Study of Sitravatinib + PD-(L)1 Checkpoint Inhibitor Regimens in Urothelial Carcinoma

Sitravatinib is an orally-available, small molecule inhibitor of a closely related spectrum of receptor tyrosine kinases (RTKs) including MET, Axl, MERTK, VEGFR family, PDGFR family, KIT, FLT3, Trk family, RET, DDR2 and selected Eph family members. Nivolumab is a human IgG monoclonal antibody that binds to the programmed cell death-1(PD-1) receptor and blocks its interaction with programmed cell death ligand-1 (PD-L1) and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response including anti-tumor immune response. Combining an immunotherapeutic PD-L1 checkpoint inhibitor with an agent that has both immune modulatory and antitumor properties could enhance the antitumor efficacy observed with either agent alone. Sitravatinib selectively inhibits key molecular and cellular pathways strongly implicated in checkpoint inhibitor resistance and therefore represents a rational strategy to enhance or restore anti-tumor immunity when combined with nivolumab, a checkpoint inhibitor therapy.

Pembrolizumab is a humanized IgG4 monoclonal antibody that binds to the PD-1 receptor and selectively blocks its interaction with PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the anti-tumor immune response. Enfortumab vedotin (enfortumab) is an investigational ADC that is comprised of a fully human anti-Nectin-4 IgG1 monoclonal antibody conjugated to MMAE via a protease-cleavable linker. Enfortumab binds to cells that express Nectin-4 with high affinity, triggering the internalization and release of MMAE in target cells, inducing cell cycle arrest and apoptotic cell death. Early efficacy results from enfortumab in combination with pembrolizumab in frontline cisplatin-ineligible urothelial carcinoma in the ongoing EV-103 study have demonstrated encouraging activity with a safety profile that appears manageable and tolerable. Addition of sitravatinib to this combination might further augment clinical activity by selectively inhibiting key molecular and cellular pathways strongly implicated in checkpoint inhibitor resistance.