PD-1/PD-L1 Monoclonal Antibody Development for Canine Cancer Therapy

PD-1 is an inhibitory receptor that binds to PD-L1 on the surface of tumor and antigen presenting cells in the tumor microenvironment, causing suppression of T-cell activity and tumor progression. Human clinical trials with anti PD-1 monoclonal antibodies, nivolumab and pembrolizumab, showed an objective response rate (ORR) of 30% to 40% with melanoma and 87% with relapsed or refractory Hodgkin’s lymphoma. Here, we have explored the development of canine PD-1/PD-L1 reagents for potential veterinary applications. An S2 insect cell expression system was utilized to produce recombinant canine PD-1Ig and PD-L1Ig and antigen-specific B cells were enriched using PD-1 and PD-L1 tetramers. Enriched B cells were fused and resulting hybridomas were screened for specific reactivity to PD-1 and PD-L1. Then, antibodies capable of blocking PD-1Ig and PD-L1Ig were selected. A total of 5 monoclonal antibodies were generated from the two rounds of immunizations and are being studied for in vitro activity in T cell assays. These canine reagents have multiple diagnostic and therapeutic applications in the context of canine oncology.