Merck and Exelixis Initiate Phase 3 Trial of Belzutifan and Zanzalintinib Combination for Advanced Renal Cell Carcinoma
Background of the LITESPARK-034 Phase 3 Trial
Global pharmaceutical companies Merck & Co. (MRK) and Exelixis (EXEL) announced on April 9, 2026, the initiation of patient enrollment for the global Phase 3 trial, 'LITESPARK-034 (NCT07489495),' to evaluate the combination therapy of belzutifan and zanzalintinib in patients with advanced renal cell carcinoma (RCC). This study will compare the overall survival (OS) and progression-free survival (PFS) benefits of the combination therapy versus belzutifan alone in patients who have progressed after treatment with immune checkpoint inhibitors (PD-1/L1 inhibitors) and VEGF-TKIs. This strategy aims to address unmet medical needs by targeting patients in the later stages with limited treatment options.
Synergistic Mechanism of Action of the Two Drugs
Belzutifan (brand name Welireg) is a first-in-class innovative drug that targets and inhibits hypoxia-inducible factor-2 alpha (HIF-2α), which is involved in tumor growth, thereby suppressing angiogenesis and tumor growth. Zanzalintinib (XL092), which binds to it, acts as a next-generation oral tyrosine kinase inhibitor (TKI) that targets multiple targets, including VEGF receptors, MET, and TAM (AXL, MER) kinases. The dual-blockade strategy, which simultaneously targets HIF-2α and the VEGFR/MET/TAM pathways, is expected to create a complementary synergy, delaying the development of resistance and contributing to improved treatment response rates.
Overcoming the Limitations of Standard Treatment for Renal Cell Carcinoma
Currently, the standard first-line treatment for advanced renal cell carcinoma is a combination therapy of immune checkpoint inhibitors and VEGF-TKIs; however, most patients experience drug resistance and disease progression. Belzutifan has already demonstrated efficacy as a later-stage treatment by receiving FDA approval in December 2023 for patients with advanced renal cell carcinoma who have previously received treatment. This trial aims to demonstrate that the addition of zanzalintinib to belzutifan monotherapy can significantly improve progression-free survival in patients with resistance, further advancing treatment options.
Market Size and Commercial Impact
The global market size for renal cell carcinoma and kidney cancer treatments is estimated at approximately $4.96 billion to $7.4 billion as of 2025, and continuous growth of more than $11.9 billion to $13.2 billion per year is expected by the mid-2030s. Merck's belzutifan achieved commercial success in 2025, with global sales of $716 million, a year-on-year increase of more than 40%. The successful completion of this combination trial will significantly expand the prescription area. Success will enable the company to capture an additional 10-15% of the late-stage treatment market and significantly expand its oncology portfolio.
Future Timeline and Key Points to Watch
The LITESPARK-034 study is currently enrolling patients in a double-blind manner, and the primary completion date is scheduled for November 2030. If the interim analysis results are positive, procedures for early approval or accelerated approval may be initiated, which is attracting significant market attention. In addition, the two companies are simultaneously conducting the Phase 3 trial 'LITESPARK-033,' which directly compares cabozantinib with patients who have failed previous anti-PD-(L)1 therapy. The results of these two trials will be key to changing the future treatment paradigm.
This Phase 3 trial, jointly conducted by Merck and Exelixis, is significant as it evaluates the first combination therapy of an HIF-2α inhibitor and a multi-TKI for patients with resistance to existing standard treatments. In the global renal cell carcinoma market, which is estimated at $5 billion to $7.4 billion as of 2025, belzutifan, with sales of $716 million, can significantly expand its commercial value by broadening its prescription scope to include late-stage combination therapy. By targeting patients who have failed existing standard treatments such as Pfizer's Inlyta and BMS's Opdivo, it is expected to create a strong competitive advantage by establishing a dominant market position as a second- and third-line treatment. In the short term, the interim analysis results of the clinical trial will be directly related to the stock prices and valuations of the partner companies, and in the medium to long term, it will be a crucial milestone in reshaping the treatment paradigm for late-stage renal cell carcinoma after the completion of the clinical trial in 2030.
Source: ClinicalTrials.gov (api_ct)