amd-070 and plerixafor

Topics: Aminoquinolines; Anti-HIV Agents; Benzimidazoles; Benzylamines; Butylamines; CCR5 Receptor Antagonists; CD4 Antigens; Cyclams; Cyclohexanes; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; HIV-1; Humans; Maraviroc; Piperazines; Pyrimidines; Receptors, CCR5; Receptors, CXCR4; T-Lymphocytes; Triazoles; Viral Tropism

Following the FDA-approval of the hematopoietic stem cell (HSC) mobilizer plerixafor, orally available and potent CXCR4 antagonists were pursued. One such proposition was AMD11070, which was orally active and had superior antagonism in vitro; however, it did not appear as effective for HSC mobilization in vivo. Here we show that while AMD11070 acts as a full antagonist, plerixafor acts biased by stimulating β-arrestin recruitment while fully antagonizing G protein. Consequently, while AMD11070 prevents the constitutive receptor internalization, plerixafor allows it and thereby decreases receptor expression. These findings are confirmed by the successful transfer of both ligands' binding sites and action to the related CXCR3 receptor. In vivo, plerixafor exhibits superior HSC mobilization associated with a dramatic reversal of the CXCL12 gradient across the bone marrow endothelium, which is not seen for AMD11070. We propose that the biased action of plerixafor is central for its superior therapeutic effect in HSC mobilization.

Topics: Aminoquinolines; Animals; Benzimidazoles; Benzylamines; beta-Arrestins; Butylamines; Cell Line, Tumor; Chlorocebus aethiops; COS Cells; Cyclams; Drug Delivery Systems; Female; Granulocyte Colony-Stimulating Factor; HEK293 Cells; Hematopoietic Stem Cell Mobilization; Hematopoietic Stem Cells; Humans; Mice; Mice, Inbred C57BL; Pharmaceutical Preparations; Receptors, CXCR3; Receptors, CXCR4

The bone marrow (BM) stromal niche can protect acute lymphoblastic leukemia (ALL) cells against the cytotoxicity of chemotherapeutic agents and is a possible source of relapse. The stromal-derived factor-1 (SDF-1)/CXCR4 axis is a major determinant in the crosstalk between leukemic cells and BM stroma. In this study, we investigated the use of AMD11070, an orally available, small-molecule antagonist of CXCR4, as an ALL-sensitizing agent. This compound effectively blocked stromal-induced migration of human ALL cells in culture and disrupted pre-established adhesion to stroma. To examine how to optimally use this compound in vivo, several combinations with cytotoxic drugs were tested in a stromal co-culture system. The best treatment regimen was then tested in vivo. Mice transplanted with murine Bcr/Abl ALL cells survived significantly longer when treated with a combination of nilotinib and AMD11070. Similarly, immunocompromised mice transplanted with human ALL cells and treated with vincristine and AMD11070 had few circulating leukemic cells, normal spleens and reduced human CD19+ cells in the BM at the termination of the experiment. These results show that combined treatment with AMD11070 may be of significant benefit in eradicating residual leukemia cells at locations where they would otherwise be protected by stroma.

Topics: Aminoquinolines; Animals; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Benzylamines; Butylamines; Cell Movement; Chemokine CXCL12; Cyclams; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Humans; Mice; Mice, Inbred C57BL; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Receptors, CXCR4; Signal Transduction; Vincristine

CXCR4 is a G-protein coupled receptor for CXCL12 that plays an important role in human immunodeficiency virus infection, cancer growth and metastasization, immune cell trafficking and WHIM syndrome. In the absence of an X-ray crystal structure, theoretical modeling of the CXCR4 receptor remains an important tool for structure-function analysis and to guide the discovery of new antagonists with potential clinical use. In this study, the combination of experimental data and molecular modeling approaches allowed the development of optimized ligand-receptor models useful for elucidation of the molecular determinants of small molecule binding and functional antagonism. The ligand-guided homology modeling approach used in this study explicitly re-shaped the CXCR4 binding pocket in order to improve discrimination between known CXCR4 antagonists and random decoys. Refinement based on multiple test-sets with small compounds from single chemotypes provided the best early enrichment performance. These results provide an important tool for structure-based drug design and virtual ligand screening of new CXCR4 antagonists.

Topics: Aminoquinolines; Artificial Intelligence; Benzimidazoles; Benzylamines; Binding Sites; Butylamines; Computer Simulation; Crystallography, X-Ray; Cyclams; Drug Design; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Humans; Ligands; Models, Molecular; Protein Binding; Pyridines; Receptors, Adrenergic, beta-2; Receptors, CXCR4; Sequence Alignment; Sequence Homology, Amino Acid; Structural Homology, Protein; Structure-Activity Relationship

CXC chemokine receptor (CXCR)4 is an HIV coreceptor and a chemokine receptor that plays an important role in several physiological and pathological processes, including hematopoiesis, leukocyte homing and trafficking, metastasis, and angiogenesis. This receptor belongs to the class A family of G protein-coupled receptors and is a validated target for the development of a new class of antiretroviral therapeutics. This study compares the interactions of three structurally diverse small-molecule CXCR4 inhibitors with the receptor and is the first report of the molecular interactions of the nonmacrocyclic CXCR4 inhibitor (S)-N'-(1H-benzimidazol-2-ylmethyl)-N'-(5,6,7,8-tetrahydroquinolin-8-yl)butene-1,4-diamine (AMD11070). Fourteen CXCR4 single-site mutants representing amino acid residues that span the entire putative ligand binding pocket were used in this study. These mutants were used in binding studies to examine how each single-site mutation affected the ability of the inhibitors to compete with (125)I-stromal-derived factor-1alpha binding. Our data suggest that these CXCR4 inhibitors bind to overlapping but not identical amino acid residues in the transmembrane regions of the receptor. In addition, our results identified amino acid residues that are involved in unique interactions with two of the CXCR4 inhibitors studied. These data suggest an extended binding pocket in the transmembrane regions close to the second extracellular loop of the receptor. Based on site-directed mutagenesis and molecular modeling, several potential binding modes were proposed for each inhibitor. These mechanistic studies might prove to be useful for the development of future generations of CXCR4 inhibitors with improved clinical pharmacology and safety profiles.

Topics: Aminoquinolines; Animals; Anti-HIV Agents; Benzimidazoles; Benzylamines; Binding Sites; Binding, Competitive; Butylamines; Cell Fusion; Cell Line; Cricetinae; Cricetulus; Cyclams; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Humans; Ligands; Models, Molecular; Mutagenesis, Site-Directed; Mutation; Pyridines; Radioligand Assay; Receptors, CXCR4