Merck and Eisai report 30% lower progression risk with Welireg-Lenvima in RCC

Merck and Eisai announced that the oral combination of WELIREG (belzutifan) plus LENVIMA (lenvatinib) met the primary endpoint in the Phase 3 LITESPARK-011 trial, reducing the risk of disease progression or death by 30% compared with cabozantinib in patients with advanced renal cell carcinoma whose cancer progressed after anti‑PD‑1/PD‑L1 therapy. The companies presented the data as a late‑breaking oral abstract at the 2026 American Society of Clinical Oncology genitourinary symposium.

According to the ASCO presentation and reporting from the conference, the combination produced a median progression‑free survival gain of approximately 4.1 months and a highly significant p value of 0.00007. Merck framed the result in a press release headline, saying WELIREG plus LENVIMA “reduced the risk of disease progression or death by 30% compared to cabozantinib” in the studied population.

Overall survival at topline was described by the sponsor as a numerical benefit only. The study lead, Robert Motzer of Memorial Sloan Kettering Cancer Center, disclosed during the presentation that the median overall survival difference between arms was seven months, but neither a hazard ratio nor a p value for survival has been published in the materials cited by the sponsors.

Investigators and company officials framed the result as clinically meaningful and novel. Eisai said the study is the first Phase 3 to show a statistically significant PFS improvement in patients whose disease progressed after PD‑1/PD‑L1 therapy versus cabozantinib. Merck positioned LITESPARK-011 as part of a broader late‑stage program for WELIREG, which is already approved in the U.S., European Union, Japan and other countries for certain patients with advanced clear‑cell RCC based on earlier trials.

Cathy Pietanza of Merck described the combined trial results in an interview as “very compelling,” showing “statistically significant and clinically meaningful improvements on their primary endpoints.” Motzer added that the Welireg-Lenvima regimen “could represent a potential new treatment option for patients with RCC that have progressed on” an immune checkpoint inhibitor and said LITESPARK-011 “is the first phase 3 trial in a post-immunotherapy setting in kidney cancer to improve outcomes versus a contemporary anti‑VEGFR tyrosine kinase inhibitor.”

Safety details for LITESPARK-011 were not published in full in the sponsor releases cited. WELIREG’s approved label warns of anemia and hypoxia. Motzer told reporters that toxicities in the trial “weren’t worse with Welireg than control, but simply that they were different.” Observers caution that complete safety tables by arm, including rates of grade 3 or higher adverse events and treatment discontinuations, are needed to judge tolerability and the net clinical benefit.

The trial addresses a common clinical gap: clear cell RCC accounts for roughly four in five kidney cancer cases, and many patients progress after frontline immune checkpoint therapies. If regulators accept the results, the regimen could offer a new second‑line option for patients whose cancers prove refractory to immunotherapy. The balance of added benefit, safety tradeoffs, and access will determine whether the combination changes standards of care for patients and health systems dealing with advanced kidney cancer.