Understanding Belzutifan: A Genitourinary Cancer Expert Shares Insights
Joining us on this insightful conversation is Dr. Brian Rini, Chief of Clinical Trials and Ingram Professor of Cancer Research at Vanderbilt Ingram Cancer Center. Dr. Rini generously reviews the latest data on belzutifan, a groundbreaking HIF inhibitor, and its application in treating refractory clear cell renal cell carcinoma (RCC).
LITESPARK-005 Study: A Breakthrough in Refractory RCC
Dr. Rini delves into the pivotal LITESPARK-005 trial, which led to belzutifan’s approval in 2023. This Phase 3 study compared belzutifan to everolimus in patients with advanced RCC who had received prior PD-1/PD-L1 and VEGF-targeted therapies.
The primary endpoints of the study were progression-free survival (PFS) and overall survival (OS). While the OS data was not statistically significant, belzutifan demonstrated a clear PFS advantage, with a hazard ratio of 0.75 and notably longer time to progression for patients in the belzutifan arm. Dr. Rini highlights that a subset of patients experienced remarkably long periods of progression-free survival, exceeding a year. This, coupled with belzutifan’s response rate advantage, suggests a potentially impactful role for the drug in this refractory patient population.
Belzutifan: Balancing Benefits and Management of Side Effects
Dr. Rini emphasizes belzutifan’s favorable safety profile, with anemia being the most common side effect. However, he acknowledges the importance of monitoring patients for hypoxia, a unique side effect of HIF inhibition, and the need for timely intervention. Regular use of pulse oximetry is encouraged to assess oxygen saturation levels and guide management.
He also discusses his practical approach to managing anemia with growth factor therapy, noting its importance in addressing the predictable anemia trend in these patients. Dr. Rini underscores the need for careful patient education and training regarding the management of belzutifan-related side effects to ensure optimal treatment outcomes.
The Search for Biomarkers: Unveiling the Responsive Subset
The impressive posterior responses observed in certain patients, despite the lack of overall survival improvement, raise the question of predictive biomarkers.
Dr. Rini suggests that the next chapter in the evolution of belzutifan’s application will involve the identification of these biomarkers. While DNA-based alterations are unlikely to be the key, he favors the role of RNA signatures, pointing to emerging research and the potential for enrichment in future trials to identify patients most likely to benefit from belzutifan therapy.
Dr. Rini mentions ongoing efforts by Merck to explore biomarkers in the belzutifan trial.
Next Steps: Guiding Patients in the Post-Belzutifan Landscape
Dr. Rini acknowledges the limited data on next-line therapies after belzutifan. He anticipates that the evolution of understanding in this area will come with time and further research. He suggests that Tivozanib, another FDA-approved treatment option for refractory RCC, could be considered as a potential next-line therapy.