39 Safety profile of belzutifan monotherapy in patients with renal cell carcinoma: A pooled analysis of 4 clinical trials

Abstract Background The first-in-class hypoxia-inducible factor-2α inhibitor, belzutifan, is indicated in the United States for the treatment of certain patients with von Hippel-Lindau (VHL) disease–associated renal cell carcinoma (RCC), central nervous system hemangioblastomas, or pancreatic neuroendocrine tumors not requiring immediate surgery and for patients with advanced RCC previously treated with a PD-(L)1 inhibitor and a vascular endothelial growth factor tyrosine kinase inhibitor. Due to its unique mechanism of action, belzutifan has a distinct safety profile. We characterized the safety profile of belzutifan monotherapy in a post hoc pooled analysis of patients with previously treated advanced clear cell RCC in the phase 1 LITESPARK-001 (NCT02974738), phase 3 LITESPARK-005 (NCT04195750), and phase 2 LITESPARK-013 (NCT04489771) studies and patients with RCC associated with VHL disease in the phase 2 LITESPARK-004 study (NCT03401788). Methods All patients who received ≥1 dose of belzutifan 120 mg orally once daily across the 4 studies were included. Severity of adverse events (AEs) were graded per the National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.03 or 5.0, and were descriptively summarized. Results A total of 576 patients were included (n = 58 [including 3 patients with advanced solid tumors other than RCC], LITESPARK-001; n = 381, LITESPARK-005; n = 76, LITESPARK-013; and n = 61, LITESPARK-004). Overall, 572 patients (99.3%) had ≥1 all-cause AE and 355 patients (61.6%) had ≥1 grade 3-5 AE. AEs led to dose modification (reduction, interruption, or discontinuation) in 288 patients (50.0%), although treatment discontinuation for AEs occurred in 37 patients (6.4%). The most common all-grade AEs were anemia (including patients with decreased hemoglobin; n = 485 [84.2%]; grade 3 or 4, n = 166 [28.8%]), fatigue (n = 246 [42.7%]; grade 3, n = 16 [2.8%]), nausea (n = 139 [24.1%]; grade 3, n = 5 [0.9%]), and dyspnea (n = 123 [21.4%]; grade 3 or 4, n = 10 [1.7%]). Hypoxia was reported in 94 patients (16.3%); grade 3 or 4 hypoxia occurred in 57 patients (9.9%). Summary and time to first onset of adverse drug reactions (AEs considered associated with belzutifan), including anemia and hypoxia, are reported in the table. Among 485 patients with anemia or decreased hemoglobin, 111 (22.9%) were treated with erythropoiesis-stimulating agent (ESA) only, 85 (17.5%) were treated with blood transfusions only, and 62 (12.8%) were treated with ESA and blood transfusions. Among 94 patients with hypoxia, 66 (70.2%) were treated with oxygen therapy. Treatment-related AEs occurred in 526 patients (91.3%) and 217 (37.7%) experienced a grade 3-5 treatment-related AE. One grade 5 adverse event (multiple organ dysfunction syndrome) was considered related to treatment. Conclusions To date, this is the largest pooled safety dataset for belzutifan monotherapy in patients with RCC. The results provide an in-depth characterization of the safety profile for belzutifan and the associated AE management strategies.