Low efficacy and high frequency of adverse events in a randomized trial of the triple nucleoside regimen abacavir, stavudine and didanosine

Discontinuation of Efavirenz in Paediatric Patients: Why do Children Switch?

BACKGROUND

Efavirenz, a non-nucleoside reverse transcriptase inhibitor (NNRTI) is used globally as first-line antiretroviral therapy (ART) in combination with a dual nucleoside backbone in adults and children from 3 years of age. Up to 40% of adults taking efavirenz report central nervous system (CNS) adverse effects, and the rates of discontinuation of efavirenz-based treatment are higher than other first-line regimens. Data on efavirenz discontinuation are more limited for children and adolescents.

OBJECTIVE

In this study, we aimed to describe our single-centre paediatric experience of efavirenz.

METHODS

Retrospective case-note audit of children and adolescents with perinatally acquired HIV who ever received efavirenz.

RESULTS

From 1998 and 2014, 51 children and adolescents aged ≤ 18 years received efavirenz-based treatment. Median age at efavirenz initiation was 9.4 years (interquartile range [IQR] 7-13). More than half (30/51; 59%) subsequently switched off efavirenz-15 (29%) following virological failure with NNRTI-associated resistance mutations, and 16 (30%) after reporting adverse effects. Of those who experienced adverse effects, one-fifth (19.6%) described CNS adverse effects, including sleep disturbance, reduced concentration, headaches, mood change and psychosis. Four children (three males) developed gynaecomastia, two developed hypercholesterolaemia, and one child developed Stevens-Johnson syndrome. Comparison between those reporting side effects and the rest of the cohort showed no difference in age, sex, initial CD4 cell count, viral suppression, length of efavirenz-based treatment, weight, or efavirenz dose per kilogram. Median time to switch was 25 months (IQR 10-71) in those who experienced side effects and 22 months (IQR 12-50) for virological failure. One individual experienced both virological failure and adverse effects.

CONCLUSION

Almost two-thirds of this paediatric cohort switched from efavirenz-based treatment to an alternative regimen, due in equal proportions to both virological failure and toxicity. The majority of side effects involved the CNS. First-line regimens with improved tolerability and a higher genetic barrier to resistance should be the preferred option for children.

Higher Virological Effectiveness of NNRTI-Based Antiretroviral Regimens Containing Nevirapine or Efavirenz Compared to a Triple NRTI Regimen As Initial Therapy in HIV-1-Infected Adults

PURPOSE

To compare outcomes of nonnucleoside reverse transcriptase inhibitors (NNRTIs) nevirapine or efavirenz versus abacavir-based regimens with a backbone of zidovudine and lamivudine as initial therapy of treatment-naive adults with HIV-1 infection in routine clinical care.

METHOD

All patients starting their first antiretroviral therapy with any of the studied regimens from January 1999 to December 2002 were included in the analysis. Rates of viral suppression (HIV-RNA below 50 copies/mL) and discontinuation of any component of the regimen were compared at 48 weeks.

RESULTS

Fifty-one patients started with one of the two NNRTI-based regimens and 49 started with the triple nucleoside regimen (3-NRTI). After 48 weeks, more patients in the NNRTI regimens (76.5%) than in the 3-NRTI (51.1%) regimen achieved a HIV-1 RNA level below the limit of detection (<1.7 log10 copies/mL; p = .008). Time to change the antiretroviral regimen was shorter with 3-NRTI (median [range]: 234 [139-329] days) than with NNRTI (346 [0-756] days) (p = .0901). More withdrawals related to drug toxicity or intolerance occurred with the 3-NRTI-based regimen.

CONCLUSION

In a routine clinical care setting, initial antiretroviral treatment with an NNRTI (nevirapine or efavirenz) plus zidovudine and lamivudine was virologically superior and safer than a 3-NRTI therapy (abacavir with the same NRTI backbone).

Once-Daily Abacavir/Lamivudine/Zidovudine plus Tenofovir for the Treatment of HIV-1 Infection in Antiretroviral-NaïveSubjects: A 48-Week Pilot Study

PURPOSE

To assess the safety and efficacy of a 4-drug, 3-tablet, once-daily (qd) regimen consisting of abacavir/lamivudine/zidovudine (ABC/3TC/ZDV; 2 tablets) and tenofovir (TDF) in antiretroviral-naïve patients with plasma HIV-1 RNA 30,000 copies/mL at 48 weeks.

METHOD

All participants received ABC/3TC/ZDV (300/150/300 mg) and TDF (300 mg) qd in this pilot, open-label, multicenter study. Intent-to-treat (ITT) analyses were conducted to evaluate virologic and immunologic efficacy.

RESULTS

Of the 123 participants enrolled, 52 (42%) prematurely discontinued study for adverse events (14), were lost to follow-up (13), had virologic nonresponse (12), and withdrew for other reasons (13). At week 48, by ITT missing=failure analysis, 41% (51/123) and 51% (63/123) of participants had plasma HIV-1 RNA <50 copies/mL and <400 copies/mL, respectively; by ITT-observed analysis, 75% (51/68) and 93% (63/68) had plasma HIV-1 RNA <50 copies/mL and <400 copies/mL, respectively; 11% (14/123) met virologic nonresponse criteria. Median week 48 change in CD4+ cell count from baseline was +127 cells/mm3. Median week 48 changes from baseline for fasting lipids were as follows: cholesterol (-9 mg/dL), HDL (+1 mg/dL), LDL (-9 mg/dL), and triglycerides (-4 mg/dL).

CONCLUSION

A high rate of premature discontinuations contributed to the overall suboptimal virologic response to ABC/3TC/ZDV+TDF qd; however, the regimen was not associated with high rates of virologic failure previously observed with TDF+ABC/3TC.

A potential event-competition bias in safety signal detection: results from a spontaneous reporting research database in France

BACKGROUND

In spontaneous reporting databases, reports of well-established drug-event associations may mask alerts that arise from other drugs (drug competition bias). However, a symmetrical event-competition bias has not yet been explored whereby known events may mask an association with new events for a given drug or drug class.

OBJECTIVE

The objective of this study was to explore the effects of event-competition bias on safety signals generated from spontaneous reporting databases.

METHODS

The drug classes tested included statins, oral anticoagulants, antipsychotics and HIV antiretrovirals. For each, a type A reaction was selected, and its potential competitive effect on the generation of other safety signals for the drug was explored. These were rhabdomyolysis/myopathy for statins, haemorrhage for oral anticoagulants, extrapyramidal syndrome for antipsychotics and lipodystrophy for HIV antiretrovirals. Signals of disproportionate reporting (SDRs) were detected using the case/non-case approach in the French research spontaneous reporting database (which contains reports from 1 January 1986 to 31 December 2001), before and after removing all reports concerning these competitor events. SDRs were considered as potential signals if not reported in the literature before 1 January 2002 but confirmed since.

RESULTS

The whole database included 207,236 reports, 4,355 of which included statins as one of the suspected drugs. The removal of reports of rhabdomyolysis/myopathy concerned 8,425 reports among which 867 involved statins. After this removal, 11 new SDRs appeared for statins that had not been detected initially. Similarly, 15 SDRs were unmasked for oral anticoagulants, six for antipsychotics and nine for HIV antiretrovirals. After literature-based assessment, five of the 41 unmasked SDRs appeared related to potential safety signals confirmed after 2002.

CONCLUSION

This study demonstrated that a masking phenomenon resulting from an event-competition effect could occur when performing signal detection using disproportionality analyses of spontaneous reporting databases. This should be taken into account when routine signal detection is performed.

A systematic review of a single-class maintenance strategy with nucleoside/nucleotide reverse transcriptase inhibitors in HIV/AIDS

BACKGROUND

Single-drug class regimens with nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) are generally not recommended as initial therapy because they are inferior compared with therapy with two NRTIs plus efavirenz. However, triple-NRTI combinations can be useful in specific circumstances such as in tuberculosis coinfection, pregnancy or dyslipidaemia. Here, we review the potential of such combinations to maintain viral suppression after induction of suppression by standard combination antiretroviral therapy (cART) and to evaluate the trade-off of NRTI-only regimens for metabolic control.

METHODS

We conducted a systematic search of the literature in two databases from 1 January 1998 up to 1 March 2013: Medline, through the search engine PubMed, and Embase.

RESULTS

A total of 11 randomized controlled trials (RCTs) with 2,105 patients and 3 observational studies with 2,639 patients were included. Studies including patients with mono- or dual-NRTI treatment before start of effective cART showed a tendency to higher failure rate because of resistance based on archived viral mutations. In studies with ART-naive subjects before start of cART, triple-NRTI combination showed virological activity comparable to two NRTIs plus a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor in all RCTs, but not in one cohort study. Switching improved serum lipids significantly.

CONCLUSIONS

Of the studied triple-NRTI combinations only abacavir/lamivudine/zidovudine was sufficiently potent. Triple-NRTI maintenance after successful induction with two-class cART appeared successful in treatment-naive subjects and remains a useful option in specific circumstances, especially when other drugs are not available or drug interactions are an issue.

[Consensus Statement by GeSIDA/National AIDS Plan Secretariat on antiretroviral treatment in adults infected by the human immunodeficiency virus (Updated January 2013)]

OBJECTIVE

This consensus document is an update of combined antiretroviral therapy (cART) guidelines for HIV-1 infected adult patients.

METHODS

To formulate these recommendations a panel composed of members of the GeSIDA/National AIDS Plan Secretariat (Grupo de Estudio de Sida and the Secretaría del Plan Nacional sobre el Sida) reviewed the efficacy and safety advances in clinical trials, cohort and pharmacokinetic studies published in medical journals (PubMed and Embase) or presented in medical scientific meetings. The strength of the recommendations and the evidence which support them are based on a modification of the criteria of Infectious Diseases Society of America.

RESULTS

cART is recommended in patients with symptoms of HIV infection, in pregnant women, in serodiscordant couples with high risk of transmission, in hepatitisB co-infection requiring treatment, and in HIV nephropathy. cART is recommended in asymptomatic patients if CD4 is <500cells/μl. If CD4 are >500cells/μl cART should be considered in the case of chronic hepatitisC, cirrhosis, high cardiovascular risk, plasma viral load >100.000 copies/ml, proportion of CD4 cells <14%, neurocognitive deficits, and in people aged >55years. The objective of cART is to achieve an undetectable viral load. The first cART should include 2 reverse transcriptase inhibitors (RTI) nucleoside analogs and a third drug (a non-analog RTI, a ritonavir boosted protease inhibitor, or an integrase inhibitor). The panel has consensually selected some drug combinations, for the first cART and specific criteria for cART in acute HIV infection, in tuberculosis and other HIV related opportunistic infections, for the women and in pregnancy, in hepatitisB or C co-infection, in HIV-2 infection, and in post-exposure prophylaxis.

CONCLUSIONS

These new guidelines update previous recommendations related to first cART (when to begin and what drugs should be used), how to monitor, and what to do in case of viral failure or adverse drug reactions. cART specific criteria in comorbid patients and special situations are similarly updated.

[Consensus document of Gesida and Spanish Secretariat for the National Plan on AIDS (SPNS) regarding combined antiretroviral treatment in adults infected by the human immunodeficiency virus (January 2012)]

This consensus document has been prepared by a panel consisting of members of the AIDS Study Group (Gesida) and the Spanish Secretariat for the National Plan on AIDS (SPNS) after reviewing the efficacy and safety results of clinical trials, cohort and pharmacokinetic studies published in medical journals, or presented in medical scientific meetings. Gesida has prepared an objective and structured method to prioritise combined antiretroviral treatment (cART) in naïve patients. Recommendations strength (A, B, C) and the evidence which supports them (I, II, III) are based on a modification of the Infectious Diseases Society of America criteria. The current antiretroviral treatment (ART) of choice for chronic HIV infection is the combination of three drugs. ART is recommended in patients with symptomatic HIV infection, in pregnancy, in serodiscordant couples with high transmission risk, hepatitis B fulfilling treatment criteria, and HIV nephropathy. Guidelines on ART treatment in patients with concurrent diagnosis of HIV infection and an opportunistic type C infection are included. In asymptomatic patients ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts <350 cells/μL; 2) when CD4 counts are between 350 and 500 cells/μL, therapy will be recommended and only delayed if patient is reluctant to take it, the CD4 are stabilised, and the plasma viral load is low; 3) therapy could be deferred when CD4 counts are above 500 cells/μL, but should be considered in cases of cirrhosis, chronic hepatitis C, high cardiovascular risk, plasma viral load >10(5) copies/mL, proportion of CD4 cells <14%, and in people aged >55 years. ART should include 2 reverse transcriptase inhibitors nucleoside analogues and a third drug (non-analogue reverse transcriptase inhibitor, ritonavir boosted protease inhibitor or integrase inhibitor). The panel has consensually selected and given priority to using the Gesida score for some drug combinations, some of them co-formulated. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures, but an undetectable viral load may be possible nowadays. Adverse events are a fading problem of ART. Guidelines in acute HIV infection, in women, in pregnancy, and to prevent mother-to-child transmission and pre- and post-exposition prophylaxis are commented upon. Management of hepatitis B or C co-infection, other co-morbidities, and the characteristics of ART in HIV-2 infection are included.

Pediatric antiretroviral therapy

The rate of perinatal HIV transmission has decreased significantly in developed countries. However, worldwide, it remains the main source of HIV infection within the pediatric population. Recent advances as a result of findings from clinical trials, viral resistance testing and the advent of new drugs have increased the options for initial treatment regimens. This article provides an overview of antiretroviral therapy in treatment-naive children, including recent pediatric data and updated guidelines from the NIH. It also provides information on new drugs approved for the pediatric age group, dosage information, drug resistance testing and monitoring suggestions for children and adolescents receiving antiretroviral therapy. Special issues pertaining to adherence, disclosure and contraception are also highlighted.

Clinical audit: virological and immunological response to combination antiretroviral therapy in HIV patients at a Sydney sexual health clinic

AIM

Bigge Park Centre (BPC) is a sexual health clinic located in a socially disadvantaged area in Southwest Sydney. This served as a retrospective clinical audit, documenting patient demographics, identifying factors associated with virological, immunological and discordant responses, evaluating the centre's ability in HIV control and investigating changes in practice from 1996 to 2007.

METHOD

Data including age, gender, ethnicity, mode of transmission, hepatitis co-infection, prior acquired immune deficiency syndrome (AIDS)-defining-illness, HIV-1 RNA and CD4+cell counts of patients on combination antiretroviral therapy (CART) for treatment of HIV with at least 1-year follow up at the BPC were analysed. Results were compared with other cohorts in medical literature.

RESULTS

BPC manages HIV patients from diverse backgrounds. Sequential monotherapy was associated with poor virological control, lower CD4+cell recovery and discordant response. When patients who had sequential monotherapy were excluded, Caucasian race, high viral load at 1 month and triple-NRTI (nucleoside reverse transcriptase inhibitor) regimen were associated with lack of virological control. Lower baseline viral load and triple-NRTI regimen were associated with lower CD4+cell recovery. Lower baseline CD4+cell count and prior diagnosis of AIDS were associated with discordant response. Virological control and CD4+cell recovery achieved were comparable to that documented in medical literature. There was no significant change over time in terms of timing of CART initiation, attainment of immunological response or virological control since the late 1990 s.

CONCLUSION

HIV control achieved at the BPC was comparable to that reported in medical literature. Enhancement of strategies to promote screening and improve adherence as well as performance of HIV resistance assessment and avoidance of triple-NRTI therapy will likely improve patient care.

TB and HIV in children - advances in prevention and management

The human immunodeficiency virus (HIV) epidemic has had a major impact on the age and gender profile of adult tuberculosis (TB) patients, resulting in increased exposure of HIV-infected and uninfected children at a very young age. Young and/or HIV-infected children are extremely vulnerable to develop severe forms of TB following recent exposure and infection. There is an urgent need to implement safe and pragmatic strategies to prevent TB in children, especially in TB endemic areas where they suffer the greatest burden of disease. The management of TB in HIV-infected children poses multiple challenges, but recent advances in the implementation of prevention of mother to child transmission (PMTCT) strategies and HIV care of infants offer hope. These include HIV testing and access to PMTCT for all pregnant women, routine testing of all HIV exposed infants and rapid initiation of antiretroviral treatment irrespective of clinical or immunological disease staging. In addition, careful scrutiny for TB exposure should occur at every health care visit, with provision of isoniazid preventive therapy (IPT) following each documented exposure event. Knowing the HIV infection status of child TB suspects is essential to optimize case management. Although multiple difficulties remain, recent advances demonstrate that the management of children with TB and/or HIV can be vastly improved by well focused interventions using readily available resources.

Combinatorial approaches to the prevention and treatment of HIV-1 infection

The discovery of the human immunodeficiency virus type 1 (HIV-1) in 1982 soon led to the identification and development of antiviral compounds to be used in treatment strategies for infected patients. Early in the epidemic, drug monotherapies frequently led to treatment failures because the virus quickly developed resistance to the single drug. Following the advent of highly active antiretroviral therapy (HAART) in 1995, dramatic improvements in HIV-1-infected patient health and survival were realized as more refined combination therapies resulted in reductions in viral loads and increases in CD4+ T-cell counts. In the absence of an effective vaccine, prevention of HIV-1 infection has also gained traction as an approach to curbing the pandemic. The development of compounds as safe and effective microbicides has intensified and has focused on blocking the transmission of HIV-1 during all forms of sexual intercourse. Initial preclinical investigations and clinical trials of microbicides focused on single compounds effective against HIV-1. However, the remarkable successes achieved using combination therapy to treat systemic HIV-1 infection have subsequently stimulated the study and development of combination microbicides that will simultaneously inhibit multiple aspects of the HIV-1 transmission process by targeting incoming viral particles, virus-infected cells, and cells susceptible to HIV-1 infection. This review focuses on existing and developing combination therapies, covering preclinical development, in vitro and in vivo efficacy studies, and subsequent clinical trials. The shift in focus within the microbicide development field from single compounds to combination approaches is also explored.

Intracellular nucleotide levels during coadministration of tenofovir disoproxil fumarate and didanosine in HIV-1-infected patients

Studies were conducted to determine if there is a mechanistic basis for reports of suboptimal virologic responses and concerns regarding the safety of regimens containing the combination of tenofovir (TFV) disoproxil fumarate (TDF) and didanosine (ddI) by assessing the pharmacokinetic consequences of coadministration of these drugs on intracellular nucleotides. This was a prospective and longitudinal study in HIV-1-infected patients of adding either TDF or ddI to a stable antiretroviral regimen containing the other drug. Intracellular concentrations of the nucleotide analogs TFV diphosphate (TFV-DP) and ddATP and the endogenous purine nucleotides dATP and 2'-dGTP in peripheral blood mononuclear cells were measured. A total of 16 patients were enrolled into the two study arms and a study extension. Intracellular TFV-DP concentrations (median, 120 fmol/10(6) cells) and ddATP concentrations (range, 1.50 to 7.54 fmol/10(6) cells in two patients) were unaffected following addition of ddI or TDF to a stable regimen containing the other drug. While coadministration of ddI and TDF for 4 weeks did not appear to impact dATP or dGTP concentrations, cross-sectional analysis suggested that extended therapy with ddI-containing regimens, irrespective of TDF coadministration, may decrease dATP and ddATP concentrations. Addition of TDF or ddI to a stable regimen including the other drug, in the context of ddI dose reduction, did not adversely affect the concentration of dATP, dGTP, TFV-DP, or ddATP. The association between longer-term ddI therapy and reduced intracellular nucleotide concentrations and this observation's implication for the efficacy and toxicity of ddI-containing regimens deserve further study.

[AIDS Study Group/Spanish AIDS Plan consensus document on antiretroviral therapy in adults with human immunodeficiency virus infection (updated January 2010)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy recommendations for adult patients with human immunodeficiency virus infection.

METHODS

To formulate these recommendations a panel made up of members of the Grupo de Estudio de Sida (Gesida, AIDS Study Group) and the Plan Nacional sobre el Sida (PNS, Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of human immunodeficiency virus (HIV) infection, the efficacy and safety of clinical trials, and cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings. Three levels of evidence were defined according to the data source: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not to recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r), but other combinations are possible. Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts below 350 cells/microl; 2) When CD4 counts are between 350 and 500 cells/microl, therapy should be started in case of cirrhosis, chronic hepatitis C, high cardiovascular risk, HIV nephropathy, HIV viral load above 100,000 copies/ml, proportion of CD4 cells under 14%, and in people aged over 55; 3) Therapy should be deferred when CD4 are above 500 cells/microl, but could be considered if any of previous considerations concurs. Treatment should be initiated in case of hepatitis B requiring treatment and should be considered for reduce sexual transmission. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures but undetectable viral loads maybe possible with the new drugs even in highly drug experienced patients. Genotype studies are useful in these situations. Drug toxicity of ART therapy is losing importance as benefits exceed adverse effects. Criteria for antiretroviral treatment in acute infection, pregnancy and post-exposure prophylaxis are mentioned as well as the management of HIV co-infection with hepatitis B or C.

CONCLUSIONS

CD4 cells counts, viral load and patient co-morbidities are the most important reference factors to consider when initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized therapy approach in order to achieve undetectable viral load under any circumstances.

Nucleoside and nucleotide HIV reverse transcriptase inhibitors: 25 years after zidovudine

Twenty-five years ago, nucleoside analog 3'-azidothymidine (AZT) was shown to efficiently block the replication of HIV in cell culture. Subsequent studies demonstrated that AZT acts via the selective inhibition of HIV reverse transcriptase (RT) by its triphosphate metabolite. These discoveries have established the first class of antiretroviral agents: nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs). Over the years that followed, NRTIs evolved into the main component of antiretroviral drug combinations that are now used for the treatment of all populations of HIV infected patients. A total of thirteen NRTI drug products are now available for clinical application: eight individual NRTIs, four fixed-dose combinations of two or three NRTIs, and one complete fixed-dose regimen containing two NRTIs and one non-nucleoside RT inhibitor. Multiple NRTIs or their prodrugs are in various stages of clinical development and new potent NRTIs are still being identified through drug discovery efforts. This article will review basic principles of the in vitro and in vivo pharmacology of NRTIs, discuss their clinical use including limitations associated with long-term NRTI therapy, and describe newly identified NRTIs with promising pharmacological profiles highlighting those in the development pipeline. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, volume 85, issue 1, 2010.

Pharmacotherapy of pediatric and adolescent HIV infection

Significant advances have been made in the treatment of human immunodeficiency virus (HIV) infection over the past two decades. Improved therapy has prolonged survival and improved clinical outcome for HIV-infected children and adults. Sixteen antiretroviral (ART) medications have been approved for use in pediatric HIV infection. The Department of Health and Human Services (DHHS) has issued "Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection", which provide detailed information on currently recommended antiretroviral therapies (ART). However, consultation with an HIV specialist is recommended as the current therapy of pediatric HIV therapy is complex and rapidly evolving.

Effect of Nucleoside and Nucleotide Reverse Transcriptase Inhibitors of HIV on Endogenous Nucleotide Pools

Background

Alterations in endogenous nucleotide pools as a result of HIV therapy with nucleoside and nucleotide reverse transcriptase inhibitors (N[t]RTIs) is a proposed mechanism for therapy-related adverse events and drug interactions resulting in treatment failure. In vitro studies were performed in order to understand the effect of N(t)RTIs on endogenous nucleotide pools.

Methods

The T-cell line CEM-CCRF was treated with control antimetabolites or the N(t)RTIs abacavir, didanosine, lamivudine, tenofovir (TFV) and zidovudine (AZT), either alone or in combination. The levels of natural 2′-deoxynucleoside triphosphates (dNTP) and ribonucleoside triphophosphates were determined by liquid chromatography coupled with triple quadrupole mass spectrometry.

Results

Antimetabolites altered nucleotide pools in a manner consistent with their known mechanisms of action. AZT was the only N(t)RTI that significantly altered dNTP pools. Incubation of 10 μM AZT, either alone or in combination with other N(t)RTIs, increased 2′-deoxyadenosine triphosphate, 2′-deoxyguanosine triphosphate and thymidine triphosphate levels by up to 1.44-fold the concentrations observed in untreated cells. At higher than pharmacological concentrations of AZT, evidence for inhibition of 2′-deoxycytidylate deaminase and enzymes involved in the salvage of thymidine was also observed. Phosphorylated metabolites of TFV are known to inhibit purine nucleoside phosphorylase (PNP). However, in contrast to a potent PNP inhibitor, TFV was unable to alter intracellular dNTP pools upon addition of exogenous 2′-deoxyguanosine.

Conclusions

N(t)RTIs have the potential to alter nucleotide pools; however, at the pharmacologically relevant concentrations, tested N(t)RTI or their combinations did not have an effect on nucleotide pools with the notable exception of AZT.

Hypercalciuria is the main renal abnormality finding in Human Immunodeficiency Virus-infected children in Venezuela

Kidney involvement in children with Human Immunodeficiency Virus (HIV) infection is increasing in prevalence in parallel with the longer survival of HIV-infected patients and the side-effects of new antiretroviral drugs. However, there are only a few reports describing renal tubular disorders in HIV+ children. This is a cross-sectional, case series study evaluating kidney disease in 26 Venezuelan HIV-infected children. The study cohort consisted of 15 girls and 11 boys, with a median age of 5.9 years (25-75th percentile: 3.6-7.8), who had been treated with antiretrovirals for 2.8 +/- 0.4 years, Overall, the patients were short for their age and gender (Z-height: -3.1; 25-75th percentile: -4.94 to -1.98), and 15 showed signs of mild to moderate malnutrition. All of the children had a normal estimated glomerular filtration rate (136 +/- 22.6 ml/min/1.73 m2), and glomerular involvement was only observed in one patient with isolated proteinuria. None had nephromegaly. In contrast, tubular disorders were commonly found. Hypercalciuria was detected in 16 of the patients (UCa/Cr = 0.28; 25-75th percentile: 0.17-0.54 mg/mg), with five of these showing crystalluria. Eight children showed hyperchloremia, and three had frank metabolic acidosis. Kidney stones were absent in all, but one boy had bilateral medullary nephrocalcinosis. Conclusion, in Venezuelan children, HIV infection per se, or its specific treatment, was commonly associated with renal tubular dysfunction, especially hypercalciuria and acidosis, potentially leading to nephrocalcinosis and growth impairment. We recommend renal tubular evaluation during the follow-up of children with HIV infection.

Poor Efficacy and Tolerability of Stavudine, Didanosine, and Efavirenz-based Regimen in Treatment-Naive Patients in Senegal

OBJECTIVE

To study the effectiveness and tolerance of an antiretroviral therapy (ART) regimen composed of the antiretroviral agents (ARVs) stavudine (d4T) plus didanosine (ddI) plus efavirenz (EFV) in patients with advanced HIV infection in Senegal.

DESIGN AND METHODS

This was an open-label, single-arm, 18-month trial in treatment-naive patients. The primary virologic end point was the percentage of patients with plasma HIV RNA < 500 copies/mL at months 6 (M6), 12 (M12) and 18 (M18). The primary analysis was done as intent-to-treat.

RESULTS

The staging of HIV disease, performed using the definitions of the US Centers for Disease Control and Prevention (CDC), was CDC stage B or C for all 40 recruited patients. At baseline, the mean CD4+ cell count was 133 +/- 92/mcL (+/- standard deviation [SD]; range 1-346), and 23% of patients had CD4+ cell counts below 50/mcL. The mean baseline plasma HIV RNA level was 5.5 +/- 0.4 log10 copies/mL (+/- SD; range 4.6-5.9). The proportion of patients with plasma HIV-1 RNA below 500 copies/mL fell during the study from 73% (95% CI [56; 85]) at M6 to 56% (95% CI [41; 73]) at M12 and 43% (95% CI [27; 59]) at M18. Plasma HIV-RNA was below 50 copies/mL in 50% of study subjects (95% CI [31; 66]) at M6, 43% (95% CI [27; 59]) at M12, and 33% (95% CI [19; 49]) at M18.The mean increase in the CD4+ cell count was 105 +/- 125/mcL (n = 38) at M3 and 186 +/- 122/mcL (n = 21) at M18. Eight patients died, including 6 because of infectious complications. The last viral load (VL) value before death was < 500 copies/mL in all these patients except 1 nonadherent patient. Fifteen patients (37.5%) had peripheral neuropathy that was severe enough in 5 patients (12.5%) to require ddI and d4T discontinuation.

CONCLUSION

Virologic efficacy combination therapy with d4T, ddI, and EFV was measured by the percentage of patients with plasma HIV RNA values below 500 copies/mL and 50 copies/mL; for both parameters, virologic efficacy decreased during the study period. This is explained by the high mortality rate (20%) and treatment modifications due to adverse events (13%). These data strengthen the recently revised World Health Organization (WHO) guidelines advocating initiation of highly active antiretroviral therapy (HAART) before profound CD4 lymphocyte depletion occurs and avoiding HAART regimens containing d4T and ddI because of treatment-limiting side effects.

Diagnostic and management challenges for childhood tuberculosis in the era of HIV

The diagnosis and management of childhood tuberculosis (TB) pose substantial challenges in the era of the human immunodeficiency virus (HIV) epidemic. The highest TB incidences and HIV infection prevalences are recorded in sub-Saharan Africa, and, as a consequence, children in this region bear the greatest burden of TB/HIV infection. The tuberculin skin test (TST), which is the standard marker of Mycobacterium tuberculosis infection in immunocompetent children, has poor sensitivity when used in HIV-infected children. Novel T cell assays may offer higher sensitivity and specificity than the TST, but these tests still fail to make the crucial distinction between latent M. tuberculosis infection and active disease and are limited by cost considerations. Symptom-based diagnostic approaches are less helpful in HIV-infected children, because of the difficulty of differentiating TB-related symptoms from those caused by other HIV-associated conditions. Knowing the HIV infection status of all children with suspected TB is helpful because it improves clinical management. HIV-infected children are at increased risk of developing active disease after TB exposure/infection, which justifies the use of isoniazid preventive therapy once active TB has been excluded. The higher mortality and relapse rates noted among HIV-infected children with active TB who are receiving standard TB treatment highlight the need for further research to define optimal treatment regimens. HIV-infected children should also receive appropriate supportive care, including cotrimoxazole prophylaxis, and antiretroviral therapy, if indicated. Despite the difficulties experienced in resource-limited countries, the management of children with TB/HIV infection could be vastly improved by better implementation of readily available interventions.

Didanosine enteric-coated capsule: current role in patients with HIV-1 infection

Didanosine, which is a synthetic nucleoside analogue intracellularly phosphorylated to the active metabolite, inhibits the activity of HIV-1 reverse transcriptase by competing with the natural substrate. Currently, didanosine is mainly provided as an enteric-coated capsule. In vitro, the molecule is active against laboratory strains and clinical isolates of HIV-1 in resting and activated T cells and monocyte/macrophages. Didanosine may select for resistance mutations that may render the drug inactive against the virus; L74V and K65R remain as the main didanosine-related mutations. In vitro, phenotypic susceptibility to didanosine was decreased beyond a defined fold change clinical cut-off (1.7), and it is considered that genotypic resistance exists when five thymidine-associated mutations or four plus M184V are present. In vivo, clinical studies have shown that didanosine retains significant antiviral activity in patients who have up to five nucleoside analogue mutations at baseline. Didanosine is useful in patients with no previous therapy, as well as in experienced patients in whom one or more antiretroviral regimens has failed.Enteric-coated didanosine is taken once daily, its co-administration with food has been recently evaluated and a reduction of the efficacy of the antiretroviral treatment was not observed. Administered with lamivudine (or emtricitabine), it can be considered a good alternative for use in the nucleoside analogue backbone included in combination therapies for antiretroviral-naive patients. Didanosine could be used in initial treatments for patients intolerant of zidovudine, abacavir or tenofovir. It can be included in once-daily combination regimens, which are more convenient and patient friendly.Prospective, observational and open-label studies, as well as clinical trials (with durations between 24 and 96 weeks), have demonstrated the safety and efficacy of didanosine plus lamivudine (or emtricitabine) plus efavirenz (or nevirapine) in previously untreated HIV-1-infected patients. The administration of didanosine to treatment-experienced patients has been evaluated in two different contexts: patients in whom previous therapies have failed (rescue therapy) and those with controlled viraemia who are switched to a didanosine-containing regimen for simplification.Adverse events associated with the administration of didanosine have been well known since the initial clinical trials with the drug. Gastrointestinal intolerance, peripheral neuropathy and hyperamylasaemia/pancreatitis were the most frequently reported. In the highly active antiretroviral therapy (HAART) era, the rate of adverse events has decreased. The tolerability of didanosine has been clearly improved with the development of the enteric-coated capsule. Severe manifestations of mitochondrial toxicity, including lactic acidosis and abnormal fat distribution, are rare complications, and occur most frequently when didanosine is used in combination with stavudine.

Unmeasured confounding caused slightly better response to HAART within than outside a randomized controlled trial

OBJECTIVE

To compare the outcome of highly active antiretroviral therapy (HAART) in HIV-infected patients initiating equivalent regimens within and outside a randomized controlled trial (RCT).

STUDY DESIGN AND SETTING

The Danish Protease Inhibitor Study (DAPIS) was a national multicenter RCT comparing initial treatment with indinavir, ritonavir, or saquinavir/ritonavir during 96 weeks. From the Danish HIV Cohort Study we identified all patients initiating one of these protease-inhibitor-based HAART regimens: 425 patients within DAPIS and 677 outside the trial. We compared viral load, CD4 count response, and mortality.

RESULTS

At weeks 96 and 240, trial participants were more likely than nonparticipants to have undetectable viral load (adjusted odds ratio [adOR] 1.28 [95% CI=0.94-1.74] and 1.70 [95% CI=1.16-2.50]) and a CD4 increase > or =100 cells/microl (adOR 1.37 [95% CI=1.03-1.82] and 1.53 [95% CI=1.04-2.25]). For antiretroviral-experienced, but not for antiretroviral-naïve patients, trial participants had a lower risk of death (mortality rate ratio [MRR]=0.46 [95% CI=0.27-0.77]) than nonparticipants. This effect was moderated in adjusted analyses (MRR=0.60 [0.33-1.07]).

CONCLUSIONS

Compared to nontrial patients, trial participants had better response to HAART. The differences were small defying the notion that results obtained in RCTs are unachievable in routine clinical practice.

[Recommendations from the GESIDA/Spanish AIDS Plan regarding antiretroviral treatment in adults with human immunodeficiency virus infection (update January 2007)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy (ART) recommendations for adult patients infected with the human immunodeficiency virus (HIV-1).

METHODS

To formulate these recommendations, a panel composed of members of the Grupo de Estudio de Sida (GESIDA; AIDS Study Group) and the Plan Nacional sobre el Sida (PNS; Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of HIV, the safety and efficacy findings from clinical trials, and the results from cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings over the last years. Three levels of evidence were defined according to the source of the data: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r). Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4+ lymphocyte counts and plasma viral load, as follows: 1) therapy should be started in patients with CD4+ counts of < 200 cells/microl; 2) therapy should be started in most patients with CD4+ counts of 200-350 cells/microl, although it can be delayed when CD41 count persists at around 350 cells/microL and viral load is low, and 3) initiation of therapy can be delayed in patients with CD4+ counts of > 350 cells/microL. The initial objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining the antiviral response. Therapeutic options are limited with the development of cross resistance and ART failure. Genotype studies are useful in these cases. More information regarding the studies analyzed and the panel recommendations for adherence, toxicity, treatment during pregnancy, patients with hepatitis B or C virus co-infection, and post-exposure prophylaxis can be accessed at www.gesida.seimc.org.

CONCLUSIONS

CD4+ lymphocyte count is the most important reference factor for initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized approach to therapy.

Prevalence and predictors of antiretroviral drug resistance in newly diagnosed HIV-1 infection

OBJECTIVES

To determine prevalence and predictors of antiretroviral drug resistance in newly diagnosed individuals with HIV-1 infection, using a systematic approach to avoid selection bias.

METHODS

Plasma samples from all persons diagnosed HIV-1 seropositive at a large London centre between April 2004 and February 2006 underwent sequencing of HIV-1 reverse transcriptase (RT) and protease genes. Subtype was assigned by phylogenetic analysis. Resistance was scored according to the IAS-USA list (2005) modified to include T215revertants and exclude isolated E44D or V118I and minor protease mutations. Recent seroconversion was identified by HIV antibody avidity testing.

RESULTS

The cohort of 239 included 169 (70.7%) males, 126 (52.7%) homosexuals, 118 (49.5%) persons of white ethnicity and 144 (60.0%) persons born outside the UK. Subtypes included B 134 (56.1%), C 46 (19.2%), A 17 (7.1%), other non-B 42 (17.6%). The prevalence of resistance mutations was 17/239 (7.1%; 95% confidence interval 4.5-11.1%), comprising 10/239 (4.2%) nucleoside/nucleotide RT inhibitor (NRTI); 4/239 (1.7%) non-nucleoside RT inhibitor (NNRTI) and 4/239 (1.7%) protease inhibitor (PI) associated mutations. Dual-class (NRTI + PI) resistance mutations were detected in 1/239 (0.4%) person. The prevalence of resistance mutations was 7/85 (8.2%) and 10/154 (6.5%) in persons with recent and established infection, respectively. In multivariate analysis, having been born in the UK and high CD4 count, but not gender, age, risk group, ethnicity or subtype, were independent predictors of resistance.

CONCLUSIONS

In an unselected UK cohort, subtypes other than B accounted for 43.9% of new HIV-1 diagnoses. The prevalence of resistance mutations was 7.1% and highest in those born in the UK.

Rate of virologic failure and selection of drug resistance mutations using different triple nucleos(t)ide analogue combinations in HIV-infected patients

Virologic failure seems to occur more frequently in HIV-infected patients treated with triple nucleoside analogue (NA) combinations than with regimens including nonnucleoside reverse transcriptase inhibitors or protease inhibitors. However, the rate of failure and resistance profiles may differ with distinct triple NA combinations. A retrospective review of all HIV-infected individuals who received triple NA combinations at our institution was conducted. Virologic failure was defined as lack of achievement of plasma HIV-RNA<50 copies/ml at week 16 following initiation of antiretroviral therapy or as viral rebound in subjects with prior undetectable viremia. Genotypic analyses were performed at the time of first virological failure. Of the 261 patients identified, 13 were drug naive, 126 had underwent simplification, and 122 were antiretroviral-experienced patients with detectable viral load. Virologic failure was recorded in 95 (36.4%) after an average follow-up of 19 months. Rates were 0.67 in drug-naive, 0.55 in simplification, and 2.38 in rescue interventions for 100 persons-month follow-up. Factors associated with virologic failure in the multivariate Cox regression analysis were rescue vs naive or simplification strategies (OR 2.6; 95% CI 1.6-4.2) and using tenofovir as part of the combination (OR 2.04; 95% CI 1.3-3.2). In contrast, the use of AZT prevented virologic failure (OR 0.52; 95% CI 0.3-0.8). M184V was the most frequent resistance mutation (75.4%), followed by T215Y (52.5%) and K65R (14.8%). Of note, K65R did not develop in patients taking AZT nor in those with prior thymidine-associated mutations (TAMs). Conversely, subjects who developed K65R did not accumulate TAMs. Virologic failure is relatively frequent in patients treated only with triple NA regimens, particularly in the setting of rescue therapy. The use of TDF might be associated with a higher risk of virologic failure and, conversely, AZT might be protective. The presence of TAMs precluded the selection of K65R in patients treated with TDF. Resistance pathways for TDF and thymidine analogues seem to be divergent and could be the basis to explore a synergism between these drugs.

Evolving simplified treatment strategies for HIV infection: the role of a single-class quadruple-nucleoside/nucleotide regimen of trizivir and tenofovir

Simplified antiretroviral regimens have been developed with the aim of improving treatment adherence and quality of life of HIV-infected patients. The single-class triple-nucleoside reverse transcriptase inhibitor combination has contributed to the improvement of the management of HIV infection, especially in patients with adherence problems and special groups of the patient population. Such a regimen remains an alternative option because of lower virological efficacy compared with the preferred multiclass antiretroviral regimens. However, recently, a nucleoside reverse transcriptase inhibitor abacavir/lamivudine/zidovudine plus tenofovir has been investigated in both antiretroviral-naive patients and in heavily pre-treated patients, as well in the setting of simplification/switching strategies. This experimental combination could be a safe and attractive option that offers the advantages of limited toxicity, few drug interactions and the use of future treatment options with new drugs, especially for patients in later stages of infection.

Switch from a first virologically effective protease inhibitor-containing regimen to a regimen containing efavirenz, nevirapine or abacavir

BACKGROUND

Treatment simplification in antiretroviral-experienced patients receiving protease inhibitor (PI)-containing antiretroviral regimens seems safe, but randomized trials have limited power to detect differences in virological rebound (VR) between different switch strategies.

METHODS

From the French Hospital Database on HIV, we selected 2462 patients with undetectable viral load (VL) who switched from a first PI-containing antiretroviral combination (cART) to a combination containing efavirenz (EFV), nevirapine (NVP) or abacavir (ABC). Factors associated with VR and with immunological efficacy (gain of > or = 50 CD4(+) cells/microl) were identified by using Cox models.

RESULTS

The 12-month Kaplan-Meier probabilities of VR were 6.8, 13.7 and 12.3% in patients switching to EFV-cART, NVP-cART and ABC-cART, respectively. Factors associated with VR were female sex, younger age, antiretroviral exposure before the first cART, time on first cART, higher VL at first cART initiation, a stavudine/didanosine backbone (rather than zidovudine/lamivudine) after the switch, and a switch to NVP or ABC [respective adjusted hazard ratio versus EFV: 1.53; 95% confidence interval (CI), 1.21-1.94; and 1.53; 95% CI, 1.12-2.08]. When the analyses were restricted to patients who were antiretroviral-naive before their first cART, NVP (but not ABC) was associated with VR. Immunological outcomes did not differ among the three switch regimens.

CONCLUSION

When VL is undetectable on a first PI-cART regimen, switching to an EFV-containing regimen is more likely to avoid VR than switching to an ABC or NVP-containing regimen. ABC may be an alternative to EFV for patients who were not exposed to antiretroviral before their first cART regimen, after checking for ABC resistance mutations.

An updated systematic overview of triple combination therapy in antiretroviral-naive HIV-infected adults

OBJECTIVE

To compare the effectiveness of three drug combination antiretroviral therapy (ART) in treatment-naive HIV-infected persons, and identify the predictors of responses.

DESIGN AND METHODS

Overview of trials identified by searching public domain publications and conference presentations. The three-drug combination therapy was defined as two nucleoside reverse transcriptase inhibitors (NRTI) or nucleotide and NRTI, and either: (1) a protease inhibitor (PI); (2) a non-nucleoside RTI (NNRTI); (3) a third NRTI; or (4) a ritonavir-boosted PI (BPI). Week 24 and 48 results for the proportions of patients with plasma HIV RNA levels < 400 and < 50 copies/ml, and change in CD4(+) cell counts were recorded.

RESULTS

Fifty-three trials met the entry criteria, and enrolled 14 264 patients into 90 treatment arms. Overall 55% of patients had plasma HIV RNA levels < 50 copies/ml at week 48 and this percentage increased with later publication dates. In unadjusted pairwise comparisons at week 48, significantly greater percentages of patients receiving NNRTI (64%) and BPI (64%) had RNA < 50 copies/ml than NRTI (54%) or PI (43%), and CD4(+) cell count increases were significantly greater in the BPI group (+200 cells/microl) than the PI (+179), NNRTI (+173), or NRTI (+161) groups. Pill count and percentage of patients with week 48 plasma HIV RNA levels < 50 copies/ml were correlated in the univariate analysis (P = 0.0053; r = -0.323), but pill count was not a significant predictor in the multivariate analyses. Drug class and baseline CD4(+) cell counts were significant predictors, but explained only a modest amount of the treatment effect, (R(2) = 0.355).

CONCLUSIONS

NNRTI and BPI-containing regimens offer superior virologic suppression over 48 weeks, supporting existing guidelines for the choice of initial ART. Pill count was not a consistent predictor of virologic suppression.

Current status of antiretroviral therapy

At present, there are 22 FDA-approved antiretroviral agents, which are categorised into four classes of drugs. Several others are in various stages of basic and clinical development. The authors of this paper review the general characteristics of each class of antiretrovirals, as well as individual investigational agents that are in advanced clinical development. A brief synopsis of US and WHO antiretroviral treatment guidelines is also provided.

HIV recombination: what is the impact on antiretroviral therapy?

Retroviral recombination is a potential mechanism for the development of multiply drug resistant viral strains but the impact on the clinical outcomes of antiretroviral therapy in HIV-infected patients is unclear. Recombination can favour resistance by combining single-point mutations into a multiply resistant genome but can also hinder resistance by breaking up associations between mutations. Previous analyses, based on population genetic models, have suggested that whether recombination is favoured or hindered depends on the fitness interactions between loci, or epistasis. In this paper, a mathematical model is developed that includes viral dynamics during therapy and shows that population dynamics interact non-trivially with population genetics. The outcome of therapy depends critically on the changes to the frequency of cell co-infection and I review the evidence available. Where recombination does have an effect on therapy, it is always to slow or even halt the emergence of multiply resistant strains. I also find that for patients newly infected with multiply resistant strains, recombination can act to prevent reversion to wild-type virus. The analysis suggests that treatment targeted at multiple parts of the viral life-cycle may be less prone to drug resistance due to the genetic barrier caused by recombination but that, once selected, mutants resistant to such regimens may be better able to persist in the population.

Early virologic failure and rescue therapy of tenofovir, abacavir, and lamivudine for initial treatment of HIV-1 infection: TONUS study

BACKGROUND

To assess the efficacy and safety of the triple NRTI combination of abacavir (ABC), lamivudine (3TC), and tenofovir (TDF) in a once-daily regimen.

METHOD

38 HIV-naive patients (pts) were treated in a prospective open-arm study over 48 weeks (W48). Virological failure was defined as never achieving plasma HIV-1 RNA < 400 copies/mL or rebound of > or = 0.7 log10.

RESULTS

12/36 (33%) pts had virologic failure at W24 and 10 additional pts had HIV RNA > 50 copies/mL at W12 or W24. There was a significant association between baseline viral load (VL) and virologic failure in 0%, 29%, and 64% pts with baseline VL levels < 4, 4-5, and > 5 log10 copies/mL, respectively (p = .014). 76% of pts developed K65R and M184V/I mutations by W24, and 19% developed M184V/I alone. At W4, 86% of pts had adequate plasma Cmin for the 3 drugs. 14 pts with K65R and M184V/I were given a rescue therapy with a successful outcome (< 50 copies/mL; median follow-up 48 weeks).

CONCLUSION

Convergent genetic pathway to resistance, in conjunction with lower antiretroviral potency, may explain the high rate of selection K65R and M184V mutations. These mutations did not appear to have a negative effect on rescue therapy with a variety of regimens.

Relationship between antiretrovirals used as part of a cART regimen and CD4 cell count increases in patients with suppressed viremia

BACKGROUND

It is unknown if the CD4 cell count response differs according to antiretroviral drugs used in combination antiretroviral therapy (cART) in patients with maximal virological suppression [viral load (VL) < 50 copies/ml].

OBJECTIVES

To compare the change in CD4 cell count over consecutive measurements with VL < 50 copies/ml at both time-points according to nucleoside backbones and other antiretrovirals used.

METHODS

Generalized linear models, accounting for multiple measurements within patients, were used to compare CD4 cell count changes after adjustment for antiretrovirals, time from starting cART, age, CD4 at first VL < 50 copies/ml, prior antiretroviral treatment, and change in CD4 cell count since starting cART.

RESULTS

We studied 28418 instances of VL < 50 copies/ml in 4041 patients. The mean annual change in CD4 cell count was +45.5/microl [95% confidence interval (CI) +39.4 to +51.6/microl). Comparing two drug nucleoside backbones, there was a lower annual change in CD4 cell count for zidovudine/lamivudine (n = 13038; -15.4/microl; P = 0.012) and for those on tenofovir (n = 1809; -27.3/microl; P = 0.029) compared to lamivudine/stavudine (n = 7339). Compared to the boosted-protease inhibitor regimen (n = 5915), use of an abacavir-based triple-nucleoside regimen was associated with a lower annual change in CD4 cell count (n = 2504 pairs; -26.1/microl; P = 0.011).

CONCLUSIONS

A nucleoside backbone of zidovudine/lamivudine or any tenofovir-based backbone was associated with significantly poorer increases in CD4 cell count compared to a nucleoside backbone of stavudine/lamivudine, as was an abacavir-based triple nucleoside regimen compared to a boosted protease inhibitor regimen. Long-term studies are needed to determine whether the differences in immunological response seen here translate into differences in the risk of clinical disease.

Antiretroviral-therapy-associated lipoatrophy: current status and future directions

Lipoatrophy is perhaps the most visibly recognisable component of antiretroviral-therapy-associated lipodystrophy due to the rarity of this form of body composition change in the general population. In this respect, it is apparent that lipoatrophy represents a form of drug toxicity specifically involving the subcutaneous fat tissue, resulting in pathological fat loss that preferentially affects the limbs and face. It is now clear that the choice and duration of nucleoside analogue reverse transcriptase inhibitor (NRTI) therapy (stavudine > zidovudine) is the dominant risk factor for clinical lipoatrophy, as well as for the pathological changes to adipose tissue that underlie the clinical syndrome. Host factors have also emerged as important modulators of lipoatrophy severity in patients receiving these NRTI drugs, including age, racial origin, and severity of immune deficiency. On the other hand, the use of selected HIV protease inhibitor drugs is more closely associated with metabolic complications such as dyslipidemia and insulin resistance and has not been convincingly linked to lipoatrophy. This review examines the clinical and pathological manifestations of lipoatrophy, and also presents information regarding the safety profile of alternative NRTI drugs, such as tenofovir and abacavir, that have not been associated with lipoatrophy risk. With increasing knowledge of lipoatrophy pathogenesis, it is likely that moderate and severe forms of this complication can now be considered a preventable complication of HIV treatment. However, it is also important to recognise that there is an ongoing burden of disease in patients who have been affected by lipoatrophy over the past six years, and that therapeutic management of established lipoatrophy will remain a challenge into the future.

Adverse effects of antiretroviral therapy for HIV infection: a review of selected topics

In the current era of HIV treatment, the toxicity profiles of antiretroviral drugs have increasingly emerged as a basis for selecting initial antiretroviral regimens as well as a reason for switching therapy in treatment-experienced patients. In this respect, an intensive research effort involving clinical research as well as basic science research over the past six years, has focused on the cluster of metabolic and body composition abnormalities that have come to be termed the 'lipodystrophy syndrome'. These data have now provided a clear and clinically relevant understanding of the individual profiles of drugs within the nucleoside analogue reverse transcriptase inhibitor , HIV protease inhibitor and non-nucleoside analogue reverse transcriptase inhibitor drug classes, and have provided a rational basis for assessing and monitoring these adverse effects in clinical practice. In this review, current and emerging drug toxicities are considered with an emphasis on lipodystrophy complications.

Patterns of resistance emerging in HIV-1 from antiretroviral-experienced patients undergoing intensification therapy with tenofovir disoproxil fumarate

Study GS-99-907 was a 48-week, phase 3, double-blind, placebo-controlled intensification trial of tenofovir disoproxil fumarate (tenofovir DF). Antiretroviral-experienced patients added tenofovir DF 300 mg once daily to their existing regimen. The patterns of HIV-1 resistance development and the corresponding virologic responses were evaluated in a virology substudy at week 48. Although 94% of these treatment-experienced patients had nucleoside-associated resistance mutations (NAMs) at baseline, addition of tenofovir DF resulted in a mean reduction in viral load of -0.59 log10 copies/mL after 24 weeks that was durable through 48 weeks. Relative to the placebo-controlled arm, patients in the tenofovir DF arm had a reduced frequency of development of resistance mutations to all classes of HIV-1 inhibitors, with reduction in new protease inhibitor (PI)-associated mutations achieving statistical significance. The K65R mutation, which occurred in 8 patients (3%), was the only emergent mutation directly associated with tenofovir DF therapy. New thymidine analogue-associated mutations (TAMs) emerged in 19% of patients by week 48. Other than K65R, the patterns of mutations that developed were not significantly different between the tenofovir DF and placebo control arms, suggesting that the background therapies caused their development. The K65R mutation emerged only in patients with no detectable TAMs at baseline, whereas new TAMs developed similarly between patients with or without TAMs at baseline. Development of K65R was associated with mostly low-level changes in phenotypic susceptibility to tenofovir DF and other nucleoside reverse transcriptase inhibitors and was not associated with viral load rebound. No novel patterns of genotypic or phenotypic resistance to tenofovir were identified. Therefore, intensification with once-daily tenofovir DF therapy resulted in a sustained reduction in HIV-1 viral load and a low risk for development of the K65R mutation in this treatment-experienced patient population.

Are Specific Antiretrovirals associated with an Increased Risk of Discontinuation due to Toxicities or Patient/Physician Choice in patients with Hepatitis C Virus Coinfection?

Background

Liver damage associated with hepatitis C (HCV) may influence the likelihood of experiencing discontinuation due to toxicities or patient/physician choice (TOXPC) in patients taking combination antiretroviral therapy (cART). Little information to address this concern is available from clinical trials as patients with HCV are often excluded.

Aims

To compare incidence rates of discontinuation due to TOXPC associated with specific antiretrovial drugs in patients with or without HCV.

Patients/methods

A total of 4929 patients from EuroSIDA under follow-up from January 1999 on a specific nucleoside pair (zidovudine/lamivudine, didanosine/stavudine, stavudine/lamivudine, or other) with a third drug (abacavir, nelfinavir, indinavir, nevirapine, efavirenz, lopinavir/ ritonavir or other boosted-protease inhibitor (PI)-containing regimen) and with known HCV serostatus were studied for the incidence of discontinuation of any nucleoside pair or third drug due to TOXPC. Incidence rate ratios were derived from Poisson regression models.

Results

In total 1358 patients had HCV (27.5%). During 12 799 person-years of follow-up there were 2141 discontinuations due to TOXPC for nucleoside pairs and 2501 for third drugs. The incidence of discontinuation due to TOXPC was consistently higher in patients with HCV after stratification by nucleoside pair or third drug. After adjustment for CD4+ count, gender, exposure group, time on HAART, region and treatment regimen, there were few differences in the rate of discontinuation due to TOXPC in those with HCV compared with those without for any nucleoside pairs or third drugs. Similar results were seen when concentrating on discontinuation due to toxicities alone.

Conclusions

Although patients with HCV generally had higher rates of discontinuation due to TOXPC compared with patients without HCV, there was little evidence to suggest that this was associated with any specific nucleoside pair or third drug used as part of cART. Our results do not suggest that any specific component of cART is more poorly tolerated in patients with HCV or that the presence of HCV should influence the choice between antiretrovirals used as part of a cART regimen.

Once-daily antiretroviral therapy: Spanish Consensus Statement

BACKGROUND

Administration of antiretroviral therapy (ART) once daily is creating extraordinary interest among the members of the scientific community and also among those who receive the therapy. However, in clinical practice, some doubts remain about its use.

OBJECTIVES

This document examines the characteristics and possibilities of treatment administered once daily.

METHODS

Consensus of 248 Spanish experts in the field.

RESULTS

Once-daily dosing is considered an added value which could favour adherence and, therefore, efficacy, as well as the quality of life of certain patients, however, the objective of adequate adherence in the long term is often difficult to achieve regardless of the treatment used. In theory, any patient can receive once-daily therapy, although some patients could particularly benefit from it, e.g. those with unfavourable social or personal circumstances, including drug users, patients whose treatment must be supervised, patients receiving multiple medications, or those who need rescue therapy after multiple treatment failures. At present, it is possible to design once-daily ART using some of the combinations of drugs considered as first-choice in national and international recommendations for antiretroviral therapy, but the options are still limited. The marketing of new drugs with this characteristic could allow us to increase the number and types of patient who can benefit from once-daily regimens, including those patients who need rescue therapy.

CONCLUSIONS

Once-daily ART is a good alternative to regimens administered several times each day when a potent combination of active drugs is available.

Early virologic failure in HIV-1 infected subjects on didanosine/tenofovir/efavirenz: 12-week results from a randomized trial

OBJECTIVE

To compare the safety and efficacy of two once-daily antiretroviral regimens containing lamivudine (3TC) or tenofovir disoproxil fumarate (TDF), each administered with didanosine (ddI) and efavirenz (EFV) as initial therapy to HIV-1-infected subjects.

METHODS

Single centre, randomized (1: 1), open-label study in antiretroviral-naive, HIV-infected adults. Subjects commenced either 3TC/ddI/EFV (3TC group) or TDF/ddI/EFV (TDF group). Safety, Medication Event Monitoring System (MEMScap) and plasma EFV concentration monitoring was performed over the study period. Comparisons between groups were assessed using chi test and linear regression analysis was used to assess the relationship between EFV concentrations and virological response.

RESULTS

Seventy-seven subjects were enrolled prior to recruitment being suspended, 36 to the 3TC group and 41 to the TDF group. Intention-to-treat analysis in which last observation carried forward (LOCF) found the mean viral log10 load [95% confidence interval (CI)] at weeks 4 and 12 to be 2.67 (2.47-2.87) and 1.83 (1.74-1.92) for the 3TC group and 2.75 (2.45-3.05) and 2.28 (1.96-2.6) for the TDF group (P = 0.013). Emergence of resistance occurred in five of 41 (12.2%) subjects in the TDF group up to week 12 compared with none of 36 in the 3TC group, (P < 0.05); these five subjects shared similar baseline characteristics (CD4+ cell counts < 200 x 10 cells/l and HIV-1 RNA > 100,000 copies/ml). Despite MEMScap monitoring showing > 99% adherence in all subjects, among the five failures, three had low EFV concentrations.

CONCLUSION

TDF/ddI/EFV as initial therapy appears to have diminished efficacy in subjects with CD4 < 200 x 10 cells/l and viral load > 100,000 copies/ml. Treatment failure with resistance was not attributable to baseline resistance, efavirenz exposure or poor adherence.

Emerging anti-HIV drugs

There are now exactly 20 anti-HIV drugs licenced (approved) for clinical use, and > 30 anti-HIV compounds under (pre)clinical development. The licensed anti-HIV drugs fall into five categories: nucleoside reverse transcriptase inhibitors (NRTIs: zidovudine, didanosine, zalcitabine, stavudine, lamivudine, abacavir and emtricitabine); nucleotide reverse transcriptase inhibitors (NtRTIs: tenofovir disoproxil fumarate); non-nucleoside reverse transcriptase inhibitors (NNRTIs: nevirapine, delavirdine and efavirenz); protease inhibitors (PIs: saquinavir, indinavir, ritonavir, nelfinavir, amprenavir, lopinavir, atazanavir and fosamprenavir); and fusion inhibitors (FIs: enfuvirtide). The compounds that are currently under clinical (Phase I, II or III) or preclinical investigation are either targeted at the same specific viral proteins as the licensed compounds (i.e., reverse transcriptase [NRTIs: PSI-5004, (-)-dOTC, DPC-817, elvucitabine, alovudine, MIV-210, amdoxovir, DOT; NNRTIs: thiocarboxanilide, UC-781, capravirine, dapivirine, etravirine, rilpivirine], protease [PIs: tipranavir, TMC-114]) or other specific viral proteins (i.e., gp120: cyanovirin N; attachment inhibitors: AIs, such as BMS-488043; integrase: L-870,812, PDPV-165; capsid proteins: PA-457, alpha-HCG); or cellular proteins (CD4 downmodulators: CADAs; CXCR4 antagonists: AMD-070, CS-3955; CCR5 antagonists: TAK-220, SCH-D, AK-602, UK-427857). Combination therapy is likely to remain the gold standard for the treatment of AIDS so as to maximise potency, minimise toxicity and diminish the risk for resistance development. Ideally, pill burden should be reduced to once-daily dosing so as to optimise the patient's compliance and reduce the treatment costs.

Lack of a Metabolic and Antiviral Drug Interaction between Tenofovir, Abacavir and Lamivudine

Objective

An anti-HIV regimen composed of the nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) tenofovir (TFV) disoproxil fumarate (TDF), abacavir (ABC) and lamivudine (3TC) has performed poorly in patients. This study evaluated the combination of TFV, ABC and 3TC for metabolic or antiviral antagonism in vitro. Design: Procedures were developed to evaluate the in vitro metabolism and antiviral activity of drug combinations of TFV, ABC and 3TC in cell types relevant for HIV infection.

Methods

Anabolism of combinations of TFV and ABC were studied over a 24 h period in the human T leukaemic CEM lymphoblast cell line and human primary peripheral blood mononuclear cells (PBMCs) stimulated with human interleukin-2 and phytohaemagglutinin. The anti-HIV activity of combinations of TFV and ABC in the presence or absence of 3TC was studied in stimulated PBMCs infected with the HXB2 strain of HIV-1.

Results

Levels of the active metabolites produced from TFV and ABC after incubation with CEM or PBMCs showed no significant change upon introduction of the other NRTI. Moreover, the pool sizes for the natural substrates of 2′-deoxyadenosine triphosphate and 2′-deoxyguanosine triphosphate were also unchanged. In anti-HIV assays in PBMCs, the combination of TFV and ABC was found to be additive with respect to inhibition of HIV replication. Addition of 3TC to the combination did not result in synergistic or antagonistic effects.

Conclusions

The poor efficacy of the triple NRTI regimen of TDF, ABC and 3TC is probably not due to a metabolic drug interaction resulting in antagonism of antiviral activity.

Adverse effects of antiretroviral therapy for HIV infection: a review of selected topics

In the current era of HIV treatment, the toxicity profiles of antiretroviral drugs have increasingly emerged as a basis for selecting initial antiretroviral regimens as well as a reason for switching therapy in treatment-experienced patients. In this respect, an intensive research effort involving clinical research as well as basic science research over the past six years, has focused on the cluster of metabolic and body composition abnormalities that have come to be termed the 'lipodystrophy syndrome'. These data have now provided a clear and clinically relevant understanding of the individual profiles of drugs within the nucleoside analogue reverse transcriptase inhibitor , HIV protease inhibitor and non-nucleoside analogue reverse transcriptase inhibitor drug classes, and have provided a rational basis for assessing and monitoring these adverse effects in clinical practice. In this review, current and emerging drug toxicities are considered with an emphasis on lipodystrophy complications.

Early virologic failure in a pilot study evaluating the efficacy of therapy containing once-daily abacavir, lamivudine, and tenofovir DF in treatment-naive HIV-infected patients

Previous investigational data using abacavir (ABC), lamuvidine (3TC), and zidovudine has suggested the possibility of triple nucleoside analogue reverse transcriptase inhibitors (NRTI) therapy as an option in the treatment of HIV infection. We performed a pilot study to assess the potency of once daily ABC+ 3TC+ tenofovir (TDF) in the treatment of HIV-infected naive patients. CD4 and HIV-viral load (VL) were followed monthly. Patients were considered to be nonresponder/failing if there was no reduction in VL by >/= 2 log(10) by week 8 and/or a rebound in VL after initial suppression. Resistance testing was then obtained. Nineteen patients naive to antiretroviral therapy (3 women and 16 men) were enrolled, of whom, 2 did not return (withdrew from study at week 2). Median VL and CD4 count at baseline were 147,167 copies per milliliter (5.16 log(10); [range, 7650->750,000]) and 277 cells/mm(3) (range, 59-598). Eight patients had VL > 100000 at baseline. Of 17 patients eligible for follow-up, 5 (27%) were responders (virologic success). Twelve patients (63%) were considered nonresponders and/or with virologic failure. The study was prematurely interrupted because of a high rate of treatment failure. Resistance testing available for 11 nonresponders (58%) showed: 2 patients with wild-type, 5 patients with M184V (reducing susceptibility to 3TC and ABC), 4 patients with M184V+K65R (K65R is responsible for reducing susceptibility to ABC, 3TC and TDF), and none with K65R alone. In conclusion, the combination of ABC, 3TC and TDF cannot be recommended for the initial regimen in HIV treatment-naive patients.

Impact of Human Immunodeficiency Virus Type 1 Subtype on First-Line Antiretroviral Therapy Effectiveness

Objective

The effectiveness of antiretroviral treatment (ART) was compared in 416 naive patients from a French clinical cohort infected with B and non-B HIV-1 subtypes.

Methods

Time to HIV viral load (VL) undetectability was calculated for each subtype group. Three other parameters were estimated 3, 6 and 12 months after enrolment: clinical progression (that is, AIDS-defining events or death), changes in CD4 cell counts from baseline and proportion of patients achieving an undetectable VL (<400 HIV-RNA copies/ml).

Results

In this cohort, 317 patients (76%) were infected with a B subtype and 99 (24%) with a non-B subtype. Median time to VL undetectability was similar in the B subtype group [147 days, 95% confidence interval (CI) 119–165] and non-B subtype group (168 days, 95% CI: 105–234; P=0.16). After adjusting for AIDS-defining events at enrolment, baseline CD4 cell counts and VL, and for the treatment on which patients were initiated, no association was found between HIV subtypes and time to VL undetectability (B subtype vs non-B subtype: hazard ratio=0.80, 95% CI: 0.62–1.02, P=0.07). In the 3, 6 and 12 months after enrolment, subtype had no impact on clinical progression, CD4 cell count or VL responses to ART. This suggests that B and non-B subtypes do not affect first-line therapy efficacy, which is encouraging in view of the worldwide spread of non-B HIV-1 subtypes and the increasing availability of ART in developing countries. However, in this study we did not take into account individual non-B subtype species, therefore further studies should be designed to evaluate the efficacy of these regimens in patients with particular non-B subtypes.

Resistance profiles and adherence at primary virological failure in three different highly active antiretroviral therapy regimens: analysis of failure rates in a randomized study

OBJECTIVES

To investigate the interplay between resistance and adherence in the virological failure of three fundamentally different highly active antiretroviral therapy (HAART) regimens.

METHODS

We retrospectively identified 56 verified primary virological failures (viral load >400 HIV-1 RNA copies/mL) among 293 patients randomized to two nucleoside reverse transcriptase inhibitors (NRTIs)+ritonavir+saquinavir (RS-arm) (n=115), two NRTIs+nevirapine+nelfinavir (NN-arm) (n=118), or abacavir+stavudine+didanosine (ASD-arm) (n=60) followed up for a median of 90 weeks. Data on adherence were collected from patient files, and genotyping was performed on plasma samples collected at time of failure.

RESULTS

Treatment interruption or poor adherence was mainly caused by side effects and accounted for 74% of failures, and was associated with absence of resistance mutations. In the 30 failing patients not switched from randomized treatment, we found resistance in two of 12 patients in the RS-arm (M184 V only), four of six patients in the NN-arm [all four had non-nucleoside reverse transcriptase inhibitor (NNRTI) mutations], and seven of 12 patients in the ASD-arm (NRTI mutations only). Two adherent patients on randomized treatment failed in the RS-arm, none in the NN-arm, and six in the ASD-arm.

CONCLUSIONS

Primary virological failure was caused mainly by treatment interruption. No primary protease inhibitor (PI) mutations were found in patients failing on boosted saquinavir, whereas resistance to NNRTIs and NRTIs was prevalent in several patients failing on regimens based on these medications.

Acute onset of pancreatitis with concomitant use of tenofovir and didanosine

OBJECTIVE

To report a case of pancreatitis associated with the combined use of didanosine and tenofovir.

CASE SUMMARY

A 51-year-old white man with HIV was initiated on antiretroviral therapy with didanosine 250 mg/day, tenofovir 300 mg/day, lamivudine 300 mg/day, stavudine 60 mg/day, and efavirenz 600 mg/day. Didanosine was prescribed at a reduced dosage due to the known interaction with tenofovir. Despite this dosage adjustment, the patient developed acute pancreatitis 10 weeks after antiretrovirals were initiated. Pancreatitis resolved spontaneously after antiretroviral discontinuation.

DISCUSSION

Our report of didanosine-induced pancreatitis secondary to concurrent use with tenofovir is the third reported case that utilized a reduced didanosine dosage. Five previous pancreatitis reports have been described using full-strength didanosine with tenofovir. The exact mechanism of action for this interaction is unknown. Utilizing the Naranjo probability scale to assess causality, a possible adverse drug reaction was determined.

CONCLUSIONS

Tenofovir and didanosine may be used cautiously in antiretroviral combination therapy. Reduced didanosine dosage (250 mg) should be used to reduce serum didanosine concentrations and subsequent toxicities. Practitioners should be aware that a significant drug interaction with resulting pancreatitis may occur even when a reduced dosage is prescribed.

The rise and fall of triple nucleoside reverse transcriptase inhibitor (NRTI) regimens

Triple nucleoside reverse transcriptase inhibitor (NRTI) regimens have attracted much interest due to their potential to (1) simplify dosing, with potential gains in adherence to treatment, and (2) reduce or even reverse dyslipidaemia associated with protease inhibitor (PI) therapy. A variety of triple NRTI combinations have been investigated, in both antiretroviral-naive and antiretroviral-experienced HIV-infected patients. Many of these trials have generated disappointing results, and some have been prematurely discontinued due to poor efficacy. This article reviews the background to the development of triple NRTI regimens, and the mounting evidence that this approach is suboptimal for antiretroviral-naive patients. Indeed, some triple NRTI regimens should never be used in this population. A role for triple NRTI combinations as a simplification strategy in treatment-experienced patients whose HIV is well controlled has been suggested, but emerging evidence indicates that such an approach can, under adequate selection pressure, lead to the emergence of mutations and viral load rebound. This commentary discusses the factors that appear to influence patients' responses to triple NRTI therapy, and their implications for patient selection.