Sitravatinib in combination with nivolumab plus ipilimumab in patients with advanced clear cell renal cell carcinoma: a phase 1 trial

Sitravatinib is an immunomodulatory tyrosine kinase inhibitor that can improve responses when combined with immune checkpoint therapy (ICT). We conducted a phase I trial to determine the optimal dose of triplet therapy with sitravatinib plus nivolumab plus ipilimumab in 22 previously untreated patients with advanced clear cell renal cell carcinoma (ccRCC). The primary endpoint was safety. The addition of even a low sitravatinib dose of 35 mg daily to nivolumab 3 mg/kg and ipilimumab 1 mg/kg resulted in high frequency of immune-related adverse events (irAEs). Subsequent dose reduction of ipilimumab to 0.7 mg/kg in combination with nivolumab 3 mg/kg allowed safe escalation of sitravatinib up to 100 mg daily. Key secondary endpoints were objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). Overall, the triplet combination in the dose-finding setting achieved an ORR of 45.5%, DCR of 86.4%, and a median PFS of 14.5 months with 72.7% of patients alive after a median follow-up of 15.7 months. Single-cell RNA-seq performed in longitudinally collected tumor biopsies from 12 patients treated with the triplet therapy identified a tumor cell-specific epithelial-mesenchymal transition (EMT)-like program associated with treatment resistance and poor outcomes in patients of this trial and in patients of the TCGA ccRCC cohort. Within the tumor microenvironment (TME), the emergence of treatment resistance was characterized by a transition from cytotoxic to exhausted T cell state and enrichment for M2-like myeloid cells. The observed changes in gene expression dynamics and cellular states in tumor cell and TME may help inform future strategies to optimize ICT efficacy.