The Pluripotent Path to Immunotherapy.

Adoptive cell therapy (ACT) enhances the patient's own immune cells' ability to identify and eliminate cancer cells. Several immune cell types are currently being applied in autologous ACT, including T cells, natural killer (NK) cells and macrophages. The cells' inherent anti-tumor capacity can be used, or they can be targeted towards tumor associated antigen through expression of a chimeric antigen receptor (CAR). Although CAR-based ACT has achieved great results in hematological malignancies, the accessibility of ACT is limited by the autologous nature of the therapy. Induced pluripotent stem cells (iPSCs) hold the potential to address this challenge, as they can provide an unlimited source for the in vitro generation of immune cells. Various immune subsets have been generated from iPSC for the application in ACT, including several T cell subsets (αßT cells, mucosal-associated invariant T cells, invariant NKT (iNKT) cells and γδT cells), as well as NK cells, macrophages and neutrophils. iPSC-derived αßT, NK and iNKT cells are currently being tested in Phase-I clinical trials. The ability to perform (multiplexed) gene editing at the iPSC level and subsequent differentiation into effector population not only expands the arsenal of ACT but allows for development of ACT utilizing cell types which cannot be efficiently obtained from peripheral blood or engineered and expanded in vitro.

Generation of T-cell-receptor-negative CD8αß-positive CAR T cells from T-cell-derived induced pluripotent stem cells.

The production of autologous T cells expressing a chimaeric antigen receptor (CAR) is time-consuming, costly and occasionally unsuccessful. T-cell-derived induced pluripotent stem cells (TiPS) are a promising source for the generation of 'off-the-shelf' CAR T cells, but the in vitro differentiation of TiPS often yields T cells with suboptimal features. Here we show that the premature expression of the T-cell receptor (TCR) or a constitutively expressed CAR in TiPS promotes the acquisition of an innate phenotype, which can be averted by disabling the TCR and relying on the CAR to drive differentiation. Delaying CAR expression and calibrating its signalling strength in TiPS enabled the generation of human TCR- CD8αß+ CAR T cells that perform similarly to CD8αß+ CAR T cells from peripheral blood, achieving effective tumour control on systemic administration in a mouse model of leukaemia and without causing graft-versus-host disease. Driving T-cell maturation in TiPS in the absence of a TCR by taking advantage of a CAR may facilitate the large-scale development of potent allogeneic CD8αß+ T cells for a broad range of immunotherapies.