Small-Molecule HIV Entry Inhibitors Targeting gp120 and gp41.

Interrupting early events in the virus life cycle, such as those prior to the formation of provirus, could effectively prevent HIV-1 infection. HIV-1 entry into host cells is mediated by the envelope glycoprotein (Env) trimer, which is composed of three gp120 exterior glycoproteins and three gp41 transmembrane glycoproteins. Hence, the development of novel inhibitors targeting these two glycoproteins could hold the key to early inhibition of HIV-1 infection. Small-molecule entry inhibitors targeting early events in the virus life cycle comprise a well-established class of useful drugs. Many libraries of small-molecule inhibitors have been established to screen potential drug candidates for a variety of targets based on computer docking, FRET, or peptide-linked assay. This chapter reviews the mechanisms of some small-molecule inhibitors targeting HIV-1 gp120 and gp41 and corresponding high-efficiency screening strategies for potential small-molecule inhibitors.

A Lipopeptide HIV-1/2 Fusion Inhibitor with Highly Potent In Vitro, Ex Vivo, and In Vivo Antiviral Activity.

Peptides derived from the C-terminal heptad repeat (CHR) region of the human immunodeficiency virus type 1 (HIV-1) fusogenic protein gp41 are potent viral entry inhibitors, and currently, enfuvirtide (T-20) is the only one approved for clinical use; however, emerging drug resistance largely limits its efficacy. In this study, we generated a novel lipopeptide inhibitor, named LP-19, by integrating multiple design strategies, including an N-terminal M-T hook structure, an HIV-2 sequence, intrahelical salt bridges, and a membrane-anchoring lipid tail. LP-19 showed stable binding affinity and highly potent, broad, and long-lasting antiviral activity. In in vitro studies, LP-19 efficiently inhibited HIV-1-, HIV-2-, and simian immunodeficiency virus (SIV)-mediated cell fusion, viral entry, and infection, and it was highly active against diverse subtypes of primary HIV-1 isolates and inhibitor-resistant mutants. Ex vivo studies demonstrated that LP-19 exhibited dramatically increased anti-HIV activity and an extended half-life in rhesus macaques. In short-term monotherapy, LP-19 reduced viral loads to undetectable levels in acutely and chronically simian-human immunodeficiency virus (SHIV)-infected monkeys. Therefore, this study offers an ideal HIV-1/2 fusion inhibitor for clinical development and emphasizes the importance of the viral fusion step as a drug target.IMPORTANCE The peptide drug T-20 is the only viral fusion inhibitor in the clinic, which is used for combination therapy of HIV-1 infection; however, it requires a high dosage and easily induces drug resistance, calling for a new drug with significantly improved pharmaceutical profiles. Here, we have developed a short-lipopeptide-based fusion inhibitor, termed LP-19, which mainly targets the conserved gp41 pocket site and shows highly potent inhibitory activity against HIV-1, HIV-2, and even SIV isolates. LP-19 exhibits dramatically increased antiviral activity and an extended half-life in rhesus macaques, and it has potent therapeutic efficacy in SHIV-infected monkeys, highlighting its high potential as a new viral fusion inhibitor for clinical use.

Functional characteristics of the natural polymorphisms of HIV-1 gp41 in HIV-1 isolates from enfuvirtide-naïve Korean patients.

HIV-1 gp41 plays a key role in viral entry. The insertion of Thr at position 4 and Met/Val/Phe substitutions at position 7 are frequently observed in the fusion peptide (FP) motif of gp41 without major enfuvirtide resistance associated with mutation in heptad repeats 1/2 (HR1/2) of HIV-1 isolates from Korean patients. Here, the influence of these mutations on their biological function was evaluated by employing HIV-1 variants with mutant FPs as shown previously and with recombinant HIV-1 using the env genes of 20 HIV-1 isolates from Korean patients. In an infectivity assay, all FP mutants showed lower infectivity than the wild-type NL4-3. In particular, the substitutions at position 7 led to much greater reductions in infectivity than the insertions at position 4. Nevertheless, the replication kinetics of most mutants were similar to those of the wild type, except that the FP mutants with an Ile insertion at position 4 and a Phe substitution at position 7 showed reduced replication. Moreover, most point mutants showed lower IC50 values for enfuvirtide than the wild type, whereas the L7M substitution resulted in a slightly increased IC50 value. The infectivity using the HIV-1 env recombinant viruses decreased in 14 cases but increased slightly in six cases compared with the wild type. Most recombinants were more susceptible to enfuvirtide than the wild type, except for three recombinants that showed slight resistance. Our findings may help to explain the potential mechanisms corresponding to the natural polymorphism of gp41 and to predict the efficiency of enfuvirtide in treatment of HIV-1-infected patients in Korea.

Incidence and risk factors for liver enzymes elevations in highly treatment-experienced patients switching from enfuvirtide to raltegravir: a sub-study of the ANRS-138 EASIER trial.

BACKGROUND: In the ANRS EASIER trial where treatment-experienced patients switched from enfuvirtide (ENF) to raltegravir (RAL), a high incidence of transaminase elevation was reported in the RAL arm. METHODS: We compared the incidence of emergent liver enzyme elevations (LEE) of grade 2 or more among patients randomized to the maintenance ENF arm or the switch RAL arm up to W24. We also assessed the overall incidence of LEE over the 48-week duration of the trial and baseline risk factors for grade 2 or more alanine aminotransferase (ALT) elevation using univariate and multivariate analyses. RESULTS: During the first 24 weeks, 6/84 (7.1 %) and 2/85 patients (2.4 %) presented with ALT elevation of grade 2 or more in the RAL and ENF arms, respectively (p = 0.21). Grade 2 or more γGT and ALP elevations were seen in 18 and 11 % (p = 0.35), and 5 and 1 % (p = 0.14) of patients in the RAL and ENF arms, respectively. The 48-week incidence of grade 2 or more LEE was 11.6 per 100-pts-years for ALT, 24.5 per 100-pts-years for γ-GT and 4.5 per 100-pts-years for ALP, respectively. In the multivariate analysis, tipranavir/ritonavir use (OR 3.66; 95 % CI [1.20-11.1], p = 0.022) and elevated ALT at baseline (OR 10.3; 95 % CI [2.67-39.6], p < 10(-3)) were significantly associated with a grade 2 or more ALT elevation during follow-up. CONCLUSION: The incidence of LEE was relatively high in these highly treatment-experienced patients switching to a RAL-based regimen. Both tipranavir/ritonavir use and high baseline ALT levels were associated with an increased risk of ALT. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00454337.

Regimen selection in the OPTIONS trial of HIV salvage therapy: drug resistance, prior therapy, and race-ethnicity determine the degree of regimen complexity.

BACKGROUND: Regimen selection for highly treatment-experienced patients is complicated. METHODS: Using a web-based utility, study team members reviewed antiretroviral (ARV) history and resistance data and recommended individual ARV regimens and nucleoside reverse transcriptase inhibitor (NRTI) options for treatment-experienced participants consisting of 3-4 of the following agents: raltegravir (RAL), darunavir (DRV)/ritonavir, tipranavir (TPV)/ritonavir, etravirine (ETR), maraviroc (MVC), and enfuvirtide (ENF). We evaluated team recommendations and site selection of regimen and NRTIs. Associations between baseline factors and the selection of a complex regimen (defined as including four ARV agents or ENF) were explored with logistic regression. RESULTS: A total of 413 participants entered the study. Participants initiated the first or second recommended regimen 86% of the time and 21% of participants started a complex regimen. In a multivariable model, ARV resistance to NRTI (odds ratio [OR] = 2.2), non-nucleoside reverse transcriptase inhibitor (NNRTI, OR = 6.2) or boosted protease inhibitor (PI, OR = 6.6), prior use of integrase strand transfer inhibitor (INSTI, OR = 25), and race-ethnicity (all P ≤ 0.01) were associated with selection of a complex regimen. Black non-Hispanic (OR = 0.5) and Hispanic participants from the continental US (OR = 0.2) were less likely to start a complex regimen, compared to white non-Hispanics. CONCLUSIONS: In this multi-center trial, we developed a web-based utility that facilitated treatment recommendations for highly treatment-experienced patients. Drug resistance, prior INSTI use, and race-ethnicity were key factors in decisions to select a more complex regimen.

Decreases in inflammatory and coagulation biomarkers levels in HIV-infected patients switching from enfuvirtide to raltegravir: ANRS 138 substudy.

Stored plasma specimens from 164 participants in the ANRS 138 trial were analyzed to determine interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), and D-dimer levels at baseline and weeks 24 and 48. These virologically suppressed, treatment-experienced patients were randomly assigned to undergo an immediate switch (IS) or a deferred switch (DS; at week 24) from an enfuvirtide-based antiretroviral therapy (ART) regimen to a raltegravir-based regimen. At week 24, a significant decrease from baseline was observed in the IS arm, compared with the DS arm, for IL-6 level (-30% vs +10%; P < .002), hsCRP level (-46% vs +15%; P < .0001), and D-dimer level (-40% vs +6%; P < .0001). At week 48, there was a reproducible decrease in levels of all biomarkers in the DS arm.

Intensification of antiretroviral therapy through addition of enfuvirtide in naive HIV-1-infected patients with severe immunosuppression does not improve immunological response: results of a randomized multicenter trial (ANRS 130 Apollo).

We studied whether addition of enfuvirtide (ENF) to a background combination antiretroviral therapy (cART) would improve the CD4 cell count response at week 24 in naive patients with advanced HIV disease. ANRS 130 Apollo is a randomized study, conducted in naive HIV-1-infected patients, either asymptomatic with CD4 counts of <100/mm(3) or stage B/C disease with CD4 counts of <200/mm(3). Patients received tenofovir-emtricitabine with lopinavir-ritonavir (LPV/r) or efavirenz and were randomized to receive ENF for 24 weeks (ENF arm) or not (control arm). The primary endpoint was the proportion of patients with CD4 counts of ≥ 200/mm(3) at week 24. A total of 195 patients were randomized: 73% had stage C disease, 78% were male, the mean age was 44 years, the median CD4 count was 30/mm(3), and the median HIV-1 RNA load was 5.4 log(10) copies/ml. Eighty-one percent of patients received LPV/r. One patient was lost to follow-up, and eight discontinued the study (four in each arm). The proportions of patients with CD4 counts of ≥ 200/mm(3) at week 24 were 34% and 38% in the ENF and control arms, respectively (P = 0.53). The proportions of patients with HIV-1 RNA loads of <50 copies/ml were 74% and 58% at week 24 in the ENF and control arms, respectively (P < 0.02), and the proportion reached 79% in both arms at week 48. Twenty (20%) and 12 patients (13%) in the ENF and control arms, respectively, experienced at least one AIDS event during follow-up (P = 0.17). Although inducing a more rapid virological response, addition of ENF to a standard cART does not improve the immunological outcome in naive HIV-infected patients with severe immunosuppression.

Monitoring the emergence of resistance mutations in patients infected with HIV-1 under salvage therapy with raltegravir in Rio de Janeiro, Brazil: a follow-up study.

The present study describes a follow-up of a prospective and observational cohort of patients infected with HIV-1 and treated with raltegravir for salvage therapy in Brazil. Two groups of patients were analyzed: switching from T20 to RAL (Group 1, n = 9) and salvage therapy containing RAL (Group 2, n = 10). Blood samples were drawn for CD4(+) T-cell counts and HIV-1 viral load determinations. Protease, reverse transcriptase, and integrase genotyping were performed at baseline and at the time of virologic failure. CD4(+) T-cells increased at 6 and 12 months in both groups; HIV-1 viral load was continuously suppressed for Group 1, and for Group 2 it significantly decreased after starting a RAL-containing regimen. Three out of 10 patients from Group 2 could not suppress HIV-1 viral load. The mutations Q148H + G140S were observed for two patients and for the third patient only mutations to PR/RT inhibitors were detected. The genotypic sensitivity score (GSS) was analyzed for all patients of Group 2 and both patients who developed resistance to raltegravir presented a GSS < 2.0 for the RAL-containing scheme, which could be associated to the lack of effectiveness of the proposed scheme. The present study describes, for the first time in Brazil, the close follow-up of a series of patients using a raltegravir-containing HAART, showing the safety of the enfuvirtide switch to RAL and the effectiveness of a therapeutic regimen with RAL in promoting immune reconstitution and suppressing HIV replication, as well as documenting the occurrence of resistance to integrase inhibitors in the country.

Short-term additional enfuvirtide therapy is associated with a greater immunological recovery in HIV very late presenters: a controlled pilot study.

OBJECTIVES: To evaluate whether the addition of enfuvirtide to standard highly active antiretroviral therapy (HAART) could confer immunovirological benefits in human immunodeficiency virus (HIV)-infected very late presenters. The current study is an open comparative therapeutic trial of standard protease inhibitor (PI)-based HAART ± additional enfuvirtide in treatment-naïve deeply immunologically impaired HIV-positive patients. METHODS: Very late presenters (CD4 <50/mm(3)), without tuberculosis and neoplasms, were alternatively allocated to two nucleoside reverse transcriptase inhibitors (NRTIs) and lopinavir/ritonavir without (control arm, CO) or with (ENF arm) enfuvirtide 90 mg bid. Enfuvirtide was administered until the achievement of viral load <50 copies/ml and for at least 24 weeks. The primary objective was the magnitude of CD4+ cell recovery at 6 months. HIV RNA was intensively monitored in the first month, and, thereafter, monthly, as for CD4+ cell count and percentage, clinical data, and plasma drug concentrations. RESULTS: Of 22 enrolled patients (11 per arm), 19 completed the study (10 in the ENF arm). Baseline CD4+ cell counts and % were comparable, with 20 CD4+/mm(3) (12-37) and a percentage of 3.3 (1.7-7.1) in the ENF arm, and 16 CD4+/mm(3) (9-29) and a percentage of 3.1 (2.3-3.8) in the CO arm, respectively. The baseline viral load was also comparable between the two arms, with 5.77 log10 (5.42-6) and 5.39 log10 (5.06-6) in the ENF and CO arms, respectively. Enfuvirtide recipients had higher CD4+ percentage at week 8 (7.6 vs. 3.6%, p = 0.02) and at week 24 (10.7 vs. 5.9%, p = 0.02), and a greater CD4+ increase at week 24 (207 vs. 134 cells/mm(3), p = 0.04), with 70% of enfuvirtide intakers versus 12.5% of controls who achieved a CD4+ cell count >200/mm(3) (p = 0.01). At 48 weeks, patients in the ENF arm had CD4+ cell counts higher than controls (251 vs. 153cells/mm(3), p = 0.04) and were also found to be faster in reaching a CD4 cell count over 200/mm(3): 18 (8-24) versus 48 (36-108) weeks (p = 0.01). Viral load decay at week 4 was greater in the ENF arm (-3 vs. -2.2 log, p = 0.04), while the proportion of patients with viral load <50 copies/ml at week 24 was comparable. CONCLUSIONS: In this pilot study, the addition of enfuvirtide to a lopinavir-based HAART was shown to be associated with a significantly faster and greater immunological recovery in newly discovered HIV-positive patients with very low CD4+ cell counts. Induction strategies using an enfuvirtide-based approach in such subjects warrant further investigation.

Enfuvirtide and cutaneous injection-site reactions.

Enfuvirtide belongs to a newer class of antiretroviral (ARV) agents called fusion inhibitors for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. Enfuvirtide blocks attachment, binding, and entry of the viral capsid into the host CD4+ cell. Administration is only available subcutaneously in a twice-daily regimen particularly for those patients who have previously failed more than one ARV regimen. Common side effects of enfuvirtide administration include fatigue, insomnia, nausea, and diarrhea; however, injection-site reactions are the most common side effect and present in nearly all individuals undergoing treatment. The spectrum of cutaneous manifestations ranges from little to no reaction to cysts, nodules, induration, or sclerodermalike lesions. These reactions are mostly variants of iatrogenically induced hypersensitivity and are self-limited.

[Analysis of the polymorphism of the genome region of HIV-1 encoding the fusion protein].

The prevalence of the mutations associated with HIV fusion inhibitor enfuvirtide resistance in Russia and CIS countries was studied. Enfuvirtide resistance mutations were not observed among studied viruses in Russia and CIS countries so far. It was found that high rate (35%) of natural polymorphism mutations were associated with enfuvirtide hypersusceptibility. It was also found that high frequency of accessory mutations N126K and E137K were observed in the HR2 region (27.5%). The accessory mutations in HR2 can contribute to increased resistance and improve viral fitness. Our data were compared with those obtained in similar previous studies.

Novel recombinant engineered gp41 N-terminal heptad repeat trimers and their potential as anti-HIV-1 therapeutics or microbicides.

Peptides derived from N-terminal heptad repeat (NHR) of the HIV-1 gp41 are generally poor inhibitors of HIV-1 entry, because they tend to aggregate and do not form a trimeric coiled-coil. In this study, we have fused portions of gp41 NHR, e.g. N36 or N28, to the T4 fibritin trimerization domain, Foldon (Fd), thus constructing novel NHR trimers, designated N36Fd or N28Fd, which could be expressed in Escherichia coli cells. The purified N36Fd and N28Fd exhibited SDS-resistant trimeric coiled-coil conformation with improved alpha-helicity compared with the corresponding N-peptides. They could interact with a C-peptide (e.g. C34) to form stable six-helix bundle and possessed potent anti-HIV-1 activity against a broad spectrum of HIV-1 strains. N28Fd was effective against T20-resistant HIV-1 variants and more resistant to proteinase K compared with T20 (enfuvirtide), a C-peptide-based HIV fusion inhibitor. Therefore, N28Fd trimer has great potentials for further development as an affordable therapeutic or microbicide for treatment and prevention of HIV-1 infection.

Switch from enfuvirtide to raltegravir lowers plasma concentrations of darunavir and tipranavir: a pharmacokinetic substudy of the EASIER-ANRS 138 trial.

We compared tipranavir and darunavir concentrations measured at steady state in 20 human immunodeficiency virus (HIV)-infected patients enrolled in the EASIER-ANRS 138 clinical trial who switched from enfuvirtide to raltegravir while maintaining the same background regimen. The geometric mean ratios of the observed predose concentration (C(trough)), maximum concentration of drug observed in plasma (C(max)), and area under the plasma concentration-time curve (AUC) before (day 0) and after (week 24) the switch were 0.49, 0.76, and 0.67 and 0.82, 0.68, and 0.64 for tipranavir and darunavir, respectively. The virologic consequences of these drug interactions have yet to be determined.

Subgroup analyses of maraviroc in previously treated R5 HIV-1 infection.

BACKGROUND: We conducted subanalyses of the combined results of the Maraviroc versus Optimized Therapy in Viremic Antiretroviral Treatment-Experienced Patients (MOTIVATE) 1 and MOTIVATE 2 studies to better characterize the efficacy and safety of maraviroc in key subgroups of patients. METHODS: We analyzed pooled data from week 48 from the two studies according to sex, race or ethnic group, clade, CC chemokine receptor 5 (CCR5) delta32 genotype, viral load at the time of screening, the use or nonuse of enfuvirtide in optimized background therapy (OBT), the baseline CD4 cell count, the number of active antiretroviral drugs coadministered, the first use of selected background agents, and tropism at baseline. Changes in viral tropism and the CD4 count at treatment failure were evaluated. Data on aminotransferase levels in patients coinfected with hepatitis B virus (HBV) or hepatitis C virus (HCV) were also analyzed. RESULTS: A treatment benefit of maraviroc plus OBT over placebo plus OBT was shown in all subgroups, including patients with a low CD4 cell count at baseline, those with a high viral load at screening, and those who had not received active agents in OBT. Analyses of the virologic response according to the first use of selected background drugs showed the additional benefit of adding a potent new drug to maraviroc at the initiation of maraviroc therapy. More patients in whom maraviroc failed had a virus binding to the CXC chemokine receptor 4 (CXCR4) at failure, but there was no evidence of a decrease in the CD4 cell count at failure in such patients as compared with those in whom placebo failed. Subanalyses involving patients coinfected with HBV or HCV revealed no evidence of excess hepatotoxic effects as compared with baseline. CONCLUSIONS: Subanalyses of pooled data from week 48 indicate that maraviroc provides a valuable treatment option for a wide spectrum of patients with R5 HIV-1 infection who have been treated previously. (ClinicalTrials.gov numbers, NCT00098306 and NCT00098722.)

Efficacy and safety of raltegravir in treatment-experienced HIV-1-infected patients switching from enfuvirtide-based regimens: 48 week results of the randomized EASIER ANRS 138 trial.

OBJECTIVES: To assess the sustainable efficacy and safety of a switch from enfuvirtide to raltegravir in patients with multidrug-resistant HIV infection. METHODS: One hundred and seventy patients with multidrug-resistant HIV infection and suppressed plasma HIV RNA levels < 400 copies/mL under an enfuvirtide-based regimen were randomized to maintain their regimen or to switch to a raltegravir-based regimen (immediate group) in a 48 week prospective, randomized, open-label trial. At week 24, patients in the maintenance arm also switched to raltegravir (deferred group). Baseline genotypic susceptibility scores (GSSs) were calculated using available historical resistance tests. Efficacy was assessed by the cumulative proportion of patients with virological failure, defined as a confirmed plasma HIV RNA ≥ 400 copies/mL up to week 48. The EASIER ANRS 138 trial is registered at ClinicalTrials.gov (NCT00454337). RESULTS: At baseline, 86% of patients had plasma HIV RNA levels <50 copies/mL and 86% had a GSS ≥ 1. Through to week 48, in the on-treatment analysis, only one patient in the immediate group, with a GSS of 0, developed virological failure. At week 48, 90% of patients in both the immediate and deferred groups had plasma HIV-1 RNA levels <50 copies/mL. Median CD4 cell counts remained stable during follow-up. Of note, 12 of 66 (18.2%) patients receiving a regimen combining raltegravir and ritonavir-boosted tipranavir experienced alanine aminotransferase elevations, which led to a switch from tipranavir to darunavir in 8 cases, without discontinuation of raltegravir. CONCLUSIONS: In well-suppressed patients with multidrug-resistant HIV infection, a switch from enfuvirtide to raltegravir is generally well tolerated and has sustained antiviral efficacy when combined with a potent background regimen.

The suppression of immune activation during enfuvirtide-based salvage therapy is associated with reduced CCR5 expression and decreased concentrations of circulating interleukin-12 and IP-10 during 48 weeks of longitudinal follow-up.

BACKGROUND: It has been suggested that patients who initiate highly active antiretroviral therapy (HAART) late in their course of infection may have suboptimal CD4 T-cell gains, persistent alterations in T-cell subsets and residual inflammation. To address this issue, we carried out a comprehensive 48-week immunological study in HIV-infected patients who had experienced failures of prior therapies, had low CD4 cell counts, and were receiving enfuvirtide-based salvage therapy. METHODS: Immunological monitoring of peripheral lymphocytes from enfuvirtide-responder patients was performed over a 48-week period. A detailed assessment of immune cell subsets, their activation state [CD38 and human leucocyte antigen (HLA)-DR expression] and homeostasis [activation-induced cell death (AICD) and Ki67 expression], and the expression of co-receptors was performed by flow cytometry. Cytokine and chemokine signatures were assessed using multianalyte profiling technology. RESULTS: Enfuvirtide-based salvage therapy induced a progressive restoration of naïve and central memory CD4 T cells, associated with a decrease in their activation state, suppression of premature priming for AICD and increased expression of Ki67. In addition, a significant decrease in C-C chemokine receptor 5 (CCR5) expression was detected on CD4 T cells, which was strongly correlated with the suppression of immune activation. Changes in circulating proinflammatory molecules occurred; i.e. there were decreases in the concentrations of interleukin (IL)-12, macrophage inflammatory protein MIP-1α, MIP-1ß, monokine induced by IFNγ (MIG) and interferon-γ-inducible protein-10 (IP-10). The decline in circulating IL-12 and IP-10 was correlated with both the reduction in the viral load and CD4 T-cell restoration. CONCLUSIONS: This study shows that suppression of HIV-1 replication with enfuvirtide-based salvage therapy in patients with low CD4 cell counts may result in an immunological benefit, characterized by the restoration of CD4 T-cell subsets associated with decreased immune activation and suppression of inflammation.

Modelling the effects of adherence to the HIV fusion inhibitor enfuvirtide.

Recently, the first drug in a new class of antiretroviral HIV drugs was approved, the fusion inhibitor enfuvirtide. We develop a mathematical model that describes the binding of the virus to T cells. We model the effect of enfuvirtide upon this process using impulsive differential equations. We find equilibria and determine stability in the case of no therapy and then when therapy is taken with perfect adherence. We determine analytical thresholds for the dosage and dosing intervals to ensure the disease-free equilibrium remains stable. We also explore the effects of partial adherence. Our theoretical results suggest that partial adherence may, at times, be worse than no therapy at all, but at other times may in fact as good as perfect adherence. It follows that patients should be counselled on the importance of adherence to this new antiretroviral drug.

Potent suppression of HIV-1 replication in humans by T-20, a peptide inhibitor of gp41-mediated virus entry.

T-20, a synthetic peptide corresponding to a region of the transmembrane subunit of the HIV-1 envelope protein, blocks cell fusion and viral entry at concentrations of less than 2 ng/ml in vitro. We administered intravenous T-20 (monotherapy) for 14 days to sixteen HIV-infected adults in four dose groups (3, 10, 30 and 100 mg twice daily). There were significant, dose-related declines in plasma HIV RNA in all subjects who received higher dose levels. All four subjects receiving 100 mg twice daily had a decline in plasma HIV RNA to less than 500 copies/ml, by bDNA assay. A sensitive RT-PCR assay (detection threshold 40 copies/ml) demonstrated that, although undetectable levels were not achieved in the 14-day dosing period, there was a 1.96 log10 median decline in plasma HIV RNA in these subjects. This study provides proof-of-concept that viral entry can be successfully blocked in vivo. Short-term administration of T-20 seems safe and provides potent inhibition of HIV replication comparable to anti-retroviral regimens approved at present.

Dynamics of enfuvirtide resistance mutations in enfuvirtide-experienced patients remaining in virological failure under salvage therapy.

BACKGROUND: Evaluation of the dynamics of enfuvirtide (ENF) resistance mutations after ENF withdrawal in patients with virological failure under salvage therapy may be helpful to optimize the management of ENF in human immunodeficiency virus (HIV)-infected patients. METHODS: Seven patients with a failing ENF-containing regimen, initiated for at least 3 months (median 6.4 months, range 3-14), were included and followed up prospectively at the time of virological failure. Genotypic analysis of the gp41 region by bulk sequencing and clonal analysis was performed in plasma and/or peripheral blood mononuclear cells to detect ENF resistance mutations. RESULTS: Genotypic profiles of ENF-resistant variants at ENF discontinuation were as follows: V38A in 3 patients, V38A+N42T+N43D in 1 patient, N43D in 2 patients, and N43K in 1 patient. Clonal analysis showed that maintaining ENF treatment after virological failure has an impact on both (1) the number of resistance profiles detected, and (2) the time of persistence of ENF-resistant variants. ENF-resistant variants were archived in HIV DNA in 5/7 patients. At 1 month after ENF withdrawal, no significant increase in HIV-1 viral load was observed. CONCLUSION: The persistence of ENF-resistant variants was found to be correlated to exposure time to failing drug. ENF withdrawal should be considered in patients with virological failure to preserve the possible efficacy of ENF recycling or upcoming entry inhibitors.

Two-year safety and tolerability study of enfuvertide use in salvage therapy of Thai HIV-1 experienced cases.

OBJECTIVE: To assess safety and tolerability of enfuvirtide, an antiretroviral, in Thai patients with advanced HIV-1 disease who have received antiretroviral treatment and failed on regimens that contain at least one of each antiretroviral (ARV) classes (PIs, NRTIs, and NNRTIs), or who have intolerance to previous antiretroviral regimens. MATERIAL AND METHOD: An open-label non-comparative study of enfuvirtide used in salvage regimens along with the backbone antiretroviral therapy of choice in Thai HIV-1 experienced cases that have been treated with at least one of each available ARV classes. RESULTS: Twenty-three patients were recruited from five participating centers. Seventeen patients (74%) completed 96 weeks of the treatment. Six patients prematurely withdrew from the present study in which three expired from HIV related complications, two withdrew consents, and one from adverse event. The most common adverse event is injection site reactions, which occurred in 22 patients. The manifestations and intensity varied from rash, erythema, edema, pain, induration, and bleeding at the injection sites, to inflammatory nodules. Most of the patients tolerated the treatment well. Enfuvirtide administered along with other antiretroviral combination provided a good control of the disease. CONCLUSION: Enfuvirtide was well tolerated by Thai patients who participated in the present study. The adverse events did not compromise the patient compliance.