Exelixis announces initial results from expansion cohort of STELLAR-001 study

Exelixis announced initial results from an expansion cohort of STELLAR-001 evaluating single-agent zanzalintinib in patients with previously treated clear cell renal cell carcinoma, or ccRCC. STELLAR-001 is a phase 1b trial evaluating zanzalintinib alone and in combination with atezolizumab in patients with locally advanced or metastatic solid tumors. The findings are being presented at 2:35 p.m. CST during the Oral Abstracts session at the 2023 International Kidney Cancer Symposium, or IKCS: North America. In this ccRCC cohort, 97% of patients had received prior immunotherapy and 81% had received prior VEGFR-tyrosine kinase inhibitor, including 53% who had received cabozantinib. Eighty-one percent of patients were intermediate risk by International Metastatic RCC Database Consortium. At a median follow-up of 8.3 months, 12 of the 32 patients enrolled in the expansion cohort had a confirmed partial response for an objective response rate of 38%; the disease control rate was 88%. Additional efficacy outcomes by prior therapy subgroups are shown in Table 1. At data cutoff, 50% of patients were continuing treatment. The median duration of response was 7.4 months for the cabozantinib-naive group and not estimable for the cabozantinib-exposed group. The safety population included 32 patients from the ccRCC expansion cohort treated at 100 mg plus 49 patients across different solid tumors from the dose-escalation stage who received single-agent zanzalintinib at doses ranging from 10-140 mg. The safety profile was similar between the ccRCC cohort and the safety population. Discontinuations due to treatment-related adverse events, or AEs, occurred in 9% of patients in the ccRCC cohort and 12% of patients in the safety population. There were three grade 5 treatment-emergent AEs in the ccRCC cohort and two more in the safety population; none were treatment-related, nor was the single grade 4 event. Of note, the rate of palmar plantar erythrodysesthesia was low with zanzalintinib.