Isolation of TCR genes with tumor-killing activity from tumor-infiltrating and circulating lymphocytes in a tumor rejection cynomolgus macaque model

Cas9-induced targeted integration of large DNA payloads in primary human T cells via homology-mediated end-joining DNA repair

The reliance on viral vectors for the production of genetically engineered immune cells for adoptive cellular therapies remains a translational bottleneck. Here we report a method leveraging the DNA repair pathway homology-mediated end joining, as well as optimized reagent composition and delivery, for the Cas9-induced targeted integration of large DNA payloads into primary human T cells with low toxicity and at efficiencies nearing those of viral vectors (targeted knock-in of 1-6.7 kb payloads at rates of up to 70% at multiple targeted genomic loci and with cell viabilities of over 80%). We used the method to produce T cells with an engineered T-cell receptor or a chimaeric antigen receptor and show that the cells maintained low levels of exhaustion markers and excellent capacities for proliferation and cytokine production and that they elicited potent antitumour cytotoxicity in vitro and in mice. The method is readily adaptable to current good manufacturing practices and scale-up processes, and hence may be used as an alternative to viral vectors for the production of genetically engineered T cells for cancer immunotherapies.

Reprogramming of Tumor-reactive Tumor-infiltrating Lymphocytes to Human-induced Pluripotent Stem Cells

Tumor-infiltrating lymphocytes (TIL) that can recognize and kill tumor cells have curative potential in subsets of patients treated with adoptive cell transfer (ACT). However, lack of TIL therapeutic efficacy in many patients may be due in large part to a paucity of tumor-reactive T cells in TIL and the exhausted and terminally differentiated status of those tumor-reactive T cells. We sought to reprogram exhausted TIL that possess T-cell receptors (TCR) specific for tumor antigens into induced pluripotent stem cells (iPSC) to rejuvenate them for more potent ACT. We first attempted to reprogram tumor neoantigen-specific TIL by αCD3 Ab prestimulation which resulted in failure of establishing tumor-reactive TIL-iPSCs, instead, T cell-derived iPSCs from bystander T cells were established. To selectively activate and enrich tumor-reactive T cells from the heterogenous TIL population, CD8⁺ PD-1⁺ 4-1BB⁺ TIL population were isolated after coculture with autologous tumor cells, followed by direct reprogramming into iPSCs. TCR sequencing analysis of the resulting iPSC clones revealed that reprogrammed TIL-iPSCs encoded TCRs that were identical to the pre-identified tumor-reactive TCRs found in minimally cultured TIL. Moreover, reprogrammed TIL-iPSCs contained rare tumor antigen-specific TCRs, which were not detectable by TCR sequencing of the starting cell population. Thus, reprogramming of PD-1⁺ 4-1BB⁺ TIL after coculture with autologous tumor cells selectively generates tumor antigen-specific TIL-iPSCs, and is a distinctive method to enrich and identify tumor antigen-specific TCRs of low frequency from TIL.

SIGNIFICANCE

Reprogramming of TIL into iPSC holds great promise for the future treatment of cancer due to their rejuvenated nature and the retention of tumor-specific TCRs. One limitation is the lack of selective and efficient methods for reprogramming tumor-specific T cells from polyclonal TIL. Here we addressed this limitation and present a method to efficiently reprogram TIL into iPSC colonies carrying diverse tumor antigen reactive TCR recombination.

The Intracellular Proteome as a Source for Novel Targets in CAR-T and T-Cell Engagers-Based Immunotherapy

The impressive clinical success of cancer immunotherapy has motivated the continued search for new targets that may serve to guide potent effector functions in an attempt to efficiently kill malignant cells. The intracellular proteome is an interesting source for such new targets, such as neo-antigens and others, with growing interest in their application for cell-based immunotherapies. These intracellular-derived targets are peptides presented by MHC class I molecules on the cell surface of malignant cells. These disease-specific class I HLA-peptide complexes can be targeted by specific TCRs or by antibodies that mimic TCR-specificity, termed TCR-like (TCRL) antibodies. Adoptive cell transfer of TCR engineered T cells and T-cell-receptor-like based CAR-T cells, targeted against a peptide-MHC of interest, are currently tested as cancer therapeutic agents in pre-clinical and clinical trials, along with soluble TCR- and TCRL-based agents, such as immunotoxins and bi-specific T cell engagers. Targeting the intracellular proteome using TCRL- and TCR-based molecules shows promising results in cancer immunotherapy, as exemplified by the success of the anti-gp100/HLA-A2 TCR-based T cell engager, recently approved by the FDA for the treatment of unresectable or metastatic uveal melanoma. This review is focused on the selection and isolation processes of TCR- and TCRL-based targeting moieties, with a spotlight on pre-clinical and clinical studies, examining peptide-MHC targeting agents in cancer immunotherapy.