Development of Mimokines, chemokine N terminus-based CXCR4 inhibitors optimized by phage display and rational design

Abstract

The chemokine receptor CXCR4 (C-X-C chemokine receptor type 4 also known as fusin or CD184 (cluster of differentiation 184)) is implicated in various biological and pathological processes of the hematopoietic and immune systems. CXCR4 is also one of the major coreceptors for HIV-1 entry into target cells and is overexpressed in many cancers, supporting cell survival, proliferation, and migration. CXCR4 is thus an extremely relevant drug target. Among the different strategies to block CXCR4, chemokine-derived peptide inhibitors hold great therapeutic potential. In this study, we used the N-terminus of vCCL2/vMIPII, a viral CXCR4 antagonist chemokine, as a scaffold motif to engineer and select CXCR4 peptide inhibitors, called Mimokines, which imitate the chemokine-binding mode but display an enhanced receptor affinity, antiviral properties, and receptor selectivity. We first engineered a Mimokine phage displayed library based on the first 21 residues of vCCL2, in which cysteine 11 and 12 were fully randomized and screened it against purified CXCR4 stabilized in liposomes. We identified Mimokines displaying up to 4-fold higher affinity for CXCR4 when compared to the reference peptide and fully protected MT-4 cells against HIV-1 infection. These selected Mimokines were then subjected to dimerization, D-amino acid, and aza-β3-amino acid substitution to further enhance their potency and selectivity. Optimized Mimokines exhibited up to 120-fold enhanced CXCR4 binding (range of 20 nM) and more than 200-fold improved antiviral properties (≤ 1 μM) compared to the parental Mimokines. Interestingly, these optimized Mimokines also showed up to 25-fold weaker affinity for ACKR3/CXCR7 and may therefore serve as lead compounds for further development of more selective CXCR4 peptide inhibitors and probes.

Discovery of Antivirals Using Phage Display

“…Amino acids, except glycine, are chiral molecules existing in either levorotatory (L) or dextrorotatory (D) forms in nature, yet the former is mostly used in construction of protein structures in life [169]. As a result of the changes in backbone side chain connectivity and geometry, D-proteins cannot be recognized by L-proteins such as proteases [170]. This feature makes D-proteins resistant to proteolytic degradation and suggests the introduction of D-amino acids to the peptide backbones as a promising approach to improve peptide stability in cells.…”

Maternal CXCR4 deletion results in placental defects and pregnancy loss mediated by immune dysregulation

“…Many chemokines and their receptors have been identified at the MFI ( 11 ). The G-protein coupled cysteine-X-cysteine (C-X-C) chemokine receptor type 4 (CXCR4) belongs to the C-X-C family and is involved in various biological processes, including leukocyte adhesion and transendothelial migration, cellular proliferation, differentiation, apoptosis, angiogenesis, and immune regulation ( 12 ). The cognate ligand for CXCR4 is C-X-C motif chemokine ligand 12 (CXCL12) and their interaction is crucial for regulating the retention of hematopoietic stem/progenitor cells within the BM, their maintenance, and subsequent mobilization from the BM niche ( 13 – 16 ).…”

“…Many chemokines and their receptors have been identified at the MFI (11). The G-protein coupled cysteine-X-cysteine (C-X-C) chemokine receptor type 4 (CXCR4) belongs to the C-X-C family and is involved in various biological processes, including leukocyte adhesion and transendothelial migration, cellular proliferation, differentiation, apoptosis, angiogenesis, and immune regulation (12). The cognate ligand CXCR4 is a key regulator of the development of NK cells and DCs, both of which play an important role in early placental development and immune tolerance at the maternal-fetal interface.…”