Structural Insights into the ADCC Mechanism and Resistance of Mogamulizumab, a First-in-Class Anti-CCR4 Therapy for Cutaneous T Cell Lymphoma

Abstract

Mogamulizumab is a humanized monoclonal antibody that targets C-C chemokine receptor 4 (CCR4) present on certain T cells in lymphomas and leukemias. This antibody-based therapy has demonstrated efficacy in treating various cutaneous T cell lymphomas (CTCLs), including mycosis fungoides and Sézary syndrome, through the depletion of CCR4-expressing T cells by antibody-dependent cellular cytotoxicity (ADCC). However, the precise epitope and binding mode of mogamulizumab responsible for its augmented ADCC activity remain undisclosed. Here, X-ray crystallographic studies of mogamulizumab in complex with a 28-residue N-terminal peptide indicated that SIYSNYYLYES (residues 14-24) would constitute the antibody epitope. Another high-resolution structure, using a short core peptide of these 11 residues, has elucidated unambiguous electron density for the bound peptide, confirming consistent binding for both peptides. This linear epitope is located in the membrane-proximal region of CCR4, facilitating the Fc-mediated effector functions, including ADCC. The structures also provide insights into the molecular basis for the resistance of the CCR4 L21V variant to mogamulizumab, which is due to a lack of structural complementarity with mogamulizumab binding. Understanding the structural basis for the mechanism of action of mogamulizumab is crucial for optimizing anti-CCR4 therapeutics to improve treatment outcomes for patients with these challenging diseases.

Keywords: C-C chemokine receptor 4 (CCR4); X-ray structure; antibody; antibody-dependent cellular cytotoxicity (ADCC); cutaneous T cell lymphoma (CTCL); drug resistance; mogamulizumab.

Figure 1

The crystal structure of mogamulizumab in complex with CCR4 N-terminal peptide. (A) The schematic drawing of CCR4 consisting of seven transmembrane (TM) helices, extracellular loops (ECLs), intracellular loops (ICLs), and a long N-terminal region. The amino acid sequence of the 28-residue peptide used in this study is presented. The residues S14 to S24, which were included in the structure of the ternary complex, are colored purple. (B) The overall structure of the ternary complex includes mogamulizumab Fab (cyan and orange), a nanobody (gray), and a 28-residue peptide (purple). The CDRs of heavy and light chains are colored yellow and green, respectively.

Figure 2

The comparison of the bound peptides. (A) The residues 14 to 24 of the 28-residue peptide within the ternary complex structure. A stereoscopic view of 2fofc electron density map calculated at 2.01 Å resolution and 1.2 σ contour level. (B) The residues 15 to 24 of the 11-residue peptide within the binary complex structure. A stereoscopic view of 2fofc electron density map calculated at 1.63 Å resolution and 1.2 σ contour level. (C) The superposition of the peptide residues within the ternary (purple) and binary (orange) complex structures.

Figure 3

The detailed interactions within the CCR4/mogamulizumab interface. (A) A stereoscopic view of the hydrogen bonds between CCR4 and mogamulizumab. Hydrogen bonds are depicted as dotted lines. (B) A stereoscopic view of the van der Waals interactions between CCR4 and mogamulizumab. CCR4 and the heavy and light chains of mogamulizumab are colored salmon, yellow, and green, respectively.

Figure 4

L21V mutation in resistance to mogamulizumab. (A) The surface representation of mogamulizumab with bound CCR4 peptide. The key residues of CCR4 for interactions are labeled. (B) The comparison of the interaction in the residue at position 21 between WT and L21V variant CCR4. The asterisk indicates a steric collision by the β-branched methyl group in the mutated valine residue. The surface is colored by electrostatic potential.

Figure 5

The molecular mechanism of mogamulizumab ADCC. (A) The structure of CCR5 in complex with its ligand CCL5 (PDB entry: 7O7F). The disulfide bond between C20 and C269 is depicted. The residues E18 and P19, which are involved in ligand binding, are labeled. The flexible N-terminal region is indicated by a dotted curve. (B) The hypothetical model of the molecular architecture of mogamulizumab binding. The two variable regions of mogamulizumab can bind to the epitope (red, residues 15–24) in both inactive CCR4 and active CCR4 (CCR4*). The heavy and light chains of mogamulizumab are colored blue and cyan. The glycans within Fc are depicted as a purple stick model. The ligand of CCR4 is colored green, and the G protein subunits are colored yellow, orange, and red.