An imidazopiperidine series of CCR5 antagonists for the treatment of HIV: the discovery of N-{(1S)-1-(3-fluorophenyl)-3-[(3-endo)-3-(5-isobutyryl-2-methyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridin-1-yl)-8-azabicyclo[3.2.1]oct-8-yl]propyl}acetamide (PF-232798)

Broad-spectrum antiviral strategy: Host-targeting antivirals against emerging and re-emerging viruses

Viral infections are amongst the most prevalent diseases that pose a significant threat to human health. Targeting viral proteins or host factors represents two primary strategies for the development of antiviral drugs. In contrast to virus-targeting antivirals (VTAs), host-targeting antivirals (HTAs) offer advantages in terms of overcoming drug resistance and effectively combating a wide range of viruses, including newly emerging ones. Therefore, targeting host factors emerges as an extremely promising strategy with the potential to address critical challenges faced by VTAs. In recent years, extensive research has been conducted on the discovery and development of HTAs, leading to the approval of maraviroc, a chemokine receptor type 5 (CCR5) antagonist used for the treatment of HIV-1 infected individuals, with several other potential treatments in various stages of development for different viral infections. This review systematically summarizes advancements made in medicinal chemistry regarding various host targets and classifies them into four distinct catagories based on their involvement in the viral life cycle: virus attachment and entry, biosynthesis, nuclear import and export, and viral release.

Structure-Based Design of Tropane Derivatives as a Novel Series of CCR5 Antagonists with Broad-Spectrum Anti-HIV-1 Activities and Improved Oral Bioavailability

Blocking the entry of an HIV-1 targeting CCR5 coreceptor has emerged as an attractive strategy to develop HIV therapeutics. Maraviroc is the only CCR5 antagonist approved by FDA; however, serious side effects limited its clinical use. Herein, 21 novel tropane derivatives (6-26) were designed and synthesized based on the CCR5-maraviroc complex structure. Among them, compounds 25 and 26 had comparable activity to maraviroc and presented more potent inhibitory activity against a series of HIV-1 strains. In addition, compound 26 exhibited synergistic or additive antiviral effects in combination with other antiretroviral agents. Compared to maraviroc, both 25 and 26 displayed higher C_max and AUC_0-∞ and improved oral bioavailability in SD rats. In addition, compounds 25 and 26 showed no significant CYP450 inhibition and showed a novel binding mode with CCR5 different from that of maraviroc-CCR5. In summary, compounds 25 and 26 are promising drug candidates for the treatment of HIV-1 infection.

Discovery of Novel CCR5 Ligands as Anticolorectal Cancer Agents by Sequential Virtual Screening

C-C chemokine receptor type 5 (CCR5) is a member of the G protein-coupled receptor. CCR5 and its interaction with chemokine ligands have been crucial for understanding and tackling human immunodeficiency virus (HIV)-1 entry into target cells. In recent years, the change in CCR5 expression has been related to the progression of different cancer types. Patients treated with the CCR5 ligand, maraviroc (MVC), showed a deceleration in tumor development especially for metastatic colorectal cancer. Based on the crystal structure of CCR5, we herein describe a multistage virtual screening protocol including pharmacophore screening, molecular docking, and protein-ligand interaction fingerprint (PLIF) postdocking filtration for discovery of novel CCR5 ligands. The applied virtual screening protocol led to the identification of four hits with binding modes showing access to the major and minor pockets of the MVC binding site. Compounds 2-4 showed a decrease in cellular proliferation upon testing on the metastatic colorectal cancer cell line, SW620, displaying 12, 16, and 4 times higher potency compared to MVC, respectively. Compound 3 induced apoptosis by arresting cells in the G0/G1 phase of the cell cycle similar to MVC. Further in vitro assays showed compound 3 drastically decreasing the CCR5 expression and cellular migration 48 h post treatment, indicating its ability to inhibit metastatic activity in SW620 cells. The discovered hits represent potential leads for the development of novel classes of anticolorectal cancer agents targeting CCR5.

HIV-1 Entry and Prospects for Protecting against Infection

Human Immunodeficiency Virus type-1 (HIV-1) establishes a latent viral reservoir soon after infection, which poses a major challenge for drug treatment and curative strategies. Many efforts are therefore focused on blocking infection. To this end, both viral and host factors relevant to the onset of infection need to be considered. Given that HIV-1 is most often transmitted mucosally, strategies designed to protect against infection need to be effective at mucosal portals of entry. These strategies need to contend also with cell-free and cell-associated transmitted/founder (T/F) virus forms; both can initiate and establish infection. This review will discuss how insight from the current model of HIV-1 mucosal transmission and cell entry has highlighted challenges in developing effective strategies to prevent infection. First, we examine key viral and host factors that play a role in transmission and infection. We then discuss preventive strategies based on antibody-mediated protection, with emphasis on targeting T/F viruses and mucosal immunity. Lastly, we review treatment strategies targeting viral entry, with focus on the most clinically advanced entry inhibitors.

Medicinal chemistry strategies toward host targeting antiviral agents

Direct‐acting antiviral agents (DAAs) represent a class of drugs targeting viral proteins and have been demonstrated to be very successful in combating viral infections in clinic. However, DAAs suffer from several inherent limitations, including narrow‐spectrum antiviral profiles and liability to drug resistance, and hence there are still unmet needs in the treatment of viral infections. In comparison, host targeting antivirals (HTAs) target host factors for antiviral treatment. Since host proteins are probably broadly required for various viral infections, HTAs are not only perceived, but also demonstrated to exhibit broad‐spectrum antiviral activities. In addition, host proteins are not under the genetic control of viral genome, and hence HTAs possess much higher genetic barrier to drug resistance as compared with DAAs. In recent years, much progress has been made to the development of HTAs with the approval of chemokine receptor type 5 antagonist maraviroc for human immunodeficiency virus treatment and more in the pipeline for other viral infections. In this review, we summarize various host proteins as antiviral targets from a medicinal chemistry prospective. Challenges and issues associated with HTAs are also discussed.

Entanglement of CCR5 and Alzheimer's Disease

Although the mechanisms of Alzheimer's disease are diverse and unclear, the past 20 years have witnessed the unprecedented development of the AD inflammation theory. As a key inflammatory receptor family, the C-C chemokine receptor family is a remarkable participant in the cause of Alzheimer's disease; of this family, CCR5 is the most widely studied. CCR5 is an essential entrance when HIV infects immune cells and is also involved in other inflammatory and immune activities. New evidence on the inevitably intertwined link between Alzheimer's disease and CCR5 indicates that CCR5 accelerates the development of Alzheimer's disease, and few studies disputed it. The role of CCR5 in Alzheimer's disease remains elusive. However, as the research progresses, this intricate relationship will gradually be uncovered.

Molecular binding mode of PF-232798, a clinical anti-HIV candidate, at chemokine receptor CCR5

The chemokine receptor CCR5 is an important anti-HIV (human immunodeficiency virus) drug target owning to its pivotal role in HIV-1 viral entry as a co-receptor. Here, we present a 2.9 Å resolution crystal structure of CCR5 bound to PF-232798, a second-generation oral CCR5 antagonist currently in phase II clinical trials. PF-232798 and the marketed HIV drug maraviroc share a similar tropane scaffold with different amino (N)- and carboxyl (C)- substituents. Comparison of the CCR5-PF-232798 structure with the previously determined structure of CCR5 in complex with maraviroc reveals different binding modes of the two allosteric antagonists and subsequent conformational changes of the receptor. Our results not only offer insights into the phenomenon that PF-232798 has higher affinity and alternative resistance profile to maraviroc, but also will facilitate the design of new anti-HIV drugs.

Clonal analysis of HIV-1 genotype and function associated with virologic failure in treatment-experienced persons receiving maraviroc: Results from the MOTIVATE phase 3 randomized, placebo-controlled trials

Detailed clonal phenotypic/genotypic analyses explored viral-escape mechanisms during maraviroc-based therapy in highly treatment-experienced participants from the MOTIVATE trials. To allow real-time assessment of samples while maintaining a blind trial, the first 267 enrolled participants were selected for evaluation. At failure, plasma samples from 20/50 participants (16/20 maraviroc-treated) with CXCR4-using virus and all 38 (13 maraviroc-treated) with CCR5-tropic virus were evaluated. Of those maraviroc-treated participants with CXCR4-using virus at failure, genotypic and phenotypic clonal tropism determinations showed >90% correspondence in 14/16 at Day 1 and 14/16 at failure. Phylogenetic analysis of clonal sequences detected pre-treatment progenitor CXCR4-using virus, or on-treatment virus highly divergent from the Day 1 R5 virus, excluding possible co-receptor switch through maraviroc-mediated evolution. Re-analysis of pre-treatment samples using the enhanced-sensitivity Trofile® assay detected CXCR4-using virus pre-treatment in 16/20 participants failing with CXCR4-using virus. Post-maraviroc reversion of CXCR4-use to CCR5-tropic occurred in 7/8 participants with follow-up, suggesting selective maraviroc inhibition of CCR5-tropic variants in a mixed-tropic viral population, not emergence of de novo mutations in CCR5-tropic virus, as the main virologic escape mechanism. Maraviroc-resistant CCR5-tropic virus was observed in plasma from 5 treated participants with virus displaying reduced maximal percent inhibition (MPI) but no evidence of IC50 change. Env clones with reduced MPI showed 1-5 amino acid changes specific to each V3-loop region of env relative to Day 1. However, transferring on-treatment resistance-associated changes using site-directed mutagenesis did not always establish resistance in Day 1 virus, and key 'signature' mutation patterns associated with reduced susceptibility to maraviroc were not identified. Evolutionary divergence of the CXCR4-using viruses is confirmed, emphasizing natural selection not influenced directly by maraviroc; maraviroc simply unmasks pre-existing lineages by inhibiting the R5 virus. For R5-viral failure, resistance development through drug selection pressure was uncommon and manifested through reduced MPI and with virus strain-specific mutational patterns.

Recent updates for designing CCR5 antagonists as anti-retroviral agents

The healthcare system faces various challenges in human immunodeficiency virus (HIV) therapy due to resistance to Anti-Retroviral Therapy (ART) as a consequence of the evolutionary process. Despite the success of antiretroviral drugs like Zidovudine, Zalcitabine, Raltegravir WHO ranks HIV as one of the deadliest diseases with a mortality of one million lives in 2016. Thus, there emerges an urgency of developing a novel anti-retroviral agent that combat resistant HIV strains. The clinical development of ART from a single drug regimen to current triple drug combination is very slow. The progression in the structural biology of the viral envelope prompted the discovery of novel targets, which can be demonstrated a proficient approach for drug design of anti-retroviral agents. The current review enlightens the recent updates in the structural biology of the viral envelope and focuses on CCR5 as a validated target as well as ways to overcome CCR5 resistance. The article also throws light on the SAR studies and most prevalent mutations in the receptor for designing CCR5 antagonists that can combat HIV-1 infection. To conclude, the paper lists diversified scaffolds that are in pipeline by various pharmaceutical companies that could provide an aid for developing novel CCR5 antagonists.

CCR5 receptor antagonists in preclinical to phase II clinical development for treatment of HIV

INTRODUCTION

The chemokine receptor CCR5 has garnered significant attention in recent years as a target to treat HIV infection largely due to the approval and success of the drug Maraviroc. The side effects and inefficiencies with other first generation agents led to failed clinical trials, prompting the development of newer CCR5 antagonists. Areas covered: This review aims to survey the current status of 'next generation' CCR5 antagonists in the preclinical pipeline with an emphasis on emerging agents for the treatment of HIV infection. These efforts have culminated in the identification of advanced second-generation agents to reach the clinic and the dual CCR5/CCR2 antagonist Cenicriviroc as the most advanced currently in phase II clinical studies. Expert opinion: The clinical success of CCR5 inhibitors for treatment of HIV infection has rested largely on studies of Maraviroc and a second-generation dual CCR5/CCR2 antagonist Cenicriviroc. Although research efforts identified several promising preclinical candidates, these were dropped during early clinical studies. Despite patient access to Maraviroc, there is insufficient enthusiasm surrounding its use as front-line therapy for treatment of HIV. The non-HIV infection related development activities for Maraviroc and Cenicriviroc may help drive future interests.

Structural Analysis of Chemokine Receptor-Ligand Interactions

This review focuses on the construction and application of structural chemokine receptor models for the elucidation of molecular determinants of chemokine receptor modulation and the structure-based discovery and design of chemokine receptor ligands. A comparative analysis of ligand binding pockets in chemokine receptors is presented, including a detailed description of the CXCR4, CCR2, CCR5, CCR9, and US28 X-ray structures, and their implication for modeling molecular interactions of chemokine receptors with small-molecule ligands, peptide ligands, and large antibodies and chemokines. These studies demonstrate how the integration of new structural information on chemokine receptors with extensive structure–activity relationship and site-directed mutagenesis data facilitates the prediction of the structure of chemokine receptor–ligand complexes that have not been crystallized. Finally, a review of structure-based ligand discovery and design studies based on chemokine receptor crystal structures and homology models illustrates the possibilities and challenges to find novel ligands for chemokine receptors.

Chemokine receptor CCR5 antagonist maraviroc: medicinal chemistry and clinical applications

The human immunodeficiency virus (HIV) causes acquired immumodeficiency syndrome (AIDS), one of the worst global pandemic. The virus infects human CD4 T cells and macrophages, and causes CD4 depletion. HIV enters target cells through the binding of the viral envelope glycoprotein to CD4 and the chemokine coreceptor, CXCR4 or CCR5. In particular, the CCR5-utilizing viruses predominate in the blood during the disease course. CCR5 is expressed on the surface of various immune cells including macrophages, monocytes, microglia, dendric cells, and active memory CD4 T cells. In the human population, the CCR5 genomic mutation, CCR5Δ32, is associated with relative resistance to HIV. These findings paved the way for the discovery and development of CCR5 inhibitors to block HIV transmission and replication. Maraviroc, discovered as a CCR5 antagonist, is the only CCR5 inhibitor that has been approved by both US FDA and the European Medicines Agency (EMA) for treating HIV/AIDS patients. In this review, we summarize the medicinal chemistry and clinical studies of Maraviroc.

Comprehensive Review in Current Developments of Benzimidazole-Based Medicinal Chemistry

The properties of benzimidazole and its derivatives have been studied over more than one hundred years. Benzimidazole derivatives are useful intermediates/subunits for the development of molecules of pharmaceutical or biological interest. Substituted benzimidazole derivatives have found applications in diverse therapeutic areas such as antiulcer, anticancer agents, and anthelmintic species to name just a few. This work systematically gives a comprehensive review in current developments of benzimidazole-based compounds in the whole range of medicinal chemistry as anticancer, antibacterial, antifungal, anti-inflammatory, analgesic agents, anti-HIV, antioxidant, anticonvulsant, antitubercular, antidiabetic, antileishmanial, antihistaminic, antimalarial agents, and other medicinal agents. This review will further be helpful for the researcher on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole drugs/compounds.

Ligand- and mutation-induced conformational selection in the CCR5 chemokine G protein-coupled receptor

We predicted the structural basis for pleiotropic signaling of the C-C chemokine type 5 (CCR5) G protein-coupled receptor (GPCR) by predicting the binding of several ligands to the lower-energy conformations of the CCR5 receptor and 11 mutants. For each case, we predicted the ∼ 20 most stable conformations for the receptor along with the binding sites for four anti-HIV ligands. We found that none of the ligands bind to the lowest-energy apo-receptor conformation. The three ligands with a similar pharmacophore (Maraviroc, PF-232798, and Aplaviroc) bind to a specific higher-energy receptor conformation whereas TAK-779 (with a different pharmacophore) binds to a different high-energy conformation. This result is in agreement with the very different binding-site profiles for these ligands obtained by us and others. The predicted Maraviroc binding site agrees with the recent structure of CCR5 receptor cocrystallized with Maraviroc. We performed 11 site-directed mutagenesis experiments to validate the predicted binding sites. Here, we independently predicted the lowest 10 mutant protein conformations for each of the 11 mutants and then docked the ligands to these lowest conformations. We found the predicted binding energies to be in excellent agreement with our mutagenesis experiments. These results show that, for GPCRs, each ligand can stabilize a different protein conformation, complicating the use of cocrystallized structures for ligand screening. Moreover, these results show that a single-point mutation in a GPCR can dramatically alter the available low-energy conformations, which in turn alters the binding site, potentially altering downstream signaling events. These studies validate the conformational selection paradigm for the pleiotropic function and structural plasticity of GPCRs.

Modeling the allosteric modulation of CCR5 function by Maraviroc

Maraviroc is a non-peptidic, low molecular weight CC chemokine receptor 5 (CCR5) ligand that has recently been marketed for the treatment of HIV infected individuals. This review discusses recent molecular modeling studies of CCR5 by homology to CXC chemokine receptor 4, their contribution to the understanding of the allosteric mode of action of the inhibitor and their potential for the development of future drugs with improved efficiency and preservation of CCR5 biological functions.

Selective and Dual Targeting of CCR2 and CCR5 Receptors: A Current Overview

The chemokine receptor 2 (CCR2) and chemokine receptor 5 (CCR5) are important mediators of leukocyte trafficking in inflammatory processes. The emerging evidence for a role of CCR2 and CCR5 receptors in human inflammatory diseases led to a growing interest in CCR2- and CCR5-selective antagonists. In this review, we focus on the recent development of selective CCR2/CCR5 receptor ligands and dual antagonists. Several compounds targeting CCR2, e.g., INCB8761 and MK0812, were developed as promising candidates for clinical trials, but failed to show clinical efficacy as presumed from preclinical models. The role of CCR5 receptors as the second co-receptor for the HIV-host cell fusion led to the development of various CCR5-selective ligands. Maraviroc is the first CCR5-targeting drug for the treatment of HIV-1 infections on the market. The role of CCR5 receptors in the progression of inflammatory processes fueled the use of CCR5 antagonists for the treatment of rheumatoid arthritis. Unfortunately, the use of maraviroc for the treatment of rheumatoid arthritis failed due to its inefficacy. Some of the ligands, e.g., TAK-779 and TAK-652, were also found to be dual antagonists of CCR2 and CCR5 receptors. The fact that CCR2 and CCR5 receptor antagonists contribute to the treatment of inflammatory diseases renders the development of dual antagonists as promising novel therapeutic strategy.

The CCR5 chemokine receptor mediates vasoconstriction and stimulates intimal hyperplasia in human vessels in vitro

AIMS

The chemokine receptor CCR5 and its inflammatory ligands have been linked to atherosclerosis, an accelerated form of which occurs in saphenous vein graft disease. We investigated the function of vascular smooth muscle CCR5 in human coronary artery and saphenous vein, vascular tissues susceptible to atherosclerosis, and vasospasm.

METHODS AND RESULTS

CCR5 ligands were vasoconstrictors in saphenous vein and coronary artery. In vein, constrictor responses to CCL4 were completely blocked by CCR5 antagonists, including maraviroc. CCR5 antagonists prevented the development of a neointima after 14 days in cultured saphenous vein. CCR5 and its ligands were expressed in normal and diseased coronary artery and saphenous vein and localized to medial and intimal smooth muscle, endothelial, and inflammatory cells. [(125)I]-CCL4 bound to venous smooth muscle with KD = 1.15 ± 0.26 nmol/L and density of 22 ± 9 fmol mg(-1) protein.

CONCLUSIONS

Our data support a potential role for CCR5 in vasoconstriction and neointimal formation in vitro and imply that CCR5 chemokines may contribute to vascular remodelling and augmented vascular tone in human coronary artery and vein graft disease. The repurposing of maraviroc for the treatment of cardiovascular disease warrants further investigation.

Design of substituted imidazolidinylpiperidinylbenzoic acids as chemokine receptor 5 antagonists: potent inhibitors of R5 HIV-1 replication

The redesign of the previously reported thiophene-3-yl-methyl urea series, as a result of potential cardiotoxicity, was successfully accomplished, resulting in the identification of a novel potent series of CCR5 antagonists containing the imidazolidinylpiperidinyl scaffold. The main redesign criteria were to reduce the number of rotatable bonds and to maintain an acceptable lipophilicity to mitigate hERG inhibition. The structure-activity relationship (SAR) that was developed was used to identify compounds with the best pharmacological profile to inhibit HIV-1. As a result, five advanced compounds, 6d, 6e, 6i, 6h, and 6k, were further evaluated for receptor selectivity, antiviral activity against CCR5 using (R5) HIV-1 clinical isolates, and in vitro and in vivo safety. On the basis of these results, 6d and 6h were selected for further development.

Impact of antiretroviral pressure on selection of primary human immunodeficiency virus type 1 envelope sequences in vitro

The initiation of drug therapy results in a reduction in the human immunodeficiency virus type 1 (HIV-1) population, which represents a potential genetic bottleneck. The effect of this drug-induced genetic bottleneck on the population dynamics of the envelope (Env) regions has been addressed in several in vivo studies. However, it is difficult to investigate the effect on the env gene of the genetic bottleneck induced not only by entry inhibitors but also by non-entry inhibitors, particularly in vivo. Therefore, this study used an in vitro selection system using unique bulk primary isolates established in the laboratory to observe the effects of the antiretroviral drug-induced bottleneck on the integrase and env genes. Env diversity was decreased significantly in one primary isolate [KP-1, harbouring both CXCR4 (X4)- and CCR5 (R5)-tropic variants] when passaged in the presence or absence of raltegravir (RAL) during in vitro selection. Furthermore, the RAL-selected KP-1 variant had a completely different Env sequence from that in the passage control (particularly evident in the gp120, V1/V2 and V4-loop regions), and a different number of potential N-glycosylation sites. A similar pattern was also observed in other primary isolates when using different classes of drugs. This is the first study to explore the influence of anti-HIV drugs on bottlenecks in bulk primary HIV isolates with highly diverse Env sequences using in vitro selection.

Pharmacological modulation of chemokine receptor function

G protein-coupled chemokine receptors and their peptidergic ligands are interesting therapeutic targets due to their involvement in various immune-related diseases, including rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, chronic obstructive pulmonary disease, HIV-1 infection and cancer. To tackle these diseases, a lot of effort has been focused on discovery and development of small-molecule chemokine receptor antagonists. This has been rewarded by the market approval of two novel chemokine receptor inhibitors, AMD3100 (CXCR4) and Maraviroc (CCR5) for stem cell mobilization and treatment of HIV-1 infection respectively. The recent GPCR crystal structures together with mutagenesis and pharmacological studies have aided in understanding how small-molecule ligands interact with chemokine receptors. Many of these ligands display behaviour deviating from simple competition and do not interact with the chemokine binding site, providing evidence for an allosteric mode of action. This review aims to give an overview of the evidence supporting modulation of this intriguing receptor family by a range of ligands, including small molecules, peptides and antibodies. Moreover, the computer-assisted modelling of chemokine receptor-ligand interactions is discussed in view of GPCR crystal structures. Finally, the implications of concepts such as functional selectivity and chemokine receptor dimerization are considered.

CCR5 antagonism in HIV infection: current concepts and future opportunities

CCR5 antagonists inhibit HIV-1 entry by blocking the interaction of HIV-1 with the CCR5 cellular receptor. In patients with established HIV-1 infection, some viral strains use an alternative coreceptor for HIV-1 entry, CXCR4; CCR5 antagonists are not effective in patients harboring these viral strains. Coreceptor tropism testing of viral strains in an individual patient is necessary prior to treating with a CCR5 antagonist. There is one CCR5 antagonist, maraviroc, that is FDA-approved for treatment of HIV-1 infection. This drug is used most commonly for the treatment of HIV-1 infection in patients who have failed other antiretroviral regimens. In addition to virologic effects, CCR5 antagonists are under investigation for immune-modulating effects and for HIV-1 prevention. Ongoing research will further elucidate the role of CCR5 antagonists in combating HIV disease.

Prospective CCR5 small molecule antagonist compound design using a combined mutagenesis/modeling approach

The viral resistance of marketed antiviral drugs including the emergence of new viral resistance of the only marketed CCR5 entry inhibitor, maraviroc, makes it necessary to develop new CCR5 allosteric inhibitors. A mutagenesis/modeling approach was used (a) to remove the potential hERG liability in an otherwise very promising series of compounds and (b) to design a new class of compounds with an unique mutant fingerprint profile depending on residues in the N-terminus and the extracellular loop 2. On the basis of residues, which were identified by mutagenesis as key interaction sites, binding modes of compounds were derived and utilized for compound design in a prospective manner. The compounds were then synthesized, and in vitro evaluation not only showed that they had good antiviral potency but also fulfilled the requirement of low hERG inhibition, a criterion necessary because a potential approved drug would be administered chronically. This work utilized an interdisciplinary approach including medicinal chemistry, molecular biology, and computational chemistry merging the structural requirements for potency with the requirements of an acceptable in vitro profile for allosteric CCR5 inhibitors. The obtained mutant fingerprint profiles of CCR5 inhibitors were used to translate the CCR5 allosteric binding site into a general pharmacophore, which can be used for discovering new inhibitors.

HIV-1 entry inhibition by small-molecule CCR5 antagonists: a combined molecular modeling and mutant study using a high-throughput assay

Based on the attrition rate of CCR5 small molecule antagonists in the clinic the discovery and development of next generation antagonists with an improved pharmacology and safety profile is necessary. Herein, we describe a combined molecular modeling, CCR5-mediated cell fusion, and receptor site-directed mutagenesis approach to study the molecular interactions of six structurally diverse compounds (aplaviroc, maraviroc, vicriviroc, TAK-779, SCH-C and a benzyloxycarbonyl-aminopiperidin-1-yl-butane derivative) with CCR5, a coreceptor for CCR5-tropic HIV-1 strains. This is the first study using an antifusogenic assay, a model of the interaction of the gp120 envelope protein with CCR5. This assay avoids the use of radioactivity and HIV infection assays, and can be used in a high throughput mode. The assay was validated by comparison with other established CCR5 assays. Given the hydrophobic nature of the binding pocket several binding models are suggested which could prove useful in the rational drug design of new lead compounds.