Targeting multiple receptor tyrosine kinases with sitravatinib: A Phase 1b study in advanced renal cell carcinoma and castrate-resistant prostate cancer.

Sitravatinib (MGCD516) is an oral inhibitor of several closely related oncogenic tyrosine kinase receptors that include VEGFR-2 (vascular endothelial growth factor receptor-2), AXL, and MET (mesenchymal-epithelial transition). The safety and antitumor activity of sitravatinib are reported in patients from two histologic cohorts (anti-angiogenesis-refractory clear cell renal cell carcinoma [RCC] and castrate-resistant prostate cancer [CRPC] with bone metastases) who participated in a Phase 1/1b study. The patients were enrolled using a 3-stage design that was based on observed objective responses. Objective response rate (ORR) was the primary endpoint. Duration of response, progression-free survival (PFS), overall survival (OS), and safety were also assessed. Overall, 48 patients (RCC n = 38, CRPC n = 10) received ≥ 1 dose of sitravatinib. Both cohorts were heavily pretreated (median number of prior systemic therapies: RCC cohort 3, CRPC cohort 6). In the RCC cohort, ORR was 25.9%, P = 0.015 (null hypothesis [ORR ≤ 10%] was rejected). Responses were durable (median duration 13.2 months). Median PFS was 9.5 months and median OS was 30.0 months. No objective responses were seen in the CRPC cohort; median PFS and OS were 5.8 months and 10.1 months, respectively. Across both cohorts, diarrhea (72.9%), fatigue (54.2%), and hypertension (52.1%) were the most frequent all-cause treatment-emergent adverse events (TEAEs). Diarrhea and vomiting (both, 6.3%) were the most frequent serious TEAEs considered related to study treatment. Sitravatinib demonstrated an acceptable safety profile and promising clinical activity in patients with clear cell RCC refractory to prior angiogenesis inhibitor therapy. Strong indicators for clinical activity were not seen in patients with CRPC and bone metastases. Clinical trial registration:ClinicalTrials.gov NCT02219711.