Feline alimentary (gastrointestinal) lymphoma is  the most common cancer diagnosed in domestic cats. The most common subtype is known as enteropathy-associated T cell lymphoma (EATL) type II, or small cell lymphoma, and accounts  for 10-20% of all tumors with approximately 200 cases per 100,000 cats reported each year. Although EATL type I, or large cell lymphoma, is less common, the prognosis is significantly worse. Standard of care for EATL type II can extend life for two years or more, while care for type I rarely extends life more than 6-9 months. Immunotherapy based on redirecting the immune system to kill cancer cells is at the forefront of cancer treatments. Given how common small cell lymphoma is, and the poor prognosis despite therapy in large cell lymphoma, the goal of our proposed research is to determine the potential of chimeric antigen receptor (CAR) natural killer (NK) cell immunotherapy for the treatment of alimentary lymphoma in cats. CAR immunotherapy involves modifying a cancer patient’s own NK cells to express specialized antigen-specific antibody/T cell receptor (TCR) fusion proteins, referred to as CARs, and re-infusing these back into the patient as a means to attack and kill their cancer.

Preliminary studies (Dr. Bais and Adoptive Therapeutics) have resulted in cloning of four different CARconstructs designed to target candidate feline EATL type I antigens CD103,gdTCR,a4b7, and CCR9. There is also a procedure in place to expand NK cells and introduce CARs based on previous studies for canine, which will be ready at the initiation of this grant. Our objective is to evaluate safety and efficacy of CAR-NK cells in cats. To accomplish this we will (1) perform in vitro killing assays with model feline lymphoma cells to determine the most effective antigen-specific CAR-NK construct to be used for subsequent studies, (2) perform pre-clinical safety studies in research cats to evaluate dose escalation levels and toxicity of re-infused NK cells, both non-modified without CAR and modified with CAR, and (3) perform preliminary clinical efficacy studies in feline cancer patients to measure tumor response by antigen-specific CAR-NK cells. In summary, these studies will offer a new therapeutic option for feline cancers, and will drive the innovation of NK-cell based immunotherapy in other species.