Compound CAR T-cells as a double-pronged approach for treating acute myeloid leukemia

Abstract

Acute myeloid leukemia (AML) bears heterogeneous cells that can consequently offset killing by single-CAR-based therapy, which results in disease relapse. Leukemic stem cells (LSCs) associated with CD123 expression comprise a rare population that also plays an important role in disease progression and relapse. Here, we report on the robust anti-tumor activity of a compound CAR (cCAR) T-cell possessing discrete scFv domains targeting two different AML antigens, CD123, and CD33, simultaneously. We determined that the resulting cCAR T-cells possessed consistent, potent, and directed cytotoxicity against each target antigen population. Using four leukemia mouse models, we found superior in vivo survival after cCAR treatment. We also designed an alemtuzumab safety-switch that allowed for rapid cCAR therapy termination in vivo. These findings indicate that targeting both CD123 and CD33 on AML cells may be an effective strategy for eliminating both AML bulk disease and LSCs, and potentially prevent relapse due to antigen escape or LSC persistence.

T-cells “à la CAR-T(e)” – Genetically engineering T-cell response against cancer

“…Latest multi-center BCMA-CAR trials results indicate a relatively safe profile (although cytokine release syndrome -CRS and transient neurotoxicity were observed) with an overall response rate over 90% [145,146]. Other antigens currently being targeted to treat hematological malignancies include CD20 for NHL, CD138 for MM [144], CD33 [147], CD123 for AML [148,149] and CD7 for certain leukemias and lymphomas [150]. Lately, using a very elegant approach to treat T-cell malignancies, Pule and colleagues isolated an antibody specific for the TCRβ1 constant region.…”

“…This system was extensively characterized in the context of CAR expression but also of conditional secretion of checkpoint inhibitors, bi-specific T-cell engagers and alternatively, immunosuppressive molecule such as IL10 or PDL1 [306]. As aforementioned, an "OR" gate is represented by bi-specific CAR or dual-CAR expressing T cells [97,148].…”

Targeting T cell malignancies using CAR-based immunotherapy: challenges and potential solutions

“…Multiple groups have also evaluated the retroviral transfer of human CD20 into T cells as a novel suicide gene mechanism for adoptive T cell therapy. Their data supports that infusion of the anti-CD20 antibody, rituximab, an approved antibody for in vivo therapeutic applications, results in efficient, specific elimination of CD20-positive T lymphocytes through ADCC [205,206,218]. Studies have also demonstrated that rituximab can eliminate CD20positive cells in vivo through inducing complementdependent cytotoxicity, a rapid and efficient mode of cell death [219].…”

AML ImmunoPET:64Cu-DOTA-anti-CD33 PET-CT imaging of AML in Xenograft mouse model

“…Several investigational CD33-targeted therapeutics have been developed for AML (26), including the recently FDA-approved anti-CD33 monoclonal antibody-drug conjugate gemtuzumab ozogamicin (GO, Mylotarg) (27), bispecific antibodies such as CD33/CD3 antibodies (28), CD33/CD123-directed CAR T cells (29). Although positive results have been reported from clinical trials of CD33-targeting drugs, dose limiting toxicities such as hepatotoxicities (30) during treatment are of concern.…”