The recent revolution in bioengineering of the cellular immune system, offers a promising new frontier of medicine with the potential to ultimately defeat cancer. Supercharging the anti-cancer power of the immune system by genetically engineering killer T lymphocytes to co-express chimeric cancer-specific antibody fragment molecules with cytoplasmic activation domains (Chimeric Antigen Receptor T cells; CAR-T cells) is leading this remarkable new clinical approach. We are developing multi-specificity CAR-T cells, initially targeted at ovarian cancer but the specificities chosen are equally applicable to a variety of adenocarcinomas including those of the gastrointestinal tract, breast, pancreas, lung, and prostate. Targeting multiple determinants should mitigate against tumour escape via mutation. We have identified two primary target molecules expressed on the cell surface of the target cells: TAG 72, a glycosylation mutant, and a second determinant (CTH CAR) commonly upregulated on many cancer cells. We initially developed a range of second generation CAR constructs with either CD28 or 4-1-BB as the signal activation domain. The relative cytotoxic efficacies of these variant CAR-T cells were evaluated using the real time impedence-based xCelligence assay. This system was also to reveal the importance of cytokine and CAR-T receptor activation on the specificity and longevity of the cytotoxic capacity. The resultant CAR-T induction, activation, specificity and safety strategies are being developed as a platform for an autologous Phase I clinical trial in ovarian cancer patients..
An additional approach that may dramatically enhance T cell clinical utility is to transfect such anti-cancer CAR constructs into iPSC cells, which themselves maybe derived from cancer specific TCR T cells (the rearranged TCR specificity is thus embedded in the iPSC). These are then re-differentiated into cytotoxic T cells to create a “limitless” expansion of such cancer killing T cells. These cells retain both the TCR specificity to cytoplasmic derived determinants plus the scFv to membrane (in our case glycosylation) determinants. By creating multiple lines of iPSC-derived “multi-antigen, cancer specific” killer T cells, we aim to service a wide number of people with this first-line cancer immunotherapy. The Australian Government has recently awarded Cartherics, (in partnership with Cell Therapies, Mesoblast, the Hudson Institute and Monash University), a grant of AUD$3million under the Cooperative Research Centre’s Project (CRC-P) program. This CRC-P for Allogeneic Stem Cell Cancer Immunotherapies* aims to produce unique allogeneic CAR-T cells derived from homozygous haplotype iPSCs that can be administered to very large numbers of histocompatible cancer patients. These cells are produced from healthy donors rather than seriously ill cancer patients, manufactured and expanded at a fraction of the cost of autologous CAR-T cells and banked until needed.