Belzutifan, as a HIF-2a inhibitor, blocks the activity of this protein. Inhibiting this protein’s functioning may reduce tumor growth, red blood cell production, and help return the cell to normal behavior. A significant number of pheo paras have cell conditions of low oxygen and overactivation of the HIF process.
How Belzutifan was tested.
Belzutifan was approved for treating advanced pheo para after undergoing a Phase 2 trial, which tested its effectiveness and safety. The full study has not yet been published. Participants included 72 patients with pheo paras that were not treatable by surgery or other means; patients also had to have stable blood pressure to participate. Participants received daily dosages of belzutifan until their disease progressed or the side effects became too problematic to continue.
The success of the study was measured primarily by the objective response rate, which is the percentage of patients whose cancer shrinks or disappears after treatment, as well as the duration of response, which is the length of time that a tumor responds to the treatment (i.e., the tumor doesn’t grow or spread). In this study, the response rate was 26% and the median (or middle) duration of response was 20.4 months. In addition, 32% of the patients were able to reduce at least one of their hypertensive medications by a minimum of 50% for at least six months.
Side effects.
Examples of the most common adverse reactions, which occurred in at least 25% of patients, include anemia, fatigue, musculoskeletal pain, decreased lymphocytes, increased potassium and calcium, and nausea. Potential interactions with a large number of other medications need to be considered (https://reference.medscape.
Cost.
As reported by Merck, the cost of Welireg is approximately $30,551 US for a 30-day supply, at typical dosage levels for adults and children weighing greater than 40 kg. This is the cash price (wholesale acquisition cost), not including discounts from insurance. Pricing may vary significantly due to several factors including brand or generic status, insurance coverage, pharmacy choice, location, and manufacturer pricing policies. Patient assistance programs are also available, find out more here.
For more information.
Merck website. (https://www.welireg.com)
https://pharmabiz.com/
https://reference.medscape.
Additional information will be coming in future published reports and conference presentations. The PPA also will be hosting a webinar on Belzutifan and other metastatic treatment options, once this additional information is available.
Sincerely,
Linda Rose-Krasnor
Chair, Board of Directors
This summary is meant to be used for informational purposes only. It is not the intention of the Pheo Para Alliance to dispense medical advice. Anyone seeking medical advice should contact their physician.