Developing the Next Generation of iPSC Cell-Based Immunotherapies

T cells are potentially curative for patients with metastatic cancer, but many patients with cancer have T cells that are 'terminally differentiated', a condition associated with treatment failure. We have observed that less differentiated T cells have a greater capacity to proliferate, persist and destroy large cancer deposits. Advances in regenerative medicine might allow the generation of rejuvenated T cells from induced pluripotent stem cells (iPSC). We have previously reported that T cells can be generated from iPSC in vitro by co-culturing them OP9 stromal cells expressing Notch-1 ligand, Delta-like-1 (OP9/DLL1). These cells have limited tumor-specificity but also exhibit unconventional and NK cell-like properties demonstrating lineage diversion into alternative lymphoid development pathways, with unknown consequences for their safety and efficacy. To generate iPSC-derived T cells with more naturalistic tumor-specific T cell programs, we sought to restore physiologic signals for selection, maturation and survival. We employed a novel 3D thymic culture system using fetal thymic tissue and generated a novel type of T cell, 'iPSC-derived thymic emigrants' (iTE). Antigen-specific CD8αβ⁺ iTE exhibited functional properties in vitro that were almost indistinguishable from natural naïve CD8αβ⁺ T cells, including vigorous expansion and robust anti-tumor activity. iPSC-derived immature T cells generated using OP9/DLL1 and 'educated' in fetal thymic organoids in a 3D culture system resembled naturally-occurring 'young' T cells, as analyzed using whole genome RNA-seq techniques. iTE recapitulated many of the transcriptional programs of naïve T cells in vivo and revealed a striking capacity for engraftment, memory formation and efficient tumor destruction. Although many milestones remain, our data show that 'Next-Gen' autologous tumor-specific T cells can realistically be generated from iPSC using 3D thymic organ tissue. Our next goal is now to employ these cells to treat patients with metastatic cancer because iPSC-derived T cells have a potentially unlimited capacity for proliferation, engraftment and anti-tumor activity.