With new FDA approval, Merck's Welireg takes another step toward blockbuster goal

Since Merck secured approval for kidney cancer pill and blockbuster hopeful Welireg (belzutifan) in August of 2021, sales have grown slowly but surely.

With a second FDA nod on Thursday for a much larger patient population, the company can anticipate a more pronounced upswing in revenue from the hypoxia-inducible factor-2 alpha (HIF-2a) inhibitor.

The U.S. regulator has given a thumbs up for Welireg to treat relapsed or refractory renal cell carcinoma (RCC) for adult patients who have not responded to a PD-1 or PD-L1 inhibitor and who have also been treated with a vascular endothelial growth factor tyrosine kinase inhibitor (VEGF-TK1).

Welireg becomes the first drug in its class for patients with advanced RCC and the first novel-class treatment in the indication since 2015, Merck noted.

The nod comes on top of its original approval to treat the rare von Hippel-Lindau disease, a hereditary condition that causes tumor growth in various organs of the body, most often in the kidney.

Merck hopes Thursday’s label expansion is the first of a few for Welireg in RCC, as the company is investigating the treatment in earlier lines of use. RCC is the most common form of kidney cancer, accounting for roughly 9 of every 10 cases.

In the phase 3 LITESPARK-005 study, Welireg outperformed Novartis’ chemotherapy Afinitor (everolimus), paving the way for the most recent green light. From a pool of 746 patients, after 12 months, 34% of those who received a daily, 120 mg dose of Welireg achieved progression-free survival. That compared with 18% for those on Afinitor.

After 18 months, those figures dropped to 22% and 9%, respectively. Welireg also produced a 22% objective response rate, compared with 4% for Afinitor.

“Despite recent progress in the treatment of advanced RCC, there is yet to be an option specifically approved for patients whose disease progresses following a PD-1 or PD-L1 inhibitor and a TKI therapy,” Toni Choueiri, the LITESPARK-005 study chair and the director of the Lank Center for Genitourinary Oncology at the Dana-Farber Cancer Institute, said in a release.

Merck gained Welireg when it purchased Peloton Therapeutics for $1.05 billion up front in 2019.

In the last three quarters, Welireg sales have climbed from $42 million to $50 million to $54 million. When it was approved in 2021, Bernstein analysts pegged Welireg’s peak sales potential between $1 billion and $1.5 billion if it gains approval to treat earlier-stage RCC patients.