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Merck’s Welireg scores FDA nod in cancers spurred by rare disease—and its label is broader than expected

Merck’s $1.1 billion bet on Peloton Therapeutics is starting to pay off.

Belzutifan, one of the most lucrative assets Merck picked up through its 2019 Peloton buy, snared its first FDA approval Friday for patients with the rare disorder known as von Hippel-Lindau (VHL) disease.

Merck’s blockbuster hopeful, now marketed as Welireg, is intended for VHL patients who require therapy for associated renal cell carcinoma, central nervous system (CNS) hemangioblastomas or pancreatic neuroendocrine tumors (pNETs) but don’t immediately require surgery, according to an FDA statement.

Merck’s Welireg will come with a list price of $26,400 per month, before discounts and rebates, a spokesperson told Fierce Pharma. Supplies will be available starting in early September.

The agency’s decision comes a month ahead of its expected September decision date, and it includes a surprisingly broader label beyond just renal cell carcinoma patients, Cantor Fitzgerald analysts said in a note to clients Friday.

Welireg’s FDA win is especially good news for Merck as it works to broaden its portfolio of oncology meds beyond its megablockbuster Keytruda, which is facing a 2028 patent cliff, the analysts note. Evaluate Pharma currently forecasts $386 million in Welireg sales by 2026.

But to turn Welireg into blockbuster material, Merck is working to push it through additional indications. The company is studying the treatment, also known as MK-6482, in late-stage trials for patients with advanced renal cell carcinoma, as well as a combo therapy with Keytruda and Eisai’s lenvatinib.

Welireg could rake in between $1 billion to $1.5 billion in annual sales if it manages to score the FDA’s nod for additional kidney cancer patients, Bernstein analysts said in a note to clients on Monday.

VHL is a rare genetic disease that causes tumours and cysts to grow throughout the body, putting patients at risk for benign blood vessel tumours and several cancers, including renal cell carcinoma, Merck notes.

The drugmaker estimates that there are about 10,000 VHL patients in the U.S. and 200,000 globally. However, analysts at Mizuho believe there could be more than double that amount of U.S. cases, or roughly 22,000. In a note to clients back in June, Mizuho analysts said the drug represents a “meaningful first-to-market market opportunity.”

The drug blocks HIF-2α (hypoxia-inducible factor-2 alpha), a protein that plays a role in regulating tissue oxygen levels. Proteins known as hypoxia-inducible factors, including HIF-2α, can accumulate in patients whose bodies don’t correctly regulate them, leading to the proliferation of red blood cells and, eventually, cancers.

As many as 70% of people with the rare disease end up developing renal cell carcinoma, although growths can form in all parts of the body, Merck says. Patients sometimes undergo surgery for their kidney tumours, although the growth often returns or new ones appear, Merck’s senior vice president and global head of clinical development Roy Baynes told Fierce Biotech last year.

Investigators tested Welireg in an open-label phase 2 trial that included 61 patients with clear cell kidney cancer linked to VHL, plus those with other VHL disease-associated tumours including pancreatic cysts, pancreatic neuroendocrine tumours, CNS hemangioblastomas and pNETs.

The once-daily 120-mg drug triggered a partial or complete response in 49% of the renal cell patients, measured by radiology assessment, the FDA said. Of the renal cell patients who responded to the drug, more than half experienced a response that lasted more than 12 months. The median time to response was eight months.

Meanwhile, investigators recorded a 63% response rate in the CNS group, which included 24 patients. In the 12 patients with pNET tumours, 83% responded.