bevirimat and HIV-Infections

Since the emergence of HIV and AIDS in the early 1980s, the development of safe and effective therapies has accompanied a massive increase in our understanding of the fundamental processes that drive HIV biology. As basic HIV research has informed the development of novel therapies, HIV inhibitors have been used as probes for investigating basic mechanisms of HIV-1 replication, transmission, and pathogenesis. This positive feedback cycle has led to the development of highly effective combination antiretroviral therapy (cART), which has helped stall the progression to AIDS, prolong lives, and reduce transmission of the virus. However, to combat the growing rates of virologic failure and toxicity associated with long-term therapy, it is important to diversify our repertoire of HIV-1 treatments by identifying compounds that block additional steps not targeted by current drugs. Most of the available therapeutics disrupt early events in the replication cycle, with the exception of the protease (PR) inhibitors, which act at the virus maturation step. HIV-1 maturation consists of a series of biochemical changes that facilitate the conversion of an immature, noninfectious particle to a mature infectious virion. These changes include proteolytic processing of the Gag polyprotein by the viral protease (PR), structural rearrangement of the capsid (CA) protein, and assembly of individual CA monomers into hexamers and pentamers that ultimately form the capsid. Here, we review the development and therapeutic potential of maturation inhibitors (MIs), an experimental class of anti-HIV-1 compounds with mechanisms of action distinct from those of the PR inhibitors. We emphasize the key insights into HIV-1 biology and structure that the study of MIs has provided. We will focus on three distinct groups of inhibitors that block HIV-1 maturation: (1) compounds that block the processing of the CA-spacer peptide 1 (SP1) cleavage intermediate, the original class of compounds to which the term MI was applied; (2) CA-binding inhibitors that disrupt capsid condensation; and (3) allosteric integrase inhibitors (ALLINIs) that block the packaging of the viral RNA genome into the condensing capsid during maturation. Although these three classes of compounds have distinct structures and mechanisms of action, they share the ability to block the formation of the condensed conical capsid, thereby blocking particle infectivity.

Topics: Anti-HIV Agents; Capsid; Capsid Proteins; Clinical Trials as Topic; Drug Resistance, Viral; HIV Infections; HIV Integrase; HIV Integrase Inhibitors; HIV-1; Humans; Indazoles; Protein Processing, Post-Translational; Pyridines; RNA, Viral; Succinates; Triterpenes; Viral Genome Packaging; Virus Assembly; Virus Replication

Novel targets for the management of HIV infection have become increasingly relevant in view of extensive drug resistance, side effects and high pill burden of some of the conventional anti-retroviral agents. Structure based drug design using X-ray crystallography, nuclear magnetic resonance, and mass spectrometry have lead to the identification of novel class of drugs targeting new stages of HIV life cycle. These agents include chemokine receptor antagonists and the integrase inhibitors which were recently approved for HIV treatment, as well as numerous other agents directed to previously untested targets such as the maturation inhibitors, zinc finger inhibitors, pharmacological CDK inhibitors, Tat-TAR interaction inhibitors, anti-CD4 monoclonal antibody, antisense oligonucleotides, oxidisers of the HIV lipid envelope and agents acting on the proviral DNA. Use of new agents with novel mechanism of action requires the development of new laboratory assays to detect viral tropism and new resistance mutations. Despite the new developments providing hope to patients and clinicians in the fights against HIV, eradication of the disease still remains elusive. This review discusses issues surrounding the development of these new agents.

Topics: Anti-HIV Agents; Drug Delivery Systems; Drug Discovery; Drug Resistance, Viral; HIV Infections; HIV Integrase Inhibitors; Humans; Receptors, Chemokine; Reverse Transcriptase Inhibitors; Succinates; Triterpenes

Topics: Anti-HIV Agents; Clinical Trials, Phase II as Topic; Dose-Response Relationship, Drug; HIV; HIV Core Protein p24; HIV Infections; Humans; Succinates; Triterpenes

Panacos Pharmaceuticals Inc is developing the HIV Gag protein and viral maturation inhibitor bevirimat for the potential oral treatment of HIV infection. Phase II clinical trials are underway and phase III trials expected to commence in 2007.

Topics: Animals; Clinical Trials, Phase II as Topic; Drug Evaluation, Preclinical; Gene Products, gag; HIV Infections; HIV-1; Humans; Succinates; Triterpenes

Bevirimat [3-O-(3',3'-dimethylsuccinyl)betulinic acid] is the first in a new class of anti-human immunodeficiency virus (HIV) drugs that inhibit viral maturation by specifically blocking cleavage of the Gag capsid (CA) precursor, CA-SP1, to mature CA protein, resulting in defective core condensation and release of immature noninfectious virions. Four cohorts of six HIV-infected adults, with CD4 counts of >200 and plasma viral loads of 5,000 to 250,000 transcripts/ml and not currently receiving antiretroviral therapy, were randomized to receive a single oral dose of placebo, 75, 150, or 250 mg of bevirimat. Thirty blood samples for drug concentrations and 20 HIV RNA measures were collected from each subject over a 20-day period. Candidate pharmacokinetic/pharmacodynamic models were fit to individual subjects by maximum likelihood followed by Bayesian estimation; model discrimination was by corrected Akaike's Information Criterion. The bevirimat pharmacokinetics was well described by an oral two-compartment linear model (r(2), 0.98), with a mean (percent coefficient of variation) half-life of 60.3 (13.6) h and apparent oral clearance of bevirimat from the plasma compartment of 0.17 (18) liters/h. HIV RNA was modeled as being produced in infected CD4 cells, with bevirimat inhibiting infection of new CD4 cells thru a Hill-type function (r(2), 0.87). Single oral doses of bevirimat were well tolerated and demonstrated a dose-dependent reduction in viral load. The average maximum reduction from baseline following the 150- and 250-mg doses was greater than 0.45 log(10), with individual patients having reductions of greater than 0.7 log(10). No bevirimat resistance mutations were detected during the course of the study.

Topics: Adult; Algorithms; Anti-HIV Agents; Bayes Theorem; Calibration; CD4 Lymphocyte Count; Double-Blind Method; Drug Resistance, Viral; HIV Infections; HIV-1; Humans; Male; Models, Statistical; RNA, Viral; Succinates; Triterpenes; Viral Load; Virus Replication

Topics: Anti-HIV Agents; Capsid Proteins; Drug Resistance, Viral; gag Gene Products, Human Immunodeficiency Virus; HIV Infections; HIV-1; Humans; Models, Molecular; Peptide Fragments; Protein Conformation; Succinates; Triterpenes; Virion; Virus Assembly; Virus Replication

Two "privileged fragments", caffeic acid and piperazine, were integrated into bevirimat producing new derivatives with improved activity against HIV-1/NL4-3 and NL4-3/V370A carrying the most prevalent bevirimat-resistant polymorphism. The activity of one of these, 18c, was increased by 3-fold against NL4-3 and 51-fold against NL4-3/V370A. Moreover, 18c is a maturation inhibitor with improved metabolic stability. Our study suggested that integration of privileged motifs into promising natural product skeletons is an effective strategy for discovering potent derivatives.

Topics: Animals; Anti-HIV Agents; Caffeic Acids; Cell Line; Chlorocebus aethiops; COS Cells; Drug Resistance, Viral; HIV Infections; HIV-1; Humans; Piperazine; Piperazines; Succinates; Triterpenes; Virus Replication

Concomitant with the release of human immunodeficiency virus type 1 (HIV-1) particles from the infected cell, the viral protease cleaves the Gag polyprotein precursor at a number of sites to trigger virus maturation. We previously reported that a betulinic acid-derived compound, bevirimat (BVM), blocks HIV-1 maturation by disrupting a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA. BVM was shown in multiple clinical trials to be safe and effective in reducing viral loads in HIV-1-infected patients. However, naturally occurring polymorphisms in the SP1 region of Gag (e.g., SP1-V7A) led to a variable response in some BVM-treated patients. The reduced susceptibility of SP1-polymorphic HIV-1 to BVM resulted in the discontinuation of its clinical development. To overcome the loss of BVM activity induced by polymorphisms in SP1, we carried out an extensive medicinal chemistry campaign to develop novel maturation inhibitors. In this study, we focused on alkyl amine derivatives modified at the C-28 position of the BVM scaffold. We identified a set of derivatives that are markedly more potent than BVM against an HIV-1 clade B clone (NL4-3) and show robust antiviral activity against a variant of NL4-3 containing the V7A polymorphism in SP1. One of the most potent of these compounds also strongly inhibited a multiclade panel of primary HIV-1 isolates. These data demonstrate that C-28 alkyl amine derivatives of BVM can, to a large extent, overcome the loss of susceptibility imposed by polymorphisms in SP1.

Topics: Alkylation; Amination; Amino Acid Sequence; Anti-HIV Agents; Capsid; Capsid Proteins; Cell Line; Drug Resistance, Viral; gag Gene Products, Human Immunodeficiency Virus; HeLa Cells; HIV Infections; HIV-1; Humans; Inhibitory Concentration 50; Molecular Sequence Data; Polymorphism, Genetic; Structure-Activity Relationship; Succinates; T-Lymphocytes; Triterpenes; Virion; Virus Replication

Maturation inhibitors are an experimental class of antiretrovirals that inhibit Human Immunodeficiency Virus (HIV) particle maturation, the structural rearrangement required to form infectious virus particles. This rearrangement is triggered by the ordered cleavage of the precursor Gag polyproteins into their functional counterparts by the viral enzyme protease. In contrast to protease inhibitors, maturation inhibitors impede particle maturation by targeting the substrate of protease (Gag) instead of the protease enzyme itself. Direct cross-resistance between protease and maturation inhibitors may seem unlikely, but the co-evolution of protease and its substrate, Gag, during protease inhibitor therapy, could potentially affect future maturation inhibitor therapy. Previous studies showed that there might also be an effect of protease inhibitor resistance mutations on the development of maturation inhibitor resistance, but the exact mechanism remains unclear. We used wild-type and protease inhibitor resistant viruses to determine the impact of protease inhibitor resistance mutations on the development of maturation inhibitor resistance.. Our resistance selection studies demonstrated that the resistance profiles for the maturation inhibitor bevirimat are more diverse for viruses with a mutated protease compared to viruses with a wild-type protease. Viral replication did not appear to be a major factor during emergence of bevirimat resistance. In all in vitro selections, one of four mutations was selected: Gag V362I, A364V, S368N or V370A. The impact of these mutations on maturation inhibitor resistance and viral replication was analyzed in different protease backgrounds. The data suggest that the protease background affects development of HIV-1 resistance to bevirimat and the replication profiles of bevirimat-selected HIV-1. The protease-dependent bevirimat resistance and replication levels can be explained by differences in CA/p2 cleavage processing by the different proteases.. These findings highlight the complicated interactions between the viral protease and its substrate. By providing a better understanding of these interactions, we aim to help guide the development of second generation maturation inhibitors.

Topics: Cell Line; Drug Resistance, Viral; gag Gene Products, Human Immunodeficiency Virus; HIV Infections; HIV Protease; HIV Protease Inhibitors; HIV-1; Humans; Mutation; Succinates; Triterpenes; Virus Assembly; Virus Replication

Bevirimat, the prototype Human Immunodeficiency Virus type 1 (HIV-1) maturation inhibitor, is highly potent in cell culture and efficacious in HIV-1 infected patients. In contrast to inhibitors that target the active site of the viral protease, bevirimat specifically inhibits a single cleavage event, the final processing step for the Gag precursor where p25 (CA-SP1) is cleaved to p24 (CA) and SP1.. In this study, photoaffinity analogs of bevirimat and mass spectrometry were employed to map the binding site of bevirimat to Gag within immature virus-like particles. Bevirimat analogs were found to crosslink to sequences overlapping, or proximal to, the CA-SP1 cleavage site, consistent with previous biochemical data on the effect of bevirimat on Gag processing and with genetic data from resistance mutations, in a region predicted by NMR and mutational studies to have α-helical character. Unexpectedly, a second region of interaction was found within the Major Homology Region (MHR). Extensive prior genetic evidence suggests that the MHR is critical for virus assembly.. This is the first demonstration of a direct interaction between the maturation inhibitor, bevirimat, and its target, Gag. Information gained from this study sheds light on the mechanisms by which the virus develops resistance to this class of drug and may aid in the design of next-generation maturation inhibitors.

Topics: Anti-HIV Agents; Binding Sites; Cell Line; gag Gene Products, Human Immunodeficiency Virus; HEK293 Cells; HIV Infections; HIV-1; Humans; Mass Spectrometry; Molecular Sequence Data; Protein Binding; Succinates; Triterpenes; Virus Assembly; Virus Replication

Bevirimat (BVM) is the first of a new class of anti-HIV drugs with a novel mode of action known as maturation inhibitors. BVM inhibits the last cleavage of the Gag polyprotein by HIV-1 protease, leading to the accumulation of the p25 capsid-small peptide 1 (SP1) intermediate and resulting in noninfectious HIV-1 virions. Early clinical studies of BVM showed that over 50% of the patients treated with BVM did not respond to treatment. We investigated the impact of prior antiretroviral (ARV) treatment and/or natural genetic diversity on BVM susceptibility by conducting in vitro phenotypic analyses of viruses made from patient samples. We generated 31 recombinant viruses containing the entire gag and protease genes from 31 plasma samples from HIV-1-infected patients with (n = 21) or without (n = 10) prior ARV experience. We found that 58% of the patient isolates tested had a >10-fold reduced susceptibility to BVM, regardless of the patient's ARV experience or the level of isolate resistance to protease inhibitors. Analysis of mutants with site-directed mutations confirmed the role of the V370A SP1 polymorphism (SP1-V7A) in resistance to BVM. Furthermore, we demonstrated for the first time that a capsid polymorphism, V362I (CA protein-V230I), is also a major mutation conferring resistance to BVM. In contrast, none of the previously defined resistance-conferring mutations in Gag selected in vitro (H358Y, L363M, L363F, A364V, A366V, or A366T) were found to occur among the viruses that we analyzed. Our results should be helpful in the design of diagnostics for prediction of the potential benefit of BVM treatment in HIV-1-infected patients.

Topics: Amino Acid Sequence; Amino Acid Substitution; Anti-HIV Agents; Base Sequence; DNA, Viral; Drug Resistance, Viral; gag Gene Products, Human Immunodeficiency Virus; Genes, gag; Genes, Viral; HIV Infections; HIV Protease; HIV-1; Humans; In Vitro Techniques; Microbial Sensitivity Tests; Molecular Sequence Data; Mutagenesis, Site-Directed; Phenotype; Recombinant Proteins; Succinates; Triterpenes

Bevirimat is the first drug of a new class of antivirals that hamper the maturation of HIV. The objective of this study was to evaluate the sequence variability of the gag region targeted by bevirimat in HIV subtype-B isolates.. Of 484 HIV subtype-B isolates, the gag region comprising amino acids 357-382 was sequenced. Of the patients included, 270 were treatment naive and 214 were treatment experienced. In the latter group, 48 HIV isolates harboured mutations associated with reverse transcriptase inhibitor resistance only, and 166 HIV isolates carried mutations associated with protease inhibitor resistance.. In the treatment-naive patient population, approximately 30% harboured an HIV isolate with at least one mutation associated with a reduced susceptibility to bevirimat (H358Y, L363M, Q369H, V370A/M/del and T371del). In HIV isolates with protease inhibitor resistance, the prevalence of bevirimat resistance mutations increased to 45%. Accumulation of mutations at four positions in the bevirimat target region, S368C, Q369H, V370A and S373P, was significantly observed. Mutations associated with bevirimat resistance were detected more frequently in HIV isolates with three or more protease inhibitor resistance mutations than in those with less than three protease inhibitor mutations.. Reduced bevirimat activity can be expected in one-third of treatment-naive HIV subtype-B isolates and significantly more in protease inhibitor-resistant HIV. These data indicate that screening for bevirimat resistance mutations before administration of the drug is essential.

Topics: Drug Resistance, Viral; gag Gene Products, Human Immunodeficiency Virus; Genotype; HIV Infections; HIV Protease Inhibitors; HIV-1; Humans; Molecular Sequence Data; Mutation; Prevalence; Sequence Analysis, DNA; Succinates; Triterpenes

Topics: Anti-HIV Agents; CCR5 Receptor Antagonists; Cyclohexanes; HIV Fusion Inhibitors; HIV Infections; HIV Integrase Inhibitors; HIV-1; Humans; Maraviroc; Piperazines; Pyrimidines; Pyrrolidinones; Quinolones; Raltegravir Potassium; Succinates; Triazoles; Triterpenes; Viral Load

Bevirimat is the first drug in the class of maturation inhibitors, which treat HIV infection by disrupting the activity of HIV protease enzyme with a mechanism of action distinct from that of conventional protease inhibitors. The absorption, distribution, metabolism and elimination characteristics of single intravenous (25 mg/kg) and oral (25 mg/kg and 600 mg/kg) doses of 14C-bevirimat were studied in male Sprague Dawley and Long Evans rats. Pharmacokinetic and mass-balance studies revealed that bevirimat was cleared rapidly (within 12-24 h) after dosing, although plasma radioactivity was quantifiable up to 168 h. Radioactive metabolites of bevirimat were responsible for approximately 60-80% of plasma radioactivity. Systemically available bevirimat was predominantly (97%) excreted via bile in the faeces, with

Topics: Administration, Oral; Animals; Anti-HIV Agents; Autoradiography; Bile; Biological Availability; Dose-Response Relationship, Drug; Feces; HIV Infections; Injections, Intravenous; Male; Rats; Rats, Long-Evans; Rats, Sprague-Dawley; Succinates; Triterpenes

Topics: Animals; Anti-HIV Agents; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antiretroviral Therapy, Highly Active; Clinical Trials as Topic; Deoxycytidine; Drug Resistance, Multiple, Viral; HIV Antibodies; HIV Fusion Inhibitors; HIV Infections; HIV Protease Inhibitors; HIV Reverse Transcriptase; HIV-1; Humans; Mutation; Nitriles; Nucleosides; Pyrimidines; Reverse Transcriptase Inhibitors; Rilpivirine; Succinates; Triterpenes; Virus Internalization

Topics: Anti-HIV Agents; HIV Infections; Humans; Succinates; Triterpenes; Viral Load

Topics: Anti-HIV Agents; HIV Infections; Humans; Succinates; Treatment Outcome; Triterpenes; Viral Load

Topics: CCR5 Receptor Antagonists; HIV Infections; HIV Integrase Inhibitors; HIV Protease Inhibitors; Humans; Receptors, CXCR4; Reverse Transcriptase Inhibitors; Succinates; Triterpenes

Topics: Animals; Anti-HIV Agents; Clinical Trials as Topic; HIV Infections; HIV-1; Humans; Succinates; Triterpenes