Merck (MRK) Announces FDA Approval of WELIREG

Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced that the U.S. Food and Drug Administration (FDA) has approved WELIREG, an oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor, for the treatment of adult patients with advanced renal cell carcinoma (RCC) following a programmed death receptor-1 (PD-1) or programmed death-ligand 1 (PD-L1) inhibitor and a vascular endothelial growth factor tyrosine kinase inhibitor (VEGF-TKI).

The approval is based on statistically significant and clinically meaningful results from LITESPARK-005, which is the only trial in advanced RCC to specifically evaluate patients who have progressed following a PD-1 or PD-L1 inhibitor and a VEGF-TKI. In the trial, WELIREG demonstrated superior progression-free survival (PFS) (HR=0.75 [95% CI, 0.63-0.90]; p=0.0008) versus everolimus in advanced RCC following treatment with both a PD-1 or PD-L1 checkpoint inhibitor and a VEGF receptor targeted therapy, given in sequence or in combination. Also, WELIREG showed an objective response rate (ORR) of 22% (n=82) (95% CI, 18-27) versus 4% (n=13) (95% CI, 2-6) for everolimus.

“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,” said Dr. Toni K. Choueiri, LITESPARK-005 study chair, director, Lank Center for Genitourinary Oncology, Dana-Farber Cancer Institute and Jerome and Nancy Kohlberg professor of medicine, Harvard Medical School. “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.”

The WELIREG label contains a boxed warning that exposure to WELIREG during pregnancy can cause embryo-fetal harm. Verify pregnancy status prior to the initiation of WELIREG. Advise patients of these risks and the need for effective non-hormonal contraception. WELIREG can render some hormonal contraceptives ineffective. WELIREG can cause severe anemia that can require a blood transfusion. Monitor for anemia before initiation of and periodically throughout treatment with WELIREG. WELIREG can cause severe hypoxia that may require discontinuation, supplemental oxygen, or hospitalization. Monitor oxygen saturation before initiation of and periodically throughout treatment with WELIREG. For more information, see “Selected Safety Information” below.

“In 2021, WELIREG became the first HIF-2α inhibitor therapy approved in the U.S. for the treatment of adult patients with certain VHL disease-associated tumors and is now approved for eligible patients with advanced RCC,” said Dr. Marjorie Green, senior vice president and head of late-stage oncology, global clinical development, Merck Research Laboratories. “This approval of WELIREG marks the first new therapeutic class available for eligible patients with advanced RCC in nearly a decade, and was based on the statistically significant progression-free survival benefit observed in patients following treatment with a PD-1 or PD-L1 inhibitor and a VEGF-TKI when compared to everolimus.”

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