Development of A Chimeric Antigen Receptor Targeting C-Type Lectin-Like Molecule-1 for Human Acute Myeloid Leukemia

Abstract

The treatment of patients with acute myeloid leukemia (AML) with targeted immunotherapy is challenged by the heterogeneity of the disease and a lack of tumor-exclusive antigens. Conventional immunotherapy targets for AML such as CD33 and CD123 have been proposed as targets for chimeric antigen receptor (CAR)-engineered T-cells (CAR-T-cells), a therapy that has been highly successful in the treatment of B-cell leukemia and lymphoma. However, CD33 and CD123 are present on hematopoietic stem cells, and targeting with CAR-T-cells has the potential to elicit long-term myelosuppression. C-type lectin-like molecule-1 (CLL1 or CLEC12A) is a myeloid lineage antigen that is expressed by malignant cells in more than 90% of AML patients. CLL1 is not expressed by healthy Hematopoietic Stem Cells (HSCs), and is therefore a promising target for CAR-T-cell therapy. Here, we describe the development and optimization of an anti-CLL1 CAR-T-cell with potent activity on both AML cell lines and primary patient-derived AML blasts in vitro while sparing healthy HSCs. Furthermore, in a disseminated mouse xenograft model using the CLL1-positive HL60 cell line, these CAR-T-cells completely eradicated tumor, thus supporting CLL1 as a promising target for CAR-T-cells to treat AML while limiting myelosuppressive toxicity.

Revisiting CLEC12A as leukaemic stem cell marker in AML: highlighting the necessity of precision diagnostics in patients eligible for targeted therapy

“…In addition, we have recently shown the relevance of the marker in myelodysplastic syndrome (MDS) and pointed out important differences in the applicability of the marker in these biologically different disease entities (Toft-Petersen et al, 2016). Given this, the CLEC12A receptor is an attractive treatment target in AML, and current developments in this regard include both CLEC12A-CD3 bispecific antibodies (Lu et al, 2014;Leong et al, 2017) and chimeric antigen receptor (CAR)-engineered T-cells (CAR-T-cells) directed against CLEC12A (Laborda et al, 2017;Tashiro et al, 2017;Wang et al, 2018) and, most recently, the development of a novel antibody-drug conjugate (Jiang et al, 2018).…”

The concept of leukaemic stem cells in acute myeloid leukaemia 25 years on: hitting a moving target

“…Much the same applies to the developing literature on targeting the CLEC12A receptor (Zhao et al , ; Lu et al , ; Laborda et al , ; Leong et al , ; Tashiro et al , ; Wang et al , ), which has also been shown to be absent on the most immature HSPCs in normal bone marrow (van Rhenen et al , ; Bill et al , ). Recent efforts in targeting this marker include the development of cytotoxic monoclonal antibodies (Zhao et al , ) and CLEC12A‐CD3 bispecific antibodies (Lu et al , ; Leong et al , ).…”

“…A first‐in‐human phase 1 clinical trial of a bispecific CLEC12A‐CD3 antibody for the treatment of relapsed/refractory AML or previously untreated elderly AML patients is currently recruiting (NCT03038230). In addition, the recently developed chimeric antigen receptor (CAR) engineered T cells (CAR‐T cells) directed against CLEC12A (Laborda et al , , Tashiro et al , , Wang et al, ) and toxin‐conjugated antibodies also seem promising (Jiang et al , ). Taken together – and given the success of other antibody‐based initiatives, most prominently rituximab – this line of anti‐LSC targeting is definitely one to follow.…”

A Bump in the Road: How the Hostile AML Microenvironment Affects CAR T Cell Therapy

“…Efforts to expand adoptive immunotherapy strategies to acute myeloid leukemia (AML) are complicated by antigen overlap between normal hematopoietic progenitor cells (HPCs) and leukemic blasts (8). Early clinical studies of CAR T cells for AML are ongoing, exploring several targets including CD123 (9, 10), CD33 (11), C-type lectin-like molecule 1 (CLL-1) (12,13), and Lewis-Y (14). Additional targets under preclinical investigation include CD135 (FLT-3 receptor) (15)(16)(17), Folate receptor β (18), CD44v6 (19), WT1 (20), B7-H3 (21-23), CD70 (24,25), and CD7 (26).…”