Diphtheria-toxin based anti-human CCR4 immunotoxin for targeting human CCR4(+) cells in vivo

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• CC chemokine receptor 4 (CCR4) is a target for CCR4(+) tumor cells and regulatory T cells (Tregs).
• CCR4 is expressed on various T-cell malignancies, including T-cell acute lymphoblastic leukemia (ALL), adult T-cell leukemia/lymphoma (ATLL), adult peripheral T cell lymphoma (PTCL), and cutaneous T cell lymphoma (CTCL).
• CCR4 is also found on the majority of effector Tregs.

Purpose of the Study:

• To develop and evaluate novel diphtheria-toxin based anti-human CCR4 immunotoxins.
• To compare the binding affinity and in vitro/in vivo efficacy of monovalent, bivalent, and single-chain fold-back diabody CCR4 immunotoxins.

Main Methods:

• Development of three diphtheria-toxin based anti-human CCR4 immunotoxin variants: monovalent, bivalent, and single-chain fold-back diabody.
• Binding analysis using flow cytometry on human CCR4(+) tumor cell lines and peripheral blood mononuclear cells (PBMCs).
• In vitro efficacy assessment of cellular proliferation and protein synthesis inhibition.
• In vivo efficacy evaluation in a human CCR4(+) tumor-bearing mouse model (NSG mice).

Main Results:

• All three immunotoxin versions demonstrated binding to CCR4(+) cells.
• The single-chain fold-back diabody exhibited the strongest binding affinity.
• In vitro, the single-chain fold-back diabody was significantly more potent (up to 200-fold) than the monovalent version in inhibiting tumor cell proliferation and protein synthesis.
• In vivo, the immunotoxin significantly prolonged survival in mice bearing human CCR4(+) acute lymphoblastic leukemia.

Conclusions:

• Novel anti-human CCR4 immunotoxins, particularly the single-chain fold-back diabody, show potent efficacy against CCR4(+) tumor cells.
• These immunotoxins represent promising therapeutic candidates for targeting CCR4(+) malignancies and Tregs in vivo.