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Smith M, Hoffman J, Sojar H, Aalinkeel R, Hsiao CB, Hicar MD. Assessment of Antibody Interference of Enfuvirtide (T20) Function Shows Assay Dependent Variability. Curr HIV Res 2019; 16:404-415. [PMID: 30836922 PMCID: PMC6710457 DOI: 10.2174/1570162x17666190228154850] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 02/21/2019] [Accepted: 02/22/2019] [Indexed: 02/06/2023]
Abstract
Background: During HIV infection, fusion of the viral and cellular membranes is dependent on folding of the gp41 trimer into a six-helix bundle. Fusion inhibitors, such as the antiretroviral Enfuvirtide (T20), interfere with the formation of the gp41 six-helix bundle. Recent in vitro studies reveal that the gp41 immunodominant region one targeting antibody 3D6 can block T20 interference, but the clinical and pathophysiologic significance of this finding is unclear. Objective/Method: We have previously characterized a number of antibodies that target conformational epitopes on gp41and herein characterized their ability to interfere with T20 in multiple assays and assess their prevalence in HIV infected subjects. Results: The T20 interference by antibody 3D6 was confirmed in a CHO-HXB2 envelope/ HeLaT4+ cell culture assay. Antibodies that target an immunodominant region one epitope, as well as a gp41 discontinuous epitope, also interfered in this assay, however, not all antibodies that targeted these epitopes showed T20 interference. This response was not due to the direct binding of T20 by the antibodies and could not be replicated utilizing TZM-bl and HL2/3 cells. Notably, serum competition studies on a panel of HIV subjects demonstrate that these conformational targeting antibodies are common in the HIV population. Conclusion: The relatively common nature of antibodies targeting these epitopes, the disparate in vitro results, and lack of reported clinical failures ascribed to such antibodies leads us to conclude that antibody interference of T20 is likely not clinically relevant. However, this warrants continued consideration with the advancement of other fusion inhibitors.
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Affiliation(s)
- Michele Smith
- Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Jonathon Hoffman
- Department of Pediatrics, Division of Infectious Diseases, University at Buffalo, Buffalo, NY, United States
| | - Hakimuddin Sojar
- Department of Pediatrics, Division of Infectious Diseases, University at Buffalo, Buffalo, NY, United States
| | - Ravikumar Aalinkeel
- Jacobs School of Medicine and Biomedical Sciences, Department of Medicine, Division of Allergy Immunology and Rheumatology, University at Buffalo, Buffalo, NY, United States
| | - Chiu-Bin Hsiao
- Temple University School of Medicine, Pittsburgh, PA, United States.,Allegheny General Hospital, Pittsburgh, PA, United States
| | - Mark Daniel Hicar
- Department of Pediatrics, School of Medicine and Biomedical Sciences, University at Buffalo, NY, United States
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Abstract
ABSTRACT HIV resistance against currently approved entry inhibitors, the chemokine receptor-5 (CCR5) antagonist maraviroc and the fusion inhibitor enfuvirtide (T-20), manifests in a complex manner that is distinct from the resistance patterns against other classes of antiretroviral drugs. Several attachment and fusion inhibitors are currently under various stages of development. Whereas CCR5 co-receptor antagonists have been widely studied until now, because patients who lack CCR5 are healthy and protected to some extent from HIV-infection, CXCR4-antagonist development has been slower, due to limited antiviral activity and potential toxicity given that CXCR4 may have essential cellular functions. Novel fusion inhibitor development is focusing on orally available small-molecule inhibitors that might replace T-20, which needs to be administered by subcutaneous injection.
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Affiliation(s)
- Victor G Kramer
- McGill AIDS Centre, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada
- Department of Experimental Medicine, McGill University, Montreal, QC, Canada
| | - Mark A Wainberg
- McGill AIDS Centre, Lady Davis Institute, Jewish General Hospital, Montreal, QC, Canada
- Department of Experimental Medicine, McGill University, Montreal, QC, Canada
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Haqqani AA, Tilton JC. Entry inhibitors and their use in the treatment of HIV-1 infection. Antiviral Res 2013; 98:158-70. [PMID: 23541872 DOI: 10.1016/j.antiviral.2013.03.017] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/18/2013] [Accepted: 03/19/2013] [Indexed: 12/20/2022]
Abstract
Entry of HIV into target cells is a complex, multi-stage process involving sequential attachment and CD4 binding, coreceptor binding, and membrane fusion. HIV entry inhibitors are a complex group of drugs with multiple mechanisms of action depending on the stage of the viral entry process they target. Two entry inhibitors are currently approved for the treatment of HIV-infected patients. Maraviroc, a CCR5 antagonist, blocks interactions between the viral envelope proteins and the CCR5 coreceptor. Enfuvirtide, a fusion inhibitor, disrupts conformational changes in gp41 that drive membrane fusion. A wide array of additional agents are in various stages of development. This review covers the entry inhibitors and their use in the treatment of HIV-infected patients.
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Affiliation(s)
- Aiman A Haqqani
- Case Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, OH 44106, USA
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Abstract
The efficacy of an antiretroviral (ARV) treatment regimen depends on the activity of the regimen's individual ARV drugs and the number of HIV-1 mutations required for the development of resistance to each ARV - the genetic barrier to resistance. ARV resistance impairs the response to therapy in patients with transmitted resistance, unsuccessful initial ARV therapy and multiple virological failures. Genotypic resistance testing is used to identify transmitted drug resistance, provide insight into the reasons for virological failure in treated patients, and help guide second-line and salvage therapies. In patients with transmitted drug resistance, the virological response to a regimen selected on the basis of standard genotypic testing approaches the responses observed in patients with wild-type viruses. However, because such patients are at a higher risk of harbouring minority drug-resistant variants, initial ARV therapy in this population should contain a boosted protease inhibitor (PI) - the drug class with the highest genetic barrier to resistance. In patients receiving an initial ARV regimen with a high genetic barrier to resistance, the most common reasons for virological failure are nonadherence and, potentially, pharmacokinetic factors or minority transmitted drug-resistant variants. Among patients in whom first-line ARVs have failed, the patterns of drug-resistance mutations and cross-resistance are often predictable. However, the extent of drug resistance correlates with the duration of uncontrolled virological replication. Second-line therapy should include the continued use of a dual nucleoside/nucleotide reverse transcriptase inhibitor (NRTI)-containing backbone, together with a change in the non-NRTI component, most often to an ARV belonging to a new drug class. The number of available fully active ARVs is often diminished with each successive treatment failure. Therefore, a salvage regimen is likely to be more complicated in that it may require multiple ARVs with partial residual activity and compromised genetic barriers of resistance to attain complete virological suppression. A thorough examination of the patient's ARV history and prior resistance tests should be performed because genotypic and/or phenotypic susceptibility testing is often not sufficient to identify drug-resistant variants that emerged during past therapies and may still pose a threat to a new regimen. Phenotypic testing is also often helpful in this subset of patients. ARVs used for salvage therapy can be placed into the following hierarchy: (i) ARVs belonging to a previously unused drug class; (ii) ARVs belonging to a previously used drug class that maintain significant residual antiviral activity; (iii) NRTI combinations, as these often appear to retain in vivo virological activity, even in the presence of reduced in vitro NRTI susceptibility; and rarely (iv) ARVs associated with previous virological failure and drug resistance that appear to have possibly regained their activity as a result of viral reversion to wild type. Understanding the basic principles of HIV drug resistance is helpful in guiding individual clinical decisions and the development of ARV treatment guidelines.
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Affiliation(s)
- Michele W Tang
- Stanford University, Division of Infectious Diseases, Stanford, CA 94305-5107, USA.
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Van Rompay KK. The use of nonhuman primate models of HIV infection for the evaluation of antiviral strategies. AIDS Res Hum Retroviruses 2012; 28:16-35. [PMID: 21902451 DOI: 10.1089/aid.2011.0234] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Several nonhuman primate models are used in HIV/AIDS research. In contrast to natural host models, infection of macaques with virulent simian immunodeficiency virus (SIV) isolates results in a disease (simian AIDS) that closely resembles HIV infection and AIDS. Although there is no perfect animal model, and each of the available models has its limitations, a carefully designed study allows experimental approaches that are not feasible in humans, but that can provide better insights in disease pathogenesis and proof-of-concept of novel intervention strategies. In the early years of the HIV pandemic, nonhuman primate models played a minor role in the development of antiviral strategies. Since then, a better understanding of the disease and the development of better compounds and assays to monitor antiviral effects have increased the usefulness and relevance of these animal models in the preclinical development of HIV vaccines, microbicides, and antiretroviral drugs. Several strategies that were first discovered to have efficacy in nonhuman primate models are now increasingly used in humans. Recent trends include the use of nonhuman primate models to explore strategies that could reduce viral reservoirs and, ultimately, attempt to cure infection. Ongoing comparison of results obtained in nonhuman primate models with those observed in human studies will lead to further validation and improvement of these animal models so they can continue to advance our scientific knowledge and guide clinical trials.
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Affiliation(s)
- Koen K.A. Van Rompay
- California National Primate Research Center, University of California, Davis, California
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7
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Abstract
Combination antiretroviral therapy for HIV-1 infection has resulted in profound reductions in viremia and is associated with marked improvements in morbidity and mortality. Therapy is not curative, however, and prolonged therapy is complicated by drug toxicity and the emergence of drug resistance. Management of clinical drug resistance requires in depth evaluation, and includes extensive history, physical examination and laboratory studies. Appropriate use of resistance testing provides valuable information useful in constructing regimens for treatment-experienced individuals with viremia during therapy. This review outlines the emergence of drug resistance in vivo, and describes clinical evaluation and therapeutic options of the individual with rebound viremia during therapy.
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Charpentier C, Jenabian MA, Piketty C, Karmochkine M, Tisserand P, Laureillard D, Bélec L, Si-Mohamed A, Weiss L. Dynamics of enfuvirtide resistance mutations in enfuvirtide-experienced patients remaining in virological failure under salvage therapy. ACTA ACUST UNITED AC 2011; 43:373-9. [DOI: 10.3109/00365548.2011.552520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Joly V, Jidar K, Tatay M, Yeni P. Enfuvirtide: from basic investigations to current clinical use. Expert Opin Pharmacother 2011; 11:2701-13. [PMID: 20977403 DOI: 10.1517/14656566.2010.522178] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD Drug resistance is a major challenge in the treatment of HIV infection. Enfuvirtide is the first entry inhibitor to have been approved for clinical use. AREAS COVERED IN THIS REVIEW Relevant information through searches of MEDLINE (1998 to June 2010) and meeting abstracts of major HIV/AIDS conferences (2003 - June 2010) using the search terms 'enfuvirtide', 'T-20' and 'fusion inhibitor'. WHAT THE READER WILL GAIN Enfuvirtide blocks HIV fusion to host cells. It works against the different HIV-1 variants but is not active against HIV-2. The recommended dosage of enfuvirtide is 90 mg b.i.d. subcutaneously. The two large Phase III pivotal clinical trials TORO 1 and 2 showed that enfuvirtide is an effective therapeutic option as rescue therapy in combination with other active antiretroviral drugs. Resistance to enfuvirtide is conferred by mutations in the HR1 region of gp41. Single and double mutations have been shown to result in high-level resistance to enfuvirtide. Postmarketing studies have been helpful to define more precisely the place of enfuvirtide in the sequence of antiretroviral therapy. TAKE HOME MESSAGE The emergence of new compounds and new classes of drugs, highly active against multiresistant virus but more convenient to administer than enfuvirtide, will probably prevent the extensive use of enfuvirtide. This drug remains attractive in some subgroups of patients because of its excellent systemic tolerance and the lack of interactions with the major cytochrome P450 isoenzymes.
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Affiliation(s)
- Véronique Joly
- Hôpital Bichat Claude Bernard, Maladies Infectieuses, 46 rue Henri Huchard, 75877 Paris Cedex 18, France.
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Vaidya NK, Rong L, Marconi VC, Kuritzkes DR, Deeks SG, Perelson AS. Treatment-mediated alterations in HIV fitness preserve CD4+ T cell counts but have minimal effects on viral load. PLoS Comput Biol 2010; 6:e1001012. [PMID: 21124866 PMCID: PMC2991251 DOI: 10.1371/journal.pcbi.1001012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Accepted: 10/26/2010] [Indexed: 11/19/2022] Open
Abstract
For most HIV-infected patients, antiretroviral therapy controls viral replication. However, in some patients drug resistance can cause therapy to fail. Nonetheless, continued therapy with a failing regimen can preserve or even lead to increases in CD4+ T cell counts. To understand the biological basis of these observations, we used mathematical models to explain observations made in patients with drug-resistant HIV treated with enfuvirtide (ENF/T-20), an HIV-1 fusion inhibitor. Due to resistance emergence, ENF was removed from the drug regimen, drug-sensitive virus regrown, and ENF was re-administered. We used our model to study the dynamics of plasma-viral RNA and CD4+ T cell levels, and the competition between drug-sensitive and resistant viruses during therapy interruption and re-administration. Focusing on resistant viruses carrying the V38A mutation in gp41, we found ENF-resistant virus to be 17±3% less fit than ENF-sensitive virus in the absence of the drug, and that the loss of resistant virus during therapy interruption was primarily due to this fitness cost. Using viral dynamic parameters estimated from these patients, we show that although re-administration of ENF cannot suppress viral load, it can, in the presence of resistant virus, increase CD4+ T cell counts, which should yield clinical benefits. This study provides a framework to investigate HIV and T cell dynamics in patients who develop drug resistance to other antiretroviral agents and may help to develop more effective strategies for treatment. The impact of antiretroviral drug-resistance on viral load, CD4+ T cells, and clinical outcomes is complex. We used mathematical models to evaluate the benefits of HIV drug therapy in the presence of drug-resistant virus. As an example, we considered resistance to enfuvirtide, the first FDA-approved fusion inhibitor. If viral load increases on drug therapy due to drug resistance, therapy with this drug may be stopped. We found that the drug resistant virus is less fit than the drug-sensitive virus in the absence of drug, and this fitness disadvantage causes the loss of drug-resistant virus during drug interruption. After the drug-sensitive virus replaces resistant virus, enfuvirtide therapy was re-administered. Analyzing the resulting viral kinetics, we demonstrate that despite the inability of the re-administered drug to suppress viral load because of the continued presence of drug resistant virus, therapy still provides benefit to the patient by preserving or increasing peripheral blood CD4+ T cell levels.
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Affiliation(s)
- Naveen K. Vaidya
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Libin Rong
- Department of Mathematics and Statistics, Oakland University, Rochester, Michigan, United States of America
| | - Vincent C. Marconi
- Emory University School of Medicine, Division of Infectious Diseases, Atlanta, Georgia, United States of America
| | - Daniel R. Kuritzkes
- Section of Retroviral Therapeutics, Brigham and Women's Hospital and Division of AIDS, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Steven G. Deeks
- Department of Medicine, University of California, San Francisco, San Francisco, California, United States of America
- San Francisco General Hospital, San Francisco, California, United States of America
| | - Alan S. Perelson
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
- * E-mail:
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Viral response to specifically targeted antiviral therapy for hepatitis C and the implications for treatment success. CANADIAN JOURNAL OF GASTROENTEROLOGY = JOURNAL CANADIEN DE GASTROENTEROLOGIE 2010; 24:385-90. [PMID: 20559582 DOI: 10.1155/2010/125435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Currently, hepatitis C virus (HCV) antiviral therapy is characterized by long duration, a multitude of side effects, difficult administration and suboptimal success; clearly, alternatives are needed. Collectively, specifically targeted antiviral therapy for HCV (STAT-C) molecules achieve rapid viral suppression and very high rapid virological response rates, and improve sustained virological response rates. The attrition rate of agents within this class has been high due to various toxicities. Regardless, several STAT-C molecules are poised to become the standard of care for HCV treatment in the foreseeable future. Optimism must be tempered with concerns related to the rapid development of drug resistance with resulting HCV rebound. Strategies including induction dosing with interferon and ribavirin, use of combination high-potency STAT-C molecules and an intensive emphasis on adherence to HCV antiviral therapy will be critical to the success of this promising advance in HCV therapy.
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12
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Bai X, Wilson KL, Seedorff JE, Ahrens D, Green J, Davison DK, Jin L, Stanfield-Oakley SA, Mosier SM, Melby TE, Cammack N, Wang Z, Greenberg ML, Dwyer JJ. Impact of the enfuvirtide resistance mutation N43D and the associated baseline polymorphism E137K on peptide sensitivity and six-helix bundle structure. Biochemistry 2010; 47:6662-70. [PMID: 18507398 DOI: 10.1021/bi702509d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enfuvirtide (ENF), the first human immunodeficiency virus type 1 (HIV-1) fusion inhibitor approved for clinical use, acts by binding to gp41 heptad repeat 1 (HR1) and preventing its interaction with the viral HR2 region. Treatment-emergent resistance to ENF has been mapped to residues within HR1, and these mutations decrease its susceptibility to ENF and may reduce viral fitness and pathogenesis, although the mechanism for these effects is not clear. N43D, a common ENF resistance mutation, was found in in vitro assays to cause a 5-50-fold in antiviral activity. We introduced this mutation into peptide models and determined the impact of this mutation by circular dichroism and X-ray crystallography. We find that the mutation results in a decrease in the thermal stability of the six-helix bundle and causes a significant change in the HR1-HR2 interface, including a loss of HR2 helicity. These data form a mechanistic basis for the decrease in ENF sensitivity and six-helix bundle stability. The E137K polymorphism, generally present at baseline in patients who develop N43D, partially compensates for the loss of stability, and we show that these residues likely form an ion pair. These data form a framework for understanding the impact of resistance mutations on viral fitness and pathogenesis and provide a pathway for the development of novel fusion inhibitor peptides.
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Affiliation(s)
- Xuefang Bai
- Protein Engineering Group and Virology Group, Trimeris, Inc., 3500 Paramount Parkway, Morrisville, North Carolina 27560, USA
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Rachlis A, Harris M, Lalonde R, Shafran SD, Tremblay C, Wainberg MA, Walmsley S. Canadian consensus guidelines for the optimal use of maraviroc in the treatment of HIV-infected adults. THE CANADIAN JOURNAL OF INFECTIOUS DISEASES & MEDICAL MICROBIOLOGY = JOURNAL CANADIEN DES MALADIES INFECTIEUSES ET DE LA MICROBIOLOGIE MEDICALE 2010; 21:159-72. [PMID: 22132003 PMCID: PMC3009577 DOI: 10.1155/2010/303474] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND AND OBJECTIVES A Canadian group, consisting of six physicians and an HIV researcher with significant experience and knowledge in HIV management, reviewed the available data and developed guidelines for Canadian health care providers (who treat HIV infection) on the appropriate use of maraviroc (UK-427,857) in HIV-infected adults. METHODS Evidence from the published literature and conference presentations, as well as the expert opinions of the group members were considered and evaluated to develop the recommendations. Feedback on the draft recommendations was obtained from this core group, as well as from four other physicians across Canada with expertise in HIV treatment and experience with the use of maraviroc. The final recommendations represent the core group's consensus agreement once all feedback was considered. RESULTS/CONCLUSIONS Recommendations were developed to guide physicians and other health care providers in the optimal use of maraviroc. The recommendations were considered in light of the fact that the decision to include maraviroc in an antiretroviral regimen depends not only on issues that concern all antiretroviral agents, such as efficacy, safety, resistance and drug interactions, but also on the issue of viral tropism, which is unique to maraviroc and other CCR5 inhibitors.
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Affiliation(s)
- Anita Rachlis
- Division of Infectious Diseases, Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario
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Tilton JC, Doms RW. Entry inhibitors in the treatment of HIV-1 infection. Antiviral Res 2009; 85:91-100. [PMID: 19683546 DOI: 10.1016/j.antiviral.2009.07.022] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 07/21/2009] [Accepted: 07/30/2009] [Indexed: 11/15/2022]
Abstract
Infection of target cells by HIV is a complex, multi-stage process involving attachment to host cells and CD4 binding, coreceptor binding, and membrane fusion. Drugs that block HIV entry are collectively known as entry inhibitors, but comprise a complex group of drugs with multiple mechanisms of action depending on the stage of the entry process at which they act. Two entry inhibitors, maraviroc and enfuvirtide, have been approved for the treatment of HIV-1 infection, and a number of agents are in development. This review covers the entry inhibitors and their use in the management of HIV-1 infection. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.
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Affiliation(s)
- John C Tilton
- Department of Microbiology, University of Pennsylvania, 301C Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, United States.
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Van Rompay KKA. Evaluation of antiretrovirals in animal models of HIV infection. Antiviral Res 2009; 85:159-75. [PMID: 19622373 DOI: 10.1016/j.antiviral.2009.07.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 07/07/2009] [Accepted: 07/13/2009] [Indexed: 01/07/2023]
Abstract
Animal models of HIV infection have played an important role in the development of antiretroviral drugs. Although each animal model has its limitations and never completely mimics HIV infection of humans, a carefully designed study allows experimental approaches that are not feasible in humans, but that can help to better understand disease pathogenesis and to provide proof-of-concept of novel intervention strategies. While rodent and feline models are useful for initial screening, further testing is best done in non-human primate models, such as simian immunodeficiency virus (SIV) infection of macaques, because they share more similarities with HIV infection of humans. In the early years of the HIV pandemic, non-human primate models played a relatively minor role in the antiretroviral drug development process. Since then, a better understanding of the disease and the development of better drugs and assays to monitor antiviral efficacy have increased the usefulness of the animal models. In particular, non-human primate models have provided proof-of-concept for (i) the benefits of chemoprophylaxis and early treatment, (ii) the preclinical efficacy of novel drugs such as tenofovir, (iii) the virulence and clinical significance of drug-resistant viral mutants, and (iv) the role of antiviral immune responses during drug therapy. Ongoing comparison of results obtained in animal models with those observed in human studies will further validate and improve these animal models so they can continue to help advance our scientific knowledge and to guide clinical trials. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.
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Affiliation(s)
- Koen K A Van Rompay
- California National Primate Research Center, University of California, Davis, CA 95616, USA.
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Survival of HIV-1 infected multidrug-resistant patients recycling enfuvirtide after a previous failure. J Acquir Immune Defic Syndr 2009; 51:179-84. [PMID: 19352200 DOI: 10.1097/qai.0b013e3181a56f46] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION A substantial proportion of HIV-1 infected multidrug-resistant patients previously exposed to enfuvirtide (ENF) have recently recycled the drug as part of their optimized backbone therapy when starting a new antiretroviral regimen including investigational drugs, but no data are available concerning the impact of this strategy on clinical outcome. We evaluated long-term survival in multidrug-resistant patients recycling ENF after a previous failure. METHODS A retrospective analysis of clinical outcomes in 32 multidrug-resistant patients receiving fewer than 3 active drugs who reintroduced ENF with those who did not. RESULTS Patients characteristics were not different in the 2 groups at the start of ENF treatment. During follow-up, 6 of the 15 patients (40%) who did not recycle ENF died, as did 3 of the 17 (17.7%) who recycled ENF. Survival probability was higher among patients who recycled ENF (P = 0.0006), also when the analysis was subdivided by CD4 cells gain (P = 0.003) or viral load decrease (P = 0.0003) at the end of the first cycle or the use of investigational drugs during follow-up (P = 0.003). CONCLUSIONS We found significantly longer survival in patients who reintroduced an ENF-containing regimen after a previous failure on the drug. We therefore suggest considering ENF recycling in patients starting a new regimen with fewer than 3 active drugs.
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Abstract
PURPOSE OF REVIEW The purpose of this review is to discuss recent pharmacological, virological, and clinical data that concern enfuvirtide usage in different antiretroviral combinations. RECENT FINDINGS Randomized, recent trials in multidrug-experienced patients suggest that antiretroviral combinations with enfuvirtide have excellent virological responses with new antiretroviral compounds, including darunavir, etravirine, raltegravir, vicriviroc, and maraviroc. Trials confirm long-term safety, in spite of moderate injection-site reactions or pain, and lack of significant interactions. Preliminary data suggest that switching from enfuvirtide to raltegravir is effective and using enfuvirtide in prophylaxis of mother-to-child transmission is well tolerated. To administer enfuvirtide in an intensification strategy in antiretroviral-naïve or experienced populations may accelerate virological decline. SUMMARY Dosage adaptations to renal insufficiency are not necessary with enfuvirtide. Spinal fluid concentrations and ombilic cord passage are negligible. Durability of virological responses with enfuvirtide in combinations has been confirmed, in spite of injection-site reactions and twice daily subcutaneous administration. Enfuvirtide should be used with at least one other fully active drug in optimized background therapy in multidrug-experienced populations, a possible exception being with entry inhibitors, which may further benefit from the addition of a third active drug. Data concerning enfuvirtide in antiretroviral combinations show accelerated viral load decline, and the possibility of switching from enfuvirtide to raltegravir without modification of optimized background therapy.
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Abstract
The entry of viruses into target cells involves a complex series of sequential steps, with opportunities for inhibition at every stage. Entry inhibitors exert their biological properties by inhibiting protein-protein interactions either within the viral envelope (Env) glycoproteins or between viral Env and host-cell receptors. The nature of resistance to entry inhibitors also differs from compounds inhibiting enzymatic targets due to their different modes of action and the relative variability in Env sequences both temporally and between patients. Two drugs that target HIV-1 entry, enfuvirtide and maraviroc, are now licensed for treatment of HIV-1 infection. The efficacy of these drugs validates entry as a point of intervention in viral life cycles and, in the context of HIV treatment, contributes to the growing armamentarium of antivirals which, in multidrug combinations, can effectively inhibit viral replication and prevent disease progression.
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Affiliation(s)
- Tom Melby
- Clinical Virology Associates, 101 E. Ellerbee St. Durham, NC 27704, USA.
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Kitchen CMR, Kroll J, Kuritzkes DR, Bloomquist E, Deeks SG, Suchard MA. Two-way Bayesian hierarchical phylogenetic models: An application to the co-evolution of gp120 and gp41 during and after enfuvirtide treatment. Comput Stat Data Anal 2009; 53:766-775. [PMID: 20442796 DOI: 10.1016/j.csda.2008.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Enfuvirtide (ENF) is a fusion inhibitor that prevents the entry of HIV virions into target cells. Studying the characteristics of viral evolution during treatment and after a treatment interruption can lend insight into the mechanisms of viral evolution and fitness. Although interruption of anti-HIV therapy often results in rapid emergence of an archived "wild-type" virus population, previous work from our group indicates that when only ENF is interrupted, viral gp41 continues to evolve forward and resistance mutations are lost due to back-mutation and remodeling of the envelope protein. To examine the co-evolution of gp120 and gp41 during ENF interruption we extend the Bayesian Hierarchical Phylogenetic model (HPM). Current HPMs enforce conditional independence across all outcomes while biologically all gene regions within a patient should return the same tree unless recombination confers an evolutionary selective advantage. A two-way-interaction HPM is proposed that provides middle ground between these two extremes and allows us to test for differences in evolutionary pressures across gene regions in multiple patients simultaneously. When the model is applied to a well-characterized cohort of HIV-infected patients interrupting ENF we find that across patients, the virus continued to evolve forward in both gene regions. Overall, the hypothesis of independence over dependence between the gene regions is supported. Models that allow for the examination of co-evolution over time will be increasingly important as more therapeutic classes are developed, each of which may impact other through novel and complex mechanisms.
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Affiliation(s)
- Christina M R Kitchen
- Department of Biostatistics, University of California, Los Angeles, CA, United States
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Marr P, Walmsley S. Reassessment of enfuvirtide's role in the management of HIV-1 infection. Expert Opin Pharmacother 2008; 9:2349-62. [PMID: 18710359 DOI: 10.1517/14656566.9.13.2349] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The development of new protease inhibitors, new non-nucleoside reverse transcriptase inhibitors and novel therapeutic drug classes has dramatically changed the approach to managing HIV-1 patients with multidrug resistant virus. This has led many clinicians to reevaluate the clinical utility of enfuvirtide. OBJECTIVES To summarize recent literature on enfuvirtide and to reassess enfuvirtide's role in the management of HIV-1 infection. METHODS MEDLINE (1990 to February Week 2 2008) and EMBASE (1990 to 2008 week 8) databases were searched using the following terms: 'enfuvirtide', 'Fuzeon', 'T20', 'HIV fusion inhibitors', and 'HIV entry inhibitor'; limits: English language. Reference lists of articles deemed relevant were hand searched for additional publications. Significant abstracts from recent international HIV conferences were also identified. CONCLUSION Enfuvirtide can optimize the response to new combinations of HIV-1 drug regimens in multiresistant patients. Its inclusion as an active agent is effective but use is impacted by its high cost, inconvenient route of administration and cosmetic side-effect profile.
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Affiliation(s)
- Patricia Marr
- University Health Network, Immunodeficiency Clinic, 13 North, Room 1314, 200 Elizabeth Street, Toronto, ON M5G2C4, Canada.
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Viral dynamics and in vivo fitness of HIV-1 in the presence and absence of enfuvirtide. J Acquir Immune Defic Syndr 2008; 48:572-6. [PMID: 18645515 DOI: 10.1097/qai.0b013e31817bbc4e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVES To estimate the in vivo fitness cost of enfuvirtide (ENF) resistance, we analyzed dynamic shifts in the HIV-1 quasispecies under changing selective pressure in 3 subjects on failing ENF-based regimens who interrupted ENF while maintaining stable background regimens. Subsequently, ENF was readministered for 4 weeks as "pulse intensification." METHODS The proportion of plasma virus carrying the V38A mutation in gp41 was quantified by allele-specific real-time polymerase chain reaction in serial samples collected from 3 subjects at 1- to 4-week intervals. Fitness differences were calculated using a method that corrected for time dependence of the viral replication rate. RESULTS The V38A mutant made up >or=85% of the quasispecies at baseline and decayed to <5% over 12-24 weeks; plasma HIV-1 RNA levels remained stable during this time. Fitness differences for mutant versus wild type ranged from -25% to -65%, providing in vivo evidence for the reduced fitness of ENF-resistant HIV-1. The V38A mutant virus reemerged rapidly during the ENF pulse. CONCLUSIONS These results demonstrate that the HIV-1 quasispecies undergoes dynamic changes in response to withdrawal and reinitiation of fusion inhibitor therapy. The relative stability of plasma HIV-1 titers during decay of V38A suggests that factors other than viral fitness likely define viral load set-point in patients with advanced disease.
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Kitchen CMR, Nuño M, Kitchen SG, Krogstad P. Enfuvirtide antiretroviral therapy in HIV-1 infection. Ther Clin Risk Manag 2008; 4:433-9. [PMID: 18728846 PMCID: PMC2504070 DOI: 10.2147/tcrm.s1962] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
It has been over 25 years since the first diagnosis of what would be known as AIDS. Although great strides in anti-HIV therapeutics have been made, there is still a great need for antiretrovirals that are effective against drug-resistant HIV. Enfuvirtide (ENF) is the first of a new class of fusion inhibitors to be approved by the US Food and Drug Administration for use in combination with other antiretroviral agents among HIV-1 infected patients with previous treatment experience. The inclusion of enfuvirtide in an optimized antiretroviral background regimen for the treatment of HIV-1 infected (treatment-experienced) patients followed the success of two critical clinical trials (TORO: T20 vs Optimized Regimen Only I and II). Even though injection-site reactions persisted in these trials, improved virological and immunological responses were observed among patients. Challenges associated with ENF treatment include the high cost of the drug, injection-site reactions, determining the optimal time to initiate treatment, and the potential for the selection of drug resistant mutants and viral evolution. ENF is a promising novel treatment for HIV infected individuals whose choices for effective treatment are limited by previous treatment and resistance. Understanding the implications of viral fitness and evolution in the presence of ENF treatment is crucial in determining effective and safe treatment regimens, particularly among treatment-experienced patients.
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Affiliation(s)
| | - Miriam Nuño
- Department of Biostatistics, UCLA School of Public HealthLos Angeles, CA USA
| | - Scott G Kitchen
- Department of Hematology and Oncology, David Geffen School of Medicine at UCLALos Angeles, CA USA
| | - Paul Krogstad
- Departments of Pediatrics and Medical Molecular Pharmacology, David Geffen School of Medicine at UCLALos Angeles, CA, USA
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Quiñones-Mateu ME, Moore-Dudley DM, Jegede O, Weber J, J Arts E. Viral drug resistance and fitness. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2008; 56:257-96. [PMID: 18086415 DOI: 10.1016/s1054-3589(07)56009-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Soria A, Cavarelli M, Sala S, Alessandrini AI, Scarlatti G, Lazzarin A, Castagna A. Unexpected dramatic increase in CD4+ cell count in a patient with AIDS after enfuvirtide treatment despite persistent viremia and resistance mutations. J Med Virol 2008; 80:937-41. [DOI: 10.1002/jmv.21138] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Bangsberg DR, Kroetz DL, Deeks SG. Adherence-resistance relationships to combination HIV antiretroviral therapy. Curr HIV/AIDS Rep 2007; 4:65-72. [PMID: 17547827 DOI: 10.1007/s11904-007-0010-0] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Early views on the relationship between adherence and resistance postulated a bell-shaped relationship that balanced selective drug pressure and improved viral suppression along a continuum of adherence. Although this conceptual relationship remains valid, recent data suggest that each regimen class may have different adherence-resistance relationships. These regimen-specific relationships are a function of the capacities of resistant virus to replicate at different levels of drug exposure, which are largely, but not entirely, determined by the impact of mutations on susceptibility of the virus and the impact of the mutations on the inherent ability of the virus to replicate efficiently. Specific patterns of adherence, such as treatment discontinuations, may influence adherence-resistance relationship to combination regimens comprised of medications with differing half-lives. Host genomics that alters antiretroviral drug distribution and metabolism may also impact adherence-resistance relationships. Optimal antiretroviral regimens should be constructed such that there is little overlap in the window of adherence that selects for antiretroviral drug resistance.
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Affiliation(s)
- David R Bangsberg
- San Francisco General Hospital, UCSF, 1001 Potrero Avenue, Building 100, Room 301, San Francisco, CA 94110, USA.
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26
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Anastassopoulou CG, Marozsan AJ, Matet A, Snyder AD, Arts EJ, Kuhmann SE, Moore JP. Escape of HIV-1 from a small molecule CCR5 inhibitor is not associated with a fitness loss. PLoS Pathog 2007; 3:e79. [PMID: 17542646 PMCID: PMC1885273 DOI: 10.1371/journal.ppat.0030079] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Accepted: 04/18/2007] [Indexed: 11/19/2022] Open
Abstract
Fitness is a parameter used to quantify how well an organism adapts to its environment; in the present study, fitness is a measure of how well strains of human immunodeficiency virus type 1 (HIV-1) replicate in tissue culture. When HIV-1 develops resistance in vitro or in vivo to antiretroviral drugs such as reverse transcriptase or protease inhibitors, its fitness is often impaired. Here, we have investigated whether the development of resistance in vitro to a small molecule CCR5 inhibitor, AD101, has an associated fitness cost. To do this, we developed a growth-competition assay involving dual infections with molecularly cloned viruses that are essentially isogenic outside the env genes under study. Real-time TaqMan quantitative PCR (QPCR) was used to quantify each competing virus individually via probes specific to different, phenotypically silent target sequences engineered within their vif genes. Head-to-head competition assays of env clones derived from the AD101 escape mutant isolate, the inhibitor-sensitive parental virus, and a passage control virus showed that AD101 resistance was not associated with a fitness loss. This observation is consistent with the retention of the resistant phenotype when the escape mutant was cultured for a total of 20 passages in the absence of the selecting compound. Amino acid substitutions in the V3 region of gp120 that confer complete AD101 resistance cause a fitness loss when introduced into an AD101-sensitive, parental clone; however, in the resistant isolate, changes elsewhere in env that occurred prior to the substitutions within V3 appear to compensate for the adverse effect of the V3 changes on replicative capacity. These in vitro studies may have implications for the development and management of resistance to other CCR5 inhibitors that are being evaluated clinically for the treatment of HIV-1 infection.
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Affiliation(s)
- Cleo G Anastassopoulou
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Andre J Marozsan
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Alexandre Matet
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Amy D Snyder
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
| | - Eric J Arts
- Division of Infectious Diseases, Department of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Shawn E Kuhmann
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail: (SEK); (JPM)
| | - John P Moore
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail: (SEK); (JPM)
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Dykes C, Demeter LM. Clinical significance of human immunodeficiency virus type 1 replication fitness. Clin Microbiol Rev 2007; 20:550-78. [PMID: 17934074 PMCID: PMC2176046 DOI: 10.1128/cmr.00017-07] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The relative fitness of a variant, according to population genetics theory, is that variant's relative contribution to successive generations. Most drug-resistant human immunodeficiency virus type 1 (HIV-1) variants have reduced replication fitness, but at least some of these deficits can be compensated for by the accumulation of second-site mutations. HIV-1 replication fitness also appears to influence the likelihood of a drug-resistant mutant emerging during treatment failure and is postulated to influence clinical outcomes. A variety of assays are available to measure HIV-1 replication fitness in cell culture; however, there is no agreement regarding which assays best correlate with clinical outcomes. A major limitation is that there is no high-throughput assay that incorporates an internal reference strain as a control and utilizes intact virus isolates. Some retrospective studies have demonstrated statistically significant correlations between HIV-1 replication fitness and clinical outcomes in some patient populations. However, different studies disagree as to which clinical outcomes are most closely associated with fitness. This may be in part due to assay design, sample size limitations, and differences in patient populations. In addition, the strength of the correlations between fitness and clinical outcomes is modest, suggesting that, at present, it would be difficult to utilize these assays for clinical management.
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Affiliation(s)
- Carrie Dykes
- Infectious Diseases Division, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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28
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Abstract
The need for new classes of antiretroviral drugs has become apparent because of increasing concern about the long-term toxic effects of existing drugs, the need to combat HIV-1 variants that are resistant to treatment, and the frequency of treatment change in drug-experienced patients. Currently, most regimens are combinations of inhibitors of two viral enzymes--reverse transcriptase and protease. Nevertheless, several steps in the HIV replication cycle are potential targets for intervention. These steps can be divided into entry steps, in which viral envelope glycoproteins and their receptors are involved, and postentry steps, involving viral accessory gene products and the cellular proteins with which they interact. New treatment options target viral entry into the cell. These treatments include the HIV fusion inhibitor enfuvirtide, and new HIV coreceptor antagonists in advanced stages of clinical development or in different stages of preclinical development. Here, we review the development of new HIV entry inhibitors, their performance in clinical trials, and their possible role in anti-HIV therapy.
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Affiliation(s)
- José A Esté
- Retrovirology Laboratory IrsiCaixa, Hospital Universitari Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Spain.
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Abstract
The management of treatment-experienced patients is complex and challenging. Fortunately, new agents continue to be developed that offer hope to those who have developed resistance to currently available agents. Knowing when, how, and in whom to use new agents is never easy and highlights the importance of expert care for HIV-infected patients. The management of treatment-experienced patients requires considerable expertise, especially now that patients with highly resistant virus can hope to achieve full virologic suppression.
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Affiliation(s)
- Joel E Gallant
- Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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