Long-term Safety and Efficacy of Belzutifan in Von Hippel-Lindau Syndrome: A VHL Coordinating Care Center Experience.

Von Hippel-Lindau (VHL) disease is a rare inherited syndrome characterized by benign and malignant neoplasms. Belzutifan, a HIF-2α inhibitor, was approved for the treatment of VHL-associated neoplasms. As a first-in-class agent, understanding tolerability and efficacy outside of a clinical trial setting and optimizing the management of adverse events (AEs) is important. We conducted a retrospective analysis of VHL patients ≥18 years old, treated with belzutifan at Vanderbilt University Medical Center, between November 2018 and December 2024. Clinical data and AEs were collected. Primary endpoint was safety; secondary endpoints included dose reduction, treatment interruption, treatment discontinuation, time to anemia onset, time to dose reduction, tumor shrinkage, objective response (per RECIST 1.1), and need for subsequent VHL-related procedures. Among 25 patients, with a median follow-up of 35.0 months, any-grade AEs occurred in 23 (92%) patients; anemia was the most frequent (64%, no grade ≥ 3). The median time to anemia onset was 3.7 months. Treatment interruption happened in 80% of the patients. The dose reduction was needed in 15 (60%) patients, with a median time of 6.8 months, and the median final dose was 80 mg. Tumor shrinkage occurred in 89% of RCC patients, 80% of CNS hemangioblastoma, and 80% of pancreatic neuroendocrine tumors (pNET). Overall, four (20%) patients experienced the progression of the disease. During follow-up, three (12%) patients required new VHL-related procedures. These findings support the long-term safety and efficacy of belzutifan in VHL disease, underscore the utility of dose reduction for AE management while demonstrating durable disease control, and a low incidence of interventional procedures.