Empowering T cells with new T cell receptors (TCR) can effectively redirect some of the most potent players of our immune system against virtually all tumor antigens. Even though TCRs have so far operated in the shadow of CARs, they harbor 2 main advantages: 1) the ability to target virtually every tumor antigen (surface and intracellular epitopes bound on major histocompatibility complex molecule and 2) the higher sensitivity (mediate activity at a lower density of antigen). Furthermore, the therapeutic value of TCR-based approaches has proved promising in clinical trials for solid tumors, such as melanoma and, more recently, pancreatic adenocarcinoma. Dressing T cells with novel identified tumor-specific TCRs would have a huge impact on cell-based immunotherapies, by providing patient’s body with a highly specific and effective living drug harboring the ability to patrol for tumor recurrence. However, due to the low frequency of cancer-specific T cells, pinpointing the exact tumor-specific TCR remains the major bottleneck for the broad use of TCR-based therapies in clinical practice.
Recently, focusing on Wilms Tumor 1 (WT1), a tumor antigen expressed on a multitude of blood and solid malignancies, and by longitudinal monitoring T cell functionality and dynamics in healthy donors and cancer patients, we designed and implemented a pipeline for the rapid isolation of tumor-specific T cells and for the thorough characterization of a library of TCRs. With this approach, we isolated 19 WT1-specific TCRs recognizing peptides restricted by different human leukocyte antigens (HLA) and displaying a wide range of functional avidities. By applying a funnel selection strategy, 2 high avidity TCRs were selected and inserted in T lymphocytes upon disruption of the endogenous TCR repertoire. TCR targeted integration into the TRAC locus combined with TRBC knock-out, was successfully employed to generate a T cell product with an improved biosafety profile while preserving T cell fitness. Of note, one TCR showed antigen-specific responses in CD4 and CD8 T-cells, and efficiently eliminated patients’ blasts and a glioblastoma cell line in vitro and in vivo in the absence of off-tumor toxicity. Stemming from these results, we have now built a library of 56 anti-tumor TCRs recognizing epitopes of tumor-associated antigens expressed by hematological and solid tumors (including cold malignancies) and restricted to HLA alleles common in the Caucasian population. T cells engineered with newly discovered TCRs, with or without the knockout of inhibitory receptors, are currently being functionally tested and prioritized with the final aim of rendering TCR-based immunotherapies an effective off-the-shelf treatment readily accessible to each tumor patient.