B7-H3 Specific CAR T Cells for the Naturally Occurring, Spontaneous Canine Sarcoma Model

Abstract

One obstacle for human solid tumor immunotherapy research is the lack of clinically relevant animal models. In this study, we sought to establish a CAR T cell treatment model for naturally occurring canine sarcomas as a model for human CAR T cell therapy. Canine CARs specific for B7-H3 were constructed using a single chain variable fragment derived from the human B7-H3-specific antibody MGA271, which we confirmed to be cross-reactive with canine B7-H3. After refining activation, transduction and expansion methods, we confirmed target killing in a tumor spheroid 3D assay. We designed a B7-H3 canine CAR T cell and achieved consistently high levels of transduction efficacy, expansion and in vitro tumor killing. Safety of the CAR T cells were confirmed in two purposely bred healthy canine subjects following lymphodepletion by cyclophosphamide and fludarabine. Immune response, clinical parameters and manifestation were closely monitored post treatments and were shown to resemble that of humans. No severe adverse events were observed. In summary, we demonstrated that similar to human cancers, B7-H3 can serve as a target for canine solid tumors. We successfully generated highly functional canine B7-H3-specific CAR T cell products using a production protocol that closely models human CAR T cell production procedure. The treatment regimen that we designed was confirmed to be safety in vivo. Our research provides a promising direction to establish in vitro and in vivo models for immunotherapy for canine and human solid tumor treatment.

Applying a clinical lens to animal models of CAR-T cell therapies

“… 65 , 66 , 67 Dogs bearing sarcomas have also been treated with B7-H3 CAR-T cells, which are also in human clinical trials ( NCT046670068 ), demonstrating feasibility and safety. 68 Many of the observations made in human CAR-T cells trials have been recapitulated in dogs, including the development of cytokine release syndrome, the emergence of antigen-negative tumor relapse, and the development of anti-mouse antibodies generated against the murine portion of the scFv used in many human and dog CAR constructs ( Figure 2 ). 69 While thus far use of the canine CAR-T cell models and clinical utilization by veterinarians is lagging behind, canine models can serve as a promising translational bridge, and activity in this area is increasing.…”

Racing CARs to veterinary immuno-oncology

“…Although clinical veterinary studies are still in the beginning phases, the potential for breakthrough therapies, like has happened for human hematologic oncology, is high. Veterinary clinical trials involving infusions of T cells and NK cells have demonstrated the feasibility and safety of harvesting and manufacturing cells for clinical use (30,78,83,98). However, to fully break into the cellular immunotherapy sector the way human medicine has, veterinary schools or other hospitals will need appropriate infrastructure for cellular manufacturing and genetic modification, or identify industry partners.…”

“…References cells (82) were more cytotoxic than HER2 CAR T cells toward canine osteosarcoma spheroids, but cytotoxicity was similar for the constructs incorporating CD28 or 4-1BB signaling domains (83). Two healthy canine subjects were then infused with either frozen or fresh autologous B7-H3 CAR T cells.…”

CAR T Cell Locomotion in Solid Tumor Microenvironment

“…In comparative oncology that studies animal tumor models that develop cancers spontaneously, pet dog models are gaining significant attraction as they are one step closer to real world cancers given not only clinical and molecular similarities but also patient heterogeneity. A number of trials using different immunotherapy approaches—including CAR T cells—are used to treat HER2+ osteosarcoma, B7-H3+ sarcomas, and gliomas [ 4 , 219 ]. However, the paucity of patient recruitment similarly seen in human trials might need more expeditious cancer models.…”