Developing a membrane-proximal CD33-targeting CAR T cell

J Immunother Cancer. 2024 May 20;12(5):e009013. doi: 10.1136/jitc-2024-009013.

Abstract

Background: CD33 is a tractable target in acute myeloid leukemia (AML) for chimeric antigen receptor (CAR) T cell therapy, but clinical success is lacking.

Methods: We developed 3P14HLh28Z, a novel CD33-directed CD28/CD3Z-based CAR T cell derived from a high-affinity binder obtained through membrane-proximal fragment immunization in humanized mice.

Results: We found that immunization exclusively with the membrane-proximal domain of CD33 is necessary for identification of membrane-proximal binders in humanized mice. Compared with clinically validated lintuzumab-based CAR T cells targeting distal CD33 epitopes, 3P14HLh28Z showed enhanced in vitro functionality as well as superior tumor control and increased overall survival in both low antigen density and clinically relevant patient-derived xenograft models. Increased activation and enhanced polyfunctionality led to enhanced efficacy.

Conclusions: Showing for the first time that a membrane-proximal CAR is superior to a membrane-distal one in the setting of CD33 targeting, our results demonstrate the rationale for targeting membrane-proximal epitopes with high-affinity binders. We also demonstrate the importance of optimizing CAR T cells for functionality in settings of both low antigen density and clinically relevant patient-derived models.

Keywords: Adoptive cell therapy - ACT; Chimeric antigen receptor - CAR; Immunotherapy; Leukemia; T cell.

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Humans
  • Immunotherapy, Adoptive* / methods
  • Leukemia, Myeloid, Acute / immunology
  • Leukemia, Myeloid, Acute / therapy
  • Mice
  • Receptors, Chimeric Antigen / immunology
  • Receptors, Chimeric Antigen / metabolism
  • Sialic Acid Binding Ig-like Lectin 3* / immunology
  • Sialic Acid Binding Ig-like Lectin 3* / metabolism
  • T-Lymphocytes / immunology
  • Xenograft Model Antitumor Assays

Substances

  • CD33 protein, human