FDA Approves Belzutifan Plus Lenvatinib for Advanced Clear Cell Kidney Cancer

On September 24, 2026, the U.S. Food and Drug Administration approved belzutifan, marketed as Welireg by Merck & Co., in combination with lenvatinib, marketed as Lenvima by Eisai, for adults with advanced renal cell carcinoma with a clear cell component whose disease progressed on or after a PD-1 or PD-L1 inhibitor. The decision covers patients with locally advanced or metastatic clear cell renal cell carcinoma (ccRCC) that advanced following checkpoint inhibitor therapy, or who relapsed within six months of completing adjuvant treatment with a PD-1 inhibitor.

Clear cell renal cell carcinoma is the most common form of kidney cancer, and for years the standard first step for advanced disease has been a PD-1 or PD-L1 checkpoint inhibitor, often paired with a tyrosine kinase inhibitor. When that approach stops working, oncologists must choose among a limited set of second line options. Until now, the most widely used comparator in that setting has been cabozantinib, a multi kinase inhibitor that has served as the backbone of later line therapy for many patients.

The regimen approved on September 24 pairs two oral drugs with entirely different mechanisms. Belzutifan is Merck's first in class hypoxia inducible factor 2 alpha (HIF-2alpha) inhibitor, a pill that targets the oxygen sensing pathway driving many clear cell tumors. Lenvatinib is Eisai's orally available multiple receptor tyrosine kinase inhibitor, a drug already used across several tumor types. According to Merck and Eisai, the combination is the first approved pairing of a HIF-2 alpha inhibitor with a multi targeted VEGFR TKI for these patients.

The approval rests on the phase 3 LITESPARK-011 trial, an open label, randomized, active controlled study that enrolled 747 patients. The FDA action converts what had been a closely watched experimental strategy into a routine option for a population that urgently needs alternatives after immunotherapy.

Key Facts

The U.S. Food and Drug Administration announced on September 24, 2026 that it had granted approval for belzutifan plus lenvatinib in advanced ccRCC after a PD-1 or PD-L1 inhibitor, based on the phase 3 LITESPARK-011 trial (NCT04586231). The trial randomized 747 patients 1:1 to receive either belzutifan and lenvatinib or cabozantinib. Eligible patients had locally advanced or metastatic ccRCC that progressed on or after a PD-1 or PD-L1 inhibitor, or within six months of completing adjuvant therapy with a PD-1 inhibitor.

The primary efficacy measure, progression free survival, favored the investigational combination. Median PFS was 14.6 months (95% CI: 11.1, 16.6) for belzutifan plus lenvatinib versus 10.6 months (95% CI: 9.2, 11.1) for cabozantinib, with a hazard ratio of 0.74 (95% CI: 0.61, 0.89) and a one sided p value of 0.00095. Merck and Eisai described the result as a 26% reduction in the risk of disease progression or death.

Objective response rate was 53% (95% CI: 47, 58) in the belzutifan plus lenvatinib arm compared with 40% (95% CI: 35, 45) for cabozantinib, with a one sided p value of 0.0002. The final analysis of overall survival did not reach statistical significance: median OS was 33.7 months (95% CI: 29.0, 46.9) versus 28.6 months (95% CI: 24.1, 31.4), with a hazard ratio of 0.85 (95% CI: 0.70, 1.03).

The recommended dosage is 20 mg of lenvatinib taken with 120 mg of belzutifan once daily until disease progression or unacceptable toxicity. The belzutifan prescribing information carries a boxed warning for embryo fetal toxicity, along with warnings and precautions for anemia and hypoxia. For the combination, the labeling also warns of cardiac dysfunction, including heart failure with reduced left ventricular ejection fraction.

The ASCO Post reported on September 25, 2026 that the review used the Assessment Aid, a voluntary submission from the applicant intended to help the FDA complete its assessment of the application.

Analysis

The headline number in LITESPARK-011 is not the roughly four month gain in median progression free survival. It is the hazard ratio of 0.74, which held across a 747 patient randomized trial and translated into a 26% reduction in the risk of progression or death. That is a meaningful treatment effect in a setting where second line options have historically produced modest improvements, and it arrives alongside an objective response rate that climbed from 40% to 53%.

What this really means is that the field now has a second validated mechanism to attack clear cell tumors after checkpoint inhibition fails. For a decade, the post immunotherapy landscape has leaned on drugs that act on blood vessel formation and related kinases. Belzutifan attacks the HIF-2alpha pathway that is central to the biology of most clear cell tumors, so this combination is not simply another drug added to the same class. It is a genuinely different way of pressing on the disease, and the trial was designed to prove it against an active comparator rather than a placebo.

The overall survival picture is the honest caveat. The ASCO Post reported on September 25, 2026 that the final analysis of overall survival was not statistically significant, with median OS of 33.7 months versus 28.6 months and a hazard ratio of 0.85 whose confidence interval crossed 1.0. That does not erase the progression free survival benefit, but it does mean the survival question remains open, and clinicians, payers and regulators will weigh how much a delay in progression is worth on its own.

Safety will also shape adoption. The ONS Voice reported on September 24, 2026 that belzutifan's labeling includes a boxed warning for embryo fetal toxicity plus warnings for anemia and hypoxia, and that the combination adds cardiac dysfunction to the list. Anemia and hypoxia are signature effects of HIF-2alpha inhibition, and cardiac dysfunction is a recognized concern for lenvatinib containing regimens, so the combination demands careful monitoring rather than a simple substitution for cabozantinib. The dosing schedule, two pills once daily, is convenient, but convenience does not remove the need for vigilance.

Why It Matters

For patients with advanced ccRCC whose disease has progressed after a PD-1 or PD-L1 inhibitor, the approval on September 24, 2026 adds a fully oral option that was studied head to head against the existing standard. That design matters because it gives clinicians comparative data rather than a single arm response rate, and it supports a direct conversation about expected benefit and risk.

The bigger picture here is about how kidney cancer is treated as a sequence rather than a single decision. First line immunotherapy combinations have improved outcomes, which means more patients reach second line treatment, which means the quality of that second line choice matters more than ever. A regimen that reduces the risk of progression by 26% against an active comparator speaks directly to that growing population, and it gives physicians a biologically distinct option when the first immune based strategy has run its course.

The collaboration structure also matters scientifically and commercially. Merck brings belzutifan, its first in class HIF-2alpha inhibitor, and Eisai brings lenvatinib, a TKI the company discovered that is already used in several tumor types. The FDA approval announced on September 24, 2026 validates a partnership model in which two companies combine a novel mechanism with an established one, and it gives both firms a new labeled indication in a competitive disease area.

Next Up

Merck and Eisai said in a September 25, 2026 statement that the LITESPARK-011 results will be presented at the upcoming European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain. That presentation will give the oncology community its first full look at the dataset, including the safety details behind the warnings for anemia, hypoxia and cardiac dysfunction.

The remaining questions are the ones the data leave open: whether the progression free survival advantage translates into a survival benefit with longer follow up, how the regimen performs in routine practice outside a controlled trial, and whether regulators in other countries follow the FDA's September 24, 2026 decision.