An “off-the-shelf” fratricide-resistant CAR-T for the treatment of T cell hematologic malignancies

Abstract

T cell malignancies represent a group of hematologic cancers with high rates of relapse and mortality in patients for whom no effective targeted therapies exist. The shared expression of target antigens between chimeric antigen receptor (CAR) T cells and malignant T cells has limited the development of CAR-T because of unintended CAR-T fratricide and an inability to harvest sufficient autologous T cells. Here we describe a fratricide resistant ‘off-the-shelf’ CAR-T (or UCART7) that targets CD7+ T cell malignancies and, through CRISPR/Cas9 gene editing, lacks both CD7 and T cell receptor alpha chain (TRAC) expression. UCART7 demonstrates efficacy against human T cell acute lymphoblastic leukemia (T-ALL) cell lines and primary T-ALL in vitro and in vivo without the induction of xenogeneic GvHD. Fratricide resistant, allo-tolerant ‘off-the-shelf’ CAR-T represents a strategy for treatment of relapsed and refractory T-ALL and non-Hodgkin’s T cell lymphoma without a requirement for autologous T cells.

Mechanisms of resistance to CAR T cell therapy

“…Manufacturing CAR T cells from third-party donors might enable the development of universal, off-theshelf products and is another method to overcome the problem of quantitatively insufficient or poor-quality CAR T cell products 62,63 . Generating such products will probably require additional genetic modification to limit CAR T cell rejection and/or GVHD but also offers opportunities to overcome resistance mechanisms, such as 'fratricide' reported with T cell antigen-targeted CAR T cell products 64 . Other novel strategies to enhance CAR-based therapeutic strategies and provide an alternative off-the-shelf product include CAR-engineered nature killer (NK) cells; indeed, preclinical and early phase clinical studies of such products are underway [65][66][67] .…”

Can one target T-cell ALL?

“…A potential strategy to overcome these obstacles is the development via CRISPR-CAS9 of fratricide-resistant T cells devoid of CD7 and TCRA that express a CAR directed against CD7. These “off the shelf” CAR T cells show efficacy against human T-ALL without xenogeneic graft-versus-host disease [53]. Yet, even if successful in controlling disease, CAR T cell pan T-cell killing would result in long-term T-cell immunosuppression and high risk of life-threatening opportunistic infections.…”

Advances in Chimeric Antigen Receptor T‐Cell Therapies for Solid Tumors

“…Experience with CD19‐directed CAR T‐cell therapy has encouraged the CAR T‐cell community to confront the problems associated with expanding this therapy to other tumor types. In fact, in the case of T‐ALL, Cooper et al . have created a CAR that targets the T‐cell antigen CD7 and, to avoid CAR T‐cell fratricide, have used CRISPR/Cas9 to delete CD7 in the CAR T cells.…”