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This is the first positive Phase 3 trial of a HIF-2 alpha inhibitor in combination with a multi-targeted tyrosine kinase inhibitor, the first for patients with RCC whose disease progressed on or after treatment with anti-PD-1/L1 therapy, and the first to improve PFS compared to a modern tyrosine kinase inhibitor
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Based on these data, the U.S. FDA has accepted for review two supplemental New Drug Applications for WELIREG plus LENVIMA in certain previously treated patients with advanced RCC
February 28, 2026--RAHWAY, N.J. & NUTLEY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, and Eisai today announced the first presentation of results from the Phase 3 LITESPARK-011 trial evaluating the dual oral regimen of WELIREG® (belzutifan), Merck’s first-in-class oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor, plus LENVIMA® (lenvatinib), an orally available multiple receptor tyrosine kinase inhibitor (TKI) discovered by Eisai, for the treatment of patients with advanced renal cell carcinoma (RCC) whose disease progressed on or after treatment with anti-programmed death receptor-1 (PD-1)/programmed death-ligand 1 (PD-L1) therapy. These data are being presented as a late-breaking oral abstract at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium (abstract #LBA417) and are included in the official ASCO GU Press Program.
At a pre-specified interim analysis with a median follow-up of 29.0 months (range, 19.3-49.2), WELIREG plus LENVIMA demonstrated a statistically significant and clinically meaningful improvement in the primary endpoint of progression-free survival (PFS), reducing the risk of disease progression or death by 30% (HR=0.70 [95% CI, 0.59-0.84]; p=0.00007) compared to cabozantinib. For WELIREG plus LENVIMA, the median PFS was 14.8 months (95% CI, 11.2-16.6) versus 10.7 months (95% CI, 9.2-11.1) for cabozantinib. A trend toward improvement in overall survival (OS), the trial’s other primary endpoint, was also observed for WELIREG plus LENVIMA (HR=0.85 [95% CI, 0.68-1.05]; p=0.06075). The median OS was 34.9 months (95% CI, 27.5-NR) for WELIREG plus LENVIMA versus 27.6 months (95% CI, 24.0-31.4) for cabozantinib. The trial is continuing, and OS will be evaluated at a subsequent analysis per the clinical trial protocol.
Based on data from the LITESPARK-011 trial, the U.S. Food and Drug Administration (FDA) has accepted two supplemental New Drug Applications (sNDA) for review seeking approval for WELIREG plus LENVIMA for the treatment of adult patients with advanced RCC with a clear cell component following a PD-1 or PD-L1 inhibitor. The FDA set a Prescription Drug User Fee Act (PDUFA), or target action date, of October 4, 2026 for both the WELIREG and LENVIMA sNDAs. Merck and Eisai will also discuss these data with regulatory authorities worldwide to support potential submissions outside the United States.
“Choosing the right treatment for patients with advanced renal cell carcinoma after immunotherapy has been an ongoing challenge, and treatment options in this setting had not previously been evaluated against a current standard of care tyrosine kinase inhibitor in a Phase 3 trial,” said Dr. Robert Motzer, Principal Investigator and Genitourinary Medical Oncologist, Memorial Sloan Kettering Cancer Center. “The LITESPARK-011 study demonstrated a 30% reduction in the risk of disease progression or death with belzutifan plus lenvatinib compared to cabozantinib, and 52.6% of patients experienced a response to treatment. These findings mark a critical step forward for these patients.”
“The LITESPARK-011 trial highlights the potential of this first-of-its-kind combination regimen to deliver a meaningful benefit for patients with advanced renal cell carcinoma whose disease progresses after PD-1/L1 therapy,” said Dr. M. Catherine Pietanza, Vice President, Global Clinical Development, Merck Research Laboratories. “These WELIREG plus LENVIMA data demonstrate important progress for patients with advanced renal cell carcinoma and reinforce our commitment to improving the lives of patients through innovative treatment strategies.”
“The LITESPARK-011 results reinforce LENVIMA's established role in renal cell carcinoma and highlight the potential of this novel combination to address an area of significant unmet need,” said Dr. Corina Dutcus, Senior Vice President, Oncology Global Clinical Development Lead at Eisai. “The acceptance of this regulatory filing is an important milestone, and we remain committed to working toward approval to bring this option to patients as soon as possible. We are grateful to the patients, their families, and the investigators, whose dedication made this research possible.”
About LITESPARK-011
LITESPARK-011 is a randomized, open-label Phase 3 trial (ClinicalTrials.gov, NCT04586231) evaluating WELIREG in combination with LENVIMA compared to cabozantinib for the treatment of patients with advanced clear cell RCC that has progressed on or after anti-PD-1/L1 therapy. The dual primary endpoints are PFS per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) as assessed by blinded independent central review (BICR) and OS. Key secondary endpoints include ORR per RECIST v1.1 as assessed by BICR, DOR per RECIST v1.1 as assessed by BICR, and safety. The trial enrolled 747 patients who were randomized to receive WELIREG (120 mg orally once daily) plus LENVIMA (20 mg orally once daily) or cabozantinib (60 mg orally once daily).
About renal cell carcinoma
Renal cell carcinoma is the most common type of kidney cancer, with about nine out of 10 kidney cancer diagnoses being RCC. In 2022, there were about 435,000 new cases of kidney cancer and approximately 156,000 deaths from the disease worldwide. RCC is about twice as common in men as in women. Most cases of RCC are discovered incidentally during imaging tests for other abdominal diseases. Approximately 30% of patients with kidney cancer are diagnosed at an advanced stage.
About Merck’s research in genitourinary cancers
Merck is advancing research aimed at helping transform the treatment landscape and broaden options for people with genitourinary (GU) cancers, including bladder, kidney and prostate cancers. Globally, GU cancers account for an estimated 2.6 million new cancer diagnoses each year, equaling over 1 in 8 of all cancer incidences. Through a robust clinical development program with more than 50 ongoing clinical trials evaluating more than 22,000 patients around the world, Merck is investigating the potential of several portfolio medicines and pipeline assets, leveraging multiple novel combination strategies, across various stages of disease, to help address unmet needs in GU cancers.
About WELIREG® (belzutifan) 40 mg tablets, for oral use
WELIREG, Merck’s first-in-class hypoxia-inducible factor 2 alpha (HIF-2α) inhibitor, is an orally administered small-molecule designed to reduce transcription and expression of HIF-2α target genes associated with cellular proliferation, angiogenesis and tumor growth. By inhibiting HIF-2α signaling, WELIREG aims to disrupt key pathways certain tumors may use to adapt to low-oxygen conditions, including those that help promote abnormal blood vessel formation and support tumor survival.
WELIREG has demonstrated antitumor activity in certain von Hippel-Lindau (VHL) disease-associated tumors, renal cell carcinoma and in pheochromocytoma or paraganglioma. As part of a broader clinical program, Merck continues to research WELIREG monotherapy and combination approaches for people with genitourinary, breast and gynecologic cancers across a range of treatment settings to further define where HIF-2α inhibition may provide clinical benefit and to better understand which patients are most likely to respond.
About the Merck and Eisai strategic collaboration
In March 2018, Eisai and Merck, known as MSD outside of the United States and Canada, through an affiliate, entered into a strategic collaboration for the worldwide co-development and co-commercialization of LENVIMA. Under the agreement, the companies jointly develop, manufacture and commercialize LENVIMA, both as monotherapy and in combination with Merck’s anti-PD-1 therapy, KEYTRUDA, and HIF-2α inhibitor, WELIREG.
Merck’s focus on cancer
Every day, we follow the science as we work to discover innovations that can help patients, no matter what stage of cancer they have. As a leading oncology company, we are pursuing research where scientific opportunity and medical need converge, underpinned by our diverse pipeline of more than 25 novel mechanisms. With one of the largest clinical development programs across more than 30 tumor types, we strive to advance breakthrough science that will shape the future of oncology. By addressing barriers to clinical trial participation, screening and treatment, we work with urgency to reduce disparities and help ensure patients have access to high-quality cancer care. Our unwavering commitment is what will bring us closer to our goal of bringing life to more patients with cancer.
About Merck
At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities.
About Eisai
Eisai’s Corporate Concept is “to give first thought to patients and people in the daily living domain, and to increase the benefits that health care provides.” Under this Concept [also known as our human health care (hhc) Concept], we aim to effectively achieve social good in the form of relieving anxiety over health and reducing health disparities. With a global network of R&D facilities, manufacturing sites and marketing subsidiaries, we strive to create and deliver innovative products to target diseases with high unmet medical needs, with a particular focus in our strategic areas of Neurology and Oncology.
In addition, our continued commitment to the elimination of neglected tropical diseases (NTDs), which is a target (3.3) of the United Nations Sustainable Development Goals (SDGs), is demonstrated by our work on various activities together with global partners.