Engineered TAP1 and TAP2 Proteins to Block the CD7 and HLA-I Surface Expression on CAR-T Cells

Chimeric antigen receptor (CAR) T-cells are a novel and powerful cancer treatment, particularly for hematologic malignancies like lymphomas or leukemias. There have been ground-breaking responses to treatment although CAR-T cell therapy is available and effective only for a minority of patients so far. The production of successful CAR-T cells has been limited by several factors. T cells sourced to manufacturer CAR-T cells is restricted to autologous T cells because of the donor HLA-I mediated immune rejection of allogenic cells. Whereas, the quantity and functional fitness of autologous T cells is usually reduced because of therapies or disease, particularly in T-cell malignancy patients. Development of CAR-T cell therapies is further limited by the selection of a suitable target. T-cell malignancies express a surface antigenic profile largely shared by healthy T cells used to manufacturer CAR-T cells. Therefore, currently there are no effective targeted therapies. CD7 has been selected as a highly suitable CAR-T target for the treatment of T-cell malignancies, due to its expression on 95% of T-ALL/Ly and in a more restricted subset of mature T-cell malignancies. Nevertheless, CD7 is also expressed by normal T cells including those used to engineer CAR-Ts. CD7 CAR-Ts have demonstrated reciprocal in vitro antigen-driven elimination termed fratricide. In this study, we designed a novel non-gene editing approach to reduce HLA-I and CD7 surface expression. Two chimeric constructs developed, CD7tap1 and CD7tap2, were composed by a CD7 single chain variable fragment (ScFv) linked to the transmembrane domain of CD8α and a truncated version of TAP1 or TAP2 molecule. Jurkat cells transduced with CD7tap1 as well as CD7tap2 have shown a reduction in CD7 cellular surface expression. Contrary, the results obtained in human T cells aren’t statistically significant to confirm the efficacy of CD7tap1 and CD7tap2.