Modeling anti-CD20 chimeric antigen receptor therapy in canine B cell lymphoma patients

Abstract

Chimeric antigen receptor (CAR) therapy has demonstrated great promise in treating human leukemias, but preclinical murine models are limited in their ability to predict safety and efficacy in humans. Given the rapid and on-going advances in CAR T cell technology in the laboratory, it now becomes necessary to identify and develop an outbred, large animal spontaneous cancer model in which the safety of novel targets and therapeutic effectiveness of re-directed T cells can be evaluated and optimized. Canines naturally develop spontaneous B cell lymphoma, and we have previously shown the feasibility of evaluating CAR T cell therapy in dogs using CD20-targeting RNA CAR T cells. To parallel human CAR T cell approaches, we have now optimized primary canine T cell transduction with lentivirus. Once peak T cell activation and artificial antigen presenting cell elimination timeframes were established, transduction yielded up to 26% CAR+ canine T cells. Canine T cells transduced with a second generation CD20-targeting CAR (CD20-28-ζ) demonstrated CAR-mediated, antigen-specific proliferation and efficient cytolysis of a CD20+ canine B cell lymphoma line in vitro. Three relapsed canine B cell lymphoma patients were treated with autologous CD20-28-ζ CAR T cells. Despite the administration of low numbers of CAR T cells, transient anti-tumor effects were observed in the first 2 patients. Following administration of ~700,000 CAR T cells/kg intravenously to the third patient, CAR T cells were found to persist and expand in the periphery and malignant nodes and disease progression was halted. This work establishes the feasibility of using the dogs with spontaneous cancer as pre-clinical models for advancing human CAR T cell therapy.