Merck (MSD) has secured US Food and Drug Administration (FDA) approval for Welireg (belzutifan), indicated for the treatment of patients with advanced renal cell carcinoma (RCC).

Patients who have not responded following either a programmed death receptor-1 (PD-1) or a programmed death-ligand 1 (PD-L1) inhibitor, and who have also been treated with a vascular endothelial growth factor tyrosine kinase inhibitor (VEGF-TKI), will be eligible for the oral drug, according to a 14 December press release.

MSD acquired Welireg when it bought Peloton Therapeutics for an upfront payment of $1.05bn in 2019. in August 2021, the drug was first approved by the FDA for the treatment of a rare disorder called von Hippel-Lindau (VHL) disease.

The FDA based its decision for the second approval of the drug on results from MSD’s LITESPARK-005 trial (NCT04195750). According to MSD, it is the only trial to evaluate patients with RCC who have progressed following PD-1 or PD-L1 inhibitor and a VEGF-TKI. A total of 746 patients were involved in the trial.

Given at 120mg, Welireg demonstrated higher progression-free survival (PFS) compared to 10mg of Novartis’ chemotherapy Afinitor (everolimus) at 12 months – 33.7% versus 17.6%. At 18 months, the PFS for Welireg patients was 22.5% versus 9% for those on Afinitor. The objective response rate (ORR) difference was even greater, 22% for MSD’s candidate versus 4% for Afinitor.

When the interim results were presented at the European Society of Medical Oncology (ESMO) Congress in October 2023, there were questions about the drug’s overall survival (OS) performance – which did not meet statistical significance. A final analysis is still underway for this measure.

Welireg is an oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor. HIF-2α is a key regulator of tumour development in kidney cells.

Renal cell carcinoma is the most common type of kidney cancer. This year, it is estimated that 81,800 adults in the US will be diagnosed with kidney cancer, based on the American Cancer Society’s statistics

Welireg comes with a boxed warning about the potential to cause embryo-foetal harm if used during pregnancy. It can also render hormonal contraceptives ineffective and cause severe anaemia and severe hypoxia.

LITESPARK-005 study chair Dr Toni Choueiri said: “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.”

“This approval of belzutifan introduces a meaningful new treatment option for certain patients, as belzutifan reduced the risk of disease progression or death compared to everolimus.”