Intracellular retention of TCRαβ/CD3 and CD7 to generate novel allogeneic CAR-T cells targeting CD7 for treating T-cell malignancies.

e14531 Background: The treatment for patients with T-ALL/LBL who relapse after hematopoietic stem cell transplantation (HSCT) are currently restricted. CD7 is highly expressed on the surface of T-ALL/LBL T cells and CAR-T cell therapy provides a promising avenue towards remission. However, CD7-targeting immunotherapies may be compromised by T-cell fratricide. Furthermore, in addition to the long production time, high cost, and high risk of production failure, the biggest challenges of autologous CAR-T cell therapy are how to isolate a sufficient number of healthy T cells from malignant T cells. Thus, allogeneic CAR-T cells can overcome these hurdles. Methods: A novel non-gene-editing allogeneic CAR-T platform was developed on the base of intracellular retention of membrane proteins, and named ThisCART (TCR and/or HLA-I intracellular sequestered). CD7-directed ThisCART cells are readily produced with a single lentiviral vector, encoding both a CD7-targeting CAR, an anti-CD7and anti-CD3 single chain antibody with the KDEL peptide fused to its C-termini. The surface expression of CAR, TCRαβ/CD3 and CD7 was measured by flow cytometer. Specific tumor cytotoxicity was evaluated both in vitro and in vivo. Furthermore, the safety of donor derived ThisCART cells were tested in a xenogeneic GvHD model. Results: The manufacturing platform of CD7 ThisCART was able to achieve over 130-folds of ex vivo CAR-T expansion in all batches, with the purity of products (CAR-positive/CD7-negative/TCRαβ-negative) above 99%. In preclinical models, CD7 ThisCART did not induce GvHD, and exhibited superior antitumor function compared to Control T. CD7 ThisCART cells were readily produced to a quantity and quality supporting clinical investigation. Conclusions: CD7 ThisCART cells based on intracellular retention of TCRαβ/CD3 complex and CD7 demonstrated superior CD7-dependent cytotoxicity and no xenogeneic GvHD in murine models. With streamlined single-vector-based production and potent cytotoxicity and favored preclinical safety profile, CD7 ThisCART warrant clinical investigation.