Lopinavir/ritonavir monotherapy or plus zidovudine and lamivudine in antiretroviral-naive HIV-infected patients

Lopinavir/ritonavir-based antiretroviral therapy in human immunodeficiency virus type 1-infected naive children: rare protease inhibitor resistance mutations but high lamivudine/emtricitabine resistance at the time of virologic failure

BACKGROUND

Lopinavir/ritonavir (LPV/r) is now the protease inhibitor regimen of choice in the first-line antiretroviral therapy for children <6 years of age.

METHODS

We included all the human immunodeficiency virus (HIV) type 1-infected highly active antiretroviral therapy (HAART)-naive children who started an LPV/r-based regimen between 2000 and 2009 at the Necker Hospital (Paris, France). Virologic failure (VF) was defined as an HIV-RNA ≥50 copies/mL. Resistance genotypic test was performed in case of VF.

RESULTS

A total of 43 children were included at a median age of 4.8 years (1.8-8.0). Median level of HIV RNA and percentage of CD4 cell count was 5.5 log₁₀ copies/mL (4.6-6) and 15% (8-27.5), respectively. HAART included LPV/r and 2 nucleoside reverse-transcriptase inhibitors, mainly lamivudine (3TC), zidovudine, and/or abacavir. The median follow-up period was 36 months (18-72). Less than 50 copies/mL of HIV RNA was observed in 46%, 67%, and 70% of the children at months 6, 9, and 12, respectively. In all, 20 children (46.5%) experienced a VF. The risk factors of primary VF were a young age and a low socioeconomic status. The genotypic resistance test, performed for 18 of 20 children with VF, revealed 1 LPV/r-resistant virus and protease inhibitor-related major mutations without LPV/r resistance in 2 other children. Of the 18 children with VF, 15 received a 3TC-based HAART: 12 of 15 (80%) harbored a 3TC-resistant virus. No virus resistant to zidovudine or abacavir was found.

CONCLUSION

In all, 70% of HAART-naive children had virologic success at month 12. The selection of LPV-resistant strains was a rare event. A high rate of selection of 3TC-mutations strengthens the recommendation to prefer a first-line 3TC-sparing regimen, particularly for children with risk factors of poor adherence.

Analysis of drug resistance during HIV RNA viraemia in the MONET trial of darunavir/ritonavir monotherapy

BACKGROUND

When patients have HIV RNA suppressed to <50 copies/ml on current treatment, switching to darunavir (DRV)/ritonavir (DRV/r) monotherapy could prevent the development of resistance to other drug classes.

METHODS

In the MONET trial, 256 patients with HIV RNA<50 copies/ml on current highly active antiretroviral therapy (57% with protease inhibitors [PIs] and 43% with non-nucleoside reverse transcriptase inhibitors) and no history of virological failure were randomized to DRV/r 800/100 mg once daily, either as monotherapy (monotherapy arm) or with two nucleoside reverse transcriptase inhibitors (NRTIs; triple therapy arm). All samples with HIV RNA ≥ 50 copies/ml were genotyped, and a virtual phenotype was calculated (VircoType HIV-1 assays; Virco BVBA, Mechelen, Belgium).

RESULTS

A total of 63 patients had ≥ 1 HIV RNA result ≥ 50 copies/ml, of whom 38 were successfully genotyped. Most HIV RNA increases were transient and in the range of 50-200 copies/ml. Overall, 36 of the 38 (95%) successfully genotyped patients showed no International AIDS Society-USA major PI mutations, DRV mutations or NRTI mutations. Two patients showed some evidence of PI resistance during transient HIV RNA elevations: one patient in the monotherapy arm had a single DRV mutation (L33F) when HIV RNA was 63 copies/ml (the virus was phenotypically sensitive to DRV [fold change 0.8]) and one PI pretreated patient taking tenofovir disoproxil fumarate/emtricitabine/DRV/r had re-emergence of pre-existing NRTI (M184V) and PI (V82I and L90M) mutations after a short treatment interruption (this virus remained phenotypically sensitive to DRV/r). Both patients showed sustained HIV RNA suppression to week 48 remaining with the same treatment.

CONCLUSIONS

Emergence of drug resistance after changing a suppressive triple antiretroviral therapy to DRV/r with or without nucleoside analogues is uncommon.

Multi-nucleoside reverse transcriptase inhibitor resistant HIV type-1 in a patient from Sierra Leone failing stavudine, lamivudine and nevirapine

We report a 33-year-old HIV type-1 (HIV-1)-infected male from Sierra Leone who harboured extensive drug resistance mutations to all nucleoside reverse transcriptase inhibitors (NRTIs) and non-NRTIs, including the multi-NRTI-resistance Q151M complex, K65R, M184I and Y181I, after using standard first-line generic fixed-dose stavudine, lamivudine and nevirapine (Triomune™) for 36 months. In the context of non-B subtypes in resource-limited countries, first-line stavudine-containing regimens have been associated with more extensive and complex mutation patterns, compared with subtype B viruses. Whether the extensive and complex NRTI resistance patterns found among African patients failing first-line antiretroviral therapy is explained by viral genetic diversity or by different patient monitoring strategies remains to be elucidated. Emerging multi-NRTI resistance in sub-Saharan Africa would not only compromise second-line treatment options and the success of antiretroviral rollout, but could also contribute to the spread of drug-resistant variants worldwide.

Effectiveness of protease inhibitor monotherapy versus combination antiretroviral maintenance therapy: a meta-analysis

BACKGROUND

The unparalleled success of combination antiretroviral therapy (cART) is based on the combination of three drugs from two classes. There is insufficient evidence whether simplification to ritonavir boosted protease inhibitor (PI/r) monotherapy in virologically suppressed HIV-infected patients is effective and safe to reduce cART side effects and costs.

METHODS

We systematically searched Medline, Embase, the Cochrane Library, conference proceedings and trial registries to identify all randomised controlled trials comparing PI/r monotherapy to cART in suppressed patients. We calculated in an intention to treat (loss-of follow-up, discontinuation of assigned drugs equals failure) and per-protocol analysis (exclusion of protocol violators following randomisation) and based on three different definitions for virological failure pooled risk ratios for remaining virologically suppressed.

FINDINGS

We identified 10 trials comparing 3 different PIs with cART based on a PI/r plus 2 reverse transcriptase inhibitors in 1189 patients. With the most conservative approach (viral load <50 copies/ml on two consecutive measurements), the risk ratios for viral suppression at 48 weeks of PI/r monotherapy compared to cART were in the ITT analysis 0.94 8 (95% CI 0.89 to 1.00) p = 0.06; risk difference -0.06 (95%CI -0.11 to 0) p = 0.05, p for heterogeneity  = 0.08, I(2) = 43.1%) and in the PP analysis 0.93 ((95%CI 0.90 to 0.97) p<0.001; risk difference -0.07 (95%CI -0.10 to -0.03) p<0.001, p for heterogeneity  = 0.44, I(2) = 0%). Reintroduction of cART in 44 patients with virological failure led in 93% to de-novo viral suppression.

INTERPRETATION

Virologically well suppressed HIV-infected patients have a lower chance to maintain viral suppression when switching from cART to PI/r monotherapy. Failing patients achieve high rates of de-novo viral suppression following reintroduction of reverse transcriptase inhibitors.

Lopinavir: the old champion

Lopinavir/ritonavir approval for use in antiretroviral treatment 10 years ago was very important for the recognition of boosted protease inhibitor (PI)-based therapy as an attractive option for first-line therapy. Being coformulated with ritonavir and having less toxicity than former PIs it allowed for effective and durable virologic suppression with less impact on quality of life. It soon became the standard of care for salvage therapy in its class. Since then, however, its central role has been challenged by new PIs with a more favorable impact on lipid profile, better gastrointestinal tolerability or that are more active in the setting of multidrug resistance. This article summarizes the main clinical studies with lopinavir and discusses its particular characteristics as well as its possible current role in antiretroviral therapy.

Prospective one-year bone loss in treatment-naïve HIV+ men and women on single or multiple drug HIV therapies

Antiretroviral therapy has decreased the rate of HIV-related mortality and extended the life span of HIV patients. Current guidelines recommend the use of a 3-drug regimen, such as two nucleoside reverse transcriptase inhibitors and a protease inhibitor, boosted by ritonavir. Osteoporosis can be associated with the HIV disease itself or with antiretroviral therapy. Many trials have been conducted employing a single drug regimen to simplify antiretroviral therapy but few studies assessed the effect of the single drug regimen on bone mineral density (BMD). The objectives of the study were to assess and compare the relative (%) changes in lumbar spine and hip BMD over 48 weeks in HIV patients treated with mono or triple antiretroviral regimens The study was conducted using data from a randomized trial (MONARK) conducted in 136 antiretroviral-naïve HIV patients (89 men and 47 women) comparing the antiviral efficacy of a single-drug protease inhibitor regimen of lopinavir/ritonavir (LPV/r) versus LPV/r in combination with zidovudine (ZDV) and lamivudine (3TC). Lumbar spine and total hip BMD were assessed in 100 patients by dual-energy X-ray absorptiometry at baseline and 48 weeks. 48 week-BMD data were available for 43 patients (mean age 37years) with a mean baseline lumbar spine Z-score of -0.1 in the LPV/r monotherapy group and for 25 patients (mean age 35.8years) with a mean baseline lumbar spine Z-score of -0.2 in the LPV/r+ZDV+3TC group. After 48weeks, lumbar spine BMD significantly decreased by 4.4% (-5.1% to -2.1%, P≤0.001) in the LPV/r group and by 4.0% (-5.0% to -1.7%, P≤0.0001) in the LPV/r+ZDV+3TC group. There was no significant difference in BMD changes between the two groups. These results suggest that bone loss is observed 48 weeks after the initiation of antiretroviral therapy, whether the patients receive a single- or triple-drug antiretroviral regimen.

A Multicenter, Open Labeled, Randomized, Phase III Study Comparing Lopinavir/Ritonavir Plus Atazanavir to Lopinavir/Ritonavir Plus Zidovudine and Lamivudine in Naive HIV-1-Infected Patients: 48-Week Analysis of the LORAN Trial

OBJECTIVE

The primary aim of the study was to compare the metabolic side effects of a nucleoside analogue-containing regimen with a nucleoside analogue-sparing double protease inhibitor regimen. A secondary goal was to test for efficacy of a double-PI regimen.

DESIGN

Multicenter, randomized, open-label, phase III clinical trial.

SUBJECTS

Adult HIV-1-infected individuals naïve to antiretroviral therapy with viral load above 400 HIV-RNA copies/ml were randomized (1:1) to either 400 mg lopinavir /100 mg ritonavir (LPV/r) BID plus 150 mg lamivudine/300 mg zidovudine (CBV) BID versus LPV/r BID plus 300 mg atazanavir (ATV) QD. Main outcome measure was the virologic failure in both groups, defined as viral load ≥50 copies/ml at week 48.

RESULTS

In the CBV/LPV/r-arm, 29 out of 35 patients [(83%; 95% confidence interval (CI) 66.9-92.2%] and 18 out of 40 patients (45%; 95% CI 29.7-61.5%) in the ATV/LPV/r-arm had a HIV-RNA level <50 copies/ml at week 48. The intent-to-treat analysis revealed inferior virologic response in the ATV/LPV/r arm (Chi-Q and Fisher´s Exact Test p<0.001) and resulted in premature termination of the trial. Eleven patients in the ATV/LPV/r-arm discontinued therapy because of virological failure. These failures mostly presented with low level replication (<1,000 copies/ml). Increases in CD4 cell counts was significantly more rapid in the ATV/LPV/r arm (p=0.02), but comparable at week 48.

CONCLUSIONS

ATV/LPV/r had less virologic efficacy than the conventional RTI-based regimen and resulted in a high virological failure rate with low level replication.

First-line antiretroviral therapy after single-dose nevirapine exposure in South Africa: a cost-effectiveness analysis of the OCTANE trial

BACKGROUND

The OCTANE trial reports superior outcomes of lopinavir/ritonavir vs. nevirapine-based antiretroviral therapy (ART) among women previously exposed to single-dose nevirapine to prevent mother-to-child HIV transmission. However, lopinavir/ritonavir is 12 times costlier than nevirapine.

METHODS

We used a computer model, with OCTANE and local data, to simulate HIV-infected, single-dose nevirapine-exposed women in South Africa. Outcomes of three alternative ART sequences were projected: no ART (for comparison), first-line nevirapine, and first-line lopinavir/ritonavir. OCTANE data included mean age (31 years) and CD4 cell count (135/μl); median time since single-dose nevirapine (17 months); and 24-week viral suppression efficacy for first-line ART (nevirapine: 85%, lopinavir/ritonavir: 97%). Outcomes included life expectancy, per-person costs (2008 US$), and incremental cost-effectiveness ratios.

RESULTS

With no ART, projected life expectancy was 1.6 years and per-person cost was $2980. First-line nevirapine increased life expectancy (15.2 years) and cost ($13 990; cost-effectiveness ratio: $810/year of life saved versus no ART). First-line lopinavir/ritonavir further increased life expectancy to 16.3 years and cost to $15 630 (cost-effectiveness ratio: $1520/year of life saved versus first-line nevirapine). First-line lopinavir/ritonavir cost-effectiveness was sensitive to prevalence of nevirapine-resistant virus at ART initiation, time from single-dose nevirapine exposure to ART initiation (6-12, 12-24, or >24 months), second-line ART efficacies, and outcomes after 24 weeks on ART.

CONCLUSIONS

First-line lopinavir/ritonavir-based ART is very cost-effective in single-dose nevirapine-exposed, South African women similar to OCTANE participants. Lopinavir/ritonavir should be initiated in women with known nevirapine resistance or single-dose nevirapine exposure less than 12 months prior, or in whom such information is unknown.

Oxymatrine inhibits hepatitis B infection with an advantage of overcoming drug-resistance

Oxymatrine (OMTR) is an anti-hepatitis drug used in China. Its mechanism of action is unknown. Recently, we found that OMTR inhibits hepatitis B virus (HBV) via down-regulating the expression of heat-stress cognate 70 (Hsc70), a host protein required for HBV DNA replication. Goal of this study was to assess the effect of OMTR on clinical HBV drug-resistance. OMTR monotherapy (oral, 12 months) reduced blood HBV DNA by 96% and HBeAg by 70% in the chronic hepatitis B (CHB) patients resistant to lamivudine (n = 17), equal to its efficacy in the naïve CHB cohort (n = 20). Liver biopsy study showed that OMTR treatment caused a decrease of Hcs70 mRNA in liver cells, parallel with a reduction of intracellular HBV DNA. Combination of lamivudine with OMTR (n = 15) (oral, 12 months) showed an enhanced anti-HBV effect as compared to lamivudine monotherapy (n = 25). The incidence of drug resistance against lamivudine in the combination group was significantly lower than that in the lamivudine group (1/15 vs 7/25; p<0.01). The results were further confirmed in vitro. Treatment of HBV(+) HepH2215 cells with sub-optimal dose of OMTR for 8 months suppressed HBV replication without inducing drug resistance, whereas lamivudine monotherapy caused drug-resistant mutation in 3 months. Combination of OMTR with lamivudine prevented HBV from developing drug resistance.

Risk of viral failure declines with duration of suppression on highly active antiretroviral therapy irrespective of adherence level

OBJECTIVE

To model the effect of adherence and duration of viral suppression on the risk of viral rebound.

METHODS

Viral rebound was defined as the first of at least two consecutive viral loads greater than 400 copies/mL after initial viral suppression. The main exposures were adherence, presence of antiretroviral class resistance before rebound or censoring date, and the percentage of follow-up time with viral suppression.

RESULTS

A total of 274 (N = 1305 [21%]) individuals experienced viral rebound. Median time of suppression before rebound was 2 years. Viral rebound was less likely to occur among those with longer duration of continuous viral suppression (odds ratio, 0.37; 95% confidence interval, 0.32 to 0.42). Among individuals with moderate levels of adherence (80% to less than 95%), the probability of virologic failure was 0.85 after being suppressed for 12 months and it was 0.08 after 72 months being suppressed (P < 0.01). Individuals with drug resistance were at a higher risk of viral rebound.

CONCLUSIONS

The risk of viral rebound decreased with longer duration of viral suppression within each of adherence strata studied. Although perfect adherence remains an important goal of therapy to prevent disease progression, individuals with long-term viral suppression may be able to miss more doses without experiencing viral rebound.

Treatment simplification in HIV-infected adults as a strategy to prevent toxicity, improve adherence, quality of life and decrease healthcare costs

Since the advent of highly active antiretroviral therapy (HAART), the treatment of human immunodeficiency virus (HIV) infection has become more potent and better tolerated. While the current treatment regimens still have limitations, they are more effective, more convenient, and less toxic than regimens used in the early HAART era, and new agents, formulations and strategies continue to be developed. Simplification of therapy is an option for many patients currently being treated with antiretroviral therapy (ART). The main goals are to reduce pill burden, improve quality of life and enhance medication adherence, while minimizing short- and long-term toxicities, reducing the risk of virologic failure and maximizing cost-effectiveness. ART simplification strategies that are currently used or are under study include the use of once-daily regimens, less toxic drugs, fixed-dose coformulations and induction-maintenance approaches. Improved adherence and persistence have been observed with the adoption of some of these strategies. The role of regimen simplification has implications not only for individual patients, but also for health care policy. With increased interest in ART regimen simplification, it is critical to study not only implications for individual tolerability, toxicity, adherence, persistence and virologic efficacy, but also cost, scalability, and potential for dissemination and implementation, such that limited human and financial resources are optimally allocated for maximal efficiency, coverage and sustainability of global HIV/AIDS treatment.

Scaling up the 2010 World Health Organization HIV Treatment Guidelines in resource-limited settings: a model-based analysis

BACKGROUND

The new 2010 World Health Organization (WHO) HIV treatment guidelines recommend earlier antiretroviral therapy (ART) initiation (CD4<350 cells/µl instead of CD4<200 cells/µl), multiple sequential ART regimens, and replacement of first-line stavudine with tenofovir. This paper considers what to do first in resource-limited settings where immediate implementation of all of the WHO recommendations is not feasible.

METHODS AND FINDINGS

We use a mathematical model and local input data to project clinical and economic outcomes in a South African HIV-infected cohort (mean age = 32.8 y, mean CD4 = 375/µl). For the reference strategy, we assume that all patients initiate stavudine-based ART with WHO stage III/IV disease and receive one line of ART (stavudine/WHO/one-line). We rank-in survival, cost-effectiveness, and equity terms-all 12 possible combinations of the following: (1) stavudine replacement with tenofovir, (2) ART initiation (by WHO stage, CD4<200 cells/µl, or CD4<350 cells/µl), and (3) one or two regimens, or lines, of available ART. Projected life expectancy for the reference strategy is 99.0 mo. Considering each of the guideline components separately, 5-y survival is maximized with ART initiation at CD4<350 cells/µl (stavudine/<350/µl/one-line, 87% survival) compared with stavudine/WHO/two-lines (66%) and tenofovir/WHO/one-line (66%). The greatest life expectancies are achieved via the following stepwise programmatic additions: stavudine/<350/µl/one-line (124.3 mo), stavudine/<350/µl/two-lines (177.6 mo), and tenofovir/<350/µl/two-lines (193.6 mo). Three program combinations are economically efficient: stavudine/<350/µl/one-line (cost-effectiveness ratio, US$610/years of life saved [YLS]), tenofovir/<350/µl/one-line (US$1,140/YLS), and tenofovir/<350/µl/two-lines (US$2,370/YLS).

CONCLUSIONS

In settings where immediate implementation of all of the new WHO treatment guidelines is not feasible, ART initiation at CD4<350 cells/µl provides the greatest short- and long-term survival advantage and is highly cost-effective.

Efficacy of darunavir/ritonavir maintenance monotherapy in patients with HIV-1 viral suppression: a randomized open-label, noninferiority trial, MONOI-ANRS 136

BACKGROUND

Darunavir/ritonavir (darunavir/r) maintenance strategy, in patients with suppressed HIV RNA viremia, is a potential long-term strategy to avoid nucleoside analogue toxicities and to reduce costs.

METHODS

MONOtherapy Inhibitor protease is a prospective, open-label, noninferiority, 96-week safety and efficacy trial in virologically suppressed patients on triple therapy who were randomized to a darunavir/r triple drug regimen or darunavir/r monotherapy. The primary endpoint was the proportion of patients with HIV RNA less than 400 copies/ml at week 48; treatment failure was defined as two consecutive HIV RNA more than 400 copies/ml (time to loss of virologic response) or any change in treatment. The trial had 80% power to show noninferiority for the monotherapy arm (delta =-10%, 90% confidence interval).

RESULTS

A total of 242 patients were screened, 225 of whom were randomized. In the per protocol efficacy analysis, treatment success was 99% on darunavir/r triple drug versus 94% on darunavir/r monotherapy (delta = -4.9%, 90% confidence interval, from -9.1 to -0.8). Similar results were found in intent-to-treat population (92 versus 87.5%, delta = -4.5%, 90% confidence interval from -11.2 to 2.1). Three patients experienced virologic failure on darunavir/monotherapy and none on darunavir/r triple drug. No resistance to protease inhibitor emerged in patients with plasma viral load above 50 copies/ml. The two groups did not differ in the number of serious adverse events.

CONCLUSION

Darunavir/r monotherapy exhibited efficacy rate over 85% with concordant results in the magnitude of difference with darunavir/r triple drug regimen in both intent-to-treat and per protocol analyses, but discordant conclusions with respect to the noninferiority margin. Patients failing on darunavir/r monotherapy had no emergence of new darunavir resistance mutations preserving future treatment options.

Lopinavir/ritonavir monotherapy versus current treatment continuation for maintenance therapy of HIV-1 infection: the KALESOLO trial

OBJECTIVES

We evaluated a monotherapy maintenance regimen with lopinavir/ritonavir versus continuing current combined antiretroviral treatment (cART) in HIV patients with suppressed plasma HIV-1 RNA.

PATIENTS AND METHODS

This was an open-label, non-inferiority, multicentre trial in 23 sites in France. Adults were randomized if they had no history of virological failure while receiving a protease inhibitor, maintained HIV-1 RNA <50 copies/mL for at least 6 months and did not change cART during the last 3 months. The primary endpoint was the proportion of patients with HIV-1 RNA <50 copies/mL at Week 48 (non-inferiority margin set at -12%) with missing data and treatment modification considered as failure. The trial has been registered in ClinicalTrials.gov under the identifier NCT00140751.

RESULTS

At Week 48, 84% (73/87) of patients in the lopinavir/ritonavir monotherapy group met the primary endpoint compared with 88% (87/99) in the cART group [difference, -4.0%, lower limit of 90% two-sided confidence interval (CI) for difference, -12.4%]. In secondary analysis with success defined as plasma HIV-1 RNA <400 copies/mL, 87% (76/87) of patients in the lopinavir/ritonavir monotherapy group were virologically suppressed compared with 88% (87/99) in the cART group (difference, -0.5%, lower limit of 90% two-sided CI for difference, -8.5%). If antiretroviral treatment intensification was taken into account, 91% (79/87) of patients in the lopinavir/ritonavir monotherapy group met the primary endpoint compared with 88% (87/99) in the cART group (difference, +2.9%, lower limit of 90% two-sided CI for difference, -4.5%). Failures of lopinavir/ritonavir monotherapy did not show acquired resistance mutations in the protease gene.

CONCLUSIONS

Lopinavir/ritonavir monotherapy did not achieve non-inferiority versus cART for maintaining plasma HIV-1 RNA <50 copies/mL. Nevertheless, the incidence of virological failure was low (mostly with HIV-1 RNA <400 copies/mL) and easily managed by treatment intensification.

Pharmacokinetics and virologic response of zidovudine/lopinavir/ritonavir initiated during the third trimester of pregnancy

OBJECTIVE

To evaluate the pharmacokinetics and HIV viral load response following initiation during the third trimester of pregnancy of zidovudine plus standard-dose lopinavir boosted with ritonavir (LPV/r), twice daily, until delivery for the prevention of mother-to-child transmission of HIV.

DESIGN

Prospective study nested within a multicenter, three-arm, randomized, phase III prevention of mother-to-child transmission of HIV trial in Thailand (PHPT-5, ClinicalTrials.gov Identifier: NCT00409591).

METHODS

Women randomized to receive 300 mg zidovudine and 400/100 mg LPV/r twice daily from 28 weeks' gestation, or as soon as possible thereafter, until delivery had intensive steady-state 12-h blood sampling performed. LPV/r pharmacokinetic parameters were calculated using noncompartmental analysis. Rules were defined a priori for a LPV/r dose escalation based on the proportion of women with an LPV area under the concentration-time curve (AUC) below 52 microg h/ml (10th percentile for LPV AUC in nonpregnant adults). HIV-1 RNA response was assessed during the third trimester.

RESULTS

Thirty-eight women were evaluable; at entry, median (range) gestational age was 29 (28-36) weeks, weight 59.5 (45.0-91.6) kg, CD4 cells count 442 (260-1327) cells/microl and HIV-1 RNA viral load 7818 (<40-402 015) copies/ml. Geometric mean (90% confidence interval) LPV AUC, Cmax and Cmin were 64.6 (59.7-69.8) microg h/ml, 8.1 (7.5-8.7) microg/ml and 2.7 (2.4-3.0) microg/ml, respectively. Thirty-one of 38 (81%) women had an LPV AUC above the AUC target. All women had a HIV-1 viral load less than 400 copies/ml at the time of delivery.

CONCLUSION

A short course of zidovudine plus standard-dose LPV/r initiated during the third trimester of pregnancy achieved adequate LPV exposure and virologic response.

Noninfectious HIV-related comorbidities and HAART toxicities: choosing alternative antiretroviral strategies

In the HAART era, clinicians are faced with the challenge of treating an aging HIV-infected population increasingly affected by severe comorbidities, which may compromise the tolerability of antiretroviral regimens. In this special population, it is imperative for physicians to carefully tailor antiretroviral treatment in order not to worsen patients’ underlying clinical conditions and to achieve both tolerability and immune–virologic efficacy. This article aims to explore the impact of standard HAART regimens on the different noninfectious HIV-related comorbidities: metabolic, cardiovascular, bone and renal diseases, in order to provide tools to fit the most appropriate antiretroviral combination according to individual clinical conditions. Clinical experience with alternative antiretroviral strategies, avoiding nucleoside reverse transcriptase inhibitor toxicities and involving new antiretroviral classes, will be reviewed to obtain an overview on future perspectives.

[Meta-analysis of the effectiveness of the strategy of monotherapy with boosted protease inhibitors in HIV+ patients]

INTRODUCTION

The objective of this study is to analyse the available evidence regarding the effectiveness of the strategy of induction maintenance with boosted protease inhibitors with ritonavir in adult HIV patients as compared to conventional treatment.

METHODS

We performed a meta-analysis of randomised controlled trials in HIV patients to compare the efficacy of a monotherapy strategy of boosted protease inhibitors as compared with conventional antiretroviral therapy. The literature search was conducted in PubMed, EMBASE (September 1999-September 2009) and in conference abstracts of the last 5 years. The Odds Ratio of treatment failure and their 95% confidence intervals were calculated. To combine the results of individual studies selected, a fixed effects model based on the Mantel-Haenszel method or random effects was used, depending on whether or not the results were heterogeneous.

RESULTS

Initially a total of 1510 publications were found, of which just 8 studies met the criteria for inclusion in the meta-analysis. The combined Odds Ratio of the 8 studies is 1.39 (95% CI 1.02-1.90) for the treatment group with conventional antiretroviral treatment, but with a confidence interval close to the limits of statistical non-significance.

CONCLUSION

The results of the combined effectiveness analysis in the meta-analysis found no significant differences between the conventional strategy and monotherapy. This strategy is considered recommended (level A evidence) in patients with no history of previous failure of protease inhibitor, with undetectable plasma viral load and signs or symptoms of nucleoside/nucleotide toxicity.

Laboratory monitoring to guide switching antiretroviral therapy in resource-limited settings: clinical benefits and cost-effectiveness

BACKGROUND

As second-line antiretroviral therapy (ART) availability increases in resource-limited settings, questions about the value of laboratory monitoring remain. We assessed the outcomes and cost-effectiveness (CE) of laboratory monitoring to guide switching ART.

METHODS

We used a computer model to project life expectancy and costs of different strategies to guide ART switching in patients in Côte d'Ivoire. Strategies included clinical assessment, CD4 count, and HIV RNA testing. Data were from clinical trials and cohort studies from Côte d'Ivoire and the literature. Outcomes were compared using the incremental CE ratio. We conducted multiple sensitivity analyses to assess uncertainty in model parameters.

RESULTS

Compared with first-line ART only, second-line ART increased life expectancy by 24% with clinical monitoring only, 46% with CD4 monitoring, and 61% with HIV RNA monitoring. The incremental CE ratio of switching based on clinical monitoring was $1670 per year of life gained (YLS) compared with first-line ART only; biannual CD4 monitoring was $2120 per YLS. The CE ratio of biannual HIV RNA testing ranged from $2920 ($87/test) to $1990 per YLS ($25/test). If second-line ART costs were reduced, the CE of HIV RNA monitoring improved.

CONCLUSIONS

In resource-limited settings, CD4 count and HIV RNA monitoring to guide switching to second-line ART improve survival and, under most conditions, are cost-effective.

Antiretroviral therapy for treatment-naïve patients: a review of recent literature and the updated guidelines

The improved efficacy and safety of antiretroviral agents have fundamentally changed the face of HIV infection. Advances in antiretroviral therapy have dramatically improved the prognosis of HIV infection, which is now on a par with other chronic illnesses. This article addresses the optimal timing of antiretroviral therapy initiation and the optimal drug choices for initial regimens, with a focus on recent data and published guidelines issued by the US Department of Health and Human Services and the International AIDS Society-USA.

Methodological issues in the use of composite endpoints in clinical trials: examples from the HIV field

BACKGROUND

In many fields, the choice of a primary endpoint for a trial is not always the ultimate clinical endpoint of interest, but rather some surrogate endpoint believed to be relevant for predicting the effect of the intervention on the clinical endpoint. The classic example of such a field is clinical HIV treatment research, where a variety of primary endpoints are used to evaluate the efficacy of new antiretroviral drugs or new combinations of existing drugs. The choice of endpoint reflects either the goal of therapy as recommended by treatment guidelines (e.g. rapid virological suppression) or the licensing requirements of official drug approval organizations (e.g. time to loss of virological response [TLOVR]).

PURPOSE

To review the diversity of endpoints used in recent clinical trials in HIV infection and highlight the methodological issues.

METHODS

We identified articles relating to antiretroviral therapy by searching PubMed and through hand searches of relevant conference abstracts. We restricted the search to randomized controlled trials conducted in HIV-infected adults published/presented from January 2005 until March 2008.

RESULTS

We identified 28 trials in antiretroviral-naive patients (i.e. patients who were starting antiretroviral therapy for the first time at the time of randomization) and 23 trials in antiretroviral-experienced patients. Most trials were performed for purposes of drug licensing, but others were focused on strategies of using approved drugs. Most trials (40 of 51) used a composite primary endpoint (TLOVR in 13). Of note, 22 of these 40 studies reported that they had used a purely virological efficacy endpoint, but the primary endpoint was actually a composite one due to the way in which missing data and treatment switches were considered as failures.

LIMITATIONS

Examples are restricted to HIV clinical trials.

CONCLUSIONS

Whilst most current HIV clinical trials use composite primary endpoints, there are substantial differences in the components that make up these endpoints. In HIV and other fields where precise definitions are variable, guidelines for standardization of definition and reporting would greatly improve the ability to compare trial results.

Monotherapy with Lopinavir/Ritonavir as maintenance after HIV-1 viral suppression: results of a 96-week randomized, controlled, open-label, pilot trial (KalMo study)

BACKGROUND

Long-term adverse events and expenses associated with HAART have led to an interest in simplified therapy. Lopinavir/ritonavir monotherapy is attractive due to its potency and high genetic barrier.

METHODS

This is a 96-week, open-label, randomized study to assess the feasibility of using LPV/r monotherapy in patients with undetectable viral load after being on successful HAART for at least 6 months. Subjects were randomized (1:1) to either switch from HAART to LPV/r monotherapy or to maintain their previous regimen.

RESULTS

60 patients were enrolled. Baseline characteristics were similar in both groups. At Week 96, by intention-to-treat analysis, 24/30 (80.0%) subjects in monotherapy group and 26/30(86.6%) in the control group had a plasma viral load of <80 copies/mL. There was one virologic failure (defined as VL not greater-than 500 copies/mL) in each arm. Genotyping testing identified no resistance-associated mutations. The patient on the monotherapy arm was successfully resuppressed to <80 copies/mL after intensification with tenofovir and lamivudine. No statistically significant differences were found with regard to changes in CD4 counts. One subject in the monotherapy group discontinued due to diarrhea. Five subjects in the control group underwent regimen changes due to drug-related toxicities. Viral load from semen samples collected at the end of follow-up was undetectable on 14/15 patients randomized to monotherapy.

CONCLUSIONS

Switching from various HAART regimens to LPV/r monotherapy in patients who were virologically suppressed and without a history of previous virologic failure was effective, safe, and well tolerated through 96 weeks.

Novel strategies in the use of lopinavir/ritonavir for the treatment of HIV infection in children

Lopinavir/ritonavir (LPV/r) is considered by many as the first choice protease inhibitor (PI) for children. This co-formulation avoids the need for children to take ritonavir separately to “boost” the levels of lopinavir. LPV/r has high virologic potency, an excellent toxicity profile and a high barrier to the development of viral resistance. However, LPV/r has poor tolerability of the oral suspension (due to the poor taste of ritonavir), difficult dosing requirements and metabolic side effects, especially hyperlipidemia. The new tablet low-dose formulation (100/25 mg) may allow more convenient antiretroviral treatment in children. Novel strategies of LPV/r in childhood could maximize its advantages. For example, infants infected with HIV despite single dose Nevirapine after birth need effective combination antiretroviral treatment. This can be given using a higher dose of LPV/r with therapeutic drug monitoring. Other novel uses include once daily LPV/r regimens in older children and adolescents and lower doses of LPV/r in certain populations, which may decrease hyperlipidemia. Heavily pre-treated children might benefit from a double PI/r regimen which includes LPV/r. The high potency of LPV/r needs to be balanced with convenient regimens, to enhance adherence and decrease toxicity whenever possible. The aim of this review is to discuss the rationale behind these novel strategies of LPV/r use in pediatric antiretroviral treatment as well as their results and limitations.

The future of antiretroviral therapy: challenges and needs

The introduction of combination antiretroviral therapy (cART) has substantially modified the natural history of HIV infection. At the beginning of the cART era the objective was focused on HIV-1-associated mortality and morbidity, but as this objective was accomplished other issues emerged, including toxicity, resistance and compliance with treatment. Moreover, the participation of other disease mechanisms, such as proinflammatory activity, in the so-called non-AIDS events is becoming increasingly important. To overcome these issues, therapeutic options have dramatically expanded, which has made the management of HIV-1-infected patients increasingly complex. The intense changes seen raise the question of what will be the future of HIV infection and its treatment. A projection into the future may help to reflect on current limitations, needs and research priorities, to optimize patient care. To debate on this topic a group of 38 experts has initiated The HIV 2020 Project, with the aim of reflecting on the future of HIV infection and identifying the needs that should be the attention of research in different areas. This document summarizes the group's conclusions on the future of antiretroviral treatment, presented as 20 relevant questions. Each question includes the current status of the topic and our vision for the future.

Switch to a raltegravir-based regimen versus continuation of a lopinavir-ritonavir-based regimen in stable HIV-infected patients with suppressed viraemia (SWITCHMRK 1 and 2): two multicentre, double-blind, randomised controlled trials

BACKGROUND

To reduce lipid abnormalities and other side-effects associated with antiretroviral regimens containing lopinavir-ritonavir, patients might want to switch one or more components of their regimen. We compared substitution of raltegravir for lopinavir-ritonavir with continuation of lopinavir-ritonavir in HIV-infected patients with stable viral suppression on lopinavir-ritonavir-based combination therapy.

METHODS

The SWITCHMRK 1 and 2 studies were multicentre, double-blind, double-dummy, phase 3, randomised controlled trials. HIV-infected patients aged 18 years or older were eligible if they had documented viral RNA (vRNA) concentration below the limit of assay quantification for at least 3 months while on a lopinavir-ritonavir-based regimen. 707 eligible patients were randomly allocated by interactive voice response system in a 1:1 ratio to switch from lopinavir-ritonavir to raltegravir (400 mg twice daily; n=353) or to remain on lopinavir-ritonavir (two 200 mg/50 mg tablets twice daily; n=354), while continuing background therapy consisting of at least two nucleoside or nucleotide reverse transcriptase inhibitors. Primary endpoints were the mean percentage change in serum lipid concentrations from baseline to week 12; the proportion of patients with vRNA concentration less than 50 copies per mL at week 24 (with all treated patients who did not complete the study counted as failures) with a prespecified non-inferiority margin of -12% for each study; and the frequency of adverse events up to 24 weeks. Analyses were done according to protocol. These trials are registered with ClinicalTrials.gov, numbers NCT00443703 and NCT00443729.

FINDINGS

702 patients received at least one dose of study drug and were included in the efficacy and safety analyses for the combined trials (raltegravir, n=350; lopinavir-ritonavir, n=352). Percentage changes in lipid concentrations from baseline to week 12 were significantly greater (p<0.0001) in the raltegravir group than in the lopinavir-ritonavir group in each study, yielding combined results for total cholesterol -12.6%vs 1.0%, non-HDL cholesterol -15.0%vs 2.6%, and triglycerides -42.2%vs 6.2%. At week 24, 293 (84.4%, 95% CI 80.2-88.1) of 347 patients in the raltegravir group had vRNA concentration less than 50 copies per mL compared with 319 (90.6%, 87.1-93.5) of 352 patients in the lopinavir-ritonavir group (treatment difference -6.2%, -11.2 to -1.3). Clinical and laboratory adverse events occurred at similar frequencies in the treatment groups. There were no serious drug-related adverse events or deaths. The only drug-related clinical adverse event of moderate to severe intensity reported in 1% or more of either treatment group was diarrhoea, which occurred in ten patients in the lopinavir-ritonavir group (3%) and no patients in the raltegravir group. The studies were terminated at week 24 because of lower than expected virological efficacy in the raltegravir group compared with the lopinavir-ritonavir group.

INTERPRETATION

Although switching to raltegravir was associated with greater reductions in serum lipid concentrations than was continuation of lopinavir-ritonavir, efficacy results did not establish non-inferiority of raltegravir to lopinavir-ritonavir.

FUNDING

Merck.

The MONET trial: darunavir/ritonavir with or without nucleoside analogues, for patients with HIV RNA below 50 copies/ml

BACKGROUND

In virologically suppressed patients, darunavir-ritonavir (DRV/r) monotherapy could maintain virological suppression similarly to DRV/r and two nucleosides.

METHODS

Two hundred and fifty-six patients with HIV RNA less than 50 copies/ml for over 24 weeks on current antiretrovirals [non-nucleoside reverse transcriptase inhibitor (NNRTI)-based (43%), or protease inhibitor-based (57%)], switched to DRV/r 800/100 mg once daily, either as monotherapy (n = 127) or with two nucleoside reverse transcriptase inhibitors (NRTIs) (n = 129). Treatment failure was defined as two consecutive HIV RNA levels above 50 copies/ml (TLOVR) by week 48, or switches off study treatment. The trial had 80% power to show noninferiority for the monotherapy arm (delta = -12%).

RESULTS

Patients were 81% male and 91% Caucasian, with mean age 44 years, and CD4 cell count of 574 cells/microl. In the primary efficacy analysis, HIV RNA less than 50 copies/ml by week 48 (per protocol) was 86.2 versus 87.8% in the monotherapy and triple therapy arms; by intent-to-treat switch equals failure, efficacy was 84.3 versus 85.3%; by a switch-included analysis, efficacy was 93.5 versus 95.1%: all three comparisons showed noninferior efficacy for DRV/r monotherapy. CD4 cell counts remained stable during the trial in both arms. One patient per arm showed at least one protease inhibitor mutation, and one patient in the triple therapy arm showed an NRTI mutation. Nine patients per arm discontinued randomized treatment for either adverse events or other reasons. No new or unexpected safety signals were detected.

CONCLUSIONS

In this study for patients with HIV RNA less than 50 copies/ml on other antiretrovirals at baseline, switching to DRV/r monotherapy showed noninferior efficacy versus triple antiretroviral therapy.

Economic efficiency of genetic screening to inform the use of abacavir sulfate in the treatment of HIV

BACKGROUND

Abacavir sulfate (abacavir) is associated with a hypersensitivity reaction (HSR) that affects 5-8% of patients. While serious complications are rare, failure to identify it, or abacavir re-challenge following HSR, can be fatal. Genetic screening for HLA-B*5701 can identify patients who are likely to experience an HSR and reduces the incidence of the reaction.

OBJECTIVE

We assessed the intrinsic and practical value, from the US healthcare system perspective, of prospective HLA-B*5701 screening among a population of antiretroviral-naive patients without elevated risk factors for cardiovascular disease, plasma HIV RNA >100,000 copies/mL, or pre-existing renal insufficiency.

METHODS

Two approaches were used to evaluate the costs and benefits of prospective screening. First, the efficiency of HLA-B*5701 screening compared with no screening prior to abacavir initiation (intrinsic value of screening) was evaluated using a 60-day decision-tree model. Next, the practical value of screening was assessed using a lifetime discrete-event simulation model that compared HLA-B*5701 screening prior to abacavir use versus initiation with a tenofovir-containing regimen. Screening-effectiveness parameters were taken from an open-label trial that incorporated screening prior to abacavir initiation and other published studies. Treatment efficacy was derived from clinical trials. Modelling assumptions, costs ($US, year 2007 values) and other parameters were derived from published sources, primary data analysis and expert opinion. Multiple one-way sensitivity and scenario analyses were performed to assess parameter uncertainty. The primary outcome measure for the short-term screening versus no screening analysis was cost per patient. For the long-term analysis, outcomes were presented as QALYs. Costs and effects were discounted at 3% per year.

RESULTS

Over the first 60 days of treatment, prospective screening prior to abacavir initiation cost an additional $US17 per patient and avoided 537 HSRs per 10,000 patients. The per-patient cost of screening was sensitive to the cost of the genetic test, HSR costs and screening performance. In the lifetime model, screening-informed abacavir use was more effective and less costly than initiation with a tenofovir-containing regimen in the base case and in sensitivity analyses.

CONCLUSIONS

Our results suggest that prospective HLA-B*5701 screening prior to abacavir initiation produces cost savings and should become a standard component of HIV care.

Treatment outcomes and plasma level of ritonavir-boosted lopinavir monotherapy among HIV-infected patients who had NRTI and NNRTI failure

BACKGROUND

Different strategies of ritonavir-boosted lopinavir monotherapy have been explored; however, data regarding salvage therapy among HIV-infected patients who failed nucleoside reverse transcriptase inhibitor (NRTI) and non-nucleoside reverse transcriptase inhibitor (NNRTI) is still limited.

METHODS

A prospective study was conducted among HIV-infected patients who failed NNRTI-based antiretroviral therapy with M184V, TAMs, and NNRTI mutations, and were naïve to protease inhibitor. LPV/r at 400/100 mg and lamivudine 150 mg were given twice daily. CD4 and HIV-1 RNA were monitored at week 0, 12, 24, and 48. LPV Cmin was assayed for the first 14 patients using HPLC.

RESULTS

There were 40 patients with a mean age of 37 years and 70% were male. Median (IQR) baseline CD4 was 123 (37-245) cells/mm(3) and median (IQR) HIV-1 RNA was 55,800 (9,670-100,000) copies/mL. By intend-to-treat analysis, 30 (75%) and 24 (60%) patients achieved HIV-1 RNA at <400 and <50 copies/mL, respectively. In as-treated analysis, the corresponding rates were 29 (83%) and 23 (67%), respectively. Low-level viral rebound was found in 6 (15%) patients at week 48. Medians CD4 at week 12, 24, 36 and 48 were 249, 283, 307, and 351 cells/mm(3) and significantly changed from baseline (all, P < 0.05). At 6 and 12 weeks, median (min-max) LPV Cmin was 6.52 (1.62-11.64) mg/L and 5.79 (0.75-16.31) mg/L, respectively. There were increments of mean total cholesterol and triglyceride at 48 weeks from baseline (P < 0.05).

CONCLUSION

LPV/r monotherapy with recycled lamivudine can maintain virological suppression in a substantial proportion of patients failing NNRTI-based regimen and provides adequate plasma concentrations of LPV although the incidence of low-level viremia is relatively high.

Protease inhibitor therapy in resource-limited settings

PURPOSE OF REVIEW

The use of protease inhibitors in resource-limited settings will increase in coming years as HIV treatment cohorts mature. We review data available to guide the expanded use of protease inhibitors in these settings.

RECENT FINDINGS

The safety and effectiveness of protease inhibitors may be affected by the context of their use, yet limited data exist regarding the use of these agents in resource-limited settings in either first or subsequent regimens. Critically, data are needed regarding optimal regimens at time of first-line nonnucleoside reverse transcriptase inhibitor-based regimen failure. A number of alternative strategies are being investigated, including dual-boosting, monotherapy and dose reduction. Despite recent progress cost, storage requirements, drug interactions and formulation continue to hinder the use of protease inhibitors, particularly for children.

SUMMARY

Protease inhibitors are the core component of second-line therapy in resource-limited settings and are used in specific situations in first-line therapy. Use of second-line regimens has been more diverse than first line, but WHO has recently prioritized regimens containing lopinavir/ritonavir or ritonavir-boosted atazanavir. As use of protease inhibitors in resource-limited settings increases evidence needs to be accrued to guide further expanded use.

HIV protease inhibitors: recent clinical trials and recommendations on use

BACKGROUND

HIV protease inhibitors (PIs) are potent antiretroviral drugs that represent a pivotal component of highly active antiretroviral therapy (HAART). PIs have evolved over the years to gain in potency, convenience, tolerability and genetic barrier to resistance.

OBJECTIVE

Updated summary of evidence-based information about the efficacy and safety of PIs on initial, simplification and rescue interventions in HIV patients.

METHODS

Review of available data reported in peer-reviewed journals, medical conferences and treatment guidelines.

RESULTS

Due to their characteristics, PIs are, and will remain, a cornerstone component in most lines of antiretroviral therapy. The antiviral activity, tolerability and convenience of PIs have improved significantly in recent years. Differences between compounds within this class may favour their use in specific situations, such as the friendly metabolic profile of atazanavir in patients with cardiovascular disease or the high genetic barrier of darunavir or tipranavir in heavily pretreated individuals with HIV.

The risk of virologic failure decreases with duration of HIV suppression, at greater than 50% adherence to antiretroviral therapy

Background

We hypothesized that the percent adherence to antiretroviral therapy necessary to maintain HIV suppression would decrease with longer duration of viral suppression.

Methodology

Eligible participants were identified from the REACH cohort of marginally housed HIV infected adults in San Francisco. Adherence to antiretroviral therapy was measured through pill counts obtained at unannounced visits by research staff to each participant's usual place of residence. Marginal structural models and targeted maximum likelihood estimation methodologies were used to determine the effect of adherence to antiretroviral therapy on the probability of virologic failure during early and late viral suppression.

Principal Findings

A total of 221 subjects were studied (median age 44.1 years; median CD4+ T cell nadir 206 cells/mm³). Most subjects were taking the following types of antiretroviral regimens: non-nucleoside reverse transcriptase inhibitor based (37%), ritonavir boosted protease inhibitor based (28%), or unboosted protease inhibitor based (25%). Comparing the probability of failure just after achieving suppression vs. after 12 consecutive months of suppression, there was a statistically significant decrease in the probability of virologic failure for each range of adherence proportions we considered, as long as adherence was greater than 50%. The estimated risk difference, comparing the probability of virologic failure after 1 month vs. after 12 months of continuous viral suppression was 0.47 (95% CI 0.23–0.63) at 50–74% adherence, 0.29 (CI 0.03–0.50) at 75–89% adherence, and 0.36 (CI 0.23–0.48) at 90–100% adherence.

Conclusions

The risk of virologic failure for adherence greater than 50% declines with longer duration of continuous suppression. While high adherence is required to maximize the probability of durable viral suppression, the range of adherence capable of sustaining viral suppression is wider after prolonged periods of viral suppression.

[Lopinavir/ritonavir monotherapy as a simplification strategy in the treatment of HIV-1 infection]

Simplification of triple antiretroviral therapy to lopinavir/ritonavir (LPV/r) monotherapy in patients with well-controlled viremia for prolonged periods (more than 6 months) without prior failure with a protease inhibitor has been proposed as a strategy that could reduce the toxicity and costs of antiretroviral therapy in the long term while also preserving other therapeutic options. The results of several studies are currently available, some of which had a large number of patients and follow-up of up to 4 years. These studies indicate that this strategy is safe and efficacious, thus allowing its clinical use when indicated. This strategy may be especially useful in reducing the costs of treatment in countries with scarce economic resources. The role of LPV/r monotherapy in the prevention and management of lipodystrophy and in improving the selection of patients with an optimal risk-benefit ratio remains to be defined.

[Lopinavir/ritonavir monotherapy. Possible indications]

Monotherapy with LPV/r maintains blocked viral replication when used as a simplification strategy from antiretroviral therapy with a boosted protease inhibitor and two nucleoside analogs in patients with an undetectable viral load for at least 6 months. This simplification strategy can be recommended to patients in these circumstances and who are able to maintain near perfect adherence. As recommended by the GESIDA guidelines, LPV/r monotherapy could be offered to patients with undetectable viral loads but who show symptoms or laboratory abnormalities attributable to nucleoside analog toxicity, or co-morbidities such as liver disease or nephropathy; LPV/r monotherapy could also be offered to patients who simply wish to take a lower number of pills. This strategy reduces treatment toxicity and costs, without jeopardizing the patient's future.

[Prognostic factors of virological response in patients treated with lopinavir/ritonavir monotherapy]

Nine clinical trials have analyzed whether the use of lopinavir-ritonavir (LPV/r) monotherapy could be a valid alternative to triple antiretroviral therapy. Four of these clinical trials included an analysis of risk factors for virological failure. The MONARK study evaluated monotherapy in treatment-naïve patients. The M03-613 trial evaluated monotherapy after a period of induction therapy with triple combination antiretroviral therapy. The study by Sprinz et al and the OK studies evaluated monotherapy as maintenance of virological suppression. The efficacy of monotherapy varied according to the scenario. In the scenario of induction-maintenance, the factors related to virological failure were suboptimal adherence and low baseline CD4 counts. In the scenario of maintenance, the factors related to virological failure were suboptimal adherence, nadir CD4 count and low hemoglobin. In treatment-naive patients, the risk of virological failure increased in patients who did not achieve a viral load of less than 400 copies/ml 4 weeks after initiating treatment and in those infected with non-B subtypes (a factor that was probably also related to suboptimal adherence).

[Lopinavir/ritonavir monotherapy for the treatment of HIV-1 infection: the emergence of resistance]

Treatment with lopinavir/ritonavir (LPV/r) monotherapy has been shown to be an effective alternative, especially in the maintenance of patients previously treated with combination therapy and prolonged virological suppression. LPV/r monotherapy is associated with a greater number of low-level viremia episodes than combination therapy, without resistance mutations being detected in the majority of patients. The incidence of the development of major resistance mutations in the OK pilot and OK04 studies was very low: 0.51 per 100 patients-year, and was mainly related to mutations in positions 46, 54 and 82, which have not compromised other therapeutic options. The contribution of low-level resistance mutations to loss of virological control seems small, and no different from that observed in combination therapy. However, this phenomenon should be studied in larger, long-term trials.

[Monotherapy in treatment-naïve patients]

The development of antiretroviral therapy (ART) with current triple drug combinations has dramatically reduced morbidity and mortality in HIV-infected patients. However, there is a need for less toxic treatments without sacrificing efficacy, as well as for less expensive drugs to facilitate universal access to this therapy. The protease inhibitors (PI) administered with ritonavir have a favorable pharmacokinetic profile and high genetic barrier and consequently are ideal candidates for use in monotherapy, thus avoiding the toxicity and cost associated with nucleoside analogs, as well as preserving drugs for future options. The promising results of studies performed with lopinavir/ritonavir (LPV/r) in induction-maintenance regimens in patients without prior failure to PIs encourage research into the cost-effectiveness of LPV/r in monotherapy from the beginning of ART. The few studies performed in this context seem to indicate the following: a) LPV/r monotherapy achieves undetectable viral loads in a large proportion of treatment-naïve patients, b) future treatment options are not compromised in patients not achieving undetectable viral loads since the likelihood of resistance mutations is low and treatment intensification achieves suppression of viral replication, and c) strategies for early detection can probably be considered in patients who will not achieve complete suppression with LPV/r monotherapy. Nevertheless, before LPV/r monotherapy can be considered a first-line option, new studies with larger samples and longer follow-up are required. These studies should pay particular attention to viral replication in areas where PI show less penetration.

Protease inhibitor resistance analysis in the MONARK trial comparing first-line lopinavir-ritonavir monotherapy to lopinavir-ritonavir plus zidovudine and lamivudine triple therapy

The MONARK study was a pilot randomized trial comparing the safety and efficacy of lopinavir-ritonavir (LPV/r) monotherapy to those of LPV/r-zidovudine-lamivudine triple therapy for antiretroviral-naïve human immunodeficiency virus type 1 (HIV-1)-infected patients. Resistance testing was performed at the time of initial screening and at the time of virological failure (defined to include low-level viremia with >50 and <400 HIV-1 virus RNA copies/ml of plasma). Changes from the baseline sequences, including mutations noted on the 2008 International AIDS Society-USA list of resistance-associated protease mutations, were considered. Drug resistance testing was performed for 38 patients (5 of 53 on triple therapy and 33 of 83 on monotherapy). By week 96 (W96), virus samples from 18 of 33 patients in the monotherapy arm showed changes from baseline sequences, and 5 of these patients had viruses with major protease inhibitor (PI) resistance-associated mutations (M46I at W40, L76V at W48, M46I and L76V at W48, L10F and V82A at W72, and L76V at W84). Data on virus phenotypes detected at the time of initial screening and the time of virological failure were available for four patients in whom major PI resistance mutations developed, and these data revealed a mean increase of 2.2-fold (range, 0.75- to 4.6-fold) in the LPV 50% inhibitory concentration. All three patients in whom the L76V PI resistance mutation developed were infected with HIV-1 subtype CRF02_AG. In the triple-therapy group, no major PI resistance mutation was selected among the three patients with protease changes by W48. No association between the baseline CD4 cell count and the viral load, the W4 and final viral loads, or the final LPV trough concentration and the emergence of a major PI resistance mutation was found. Major PI resistance-associated mutations were detected in 5 (6%) of 83 patients treated with LPV/r monotherapy, suggesting that LPV/r monotherapy is an inappropriate first option. The mutation L76V may be considered in further studies of lopinavir resistance.

Good response to lopinavir/ritonavir-containing antiretroviral regimens in antiretroviral-naive HIV-2-infected patients

In 29 antiretroviral-naive HIV-2-infected patients starting lopinavir/ritonavir-containing regimen, the median CD4 cell count change from baseline (142 cells/microl) was +71 cells/microl at week 24 and +132 cells/microl at week 96. Seventeen (59%) patients had a CD4 cell count increase of at least 50 cells/microl and undetectable HIV-2 RNA at week 24 and were considered as responders to treatment. This sustained elevation of CD4 cell count in the first 2 years of combination antiretroviral therapy shows the potential for lopinavir/ritonavir regimens as first-line therapy in HIV-2 infection.

Efficacy and safety of ritonavir-boosted dual protease inhibitor therapy in antiretroviral-naive HIV-1-infected patients: the 2IP ANRS 127 study

OBJECTIVES

We evaluate the efficacy and tolerability of ritonavir-boosted dual protease inhibitor as a nucleoside reverse transcriptase inhibitor-sparing regimen in a prospective open-label randomized pilot trial in antiretroviral-naive patients.

METHODS

Thirty patients received fosamprenavir/atazanavir/ritonavir (Group 1) and 31 patients received saquinavir/atazanavir/ritonavir (Group 2). The primary endpoint for efficacy was the rate of early virological success, defined as plasma viral load <50 copies/mL at week 16. The study is registered with ClinicalTrials.gov (NCT00122603).

RESULTS

At baseline, median (range) viral load was 4.8 log(10) copies/mL (4.0-5.7) and the median CD4 cell count was 271/mm(3) (197-740). Viral load was <50 copies/mL in 12/30 patients [40%, 95% confidence interval (CI) 23%-58%] and 13/31 patients (42%, 95% CI 25%-59%) at week 16 in Groups 1 and 2, respectively. Patients with failing regimens (viral load >or=400 copies/mL at week 16 or >or=50 copies/mL at week 24) were switched to a standard antiretroviral regimen. At week 48, by an intention-to-treat analysis, 23/30 patients (77%) and 26/31 patients (84%) had plasma HIV-1 RNA <50 copies/mL in Groups 1 and 2, respectively. Four patients discontinued treatment for adverse events, all before week 4. No major changes in the protease gene were detected at treatment failure relative to baseline. Baseline viral load <50 000 copies/mL was the only predictor of virological success at week 16.

CONCLUSIONS

Ritonavir-boosted dual protease inhibitor regimens targeting only one step of viral replication were insufficient to rapidly suppress plasma HIV RNA to <50 copies/mL in antiretroviral-naive patients with high viral load at baseline.

Seven-Year Follow-Up on Lopinavir/ Ritonavir Monotherapy

Previous studies of lopinavir/ritonavir (LPV/r) monotherapy have shown that over 70% of patients achieved HIV RNA levels <500 copies/mL over a follow-up period of 48 to 96 weeks, but the long-term durability is undetermined. Herein, the authors report 2 patients that started LPV/r monotherapy after virologic failure on an NNRTIbased regimen and have been successfully treated for greater than 7 years. Both patients demonstrated long-term control of viral replication over the course of treatment, although the first patient had 3 viral load blips and the second had 1 blip under 400 copies/mL. Both patients had increases in CD4+ lymphocyte counts. The first patient from 96 cells/μL to 378 cells/μL and the second patient from 71 cells/μL to 411 cells/μL. To the authors knowledge, these 2 cases represent the longest experience with LPV/r monotherapy and provide some measure of reassurance about the durability of LPV/r for control of HIV replication.

Timing the emergence of resistance to anti-HIV drugs with large genetic barriers

New antiretroviral drugs that offer large genetic barriers to resistance, such as the recently approved inhibitors of HIV-1 protease, tipranavir and darunavir, present promising weapons to avert the failure of current therapies for HIV infection. Optimal treatment strategies with the new drugs, however, are yet to be established. A key limitation is the poor understanding of the process by which HIV surmounts large genetic barriers to resistance. Extant models of HIV dynamics are predicated on the predominance of deterministic forces underlying the emergence of resistant genomes. In contrast, stochastic forces may dominate, especially when the genetic barrier is large, and delay the emergence of resistant genomes. We develop a mathematical model of HIV dynamics under the influence of an antiretroviral drug to predict the waiting time for the emergence of genomes that carry the requisite mutations to overcome the genetic barrier of the drug. We apply our model to describe the development of resistance to tipranavir in in vitro serial passage experiments. Model predictions of the times of emergence of different mutant genomes with increasing resistance to tipranavir are in quantitative agreement with experiments, indicating that our model captures the dynamics of the development of resistance to antiretroviral drugs accurately. Further, model predictions provide insights into the influence of underlying evolutionary processes such as recombination on the development of resistance, and suggest guidelines for drug design: drugs that offer large genetic barriers to resistance with resistance sites tightly localized on the viral genome and exhibiting positive epistatic interactions maximally inhibit the emergence of resistant genomes.

Predictors of loss of virologic response in subjects who simplified to lopinavir/ritonavir monotherapy from lopinavir/ritonavir plus zidovudine/lamivudine

Previous studies have demonstrated that lopinavir/ritonavir monotherapy maintained plasma HIV-1 RNA suppression in a large proportion of antiretroviral naive subjects. However, more subjects receiving lopinavir/ritonavir monotherapy experienced confirmed virologic rebound >50 copies/ml compared to a standard three-drug HAART regimen. In this study, we sought to determine the factors associated with maintenance of virologic suppression in subjects receiving lopinavir/ritonavir monotherapy. Antiretroviral-naive HIV-1-infected volunteers were randomized 2:1 to initiate a lopinavir/ritonavir-based combination regimen followed by simplification to lopinavir/ritonavir monotherapy or an efavirenz-based triple combination therapy and followed for 96 weeks. Potential predictors of time to loss of virologic response included baseline demographics, baseline HIV-1 RNA levels, baseline CD4(+) T cell counts, adherence as determined by 4-day subject recall, duration of HIV-1 RNA <50 copies/ml prior to simplification, and lopinavir concentrations. By the Cox proportional hazards model, higher reported adherence levels and higher baseline CD4(+) T cell counts were associated with a greater likelihood of maintaining virologic suppression while receiving lopinavir/ritonavir monotherapy. Lopinavir concentrations, including trough concentrations, were not significantly associated with virologic outcomes. This analysis suggests that adherence and higher baseline CD4(+) T cell counts may help to predict who will sustain virologic suppression with lopinavir/ritonavir monotherapy. The data also suggest that measuring lopinavir concentrations is not useful in predicting virologic response in these patients.

[Darunavir as first-line therapy. The TITAN study]

Lopinavir/ritonavir (LPV/r) has been the gold standard in first line rescue treatment for many years. No other boosted protease inhibitor (PI/r) has managed to demonstrate that it is superior to LPV/r. In this regard, the TITAN study compared the efficacy and safety of darunavir (DRV/r) in 595 patients, at a dose of 600/100 mg two times a day against the normal LPV/r dose, combined with at least 2 other optimised antiretroviral drugs. The efficacy of the treatment at 48 weeks (VL<400 copies/mL) was significantly higher in the DRV/r goup compared to the LPV/r group, both in the analysis by protocol (77% vs. 68%), the non-inferiority of DRV/r being demonstrated (estimated difference +9%, 95% CI 2-16), and by intention to treat (77% vs. 67%), the superiority of DRV/r being demonstrated (estimated difference 10%, 95% CI 2-17%). The incidence of diarrhoea and increase in triglycerides was higher in the LPV/r group. The differences in efficacy of both treatments in favour of DRV/r started to be seen from a basal primary mutation in the protease, with these differences increasing as the number of these mutations increased. In patients with virological failure, DRV/r protected the protease and reverse transcriptase against mutations, thus preserving future therapeutic options. We have some theoretical and clinical data available that enables us to consider the possibility of administering DRV/r once a day in some patients with a few mutations in the protease and in those where this dosing regime is considered important. With the results of the TITAN study, DRV/r must be considered the new gold standard in first line rescue, at least in those patients with a primary mutation in the protease.