A comparison of stavudine plus lamivudine versus zidovudine plus lamivudine in combination with indinavir in antiretroviral naive individuals with HIV infection: selection of thymidine analog regimen therapy (START I)

HIV nucleoside reverse transcriptase inhibitors

More than 40 years into the pandemic, HIV remains a global burden and as of now, there is no cure in sight. Fortunately, highly active antiretroviral therapy (HAART) has been developed to manage and suppress HIV infection. Combinations of two to three drugs targeting key viral proteins, including compounds inhibiting HIV reverse transcriptase (RT), have become the cornerstone of HIV treatment. This review discusses nucleoside reverse transcriptase inhibitors (NRTIs), including chain terminators, delayed chain terminators, nucleoside reverse transcriptase translocation inhibitors (NRTTIs), and nucleotide competing RT inhibitors (NcRTIs); focusing on their history, mechanism of action, resistance, and current clinical application, including long-acting regimens.

Twenty-Five Years of Lamivudine: Current and Future Use for the Treatment of HIV-1 Infection

Supplemental Digital Content is Available in the Text.

Innovation in medicine is a dynamic, complex, and continuous process that cannot be isolated to a single moment in time. Anniversaries offer opportunities to commemorate crucial discoveries of modern medicine, such as penicillin (1928), polio vaccination (inactivated, 1955; oral, 1961), the surface antigen of the hepatitis B virus (1967), monoclonal antibodies (1975), and the first HIV antiretroviral drugs (zidovudine, 1987). The advent of antiretroviral drugs has had a profound effect on the progress of the epidemiology of HIV infection, transforming a terminal, irreversible disease that caused a global health crisis into a treatable but chronic disease. This result has been driven by the success of antiretroviral drug combinations that include nucleoside reverse transcriptase inhibitors such as lamivudine. Lamivudine, an L-enantiomeric analog of cytosine, potently affects HIV replication by inhibiting viral reverse transcriptase enzymes at concentrations without toxicity against human polymerases. Although lamivudine was approved more than 2 decades ago, it remains a key component of first-line therapy for HIV because of its virological efficacy and ability to be partnered with other antiretroviral agents in traditional and novel combination therapies. The prominence of lamivudine in HIV therapy is highlighted by its incorporation in recent innovative treatment strategies, such as single-tablet regimens that address challenges associated with regimen complexity and treatment adherence and 2-drug regimens being developed to mitigate cumulative drug exposure and toxicities. This review summarizes how the pharmacologic and virologic properties of lamivudine have solidified its role in contemporary HIV therapy and continue to support its use in emerging therapies.

Comparative efficacy and safety of first-line antiretroviral therapy for the treatment of HIV infection: a systematic review and network meta-analysis

BACKGROUND

New antiretroviral therapy (ART) regimens for HIV could improve clinical outcomes for patients. To inform global guidelines, we aimed to assess the comparative effectiveness of recommended ART regimens for HIV in ART-naive patients.

METHODS

For this systematic review and network meta-analysis, we searched for randomised clinical trials published up to July 5, 2015, comparing recommended antiretroviral regimens in treatment-naive adults and adolescents (aged 12 years or older) with HIV. We extracted data on trial and patient characteristics, and the following primary outcomes: viral suppression, mortality, AIDS defining illnesses, discontinuations, discontinuations due to adverse events, and serious adverse events. We synthesised data using network meta-analyses in a Bayesian framework and included older treatments, such as indinavir, to serve as connecting nodes. We defined network nodes in terms of specific antivirals rather than specific ART regimens. We categorised backbone regimens and adjusted for them through group-specific meta-regression. We used the GRADE framework to interpret the strength of inference.

FINDINGS

We identified 5865 citations through database searches and other sources, of which, 126 articles related to 71 unique trials were included in the network analysis, including 34 032 patients randomly assigned to 161 treatment groups. For viral suppression at 48 weeks, compared with efavirenz, the odds ratio (OR) for viral suppression was 1·87 (95% credible interval [CrI] 1·34-2·64) with dolutegravir and 1·40 (1·02-1·96) with raltegravir; with respect to viral suppression, low-dose efavirenz was similar to all other treatments. Both low-dose efavirenz and integrase strand transfer inhibitors tended to be protective of discontinuations due to adverse events relative to normal-dose efavirenz. The most protective effect relative to efavirenz in network meta-analyses was that of dolutegravir (OR 0·26, 95% CrI 0·14-0·47), followed by low-dose efavirenz (0·39, 0·16-0·92). Owing to insufficient data, we could make no conclusions about serious adverse events. Low event rates also limited the quality of evidence with regard to mortality and AIDS defining illnesses.

INTERPRETATION

The efficacy and safety of ART has substantially improved with the introduction of newer drug classes of antiretrovirals that are now available to patients and HIV care providers. Their improved tolerance could be part of a larger solution to improve retention, which is a challenge, particularly in low-income and middle-income country settings.

FUNDING

The World Health Organization.

Changing utilization of Stavudine (d4T) in HIV-positive people in 2006-2013 in the EuroSIDA study

OBJECTIVES

The long-term side effects of stavudine (d4T) led to recommendations in 2009 to phase out use of this drug. We aimed to describe temporal patterns of d4T use across Europe.

METHODS

Patients taking combination antiretroviral therapy (cART) in EuroSIDA with follow-up after 1 January 2006 were included in the study. cART was defined as d4T-containing [d4T plus at least two other antiretrovirals (ARVs) from any class] or non-d4T-containing (at least three ARVs from any class, excluding d4T). Poisson regression was used to describe temporal changes in the prevalence of d4T use and factors associated with initiating d4T.

RESULTS

A total of 5850 patients receiving cART on 1 January 2006 were included in the current analysis, rising to 7768 patients on January 1 2013. During this time, the prevalence of d4T use fell from 11.2% to 0.7%, with an overall decline of 19% per 6 months [95% confidence interval (CI) 19-20%]. d4T use declined fastest in Northern Europe [26% (95% CI 23-29%) per 6 months], and slowest in Eastern Europe [17% (95% CI 16-19%) per 6 months]. In multivariable Poisson regression models, new d4T initiations decreased by 14% per 6 months [adjusted incidence rate ratio (aIRR) 0.86; 95% CI 0.80-0.91]. Factors associated with initiating d4T were residence in Eastern Europe (aIRR 4.31; 95% CI 2.17-9.98) versus other European regions and HIV RNA > 400 copies/mL (aIRR 3.11; 95% CI 1.60-6.02) versus HIV RNA < 400 copies/mL.

CONCLUSIONS

d4T use has declined sharply since 2006 to low levels in most regions; however, a low but persistent level of d4T use remains in Eastern Europe, where new d4T initiations post 2006 are also more common. The reasons for the regional differences may be multifactorial, but it is important to ensure that all clinicians treating HIV-positive patients are aware of the potential harmful effects associated with d4T.

Increased bone resorption during tenofovir plus lopinavir/ritonavir therapy in Chinese individuals with HIV

We sought to evaluate the effects of antiretroviral therapy on skeletal metabolism in Chinese individuals with human immunodeficiency virus. Patients switched to tenofovir/lamivudine + lopinavir/ritonavir after treatment failure had an increase in bone resorption marker levels by nearly 60%, which is greater than the magnitude previously described in non-Chinese populations.

INTRODUCTION

Few studies have evaluated the effects of antiretroviral therapy on skeletal metabolism in Asian populations infected with human immunodeficiency virus (HIV).

METHODS

We performed a secondary analysis of bone turnover markers (BTM) at baseline and 2 years in stored plasma samples collected from 2/2009 to 1/2013 as part of a multi-center trial. Two groups were compared: (1) treatment-naïve patients initiated on zidovudine (AZT)/lamivudine (3TC) plus nevirapine (NVP) and (2) patients who failed first-line therapy and were switched to tenofovir (TDF)/3TC plus lopinavir/ritonavir (LPVr). Tests included the bone resorption marker, C-terminal cross-linking telopeptide of type-1 collagen (CTX), and the bone formation marker procollagen type 1 N-terminal propeptide (P1NP).

RESULTS

In the TDF/3TC + LPVr group, samples were available from 59 patients at baseline and 56 patients at 2 years. Of these, 36 patients had samples available from both time points. In the AZT/3TC + NVP group, plasma samples were analyzed from 82 participants at baseline and of those, 61 had samples at 2 years. Median change over 2 years was greater in the TDF/3TC + LPVr group for both CTX (+0.24 ng/mL, interquartile ranges (IQR) 0.10-0.43 vs. +0.09 ng/mL, IQR -0.03 to 0.18, p = 0.001) and P1NP (+25.5 ng/mL, IQR 2.4-51.3 vs. +7.11 ng/mL, IQR -4.3 to 21.6, p = 0.012). Differences remained after adjusting for potential confounders in the multivariable analysis.

CONCLUSIONS

Switching to TDF/3TC + LPVr after treatment failure resulted in greater increases in BTMs than initiation with AZT/3TC + NVP in Chinese patients with HIV. Following this change, bone resorption marker levels increased by nearly 60 %, which is greater than the 25-35% increase from baseline described previously in non-Chinese populations. Further studies are warranted to elucidate these findings.

Efficacy and Safety of Abacavir Plus Lamivudine Versus Didanosine Plus Stavudine When Combined with a Protease Inhibitor, a Nonnucleoside Reverse Transcriptase Inhibitor, or Both in HIV-1 Positive Antiretroviral-Naive Persons

PURPOSE

The combination of abacavir + lamivudine (ABC+3TC) versus didanosine + stavudine (ddI+d4T), each combined with other classes of antiretrovirals (ARVs) in ARV-naive patients, was compared for the combined endpoint of time to plasma HIV RNA >50 copies/mL (at or after the 8-month visit) or death (primary endpoint) in a nested substudy of an ongoing multicenter randomized trial.

METHOD

The substudy enrolled 182 patients; mean HIV RNA and CD4+ cell counts at baseline were 5.1 log10 copies/mL and 212 cells/mm3, respectively.

RESULTS

After a median follow-up of 28 months, rates of primary endpoint were 57.2 and 67.8 per 100 person-years for the ABC+3TC and ddI+d4T groups (hazard ratio [HR]=0.81, 95% confidence interval [CI] 0.58-1.14, p=.23).

CONCLUSION

There was a trend for treatments containing ABC+3TC to be better than treatments containing ddI+d4T with respect to HIV RNA decreases, CD4+ cell count increases, and tolerability.

Early warning indicators for first-line virologic failure independent of adherence measures in a South African urban clinic

We sought to develop individual-level Early Warning Indicators (EWI) of virologic failure (VF) for clinicians to use during routine care complementing WHO population-level EWI. A case-control study was conducted at a Durban clinic. Patients after ≥ 5 months of first-line antiretroviral therapy (ART) were defined as cases if they had VF [HIV-1 viral load (VL)>1000 copies/mL] and controls (2:1) if they had VL ≤ 1000 copies/mL. Pharmacy refills and pill counts were used as adherence measures. Participants responded to a questionnaire including validated psychosocial and symptom scales. Data were also collected from the medical record. Multivariable logistic regression models of VF included factors associated with VF (p<0.05) in univariable analyses. We enrolled 158 cases and 300 controls. In the final multivariable model, male gender, not having an active religious faith, practicing unsafe sex, having a family member with HIV, not being pleased with the clinic experience, symptoms of depression, fatigue, or rash, low CD4 counts, family recommending HIV care, and using a TV/radio as ART reminders (compared to mobile phones) were associated with VF independent of adherence measures. In this setting, we identified several key individual-level EWI associated with VF including novel psychosocial factors independent of adherence measures.

Comparison of tenofovir, zidovudine, or stavudine as part of first-line antiretroviral therapy in a resource-limited-setting: a cohort study

BACKGROUND

Tenofovir (TDF) is part of the WHO recommended first-line antiretroviral therapy (ART); however, there are limited data comparing TDF to other nucleoside reverse transcriptase inhibitors in resource-limited-settings. Using a routine workplace and community-based ART cohort in South Africa, we assessed single drug substitution, HIV RNA suppression, CD4 count increase, loss-from-care, and mortality between TDF, stavudine (d4T) 30 mg dose, and zidovudine (AZT).

METHODS

In a prospective cohort study we included ART naïve patients aged ≥17 years-old who initiated ART containing TDF, d4T, or AZT between 2007 and 2009. For analysis of single drug substitutions we used a competing-risks time-to-event analysis; for loss-from-care, mixed-effect Poisson modeling; for HIV RNA suppression, competing-risks logistic regression; for CD4 count slope, mixed-effects linear regression; and for mortality, proportional hazards modeling.

RESULTS

Of 6,196 patients, the initial drug was TDF for 665 (11%), d4T for 4,179 (68%), and AZT for 1,352 (22%). During the first 6 months of ART, the adjusted hazard ratio for a single drug substitution was 2.3 for d4T (95% confidence interval [CI]: 0.27, 19) and 5.2 for AZT (95% CI: 1.1, 23), compared to TDF; whereas, after 6 months, it was 10 (95% CI: 5.8, 18) and 4.4 (95% CI: 2.5, 7.8) for d4T and AZT, respectively. Virologic suppression was similar by agent; however, CD4 count rise was lowest for AZT. The adjusted hazard ratio for loss-from-care, when compared to TDF, was 1.5 (95% CI: 1.1, 1.9) for d4T and 1.2 (95% CI: 1.1, 1.4) for AZT. The adjusted hazard ratio for mortality, when compared to TDF, was 2.7 (95% CI: 2.0, 3.5) and 1.4 (95% CI: 1.3, 1.5) and for d4T and AZT, respectively.

DISCUSSION

In routine care, TDF appeared to perform better than either d4T or AZT, most notably with less drug substitution and mortality than for either other agent.

Stavudine extended release (once-daily, Bristol-Myers Squibb) for the treatment of HIV/AIDS

INTRODUCTION

Stavudine extended release (d4T XR) was a formulation which tried to solve the two main problems associated with the use of stavudine immediate release (d4T IR). These were twice daily dosing schema at a time when most formulations were long-life allowing once daily dosing; and that the use of d4T IR was associated with long-term toxicity through mitochondrial toxicity clinically expressed as peripheral neuropathy, pancreatitis and above all, lipodystrophy. The link between stavudine exposure and lipodystrophy had a great negative impact on its use in clinical practice.

AREAS COVERED

The authors cover the most relevant papers related to the efficacy and safety of d4T XR-based antiretroviral therapy.

EXPERT OPINION

The development of d4T XR has only been partially successful with regard to its objectives. Improved pharmacokinetic properties allow its once daily dosing, and although it exhibits less mitochondrial toxicity it is still hampered by its development in a significant proportion of patients. This has caused its use to be almost residual in industrialised countries. As of now, d4T XR has not been made available in developing countries, despite the extended use of the immediate-release formulation. Currently, if there is no other chance of starting combination antiretroviral therapy, d4T XR could play a role in the treatment of HIV infection.

Drug safety evaluation profile of stavudine plus lamivudine for HIV-1/AIDS infection

INTRODUCTION

The lamivudine (3TC) + stavudine (d4T) combination is still widely used as part of first-line therapy for HIV-1-infected patients in low-resource countries. This review is intended to assess the benefits and risks in terms of safety of d4T + 3TC-based combination antiretroviral therapy (ART) for the treatment of HIV-1 infection.

AREAS COVERED

The most relevant papers related to the safety of d4T + 3TC-based ART were selected and summarized.

EXPERT OPINION

In industrialized countries, the 3TC + d4T combination is not recommended for initial therapy because of long-term metabolic toxicities associated with d4T. In developing countries, it may have a role in the treatment of HIV-infected patients if there is no other chance for starting antiretroviral therapy.

Predictors of immune recovery and the association with late mortality while on antiretroviral treatment in Cambodia

The objectives of this study were to examine the association of the on-treatment CD4 cell count with late mortality (after >6 months of antiretroviral treatment [ART]) and to identify the determinants of the long-term CD4 cell count evolution after treatment initiation. We conducted a retrospective analysis including all antiretroviral (ARV)-naïve adults initiating ART in a tertiary hospital in Phnom Penh, Cambodia from 2003-2010. We used Cox proportional hazards modelling (mortality analysis), including time-updated CD4 counts, and mixed-effects modelling (CD4 response over time). Overall, 2840 patients were included (47% male, median age: 34 years, median baseline CD4 count: 78 cells/μL). The median time on ART was 2.5 years (IQR 1.1-4.3); 71 patients died after >6 months of ART. The baseline CD4 count was the main determinant of the on-treatment CD4 cell count. Time-updated CD4 cell counts was the strongest determinant of late mortality with a HR of 0.32 (95% CI 0.16-0.63) and 0.29 (95% CI 0.11-0.71) for CD4 values of 200-350 cells/μL and 350-500 cells/μL respectively. We conclude that baseline CD4 counts strongly determine the long-term immune recovery, which critically affects late mortality. This calls for increased efforts for early ART initiation and availability of CD4 count testing in low-income countries.

Cutaneous toxicities of antiretroviral therapy for HIV: part I. Lipodystrophy syndrome, nucleoside reverse transcriptase inhibitors, and protease inhibitors

Antiretroviral medications for the treatment of HIV are common drugs with diverse and frequent skin manifestations. Multiple new cutaneous effects have been recognized in the past decade. Dermatologists play an important role in accurately diagnosing and managing the cutaneous toxicities of these medications, thereby ensuring that a patient has as many therapeutic options as possible for life-long viral suppression. Part I of this two-part series on the cutaneous adverse effects of antiretroviral medications will discuss HIV-associated lipodystrophy syndrome, which can be seen as a result of many antiretroviral medications for HIV, and the specific cutaneous effects of the nucleoside reverse transcriptase inhibitors and protease inhibitors.

Immunological profile in persons under antiretroviral therapy in a rural Nigerian hospital

Human immunodeficiency virus (HIV) contributes significantly to morbidity and mortality in sub-Saharan Africa, with Nigeria having the third highest burden of HIV infection globally; efforts are made to increases access to HIV/AIDS care and treatment. This has currently reached rural areas with limited manpower and laboratory evaluation capacity. This review is necessitated by the paucity of interim report on treatment profile in Nigerian rural areas. We report on the immunological profile of patients on antiretroviral therapy (ART) in Otukpo General Hospital, a rural Nigerian hospital. This is a retrospective cohort study of patients receiving ART treatment and care, on April 2009, when 2347 patients were under ART therapy. Out of these, 96 patients were selected by simple random sampling from hospital register, with their data abstracted from standardized Ministry of Health registers and facility documents kept at the hospital, and analyzed for descriptive and biometric measures. Ninty-six patients (29% males) with a median age of 35 years, median baseline CD4 lymphocyte count 221 cells/mL, median one year CD4 lymphocyte count of 356 cells/mL and median one year CD4 lymphocyte increment of 124 cells/mL were studied. There is no statistically significant difference in baseline CD4 lymphocyte count when data is disaggregated by type of drug regimen (AZT, D4T and TDF). Fourty-four percent, 23% and 33% of patients were on TDF, D4T & AZT based regimen, respectively (P=0.66). Increment of >100 cells/mL was seen in 64.58% of the reviewed patients. There was a higher CD4 lymphocyte count increment in patients on TDF & D4T compared with those in AZT based regimens (ANOVA; P<0.0003). Multivariate linear regression model showed one year CD4 lymphocyte count, one year increment in CD4 lymphocyte count, WBC count, and absolute neutrophil count to be significant correlates of baseline CD4 lymphocyte count (P<0.0001). Equally, multivariate logistic regression found age, platelet count and CD4 lymphocyte count at 12 months showed to be significant predictors of CD4 lymphocyte increment above 100 cells/µL (P<0.0001). Despite advanced disease presentation and a very large-scale program, high quality HIV/AIDS care was achieved as indicated by good short-term, immunologic outcomes, while TDF & D4T induce higher immunological recovery compared with AZT. This report suggests that quality HIV care and treatment can be effective despite the challenges of a resource-limited setting.

Stavudine or zidovudine in three-drug combination therapy for initial treatment of HIV infection in antiretroviral-naïve individuals

BACKGROUND

The introduction of highly active antiretroviral therapy (ART) as treatment for HIV infection has greatly improved mortality and morbidity for adults and children living with HIV around the world. Two common medications given in first-line antiretroviral therapy are the nucleoside reverse transcriptase inhibitors (NRTI) stavudine (d4T) or zidovudine (AZT).

OBJECTIVES

To assess the efficacy of d4T compared to AZT in combination with one NRTI and one non-nucleoside reverse transcriptase inhibitor (NNRTI), two additional NNRTIs, or one NRTI and one protease inhibitor (PI), as part of first-line ART for HIV-infected people in low-resource settings.

SEARCH STRATEGY

Standard Cochrane methods were used to search electronic databases and conference proceedings with relevant search terms without limits to language.

SELECTION CRITERIA

Randomised controlled trials of HIV-infected patients 5 years of age and older were included. Primary outcomes of interest included mortality, severe adverse events, virologic response to ART, and adherence/tolerance/retention. Secondary outcomes included immunologic response to ART, development of ART drug resistance, and prevention of sexual transmission of HIV.

DATA COLLECTION AND ANALYSIS

Two authors assessed each reference for inclusion and exclusion criteria established a priori. Data were abstracted independently using a standardised abstraction form.

MAIN RESULTS

Nine randomised controlled trials were identified as meeting the inclusion criteria. The nine trials enrolled 2,159 participants but looked at a multiplicity of drug combinations. Despite this, a reasonably robust literature suggests no statistically significant difference between the two drug combinations, including severe adverse events and adherence/tolerance/retention. The quality of the literature was found overall to be low to very low for all key outcomes. Only one study reported on drug resistance, and no studies reported on sexual transmission of HIV. The length of follow-up time and study settings varied greatly.

AUTHORS' CONCLUSIONS

While ideally future research would focus on direct comparison of standard therapeutic combinations of d4T+3TC+an NNRTI and AZT+3TC+an NNRTI to compare these regimens more directly, it is unlikely that additional trials will be mounted. Observational studies should focus on understanding outcomes, including toxicity and tolerability, in low- and middle-income countries.

Mitochondrial DNA base excision repair and mitochondrial DNA mutation in human hepatic HuH-7 cells exposed to stavudine

The mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is due to the inhibition of mitochondrial DNA (mtDNA) polymerase gamma (Pol gamma), resulting in a blockade of mtDNA replication and subsequent disruption of cellular energetics. Because mtDNA Pol gamma is not only involved in mtDNA replication but also responsible for mtDNA repair, we hypothesize that mitochondrial oxidative stress leads to changes in the balance between mtDNA repair and mutation following stavudine (d4T) treatment. However, the mechanisms underlying how changes in mtDNA base excision repair (mtBER) lead to mtDNA mutation remain unclear. To test this hypothesis, total mitochondrial repair capability, different steps of mtBER, mtDNA mutations in D-loop, and oxidative stress were all assessed in cultured HuH-7 human hepatoblast cells treated with d4T for 2 weeks. Assessment by denaturing Southern blotting and quantitative PCR revealed that d4T significantly reduced in vivo repair of H(2)O(2) damaged mtDNA in HuH-7 cells. d4T reduced total in vitro mtBER and DNA Pol gamma capability, but did not affect mtDNA oxoguanine glycosylase and apurinic/apyrimidinic endonuclease activity in HuH-7 cells. In addition, d4T treatment is associated with a significant increase in the frequency of mtDNA mutations in HuH-7 cells. In conclusion, d4T treatment reduces mtBER and contributes mechanistically to NRTI-induced mtDNA mutation. These events may potentially be associated with some diseases linked to mtDNA mutation.

Predictors of CD4+ cell count response and of adverse outcome among HIV-infected patients receiving highly active antiretroviral therapy in a public hospital in Peru

OBJECTIVES

Our aim was to investigate CD4+ cell recovery and adverse outcome after highly active antiretroviral therapy (HAART) under the Peruvian National Program for HIV.

METHODS

A prospective, observational study was conducted between May 2004 and September 2005. Data were collected from records of patients receiving HAART at a public hospital under the Peruvian National Program for HIV. Predictors of CD4+ cell count recovery and adverse outcome were analyzed by multiple regression.

RESULTS

Three hundred and twenty-six patients were included in the study. The mean increase in CD4+ cell count at six months was 114 cells/microl (95% confidence interval: 103-126). Patients with a lower CD4+ cell count at baseline and those starting HAART with a didanosine-based regimen had a higher increase in CD4+ cell count at six months. Patients starting HAART with a stavudine-based regimen had a lower increase in CD4+ cell count at six months. World Health Organization clinical stage IV at diagnosis of HIV infection, a low body weight at baseline, and starting HAART with a stavudine-based regimen were independently associated with an adverse outcome.

CONCLUSIONS

The CD4+ cell response to HAART under Peruvian National Program for HIV was comparable with reports from other countries. However, the fact that advanced clinical disease predicted adverse outcome emphasizes the need for earlier access to HAART.

Antiretroviral therapy : optimal sequencing of therapy to avoid resistance

In the second decade of highly active antiretroviral therapy, drug regimens offer more potent, less toxic and more durable choices. However, strategies addressing convenient sequential use of active antiretroviral combinations are rarely presented in the literature. Studies have seldom directly addressed this issue, despite it being a matter of daily use in clinical practice. This is, in part, because of the complexity of HIV-1 resistance information as well as the complexity of designing these types of studies. Nevertheless, several principles can effectively assist the planning of antiretroviral drug sequencing. The introduction of tenofovir disoproxil fumarate, abacavir and emtricitabine into current nucleoside backbone options, with each of them selecting for an individual pattern of resistance mutations, now permits sequencing in the context of previously popular thymidine analogues (zidovudine and stavudine). Similarly, newer ritonavir-boosted protease inhibitors could potentially be sequenced in a manner that uses the least cross-resistance prone protease inhibitor at the start of therapy, while leaving the most cross-resistance prone drugs for later, as long as there is rationale to employ such a compound because of its utility against commonly observed drug-resistant forms of HIV-1.

Antiretroviral therapy using zidovudine, lamivudine, and efavirenz in South Africa: tolerability and clinical events

OBJECTIVE

To describe the safety and tolerability of zidovudine, lamivudine, and efavirenz in a low-income setting.

DESIGN

We conducted a prospective cohort study in a workplace HAART programme in South Africa, which uses a first-line regimen of efavirenz, zidovudine, and lamivudine and provides routine clinical and laboratory monitoring 6-monthly pre-HAART and at 2, 6, 12, 24, 36, 48 weeks during HAART.

METHODS

We assessed the incidence of specified clinical and laboratory events (AIDS Clinical Trials Group grade 3 or higher) and associated regimen changes, hospitalizations, and deaths one year before HAART initiation and one year on-HAART using person-year analysis.

RESULTS

Between November 2002 and October 2005, 853 subjects (98% male, median age 40 years, and median CD4 cell count at HAART initiation 186 cells/mul) met enrollment criteria. The incidence of events on-HAART was higher than pre-HAART for neutropenia and nausea/vomiting. Dizziness was common early after HAART initiation (not evaluated pre-HAART). Of those with neutropenia, 88% had no apparent clinical consequences. The incidence of anemia, hepatotoxicity, peripheral neuropathy, and rash was similar or higher pre-HAART than on-HAART. Mean hemoglobin rose during the time on-HAART and was higher at 24 and 48 weeks than at baseline (P < 0.001).

DISCUSSION

This regimen was well tolerated with a short-term increase in neutropenia, nausea, and probably neurocerebellar events. Most significantly, in contrast to reports from high-income countries, we observed a long-term improvement in the hemoglobin concentration.

InforMatrix nucleoside/nucleotide reverse transcriptase inhibitor 'backbones'

InforMatrix is an interactive decision matrix technique. This paper describes the use of InforMatrix to determine an order of merit within the various nucleoside and nucleotide reverse transcriptase inhibitors. In the order of merit, six criteria (effectiveness, safety, tolerance, convenience, usability and costs) are weighted against each other. Data necessary for this weighting process are derived from literature as well as personal practical experience. This article gives an overview of the most relevant information from clinical trials, cohort studies and databases concerning backbones consisting of two nucleoside/nucleotide reverse transcriptase inhibitors in the treatment of HIV infections, as well as a description of the interactive decision matrix technique. By using this interactive matrix technique, a rational consideration of the treatment options for backbones consisting of two nucleoside/nucleotide reverse transcriptase inhibitors becomes possible.

Review: immunologic response to protease inhibitor-based highly active antiretroviral therapy: a review

A substantial body of evidence indicates that CD4 cell count is an important independent prognostic indicator for progression of HIV disease. Consequently, in addition to plasma HIV RNA levels, CD4 cell count change is considered to be a key surrogate marker for disease progression in clinical practice and in clinical studies. Given the relationship between changes in CD4 count and disease progression, it is notable that protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) can rapidly increase CD4 cell count early in treatment in both therapy-naïve and -experienced patients, and can sustain clinically relevant levels beyond 24 weeks. A number of trials with a follow-up of more than 3 years allow us to conclude that the gains in CD4 counts are maintained in a durable manner. This review evaluated randomized studies of PI-based and PI-boosted HAART (published between January 1996 and February 2006) to determine the effect of PI-based therapy on CD4 cell count. Only studies that assessed CD4 response in the overall patient population were included. Four mechanisms have been proposed to account for the rapid increase in CD4 cell count that occurs with HAART: CD4 cell redistribution from lymphatic tissues, increased CD4 cell production, reduction of apoptotic CD4 cells and the recovery of hematopoietic activity in bone marrow. Further research is required to clarify the relative importance of these mechanisms and ways in which they might be enhanced.

Strategies for the optimal sequencing of antiretroviral drugs toward overcoming and preventing drug resistance

Drug regimens now offer more potent, less toxic and more durable choices in the treatment of HIV disease than ever before. This has led to a need to consider the convenient, sequential use of active antiretroviral combinations. Ritonavir-boosted protease inhibitors (PIs) can now be potentially sequenced in a manner that uses the least cross-resistance-prone PI at the start of therapy while leaving the most cross-resistance-prone drug for later, if the latter retains activity against commonly observed drug-resistant forms. Similarly, such new drugs as tenofovir, abacavir and emtricitabine, which make up current nucleoside backbone options, can be potentially sequenced, since each of them selects for an individual pattern of resistance mutations that are generally distinct from those selected by previously popular thymidine analogs such as zidovudine and stavudine.

CD4+ T-Cell Count Increase in HIV-1-Infected Patients with Suppressed Viral Load Within 1 year after start of antiretroviral therapy

Background

CD4+ T-cell recovery in patients with continuous suppression of plasma HIV-1 viral load (VL) is highly variable. This study aimed to identify predictive factors for long-term CD4+ T-cell increase in treatment-naive patients starting combination antiretroviral therapy (cART).

Methods

Treatment-naive patients in the Swiss HIV Cohort Study reaching two VL measurements <50 copies/ml >3 months apart during the 1st year of cART were included ( n=1,816 patients). We studied CD4+ T-cell dynamics until the end of suppression or up to 5 years, subdivided into three periods: 1st year, years 2–3 and years 4–5 of suppression. Multiple median regression adjusted for repeated CD4+T-cell measurements was used to study the dependence of CD4+ T-cell slopes on clinical covariates and drug classes.

Results

Median CD4+ T-cell increases following VL suppression were 87, 52 and 19 cells/μl per year in the three periods. In the multiple regression model, median CD4+ T-cell increases over all three periods were significantly higher for female gender, lower age, higher VL at cART start, CD4+ T-cell <650 cells/μ l at start of the period and low CD4+ T-cell increase in the previous period. Patients on tenofovir showed significantly lower CD4+T-cell increases compared with stavudine.

Conclusions

In our observational study, long-term CD4+ T-cell increase in drug-naive patients with suppressed VL was higher in regimens without tenofovir. The clinical relevance of these findings must be confirmed in, ideally, clinical trials or large, collaborative cohort projects but could influence treatment of older patients and those starting cART at low CD4+ T-cell levels.

Protease Inhibitor-Based Regimens for HIV Therapy

Antiretroviral (ARV) treatment strategies for HIV-infected patients continue to evolve. Over the past few years, there was a shift towards the use of nonnucleoside reverse transcriptase inhibitor-based regimens, mostly because of better tolerability, a lower pill burden, and improved adherence relative to using protease inhibitor (PI)-based regimens. Although the 2 strategies do afford similar potency and durability, the PI-based regimens provide a higher genetic barrier to the development of ARV resistance. This has become progressively more important for reasons that include increasing rates of baseline ARV resistance in newly infected patients and the risk of developing ARV resistance in treated populations with suboptimal adherence. With the introduction of novel ARVs and reformulated agents with more convenient dosing requirements, improved tolerability, and unique resistance characteristics, boosted PI-based strategies are increasingly being considered when initiating therapy in ARV-naive patients. In this article, the evidence for the use of boosted PIs as early therapy is reviewed, with emphasis on data available from comparative randomized controlled trials.

Resistance costs and future drug options of antiretroviral therapies: analysis of the role of NRTIs, NNRTIs, and PIs in a large clinical cohort

OBJECTIVE

To investigate future drug options (FDOs), resistance cost (RCVF), and virologic response to genotypic-driven rescue highly active antiretroviral therapy (HAART), according to type of therapy.

METHOD

This was a retrospective analysis in naïve or antiretroviral-experienced patients. Virologic response was defined as HIV RNA <50 copies.

RESULTS

There were 108 patients failing first-line HAART; there were 328 experienced patients. FDOs were reduced in subjects failing a thymidine-analogue (TA) regimen (median 3.65, IQR 1.29 ) compared to patients without TA (median 3.82, IQR 1.12) (p = .011). FDOs after first failure were higher for patients with non-nucleoside reverse transcriptase inhibitor (NNRTI; median 3.82; IQR 1.24) than with protease inhibitor (PI; median 3.64, IQR 1.15) (p = .027). In experienced patients, FDOs were much higher for TA (p = .005). Patients responding to genotypic-modified regimens had higher FDOs (median 3.9 4, IQR 2.53) than patients not responding (median 2.18, IQR 3.65) (p > .0001). Switching from an NNRTI-based HAART to a boosted PI had a higher chance (48.1%) of achieving a full virologic suppression, compared to switching from PI to NNRTI (21.4%, p < .0001).

CONCLUSION

FDOs and RCVF are parameters that can quantify the therapeutic choices at virologic failure. Different drugs induce different FDOs and RCVF. In successive-line regimens, the higher antiviral effect and genetic barrier of boosted PIs may overcome the limits of using nucleoside reverse transcriptase backbones, with only partial effectiveness.

Treatment initiation with zidovudine-containing potent antiretroviral therapy impairs CD4 cell count recovery but not clinical efficacy

OBJECTIVE

Zidovudine-containing antiretroviral therapy has been associated with a lower rise in absolute CD4 cell counts in several randomized trials. We examined the predictive factors for this phenomenon and assessed its impact on clinical progression during treatment in a large patient cohort.

DESIGN

An analysis of data from the Swiss HIV Cohort Study.

METHODS

All 2177 treatment-naive adults who began potent antiretroviral therapy (ART) between September 1995 and September 2004 were included. Exclusion criteria were previous ART and treatment duration of less than 3 months. Follow-up was censored in the case of a treatment switch or stop.

RESULTS

A total of 1312 patients initiated zidovudine-containing ART and 865 started ART without zidovudine. Except for slightly higher absolute CD4 cell counts in the zidovudine group, prognostic characteristics at baseline and viral suppression during treatment did not differ. During an observation time of 2343 and 1486 patient-years, the CD4 cell count increased by a median of 221 versus 286 cells/microl at 2 years and 290 versus 379 cells/microl at 4 years in the zidovudine versus no zidovudine group; however, the rise in the percentage of CD4 cells was similar in both groups. The zidovudine group had a significantly slower rise in total lymphocytes and haemoglobin. In multivariable Cox models, the hazard for new HIV-associated clinical events was not affected by zidovudine-containing ART.

CONCLUSION

Over 4 years, zidovudine led to a smaller increase in absolute, but not percentage, CD4 cell counts. The effect can be explained as a slower rise in total lymphocytes and has no impact on clinical efficacy.

Systematic review of clinical trials evaluating low doses of stavudine as part of antiretroviral treatment

Stavudine is a nucleoside analogue used for the treatment of HIV-1 infection, as part of highly active antiretroviral treatment. In developing countries, stavudine is used widely, owing to low cost and inclusion in generic fixed-dose combinations. In developed countries, stavudine is now rarely used, although it is highly effective. This is because newer drugs show lower rates of mitochondrial toxicities, such as lipoatrophy, peripheral neuropathy and lactic acidosis. In the development of stavudine, there was evidence that a dosage of 20-30 mg b.i.d. was effective, but the 40-mg b.i.d. dose gained regulatory approval. This review analyses the clinical trials conducted before and after the regulatory approval of stavudine, and shows that the dose of 30 mg b.i.d. has equivalent antiviral efficacy (given the caveats of meta-analysis), with some evidence of lower rates of peripheral neuropathy and lipoatrophy. With limited resources for HIV-1 treatment in developing countries, and only 25% of eligible patients receiving highly active antiretroviral treatment, low-cost treatment options such as stavudine still need to be pursued, if safety can be improved by dose optimisation.

Lopinavir plus ritonavir: a novel protease inhibitor combination for HIV infections

Lopinavir is a protease inhibitor (PI) for the treatment of HIV infection that was specifically designed to overcome the shortcomings of earlier agents in this class. It is the only PI coformulated with ritonavir, whose pharmacological boosting effect results in a highly potent, well-tolerated, clinically effective antiretroviral agent with a high genetic barrier to resistance. Lopinavir/ritonavir is a recommended first-line option for antiretroviral-naive patients initiating PI-based therapy, and has an equally important role in the management of treatment-experienced individuals. Its favorable pharmacological and clinical characteristics have recently prompted investigators to explore its potential novel applications in HIV monotherapy and double-boosted regimens.

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.

The Effect of HIV-1 Resistance Mutations after First-Line Virological Failure on the Possibility to Sequence Antiretroviral Drugs in Second-Line Regimens

Background

One of the more vigorous debates in the field of highly active antiretroviral therapy (HAART) is how to start it and what the optimal drug sequence is.

Methods

A retrospective cohort analysis was performed. The aim was to evaluate which variables could influence the virological response to second-line genotypic-based HAART in patients with virological documented first-line HAART failure. A positive response was defined as a confirmed HIV RNA level <50 copies/ml.

Results

Two hundred and eight patients were included. Demographic characteristics, risk factors for HIV acquisition, and drugs included in the initial treatment did not significantly influence the considered outcome. According to a multiple logistic model, the presence of thymidine analogue mutations (TAMs) had a negative association with the virological outcome ( P=0.006), whereas the use of a boosted protease inhibitor (PI) in second-line HAART was positively associated with the endpoint ( P=0.001). Patients receiving a genotypic-based second-line HAART containing a boosted PI achieved a viral load <50 copies/ml in a 74.2% of cases compared with 52.2% of those whose therapy did not contain a boosted PI. This difference was statistically significant ( P=0.002) with an odds ratio (OR) of 2.63 and a 95% confidence interval (CI) ranging from 1.46 to 4.76. This last variable positively influenced the outcome even when the analysis was restricted to patients harbouring a virus presenting TAMs. In this case, second-line HAART was successful in 66.7% of cases with an OR of 3.25 and a 95% CI ranging from 1.28 to 8.25 ( P=0.014).

Conclusions

the wider range of available therapeutic options has made resistance and drug-sequencing considerations a crucial point in selecting first-line HAART. Our data indicate that, by limiting the risk of selecting or accumulating TAMs, it could be possible to save further therapeutic options. In second-line regimens, the higher antiviral effect and genetic barrier of boosted PIs may overcome the limits of the use of NRTI backbones, which retain only a partial effectiveness.

Effect of baseline- and treatment-related factors on immunologic recovery after initiation of antiretroviral therapy in HIV-1-positive subjects: results from ACTG 384

OBJECTIVE

To assess the effect of baseline- and treatment-related factors on immunologic recovery after initiation of antiretroviral therapy (ART).

METHODS

Nine hundred eighty antiretroviral-naive HIV-1+ subjects were randomized to start stavudine/didanosine or zidovudine/lamivudine with nelfinavir, efavirenz, or both nelfinavir and efavirenz.

RESULTS

Greater CD4 cell recovery was associated with age of 40 years or younger, female sex, higher baseline naive/memory CD4 cell ratio, higher baseline virus load (VL), and virologic suppression (VS). Most subjects who maintained an undetectable VL had a substantial increase in CD4 cell count, but 13% of the subjects did not, even after 3 years of VS. Persistent T-cell activation was associated with lower CD4 cell recovery, even in subjects who achieved VS. Initial treatment assignment did not affect total CD4 cell recovery, naive/memory CD4 cell reconstitution, or decline in T-cell activation. In addition to CD4 cell recovery, B-cell counts rose substantially after ART initiation.

CONCLUSIONS

In this large randomized trial, younger age, female sex, higher naive/memory CD4 cell ratio, higher baseline VL, and VS were associated with greater CD4 cell increase, whereas persistent T-cell activation was associated with impaired CD4 cell recovery after ART initiation. Initial treatment assignment did not affect CD4 cell reconstitution.

Sustained improvement of dyslipidaemia in HAART-treated patients replacing stavudine with tenofovir

OBJECTIVE

To describe the 12-month evolution of lipid profile in HIV-infected virologically suppressed patients substituting tenofovir for stavudine.

DESIGN AND METHODS

'Recover' was a prospective, multicenter, switch study conducted at 120 HIV units across Spain designed to identify single nucleoside analogue substitution due to adverse events in real practice. Tenofovir substituted stavudine in 873 adult patients. No other substitutions were allowed. This lipid sub-study included 352 randomly recruited patients with complete follow-up and lipid parameters.

MAIN OUTCOME MEASURES

Changes in fasting levels of total cholesterol (TC), high and low-density lipoprotein cholesterol (HDL-C and LDL-C), and triglycerides (TG) at 48 weeks, and their cardiovascular risk (CVR) translation.

RESULTS

At 48 weeks, there was a sustained reduction in median TC (-17.5 mg/dl; P < 0.001), LDL-C (-8.1 mg/dl; P < 0.001), and TG (-35 mg/dl; P < 0.001). HDL-C remained roughly unchanged (-0.8 mg/dl). Patients with baseline hyperlipidaemia showed greater reductions in LDL-C (-29 mg/dl; P < 0.001) and TG (-76 mg/dl; P < 0.001). The greatest TG reduction was observed in patients with severe hyper-TG (-266 mg/dl; P < 0.001). The estimated 10-year CVR decreased in all patients (P < 0.001), and to a higher extent in patients with baseline hyperlipidaemia. There was a trend towards reduction according to the use of lipid-lowering agents (11.6% to 9,9%; P = non-significant).

CONCLUSIONS

The substitution of tenofovir for stavudine causes a sustained improvement of dyslipidaemia. The reduction, although modest, is robust and sustained over time, and significantly reduces the CVR. This switch strategy is safe and contributes to an improvement in the lipid profile, especially TG, in HAART-treated patients.

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.

Minimizing resistance consequences after virologic failure on initial combination therapy: a systematic overview

OBJECTIVE

To identify optimal first-line therapies based on the rate of virologic success (VS) and the preservation of future treatment options in antiretroviral therapy (ART)-naive subjects.

DESIGN

Systematic overview of genotypic resistance mutations from clinical trials of combination ART.

METHODS

Various sources were searched for studies in ART-naive subjects providing virologic response rates and genotypes from subjects with virologic failure. The International AIDS Society-USA genotypic resistance guidelines were used to calculate regimen resistance cost (RCreg) and number of active drug (AD) scores for each regimen and to rank the regimens.

RESULTS

Intra- and interstudy comparisons showed higher VS rates for nonnucleoside reverse transcriptase inhibitor (NNRTI) regimens (range: 51%-76%) and boosted protease inhibitor (boosted PI) regimens (range: 55%-79%). Boosted PI failures had the lowest RCreg (range: 0.12-0.21) and the highest AD (range: 19.80-20.18) scores. NNRTI failures had higher RCreg (range: 0.00-1.22) and lower AD (range: 16.83-21) scores.

CONCLUSIONS

NNRTI and boosted PI regimens provide the highest rates of VS in treatment-naive HIV-infected persons. Treatment option scores were higher in subjects who failed boosted PI- containing regimens versus NNRTI-containing regimens, however.

The role of nucleoside and nucleotide reverse transcriptase inhibitor backbones in antiretroviral therapy

Several dual nucleoside reverse transcriptase inhibitor (NRTI) combinations provide efficacy when combined with a 3rd agent. However, there are a number of issues with current NRTI and nucleotide reverse transcriptase inhibitor (NtRTI) combinations that often lead to treatment failure and limited treatment options. These issues include suboptimal potency, drug interactions, toxicities, tolerability issues, and selection of resistance mutations that confer cross-resistance. Options for simplified NRTI backbones include fixed-dose combinations and agents that allow once-daily dosing; however, once-daily treatment choices are currently limited because of a lack of data on potential combinations. This article provides an historical perspective on the use of NRTI backbones in the treatment of HIV infection and outlines the advantages and disadvantages of currently available backbone combinations. In addition, it provides a brief introduction to backbone combinations under investigation as potential options for initial therapy. In an environment where several NRTI/NtRTI backbones offer comparable efficacy, treatment decisions will increasingly be made based on toxicity, resistance, and convenience considerations.

Treatment comparisons for a partially categorical outcome applied to a biomarker with assay limit

The plasma level of HIV-RNA has been shown to be a strong prognostic biomarker for clinical progression and death in HIV infected patients and is widely used as the primary outcome in clinical trials to evaluate antiretroviral treatments. Currently approved assays to measure HIV-RNA levels have a lower limit of reliable quantification (LoQ). Current regulatory guidelines recommend using the proportion of patients achieving HIV-RNA levels below the assay limit at a certain time point (e.g. 24 or 48 weeks) as the primary endpoint for regulatory approval. However, a substantial decrease in HIV-RNA that does not go below the LoQ still is considered clinically beneficial for patients with advanced diseases who have failed many other therapies and are unlikely to maximally suppress the virus and achieve HIV-RNA levels below the LoQ. An experimental treatment may not be distinguishable from a control solely in terms of the proportions of patients whose HIV-RNA levels fall below the LoQ. The sensitivity of the comparison between the experimental treatment and the control could be increased by considering as well the difference between the treatments with respect to the HIV-RNA reductions of patients not achieving HIV-RNA levels below the LoQ. In this paper, we introduce a best-rank analysis which assigns the best rank to patients who achieve the HIV-RNA levels below the LoQ and applies the Mann-Whitney-Wilcoxon rank test to compare the two treatment groups. The Mann-Whitney-Wilcoxon statistic is shown to be a weighted sum of two statistics: one to compare the proportions of patients achieving the HIV-RNA levels below the LoQ and one to compare the viral reductions in patients with HIV-RNA levels above the LoQ. The corresponding statistical null and alternative hypotheses and the clinical interpretations of this best-rank test procedure are also discussed. An example is used to illustrate this approach and a simulation study is used to compare this approach with other methods.

Initial antiretroviral therapy in chronically-infected HIV-positive adults

Currently, there are 20 individual antiretroviral drugs and two co-formulation products that are approved by the FDA for the treatment of HIV-infected individuals. It is widely accepted that the selection of an appropriate first-line regimen is critical in assuring durable treatment response. This article reviews the factors that should be considered in the selection of an initial antiretroviral regimen and present the currently available evidence regarding the status of individual antiretroviral agents and treatment strategies relative to these factors.

Triple nucleoside reverse transcriptase inhibitor therapy in children

Much of the success attributed to HIV therapy in the last few years has resulted from improved ways of using existing drugs in combination therapy regimens. The availability of new, more potent drugs such as protease inhibitors and more accurate viral load tests to aid decisions to start or change treatment has also contributed to the success. Published recommendations for pediatric HIV therapy, generated by a panel of experts and specialists, are readily available and regularly updated. Preferred regimens of 'potent' therapy (referred to as highly active antiretroviral therapy, or HAART) currently consist of two nucleoside reverse transcriptase inhibitors (NRTIs) combined with either a non-nucleoside reverse transcriptase inhibitor (NNRTI) or a protease inhibitor. More intense four-drug regimens using an NNRTI or a second protease inhibitor as a fourth drug are being evaluated. Problems with HAART include: unpalatable drug formulations and adverse effects, coupled with lack of data on the pharmacokinetics, efficacy, and safety of various drug combinations. Adherence is a major factor influencing the efficacy and outcome of antiretroviral therapy. Many children cannot adhere to complex multidrug regimens, which cause virologic failure, despite excellent CD4+ cell count responses. This means a rapid progression through the limited number of treatment regimens available. Simpler regimens such as those containing three NRTIs have been proposed as a method of treatment that will allow suppression of the virus, yet circumvent many of the problems previously mentioned. An additional benefit would be the preservation of antiretroviral drugs from other classes for future treatment options if required. The major advantages of triple NRTI regimens are the simplicity of the regimen, good tolerability, few drug-drug interactions, and infrequent adverse effects coupled with a low pill burden. However, abacavir hypersensitivity remains a major problem. Up to 3% of patients may develop an early idiosyncratic hypersensitivity reaction - fever, malaise, and mucositis with or without rash, which can progress to more advanced stages of shock and death. A major concern is the apparently inferior virologic control of triple NRTI therapy as demonstrated in the AIDS Clinical Trials Group A5095 study with zidovudine/lamivudine/abacavir (Trizivir) combination in adults. Such a combination should only be considered in special situations. Examples cited include informed patient choice based on anticipated poor adherence on other treatment regimens, or if concomitant drugs such as tuberculosis medication are prescribed. The low pill burden of triple NRTI regimens (especially if combined in a single pill such as Trizivir), offers hope that regimen simplification may still be possible in the future.

Incorporating durability information in the comparison of proportions of patients with HIV suppression

In some HIV clinical trials, the proportion of patients who achieve treatment success at a clinically meaningful time point (e.g., 16 or 24 weeks) and the subsequent durability of the treatment success after that time point are collected from two exclusive followup intervals. Two treatments are usually compared in terms of the proportion of patients achieving treatment success at the pre-defined time point and the subsequent durability information is ignored. However, combining the failure/success proportion at the pre-defined time point and the subsequent durability information in one test statistic could be more powerful if the experimental treatment is more efficacious than the control in that either fewer patients fail the experimental treatment at this time point or the responding patients have longer duration of viral suppression. In this paper, we propose a time-to-event type potency/durability endpoint which captures the information from the two exclusive followup intervals. A linear rank statistic to compare the two treatments in terms of this potency/durability endpoint can be interpreted as a weighted statistic to incorporate the potency information at a clinically meaningful time point (e.g., 16 or 24 weeks) and the durability information after that time point. The statistical hypotheses being tested by using this potency/durability endpoint and their clinical interpretations are discussed. A clinical endpoint study in anti-retroviral treatment naive patients is used to illustrate this method. Simulation studies show that this method is more powerful than comparing the success rates alone when the experimental treatment is also more durable in maintaining long term success.

Abacavir versus zidovudine combined with lamivudine and efavirenz, for the treatment of antiretroviral-naive HIV-infected adults

BACKGROUND

Zidovudine, lamivudine, and efavirenz comprise a highly effective and well-tolerated triple regimen for antiretroviral-naive patients. Evaluating other unique nucleoside reverse-transcriptase inhibitor (NRTI) combinations for long-term viral suppression is desirable.

METHODS

This multicenter, randomized, double-blind noninferiority clinical trial compared the efficacy and safety of abacavir with that of zidovudine plus lamivudine and efavirenz in 649 antiretroviral-naive HIV-infected patients. The primary objective was a comparison of proportions of patients achieving plasma HIV-1 RNA levels <or=50 copies/mL through week 48 of the study.

RESULTS

At study week 48, 70% of patients in the abacavir group, compared with 69% in the zidovudine group, maintained confirmed plasma HIV-1 RNA levels of <or=50 copies/mL (in the intent-to-treat exposed population). Virologic failure was infrequent (6% in the abacavir group and 4% in the zidovudine group). There was a significant CD4(+) cell response (209 cells/mm(3) in the abacavir group and 155 cells/mm(3) in the zidovudine group). Safety profiles were as expected.

CONCLUSION

Abacavir provided an effective and durable antiretroviral response that was noninferior to zidovudine, when combined with lamivudine and efavirenz.

Changes in hematologic parameters and efficacy of thymidine analogue-based, highly active antiretroviral therapy: a meta-analysis of six prospective, randomized, comparative studies

BACKGROUND

Hematologic changes that occur with HIV infection and antiretroviral therapy may impact the quality of life of patients and have been associated with morbidity and mortality. The management of anemia and neutropenia has improved survival in persons with HIV.

OBJECTIVES

This meta-analysis was performed to assess the changes in hemoglobin (Hb) levels and neutrophil counts that occur during thymidine analogue-based triple therapy and to establish whether different regimens of triple therapy are similar in efficacy based on CD4(+) T-cell count and viral load changes.

METHODS

This was a meta-analysis of the impact of zidovudine (AZT) compared with stavudine (d4T) in triple therapy regimens in HIV patients with regard to hematologic parameters and efficacy markers. The peer-reviewed literature was searched with use of MEDLINE, PubMed, EMBASE, and the Cochrane database of systematic reviews (key terms: HIV, antiretroviral therapy, CD4, viral load, three, triple, and highly active antiretroviral therapy [HAART]). Searches were initially not limited by publication type, study design, date, or language but subsequently were sorted to include only studies performed in treatment-naive adult patients; randomized; and comparative of a regimen that included d4T with a regimen that included AZT; to involve regimens that included a minimum of 3 drugs each; and to include hematologic outcomes data. Outcomes were CD4(+), viral load, and hematologic parameters.

RESULTS

This meta-analysis included 6 studies. Treatment efficacy as measured by changes in CD4(+) T-cell counts and viral load did not differ significantly between regimens. Hb levels decreased with AZT treatment by a mean (SE) 0.4 (0.05) g/dL and 0.2 (0.06) g/dL at weeks 24 and 48, respectively, but increased with d4T treatment by 0.45 (0.03) g/dL and 0.58 (0.04) g/dL, respectively. All grades of anemia and neutropenia events were consistently more common with AZT-based regimens relative to d4T-based therapy.

CONCLUSIONS

AZT-based HAART has a greater negative impact on hematologic parameters relative to d4T-based regimens. AZT recipients are more likely than d4T recipients to experience anemia and neutropenia events of any grade, and AZT is associated with a net decrease in Hb level relative to a net increase with d4T. These factors may influence the choice of drug used in the treatment of certain patient populations.

The reassurance of experience

Stavudine is a potent nucleoside analogue and a well-recognized component of highly active antiretroviral therapy. Clinical trials have shown stavudine to have a superior or at least comparable virological efficacy and immune reconstitution when compared with other nucleoside analogues. Studies have shown that the prevalence of phenotypic resistance to stavudine is low compared with that of zidovudine, lamivudine and abacavir, and any loss of sensitivity to stavudine is slow to develop and of low intensity. Stavudine has a low incidence of clinically significant adverse events, and those experienced are generally long-term, manageable class effects.

Primary nelfinavir (NFV)-associated resistance mutations during a follow-up period of 108 weeks in protease inhibitor naïve patients treated with NFV-containing regimens in an HIV clinic cohort

BACKGROUND

Nelfinavir (NFV) is a widely prescribed HIV-1 specific protease inhibitor (PI). However, there are only a few reports that have described the long-term effects of NFV-containing regimens, especially with regard to the emergence of drug resistance in inner-city clinics.

OBJECTIVES

The aim of this study was to investigate the clinical and virologic responses to treatment with NFV-containing regimens for up to 108 weeks and determine the timing and rate of emergence of primary NFV-resistance associated mutations in daily clinical practice.

STUDY DESIGN

A cohort study in an inner-city clinic. Our study included 51 consecutive patients who were PI-nai;ve and commenced therapy in February 1997 through April 1999.

RESULTS AND CONCLUSIONS

The proportions of patients who continued the same therapeutic regimen and showed virologic success (viral load <400 copies/ml) up to 108 weeks were 78 and 63%, respectively, based on intent-to-treat analysis. Among patients with a viral load persistently >400 copies/ml at week 12 (n=30), 11 developed primary NFV-resistance associated mutations by 108 weeks (stratified log-rank test; P<0.05). The Cox proportional hazard model showed that prior use of reverse transcriptase inhibitors (n=22) (relative hazard (RH); 2.10, 95% CI; 0.67-6.62), prior AIDS diagnosis (n=6) (RH; 1.70, 95% CI; 0.37-7.77), CD4 < 200/microl at baseline (n=19) (RH; 2.48, 95% CI; 0.78-7.81) and viral load >30,000 copies/ml at baseline (n=21) (RH; 2.10, 95% CI; 0.67-6.62) were not independent predictors of the NFV-resistance, although some tendency was noted. In total, 77% of the patients continued NFV-containing treatment without the NFV-resistance for 108 weeks. The viral load at week 12 could be used as a predictor of treatment success in our cohort study.

Antiretroviral Therapy: When and What to Start-- An American Perspective

The major US treatment guidelines recently recommended starting antiretroviral therapy (ART) later in the course of HIV infection due to an increasing awareness of the difficulties associated with these regimens. Most of the data to support this change come from observational cohort studies. When deciding to start ART, a number of patient-specific factors and other issues should be considered. Given the many choices for initial ART, one should individualize the choice, taking into account antiretroviral regimen potency, durability, side effects, toxicities, and convenience to ensure a sustained clinical benefit for the patient.