Combination casdatifan plus cabozantinib expansion cohort of phase 1 ARC-20 study in previously treated patients with clear cell renal cell carcinoma.

4506 Background: Hypoxia-inducible factor 2-alpha (HIF-2α) is highly dysregulated in clear cell renal cell carcinoma (ccRCC), resulting in increased expression of proteins involved with angiogenesis, proliferation, and cancer cell survival. Casdatifan is an orally bioavailable small-molecule HIF-2α inhibitor. We investigated the safety and efficacy of casdatifan in combination with the anti–vascular endothelial growth factor receptor tyrosine kinase inhibitor (VEGFR-TKI) cabozantinib in previously treated patients with ccRCC in an expansion cohort (casdatifan + cabozantinib) of the phase 1, open-label ARC-20 (NCT05536141) trial. Methods: Patients enrolled in the casdatifan + cabozantinib expansion cohort were previously treated with immunotherapy (IO) alone or with anti-VEGF therapies. Casdatifan 100 mg and cabozantinib 60 mg were given orally once daily. Endpoints included the incidence of treatment-emergent adverse events (AEs) and objective response rate (ORR) by RECIST v1.1. This study is ongoing; data as of January 3, 2025, are reported. Results: Overall, 27 patients with a median (range) follow-up of 2.9 (0.1–6.8) months were enrolled. At data cut off, prior treatment settings included adjuvant only (n = 5/26) and metastatic (1L n = 17/26; 2L n = 4/26). Prior therapies included IO only (n = 15/26) or IO plus VEGFR-TKI (n = 11/26). All grade AEs occurred in 89% of patients with the most common being anemia (n = 16 [59%]) and fatigue (n = 15 [56%]). Most common ( > 10%) grade ≥3 AEs were anemia (n = 7 [26%]) and hypoxia (n = 3 [11%]). No cardiac events were reported. AEs leading to casdatifan-only, cabozantinib-only, or both casdatifan + cabozantinib dose reductions occurred in 3 (11%), 7 (26%), and 2 (7%) patients, respectively. Only one (4%) pt discontinued due to an AE, hypoxia related to casdatifan. Responses continue to be observed among the efficacy evaluable population (n = 22; as of January 27, 2025) with ORR of 41% (n = 1 complete response; n = 8 partial response). Activity was seen across all IMDC risk groups. Conclusions: In previously treated patients with ccRCC, casdatifan 100 mg in combination with cabozantinib 60 mg had a manageable AE profile with promising clinical activity. These data support continued evaluation of this combination in the phase 3 PEAK-1 clinical trial. Clinical trial information: NCT05536141 .