Atazanavir plus ritonavir or saquinavir, and lopinavir/ritonavir in patients experiencing multiple virological failures

Comparison of Markov model and discrete-event simulation techniques for HIV

BACKGROUND

Markov models have been the standard framework for predicting long-term clinical and economic outcomes using the surrogate marker endpoints from clinical trials. However, they are complex, have intensive data requirements and are often difficult for decision makers to understand. Recent developments in modelling software have made it possible to use discrete-event simulation (DES) to model outcomes in HIV. Using published results from 48-week trial data as model inputs, Markov model and DES modelling approaches were compared in terms of clinical outcomes at 5 years and lifetime cost-effectiveness estimates.

METHODS

A randomly selected cohort of 100 antiretroviral-naive patients with a mean baseline CD4+ T-cell count of 175 cells/mm3 treated with lopinavir/ritonavir was selected from Abbott study M97-720. Parameter estimates from this cohort were used to populate both a Markov and a DES model, and the long-term estimates for these cohorts were compared. The models were then modified using the relative risk of undetectable viral load as reported for atazanavir and lopinavir/ritonavir in the published BMS 008 study. This allowed us to compare the mean cost effectiveness of the models. The clinical outcomes included mean change in CD4+ T-cell count, and proportion of subjects with plasma HIV-1 RNA (viral load [VL]) <50 copies/mL, VL 50-400 copies/mL and VL >400 copies/mL. US wholesale acquisition costs (year 2007 values) were used in the mean cost-effectiveness analysis, and the cost and QALY data were discounted at 3%.

RESULTS

The results show a slight predictive advantage of the DES model for clinical outcomes. The DES model could capture direct input of CD4+ T-cell count, and proportion of subjects with plasma HIV-1 RNA VL <50 copies/mL, VL 50-400 copies/mL and VL >400 copies/mL over a 48-week period, which the Markov model could not. The DES and Markov model estimates were similar to the actual clinical trial estimates for 1-year clinical results; however, the DES model predicted more detailed outcomes and had slightly better long-term (5-year) predictive validity than the Markov model. Similar cost estimates were derived from the Markov model and the DES. Both models predict cost savings at 5 and 10 years, and over a lifetime for the lopinavir/ritonavir treatment regimen as compared with an atazanavir regimen.

CONCLUSION

The DES model predicts the course of a disease naturally, with few restrictions. This may give the model superior face validity with decision makers. Furthermore, this model automatically provides a probabilistic sensitivity analysis, which is cumbersome to perform with a Markov model. DES models allow inclusion of more variables without aggregation, which may improve model precision. The capacity of DES for additional data capture helps explain why this model consistently predicts better survival and thus greater savings than the Markov model. The DES model is better than the Markov model in isolating long-term implications of small but important differences in crucial input data.

[Utility of atazanavir in special populations]

ART (antiretroviral therapy) currently continues to indefinitely prolong the survival of patients who live with HIV. Due to this, we are increasingly faced with specific problems that previously did not have time to develop or did not have the importance that they have now, and which are related to the existence of special patient populations. Examples of situations that characterise these special populations are: co-infection with hepatitis virus B and/or C, pregnancy, lipodystrophy, cardiovascular risk, renal failure, treatment of children and adolescents, immigrant health care, and the management of patients receiving methadone replacement therapy, among others. In this article we review the role that Atazanavir (ATV) can play in the ART of patients in the situations mentioned, except those that are already dealt with specifically in other articles, such as co-infection by hepatitis virus B and/or C.

[Viral resistance and genetic barrier of atazanavir]

Resistance to protease inhibitors (PI) is generally due to a mutation in the protease gene. Different changes have been described for each PI. The I 50L mutation is characteristic of resistance to atazanavir (ATV). It does not produce cross resistance to other PI; but it does increase susceptibility to all of them (hypersusceptibility). When PI are given concomitantly with low doses of ritonavir, the exposure to higher levels of PI requires that multiple resistance mutations have to be selected in the protease so that there is a significant loss of susceptibility. For the majority of PI/r, including ATV/r, >or=5 mutations in the protease are required to produce a compromise in the virological response. Despite having a moderate genetic barrier when not boosted with ritonavir, the prolonged half life of ATV minimises the risk of resistance in clinical practice.

[Efficacy of atazanavir in treatment-naive patients]

The characteristics of atazanavir (convenient doses, good tolerance, and excellent lipid profile) makes it an attractive drug to be included in initial regimes. Clinical trials have been performed on patients with no previous antiretroviral treatment, either atazanavir without boost (400 mg once per day) or atazanavir boosted with ritonavir (400/100 mg). Although atazanavir without boost is effective, there is a tendency for a higher number of failures and a higher development of resistant mutations than in patients who fail with boosted atazanavir. Therefore, it is recommended to use boosted atazanavir in patients that start on treatment. In clinical studies, boosted atazanavir can be used with any nucleoside analogue. No pharmacokinetic or pharmacodynamic interaction problems have been detected with the two nucleoside combinations at fixed doses (tenofovir/FTC, abacavir/3TC). Randomised clinical studies have been carried out that compared atazanavir with other boosted protease inhibitors. In the comparative study with lopinavir/ritonavir administered two times a day, atazanavir/ritonavir once per day demonstrated noninferiority, with a similar efficacy regardless of the patient baseline viral load. The atazanavir/ritonavir virological efficacy did not appear to be affected by the baseline immunological status of the patients, which did influence the lopinavir/ritonavir response. Atazanavir/ritonavir is a useful drug combination in the initial treatment of HIV infected adult patients. Its increased virological and immunological efficacy, together with its ease of administration, good tolerance and excellent lipid profile makes it a PI of choice in these patients.

Atazanavir: its role in HIV treatment

Azatanavir is a protease inhibitor (PI) approved for the treatment of HIV-1 infection. Atazanavir is a substrate and inhibitor of cytochrome P450 isozyme 3A and an inhibitor and inducer of P-glycoprotein. It has similar virologic efficacy as efavirenz and ritonavir-boosted lopinavir in antiretroviral-naive individuals. Its impact on lipids is less than other PIs and it is suitable for those in whom hyperlipidemia is undesirable. Ritonavir boosting of atazanavir enhances the bioavailability of atazanavir but may result in some elevation of lipids and is recommended for treatment-experienced patients and those receiving efavirenz or tenofovir. Ritonavir-boosted atazanavir has similar antiviral activity as ritonavir-boosted lopinavir in both antiretroviral therapy-naive and -experienced patients. Atazanavir causes unconjugated bilirubinemia in over 40% of patients but results in less than 2% discontinuations. Atazanavir is licensed for once-daily use and atazanavir/ritonavir competes with lopinavir/ritonavir as the most commonly prescribed PI.

Chronic viral hepatitis may diminish the gains of HIV antiretroviral therapy in sub-Saharan Africa

There is a heavy burden of HIV-hepatitis B virus (HBV) and HIV-hepatitis C virus (HCV) co-infection in many regions of the developing world. An often unmentioned illness, issues of poverty, socio-economic status, nutrition, access to medical care, and mistrust of Western-style medicine conspire to reduce the opportunity to receive clinical work-up and treatment for chronic viral hepatitis. We discuss key issues specific to the treatment of viral hepatitis and obstacles to success with this endeavor in the context of HIV co-infection in Africa. We predict that provision of viral hepatitis antiviral therapy will become a more pressing issue as more HIV-infected patients receive lifesaving combination antiretroviral therapy only to succumb thereafter from viral hepatitis-induced liver disease. Given the lessons learned from combination antiretroviral rollout in sub-Saharan Africa, establishing expertise and infrastructure for viral hepatitis care and antiviral therapy is relevant. Failure to act now may diminish the milestones and the gains made with antiretroviral therapy in the developing world.

Atazanavir in patients with persistent viral replication despite HAART: results from the French prospective NADIS cohort

OBJECTIVE

To assess virological efficacy of a ritonavir-boosted atazanavir (ATV/r)-containing regimen in patients with persistent viral replication despite HAART.

PATIENTS AND METHOD

Prospective cohort of French HIV-infected patients. Patients were included if pretreated and viral load (VL) >400 copies/mL at the time of ATV/r first prescription (baseline). Demographic and epidemiologic data, therapeutic history, and clinical and biological values at baseline and during follow-up were analyzed. Primary endpoint was failure of the regimen defined as either VL>400 copies/mL at Week 24 or treatment interruption before Week 24. Multivariate analysis was performed of baseline characteristics related with treatment failure.

RESULTS

There were 424 patients with available data. Primary endpoint was met by 36%: 24% VL>400 copies/mL and 12% treatment interruption. Treatment interruption due to drug-related toxicity was significantly more frequent in women (20.5% vs. 8.8%, p= .001). Female gender (adjusted odds ratio [OR]=1.91), previous use of lopinavir (LPV; OR=2.76), number of new drugs and of active drugs in the regimen (OR=0.48 and 0.3, respectively), and baseline VL (OR=1.75) were independently related with treatment failure.

CONCLUSION

ATV/r-containing regimens, because of low pill burden and good tolerance, can be a useful strategy as long as the patients did not suffer previous LPV failures. The issue of gender deserves further studies in larger populations.

Lopinavir/ritonavir in the treatment of HIV-1 infection: a review

Lopinavir/ritonavir is the first and only coformulated HIV-1 protease inhibitor (PI). Large clinical trials have demonstrated lopinavir/ritonavir's clinical efficacy in both antiretroviral-naïve and -experienced patients. The immunologic and virologic benefits of treatment with this agent have been proven in HIV-infected adults, adolescents, and children. Smaller studies support the use of lopinavir/ritonavir monotherapy as a therapeutic option in certain patients. The drug is characterized by a high genetic barrier to resistance, and appears to be more forgiving of non-adherence than earlier, unboosted PIs. The most frequent side effects observed are diarrhea, nausea, and vomiting. These gastrointestinal adverse effects are generally mild to moderate. Metabolic derangements, including hyperlipidemia and glucose intolerance, have also been observed in lopinavir/ritonavir recipients. As the menu of available antiretroviral agents continues to expand, lopinavir/ritonavir remains a proven and effective drug for the treatment of HIV infection.

Virologic response to lopinavir-ritonavir-based antiretroviral regimens in a multicenter international clinical cohort: comparison of genotypic interpretation scores

Several genotypic interpretation scores have been proposed for the evaluation of susceptibility to lopinavir/ritonavir (LPV/r) but have not been compared using an independent data set. This study was a retrospective multicenter cohort of patients initiating LPV/r-based therapy. The virologic response (VR) was defined as a viral load of <500 copies/ml at week 24. The genotypic interpretation scores surveyed were the LPV mutation score, the ViroLogic score, the ATU score, the Stanford database score, and the International AIDS Society-USA mutation list. Of the 103 patients included in the analysis, 76% achieved VR at 24 weeks. For scores with clinical breakpoints defined (LPV mutation, ATU, ViroLogic, and Stanford), over 80% of the patients below the breakpoints achieved VR, while 50% or less above the breakpoints responded. Protease mutations at positions 10, 54, and 82 and at positions 54, 84, and 90 were associated with a lack of VR in the univariate and multivariate analyses, respectively. The area under the receiver-operator characteristic curves for the five genotypic interpretation scores studied ranged from 0.73 to 0.76. The study confirms that the currently available genotypic interpretation scores which are widely used by clinicians performed similarly well and can be effectively used to predict the virologic activity of LPV/r in treatment-experienced patients.

Long-term pharmacokinetic efficacy and safety of low-dose ritonavir as a booster and atazanavir pharmaceutical formulation based on solid dispersion system in rats

Atazanavir (ATV) is clinically coadministered with low-dose ritonavir (RTV), which boosts the oral bioavailability (BA) of ATV by inhibiting cytochrome P450 (CYP) 3A, and P-glycoprotein (Pgp) via the same metabolic pathway; however, it is well known that in the chronic phase, the inhibition effect of RTV on Pgp and CYP3A becomes an induction effect. In this study, we investigated the long-term efficacy and safety of RTV-boosted ATV in rats with a clinical relevant dosage of ATV and RTV, 7 mg/kg and 2 mg/kg, respectively, and drew a direct comparison with RTV-boosted ATV and the previously reported ATV pharmaceutical formulation based on a solid dispersion system (ATV-SLS SD+G). Rats received RTV-boosted ATV or ATV-SLS SD+G for 14 d in the pharmacokinetic study. In addition, after 14-d repeated administration of each formulation, cyclosporine A (CyA) was administered to rats and Western blot analysis of Pgp and CYP3A was performed to investigate the impact on pharmacokinetic interaction of each ATV formulation. After repeated administration of both formulations, there was no significant difference between ATV pharmacokinetic parameters on day 1 and 14; therefore, it was considered that the long-term efficacy of both ATV formulations was maintained. However, after treatment with RTV-boosted ATV, the Cmax and AUC0-infinity of the following CyA significantly decreased to 49% and 47% in comparison to the control, respectively, and the Pgp expression in the small intestine by Western blot analysis was approximately 2-fold higher than the control, whereas after treatment with ATV pharmaceutical formulation, neither significant alteration of CyA nor notable change in the expression of intestinal Pgp and hepatic CYP3A was observed. Therefore, it was considered that the BA of CyA after treatment with RTV-boosted ATV would decrease by the induction effect of RTV in chronic phase as described above. The results of this study revealed that the chronic use of low-dose RTV as a booster has great potential to compromise drug-drug interactions; therefore, it is recommended that the BA of protease inhibitors be improved by a pharmaceutical approach without pharmacokinetic interaction by RTV.

Experience with tenofovir disoproxil fumarate for antiretroviral therapy

BACKGROUND AND RATIONALE/OBJECTIVE: Tenofovir disoproxil fumarate was approved in the US in 2001 and a few months later by the European Medicines Evaluation Agency for use in the EU, initially for treatment-experienced HIV patients with early virological failure. The following year the HIV indication was expanded to include antiretroviral treatment naïve adults over 18 years of age.

RESULTS AND CONCLUSIONS

Ongoing clinical trials of tenofovir disoproxil fumarate's safety and efficacy have confirmed its position as a long-term, safe, effective and convenient backbone component in combination antiretroviral therapy for HIV-infected patients. With its favourable resistance profile, it is also an option for treatment-experienced patients. This article describes the efficacy and safety of tenofovir disoproxil fumarate from ongoing and recent clinical trials, and key aspects of its broad, clinical experience since its introduction.

Scaling up antiretroviral therapy in South Africa: the impact of speed on survival

BACKGROUND

Only 33% of eligible human immunodeficiency virus (HIV)-infected patients in South Africa receive antiretroviral therapy (ART). We sought to estimate the impact of alternative ART scale-up scenarios on patient outcomes from 2007-2012.

METHODS

Using a simulation model of HIV infection with South African data, we projected HIV-associated mortality with and without effective ART for an adult cohort in need of therapy (2007) and for adults who became eligible for treatment (2008-2012). We compared 5 scale-up scenarios: (1) zero growth, with a total of 100,000 new treatment slots; (2) constant growth, with 600,000; (3) moderate growth, with 2.1 million; (4) rapid growth, with 2.4 million); and (5) full capacity, with 3.2 million.

RESULTS

Our projections showed that by 2011, the rapid growth scenario fully met the South African need for ART; by 2012, the moderate scenario met 97% of the need, but the zero and constant growth scenarios met only 28% and 52% of the need, respectively. The latter scenarios resulted in 364,000 and 831,000 people alive and on ART in 2012. From 2007 to 2012, cumulative deaths in South Africa ranged from 2.5 million under the zero growth scenario to 1.2 million under the rapid growth scenario.

CONCLUSIONS

Alternative ART scale-up scenarios in South Africa will lead to differences in the death rate that amount to more than 1.2 million deaths by 2012. More rapid scale-up remains critically important.

Seven-year efficacy of a lopinavir/ritonavir-based regimen in antiretroviral-naïve HIV-1-infected patients

OBJECTIVE

Evaluate efficacy and tolerability of lopinavir/ritonavir (LPV/r) plus stavudine and lamivudine long term in antiretroviral-naïve patients.

DESIGN

Open-label follow-up of prospective, randomized, multicenter trial.

METHOD

Antiretroviral-naïve HIV-infected subjects (N = 00) received of 3 doses of LPV/r plus stavudine and lamivudine for 48 weeks then received LPV/r soft-gel capsules 400/00 mg plus stavudine and lamivudine. After 6 years, subjects replaced stavudine with tenofovir.

RESULTS

At 7 years, by intent-to-treat analysis, 61 % had plasma HIV-RNA <400 copies/mL and 59% had < 50 copies/mL. Thirty-nine subjects discontinued treatment due to adverse events (n = 6), personal/other reasons (0), loss to follow-up (9), and noncompliance (4). Among 28 subjects qualifying for drug resistance testing, no protease inhibitor or stavudine resistance was observed and 4 showed lamivudine resistance. Most common drug-related moderate or severe adverse events were diarrhea (28%), nausea (6%), and abdominal pain (11 %). Subjects who received stavudine (median 6.6 years) and switched to tenofovir demonstrated significant improvements in total cholesterol (p = .009), triglycerides (p = .023), apolipoprotein C-III (p < .001 ), adiponectin (p = .008), fasting insulin (p = .04), and leptin (p = .03).

CONCLUSION

LPV/r-based therapy demonstrated sustained efficacy with no protease inhibitor or stavudine resistance through 7 years in antiretroviral-naïve patients. Switching from stavudine to tenofovir resulted in significant improvements in multiple metabolic parameters.

Interruption of antiretroviral therapy and risk of cardiovascular disease in persons with HIV-1 infection: exploratory analyses from the SMART trial

BACKGROUND

The SMART trial found a raised risk of cardiovascular disease (CVD) events in patients undergoing CD4+ T cell-count guided intermittent antiretroviral therapy (ART) compared with patients on continuous ART. Exploratory analyses were performed to better understand the reasons for this observation.

METHODS

A total of 5,472 patients with CD4+ T-cell counts >350 cells/mm3 were recruited and randomized to either continuous ART (the viral suppression arm; VS) or CD4+ T-cell count-guided use of ART (the drug conservation arm; DC).

RESULTS

Major CVD events developed in 79 patients. The hazard ratio (HR) for risk of CVD events for DC versus VS was 1.57 (95% confidence interval 1.00-2.46; P=0.05). There was no evidence that being off ART or a higher current HIV viral load were associated with increased CVD risk. Total cholesterol and low-density lipoprotein cholesterol were reduced as a result of ART interruption in DC patients but so was high-density lipoprotein (HDL) cholesterol, leading to a net unfavourable change in the total/HDL cholesterol ratio.

CONCLUSIONS

Reasons for the higher risk of CVD for DC compared with VS patients remain unclear. There was no clear evidence to suggest that ART interruption per se or a higher HIV viral load were associated with an increased CVD risk in the DC group. Lipid changes were less favourable among DC compared with VS patients, which could offer a partial explanation.

Viro-immunologic response to ritonavir-boosted or unboosted atazanavir in a large cohort of multiply treated patients: the CARe Study

Currently, comparative data able to define the potency of boosted versus unboosted atazanavir in highly pretreated HIV-infected patients are limited. Specifically, in clinical practice it is very important to establish whether atazanavir-boosting with ritonavir warrants potency and efficacy that overcome the profile of unboosted drug. For this reason, our goal was to evaluate viro-immunologic determinants of response to atazanavir, in unboosted ATV400 or boosted ATV300/r formulation, from baseline to week 48 in highly pretreated HIV-infected patients enrolled in a prospective observational Italian study. Data from 354 patients included in an atazanavir "Early Access Program" (AI424-900) with baseline viremia 500 copies per milliliter or more and with an available virologic follow-up were examined using as-treated analysis. Of these, 200 (56.5%) and 154 (43.5%), respectively, received regimens containing ATV300/r or ATV400. Virologic success (VS) was defined as reaching viremia of less than 500 copies per milliliter during follow-up. Estimated median time to VS was 8 weeks in the ATV300/r group and 13 weeks in the ATV400 group. Proportion of patients achieving VS was higher in the ATV300/r group than in ATV400 group at week 12 (66% versus 47%), as well as at week 48 (86% versus 64%). At multivariate Cox regression, receiving ATV300/r dosing was independently associated with increased probability of achieving VS [adjusted hazard ratio (AHR): 1.57; 95% confidence interval (CI): 1.19-2.06]. Conversely, CDC stage C, higher baseline viral load, and more experience with protease inhibitors (PIs) were associated with poorer virologic response. In an unselected population of highly pretreated HIV-infected individuals, receiving atazanavir as part of antiretroviral regimen results in effective virologic response and immunologic recovery. The antiviral efficacy of atazanavir is greater when boosted with low-dose ritonavir.

Darunavir: a nonpeptidic antiretroviral protease inhibitor

BACKGROUND

Protease inhibitors were a major therapeutic breakthrough in the mid-1990s for the treatment of HIV infection, which resulted in improved life expectancy for patients who had failed previous therapies. With time and evolution of the virus, however, there is a new population of patients with treatment-resistant disease and few treatment options. Darunavir is a synthetic nonpeptidic analogue of amprenavir with enhanced activity against resistant virus that became available in 2006.

OBJECTIVES

The purpose of this review was to describe the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, and clinical efficacy of darunavir. Also discussed are the published clinical experience with darunavir, its adverse events, drug interactions, pharmacoeconomics, and dosing and administration.

METHODS

A MEDLINE and EMBASE search (English-language only) was performed from January 1996 through April 2007 using the key words darunavir and TMC114. Abstracts from relevant scientific meetings were searched for the years 2000 through 2007. Additionally, the US Food and Drug Administration Web site was accessed to review the new drug application summary and data presented therein.

RESULTS

Darunavir was found to maintain antiretroviral activity against HIV with protease inhibitor mutations in 6 studies. Clinical efficacy and safety data are limited to 4 controlled and 2 uncontrolled trials. In 2 large Phase IIb clinical studies, viral suppression at 48 weeks to undetectable levels in heavily pretreated patients was achieved in 45% of patients compared with 10% of patients in the control group (P < 0.001). The addition of enfuvirtide enhanced this response rate to 58% compared with 11% of the patients who did not receive enfuvirtide (P < 0.001). Gastrointestinal symptoms, nausea, and headache were the most commonly reported events.

CONCLUSIONS

Darunavir has improved activity against resistant HIV isolates in patients with few treatment choices, particularly when enfuvirtide is added. The safety profile of darunavir is comparable to other protease inhibitors based on early data.

The cost-effectiveness of antiretroviral therapy for treating HIV disease in the Caribbean

BACKGROUND

Antiretroviral therapy (ART) recently became available in the Organization of Eastern Caribbean States (OECS). Survival benefits and budgetary implications associated with universal access to ART have not been examined in the Caribbean.

METHODS

Using a state-transition simulation model of HIV with regional data, we projected survival, cost, and cost-effectiveness of treating an HIV-infected cohort. We examined 1 or 2 ART regimens and cotrimoxazole. In sensitivity analysis, we varied HIV natural history and ART efficacy, cost, and switching criteria.

RESULTS

Without treatment, mean survival was 2.30 years (mean baseline CD4 count = 288 cells/microL). One ART regimen with cotrimoxazole when the CD4 count was <350 cells/microL provided an additional 5.86 years of survival benefit compared with no treatment; the incremental cost-effectiveness ratio was $690 per year of life saved (YLS). A second regimen added 1.04 years of survival benefit; the incremental cost-effectiveness ratio was $10,960 per YLS compared with 1 regimen. Results were highly dependent on second-line ART costs. Per-person lifetime costs decreased from $17,020 to $9290 if second-line ART costs decreased to those available internationally, yielding approximately $8 million total savings.

CONCLUSIONS

In the OECS, ART is cost-effective by international standards. Reducing second-line ART costs increases cost-effectiveness and affordability. Current funding supports implementing universal access regionally over the next year, but additional funding is required to sustain lifetime care for currently infected persons.

Potential risks and benefits of HIV treatment simplification: a simulation model of a proposed clinical trial

BACKGROUND

In recent studies, subjects who had achieved suppression of the human immunodeficiency virus (HIV) RNA level while receiving an initial 3-drug antiretroviral regimen successfully maintained suppression while receiving treatment with a "boosted" protease inhibitor (PI) alone. We projected the long-term outcomes of this treatment simplification strategy to inform the design of a proposed multicenter, randomized clinical trial.

METHODS

We used published studies to estimate the efficacy, adverse effects, and cost of a sequence of HIV drug regimens for the simplification strategy, compared with those outcomes for the current standard-of-care (SOC) strategy. Using a published simulation model of HIV disease, we projected life expectancy, discounted quality-adjusted life expectancy (QALE), and discounted lifetime medical costs for each strategy.

RESULTS

Subjects who have not developed PI-resistant HIV infection at the time of failure of the simplification regimen have a greater life expectancy (27.9 vs. 27.1 years) and QALE (14.9 vs. 14.7 years), compared with SOC subjects, because they receive an additional line of therapy without negative consequences for future treatment options. The QALE for the simplification strategy remains higher than that for the SOC, unless a large proportion of patients experiencing virologic failure while receiving the simplification regimen develop PI resistance. Depending on the probability of simplification regimen failure, the advantage is maintained even if HIV develops PI resistance in 42%-70% of subjects. Projected lifetime costs are $26,500-$72,400 per person lower for the simplification strategy than for the SOC strategy.

CONCLUSIONS

An HIV treatment simplification strategy involving use of a boosted PI alone may lead to longer survival overall at lower cost, compared with the SOC combination therapy, because the simplification strategy potentially adds an additional line of therapy. The risk of emergence of PI resistance during treatment with a simplified regimen is a critical determinant of the viability of this strategy.

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.

Cost effectiveness of lopinavir/ritonavir compared with atazanavir plus ritonavir in antiretroviral-experienced patients in the US

OBJECTIVE

To estimate the cost effectiveness and long-term combined effects of HIV disease and antiretroviral (ARV) therapy-related risk for coronary heart disease (CHD) on quality-adjusted survival and healthcare costs for ARV-experienced patients.

METHODS

A previously validated Markov model was updated and supplemented with the Framingham CHD risk equation. The representative patient in the model was male, aged 37 years and had a baseline 10-year CHD risk of 4.6%. Patients started with either lopinavir/ritonavir (LPV/r) or ritonavir-boosted atazanavir (ATV+RTV) as the protease inhibitor (PI). The proportions of patients with viral suppression below 400 and 50 copies/mL, respectively, at week 48 reported in clinical trials were used to estimate the differences between these two therapies. The daily ARV costs were $US 24.60 for LPV/r capsules (2005 costs) and $US 26.54 for LPV/r tablets (2006 costs), $US 29.76 for ATV and $US 8.57 for ritonavir (2005 costs). Costs of other ARV drugs were taken from average wholesale drug reports for 2005. The cost of AIDS events was estimated from Medicaid billing databases and reflected a medical care system perspective and 2005 treatment costs. Cost-effectiveness calculations assumed a lifetime time horizon. The effects of different model assumptions were tested in a multiway sensitivity analysis by combining extreme values of parameters.

RESULTS

The model estimated a clinical and economic advantage to using LPV/r over ATV+RTV, which varied depending upon the use of LPV/r capsules or tablets. Using LPV/r capsules was comparatively beneficial for ARV-experienced patients in quality-adjusted life-months (QALMs) of 4.6 (corrected for differences in CHD risk) compared with ATV+RTV. In addition, there were 5- and 10-year overall per-patient cost savings of $US 17,995 and $US 21,298, respectively. Estimates for the LPV/r tablet formulation approved in 2005 (assuming similar efficacy) improved cost savings over 5- and 10-year periods to $US 19,598 and $US 23,126 per patient, respectively, because of a drug price differential. Sensitivity analysis tested numerous assumptions about the model cost and efficacy parameters and found that the results were robust to most changes. Model limitations were the uncertainty associated with the model parameters used.

CONCLUSION

LPV/r appears to be a highly cost-effective regimen relative to ATV+RTV for the treatment of HIV. The long-term CHD risk associated with LPV/r was minimal compared with the increased risk of AIDS/death and costs projected for a less efficacious PI-based regimen.

Should we now adopt the HIV-RNA < 50 copy endpoint for clinical trials of antiretroviral-experienced as well as naive patients?

In the TORO, RESIST and POWER trials, the HIV-RNA < 50 copy endpoint showed the strongest durability over time, whereas HIV-RNA reductions of more than 1 log10 or below 400 copies/ml were less sustained during 48 weeks of treatment. Clinical trials of new antiretroviral drugs in highly experienced patients also show high rates of HIV-RNA suppression below 50 copies/ml. HIV-RNA suppression below 50 copies/ml should now become the standard efficacy endpoint across trials of both naive and experienced patients.

Efficacy and safety of darunavir-ritonavir compared with that of lopinavir-ritonavir at 48 weeks in treatment-experienced, HIV-infected patients in TITAN: a randomised controlled phase III trial

BACKGROUND

The protease inhibitor darunavir has been shown to be efficacious in highly treatment-experienced patients with HIV infection, but needs to be assessed in patients with a broader range of treatment experience. We did a randomised, controlled, phase III trial (TITAN) to compare 48-week efficacy and safety of darunavir-ritonavir with that of lopinavir-ritonavir in treatment-experienced, lopinavir-naive patients.

METHODS

Patients received optimised background regimen plus non-blinded treatment with darunavir-ritonavir 600/100 mg twice daily or lopinavir-ritonavir 400/100 mg twice daily. The primary endpoint was non-inferiority (95% CI lower limit for the difference in treatment response -12% or greater) for HIV RNA of less than 400 copies per mL in plasma at week 48 (per-protocol analysis). TITAN (TMC114-C214) is registered with ClinicalTrials.gov, number NCT00110877.

FINDINGS

Of 595 patients randomised and treated, 187 (31%) were protease inhibitor naive; 476 of 582 (82%) were susceptible to four or more protease inhibitors. At week 48, significantly more darunavir-ritonavir than lopinavir-ritonavir patients had HIV RNA of less than 400 copies per mL (77% [220 of 286] vs 68% [199 of 293]; estimated difference 9%, 95% CI 2-16). Fewer virological failures treated with darunavir-ritonavir than with lopinavir-ritonavir developed primary protease inhibitor mutations (21% [n=6] vs 36% [n=20]) and nucleoside analogue-associated mutations (14% [n=4] vs 27% [n=15]). Safety data were generally similar between the groups; grade 3 or 4 adverse events occurred in 80 (27%) darunavir-ritonavir and 89 (30%) lopinavir-ritonavir patients.

INTERPRETATION

In lopinavir-naive, treatment-experienced patients, darunavir-ritonavir was non-inferior to lopinavir-ritonavir treatment in terms of our virological endpoint, and should therefore be considered as a treatment option for this population.

Effect of concomitantly administered rifampin on the pharmacokinetics and safety of atazanavir administered twice daily

The potent induction of hepatic cytochrome P450 3A isoforms by rifampin complicates therapy for coinfection with human immunodeficiency virus (HIV) and Mycobacterium tuberculosis. We performed an open-label, single-arm study to assess the safety and pharmacokinetic interactions of the HIV protease inhibitor atazanavir coadministered with rifampin. Ten healthy HIV-negative subjects completed pharmacokinetic sampling at steady state while receiving 300 mg atazanavir every 12 h without rifampin (period 1), 300 mg atazanavir every 12 h with 600 mg rifampin every 24 h (period 2), and 400 mg atazanavir every 12 h with 600 mg rifampin every 24 h (period 3). During period 1, the mean concentration of drug in serum at 12 h (C(12 h)) was 811 ng/ml (range, 363 to 2,484 ng/ml) for atazanavir, similar to historic seronegative data for once-daily treatment with 300 mg atazanavir boosted with 100 mg ritonavir. During periods 2 and 3, the mean C(12 h) values for atazanavir were 44 ng/ml (range, <25 to 187 ng/ml) and 113 ng/ml (range, 39 to 260 ng/ml), respectively, well below historic seronegative data for once-daily treatment with 400 mg atazanavir without ritonavir. Although safe and generally well tolerated, 300 mg or 400 mg atazanavir administered every 12 h did not maintain adequate plasma exposure when coadministered with rifampin.

The Safety, Efficacy, and Pharmacokinetic Profile of a Switch in Antiretroviral Therapy to Saquinavir, Ritonavir, and Atazanavir Alone for 48 Weeks and a Switch in the Saquinavir Formulation

BACKGROUND

Toxicities observed with current combination antiretroviral therapy (CART) warrant a search for novel options, such as class-sparing regimens. Ritonavir-boosted double-protease inhibitor (PI)-only regimens are such an option but are prone to pharmacokinetic interactions.

METHODS

This 48-week randomized study examined the safety and efficacy of a switch in CART to a once-daily regimen of saquinavir (SQV), ritonavir (RTV), and atazanavir (ATV) that did not include nucleoside reverse-transcriptase inhibitors (NRTIs). The study also assessed the pharmacokinetic profile of a change in the SQV formulation, from 200 mg to 500 mg, in 2 regimens (SQV-RTV twice per day plus NRTIs [arm 1] and SQV-RTV-ATV once per day without NRTIs [arm 2]) in human immunodeficiency virus type 1-infected subjects (plasma human immunodeficiency virus RNA level, <50 copies/mL). Patients underwent an initial SQV formulation change or a CART change to SQV-RTV-ATV with intense pharmacokinetic sampling. All patients were subsequently assigned to receive SQV-RTV-ATV (1500, 100, and 300 mg once per day, respectively) without NRTIs for 48 weeks. The primary end point was the percentage of patients who experienced virologic failure.

RESULTS

Of 25 subjects enrolled, scleral icterus was the most common adverse event (3 patients [12.5%]). Three subjects (12.5%) experienced virologic failure; and mean (+/- standard error of the mean) increase in the CD4(+) lymphocyte count was 63 +/- 36 cells/ mu L over 48 weeks (P=.012). The SQV geometric mean area under the time curve parameters were not significantly altered for the 2 SQV formulations (arm 1, 23.32 vs. 18.76 ngxh/mL [geometric mean ratio, 0.80] for the 200-mg vs. 500-mg formulations, respectively; arm 2, 50.31 vs. 44.79 ngxh/mL [geometric mean ratio, 0.88], for the 200-mg vs. 500-mg formulations, respectively).

CONCLUSIONS

A CART regimen of SQV-RTV-ATV alone demonstrated sustained virologic efficacy and was associated with significant increases in the CD4(+) lymphocyte count.

Long-Term suppression of HIV infection: benefits and limitations of current treatment options

HIV type 1, a causative agent of AIDS, is a source of worldwide morbidity and mortality. There are an estimated 1 million people in North America currently living with HIV infection, and more than 40,000 new cases occur annually. Before the advent of highly active antiretroviral therapy (HAART), the mortality rate of HIV infection was nearly 100%, and life expectancy was short. However, successful HAART delays the onset of AIDS, allowing patients to live with chronic HIV infection for 20 years or more. HAART usually consists of a combination of protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs), and/or nonnucleoside reverse transcriptase inhibitors (NNRTIs). Although these agents are highly efficacious in delaying the onset of AIDS, their clinical utility is limited by viral resistance, nonadherence to therapy, and drug toxicity. Consequently, multidrug regimens are necessary for successful treatment. Initial NNRTI-based HAART regimens are effective at reducing viral load and boosting CD4(+) cell counts. NNRTI resistance is uncommon, but should it occur, the NNRTI-based therapy needs to be quickly replaced by a PI-based therapy. Triple NRTI-based regimens are recommended only if NNRTI- or PI-based regimens cannot be used. When developing a multidrug regimen, it is also important to select HAART agents with limited adverse effects. Because each HAART agent has its own unique adverse effect profile, selecting a regimen with a favorable profile may be difficult. For example, certain PIs produce adverse metabolic effects that may increase the risk of developing cardiovascular disease. In contrast, NNRTI-based therapies have a different side effect profile. Because each HAART agent has specific limitations, tailoring a regimen to the individual patient is of paramount importance for achieving optimal outcomes.

Relative antiviral efficacy of ritonavir-boosted darunavir and ritonavir-boosted tipranavir vs. control protease inhibitor in the POWER and RESIST trials

OBJECTIVE

To compare the relative antiviral efficacy of TMC114 with low-dose ritonavir (TMC114/r) and tipranavir with low-dose ritonavir (TPV/r) vs. control protease inhibitor (CPI) in treatment-experienced patients, using data from the POWER 1/2 and RESIST 1/2 trials. These trials recruited antiretroviral-experienced patients with HIV RNA > 1000 HIV-1 RNA copies/mL and at least one primary PI mutation, and used optimized nucleoside reverse transcriptase inhibitors with or without enfuvirtide, plus investigator-selected CPI in the control arms.

METHODS

For the POWER trials, data from the 600/100 mg twice a day (bid) dose and CPI arms (n=201) were included, while all data from the RESIST trials (TPV/r 500/200 mg bid and CPI; n=1159) were included. The difference in week 24 efficacy (intent to treat) for the new PI vs. CPI was compared between the trials.

RESULTS

Overall baseline characteristics were well matched across the trials. At week 24, 72% of TMC114/r patients achieved a > or =1 log(10) copies/mL reduction in HIV RNA compared with 40% of TPV/r patients (for CPI patients, this percentage was 21 and 18%, respectively, in the POWER and RESIST trials). The treatment benefit of TMC114/r over CPI in the POWER trials was greater (outside the 95% confidence intervals) than the benefit of TPV/r over CPI in the RESIST trials, for the 24-week HIV RNA endpoints of 1 log(10) copies/mL reduction, <400 copies/mL and <50 copies/mL, and also for the mean rise in CD4 count. In sensitivity analysis, this difference in efficacy was strongest for those who did not also use enfuvirtide.

CONCLUSIONS

Given the caveats of this type of analysis (for example, possible differences in trial conduct, and undetected differences in baseline resistance profiles), the efficacy benefits of TMC114/r vs. CPI in the POWER trials appear to be greater than the benefits of TPV/r vs. CPI in the RESIST trials, for patients who did not also use enfuvirtide.

Efficacy and safety of darunavir-ritonavir at week 48 in treatment-experienced patients with HIV-1 infection in POWER 1 and 2: a pooled subgroup analysis of data from two randomised trials

BACKGROUND

The continuing, randomised, multinational, phase IIB POWER 1 and 2 studies aim to evaluate efficacy and safety of darunavir in combination with low-dose ritonavir in treatment-experienced HIV-1-infected patients. We did a pooled subgroup analysis to update results at week 48 for patients receiving the recommended dose of darunavir-ritonavir compared with those receiving other protease inhibitors (PIs).

METHODS

After 24-week dose-finding phases and primary efficacy analyses, patients randomised to receive darunavir-ritonavir were given 600/100 mg twice daily, and patients receiving control PIs continued on assigned treatment into the longer-term, open-label phase; all patients continued on optimised background regimen. We assessed patients who had reached week 48 or discontinued earlier at the time of analysis; for the darunavir-ritonavir group, only patients who received 600/100 mg twice daily from baseline were included. Analyses were intention-to-treat. The POWER 2 study (TMC114-C202) is registered with ClinicalTrials.gov (NCT00071097).

FINDINGS

At week 48, 67 of 110 (61%) darunavir-ritonavir patients compared with 18 of 120 (15%) of control PI patients had viral load reductions of 1 log10 copies per mL or greater from baseline (primary endpoint; difference in response rates 46%, 95% CI 35%-57%, p<0.0001). Based on a logistic regression model including stratification factors (baseline number of primary PI mutations, use of enfuvirtide, baseline viral load) and study as covariates, the difference in response was 50% (odds ratio 11.72, 95% CI 5.75-23.89). In the darunavir-ritonavir group, rates of adverse events were mostly lower than or similar to those in the control group when corrected for treatment exposure. No unexpected safety concerns were identified.

INTERPRETATION

Efficacy responses with darunavir-ritonavir 600/100 mg twice daily plus optimised background regimen were greater than those with control PI and were sustained to at least week 48, with favourable safety and tolerability in treatment-experienced patients. This regimen could expand the treatment options available for such patients.

Once-daily therapies for the treatment of HIV infection

For patients initiating antiretroviral therapy, there are several well-tolerated once-daily regimens from which to choose. Once-daily antiretroviral therapy may be ideal for patient adherence and convenience. However, results of a few recent clinical trials exploring new once-daily regimens have shown that one cannot assume that any three-drug combination will be successful. Once-daily therapy options for treatment-experienced patients are more limited but may be successful depending on prior antiretroviral treatment exposure and resistance mutations. Current approaches to once-daily therapy include simplifying successful regimens and investigating novel antiretroviral agents with long half-lives.

Atazanavir/ritonavir: a valuable once-daily HIV protease inhibitor with little impact on lipid profile

Atazanavir is the first once-daily azapeptide HIV protease inhibitor that may offer simpler and safer protease inhibitor-based highly active antiretroviral therapy, as it has been associated with less hyperlipemia and diarrhea compared with the other drugs of the same class. The typical side effect of atazanavir is an asymptomatic increase in serum unconjugated bilirubin. Ritonavir-boosted atazanavir has proved to be effective in treatment-naive HIV-infected individuals, and there is no evidence that it leads to the selection of mutations conferring cross-resistance to other protease inhibitors. Its efficacy in patients harboring drug-resistant variants is not statistically different from that of the reference protease inhibitor, lopinavir/ritonavir. It has been approved by the US FDA for use in drug-experienced HIV-infected patients, although atazanavir/ritonavir-based regimens have now been included among those recommended by the International AIDS Society  – USA Panel and the Department of Health and Human Services Panel as initial treatment. The aim of this article is to describe the pharmacological characteristics of atazanavir/ritonavir, and the results of the main clinical trials investigating the safety and efficacy of this antiretroviral combination.

CYP3A5 genotype has an impact on the metabolism of the HIV protease inhibitor saquinavir

CYP3A is the main enzyme subfamily involved in the metabolism of the HIV protease-inhibitor saquinavir. We hypothesized that individuals homozygous for CYP3A5*1 might have a higher oral clearance of saquinavir, compared with subjects lacking functional CYP3A5 alleles. A single-dose pharmacokinetic trial of saquinavir soft gel capsules, 1,200 mg, was performed in 16 black Tanzanian healthy volunteers with two functional CYP3A5 alleles (*1/*1) and in 18 volunteers without functional CYP3A5 alleles (both alleles being either *3, *6, or *7). The median area under the plasma concentration-time curve (AUC)0-24 reached among subjects with two functional alleles was 1,410 ng h/ml (interquartile range (IQR) 826-1,929), whereas it was 2,138 ng h/ml (IQR 1,380-3,331) in subjects without (P=0.0533, Mann-Whitney U-test). The median ratio of saquinavir over its M2 plus M3 hydroxy metabolites in urine was 64 (IQR 52-73) in subjects with two functional alleles, whereas it was 145 (IQR 89-181) in those without (P=0.000078, Mann-Whitney U-test). In conclusion, saquinavir is metabolized by CYP3A5. The median AUC0-24 for saquinavir among individuals with two functional CYP3A5 alleles was 34% lower than among those with no functional alleles. To clarify the clinical importance of the CYP3A5 polymorphism, further studies should be conducted on saquinavir, dosed to steady state, in the presence of ritonavir boosting.

Pharmaceutical Approach to HIV Protease Inhibitor Atazanavir for Bioavailability Enhancement Based on Solid Dispersion System

Atazanavir (ATV) is a low oral bioavailability (BA) compound and, clinically, is generally coadministrated with ritonavir (RTV), which boosts the oral BA of ATV by inhibiting cytochrome P450 (CYP) 3A, and P-glycoprotein (Pgp) via the same metabolic pathway. However, depending on pharmacokinetic interaction, RTV-boosted ATV has great potential for other comedication. In this study we demonstrated the pharmaceutical approach to BA improvement of ATV without RTV in rats, based on the solid dispersion system using sodium lauryl sulfate (SLS) as a carrier and Gelucire 50/13 as an absorption enhancer. ATV solid dispersions in SLS were prepared by a conventional solvent method and, at ratios of ATV to SLS of 1 : 2 and 1 : 3, were demonstrated to form an amorphous state in powder X-ray diffraction (PXRD) analysis and exhibited 2.26- and 2.36-fold improvement in a dissolution test in comparison to bulk ATV, respectively. After oral administration to rats, ATV solid dispersion in SLS at a ratio of 1 : 2 showed a 3.5-fold increase in BA compared with bulk ATV. Moreover, the addition of Gelucire 50/13 to ATV solid dispersion, at a total ratio of Gelucire 50/13, ATV and SLS 1 : 1 : 2 gave 7.0- and 4.7-fold increase in Cmax and BA compared with bulk ATV, respectively, when the relative BA to RTV-boosted ATV reached 93%. The results in this study proved that a pharmaceutical approach could improve the bioavailability of ATV without pharmacokinetic interaction with RTV.

Evolution of HIV resistance mutations in patients maintained on a stable treatment regimen after virologic failure

OBJECTIVE

We compared the rate of emergence of thymidine analogue mutations (TAMs) and major protease inhibitor mutations in adherent patients who remained on stable treatment with a thymidine analogue and/or protease inhibitor after the onset of virologic failure.

DESIGN

Follow-up genotypic resistance testing was done using archived plasma obtained from patients having 0 or 1 TAM and/or 0 or 1 major protease inhibitor resistance mutation at the onset of virologic failure.

RESULTS

The median duration of observed failure was 691 days. There were 41 thymidine analogue regimens and 34 protease inhibitor regimens; concomitant ritonavir was used 4 times. New major protease inhibitor mutations emerged more rapidly than did new TAMs (P = 0.0019); new TAMs emerged more rapidly in thymidine analogue regimens that did not include lamivudine (P = 0.0073). The emergence of TAMs and major protease inhibitor mutations did not differ if lamivudine was not part of the thymidine analogue regimen. The evolution of CD4 cell counts and plasma viral loads (pVLs) during virologic failure was similar regardless of whether or not a new TAM or major protease inhibitor mutations emerged or, for thymidine analogue-containing regimens, whether lamivudine was or was not used.

CONCLUSIONS

Major protease inhibitor mutations arose more frequently and rapidly than did TAMs in patients with sustained virologic failure who received lamivudine.

Lopinavir/ritonavir: a review of its use in the management of HIV infection

Coformulated lopinavir/ritonavir (Kaletra) is a boosted protease inhibitor (PI) containing lopinavir and low-dose ritonavir. It is approved for use in combination with other antiretroviral drugs for the treatment of HIV infection in adults, adolescents and children aged >or=6 months (in the US) or >or=2 years (in the EU).Lopinavir/ritonavir-based antiretroviral therapy (ART) is generally well tolerated and has shown durable virological efficacy in clinical trials in ART-naive and -experienced patients with virological failure. Lopinavir/ritonavir is one of the preferred PIs for first-line treatment of HIV infection in adults, adolescents and children, according to US and British guidelines, reflecting its comparatively better virological efficacy than nelfinavir and low incidence of de novo resistance during long-term treatment. Lopinavir/ritonavir-based treatment may produce a more effective virological response than other PI-based regimens in single PI-experienced, non-nucleoside reverse transcriptase inhibitor (NNRTI)-naive patients. In PI- and NNRTI-experienced patients, atazanavir/saquinavir was inferior to lopinavir/ritonavir; further well designed trials are required to determine the comparative efficacy of lopinavir/ritonavir versus other PIs such as ritonavir-boosted atazanavir, or fosamprenavir or tipranavir in these patients. Lopinavir/ritonavir is more likely than atazanavir (alone or boosted) or nelfinavir to cause hypertriglyceridaemia and is associated with a higher incidence of hypercholesterolaemia than atazanavir (alone or boosted). The new lopinavir/ritonavir tablet coformulation offers a reduced pill count and lack of food interaction, and ART-naive patients in the US and Canada, who are not receiving efavirenz, nelfinavir, nevirapine or amprenavir, may benefit from convenient once-daily administration of lopinavir/ritonavir. Thus, lopinavir/ritonavir is a convenient, effective option for use in the treatment of HIV infection in ART-naive and -experienced adults, adolescents and children.

Alteraciones lipídicas y riesgo cardiovascular asociado a la terapia antirretroviral

Dyslipidemia is common in HIV-infected patients receiving antiretroviral therapy (ART) and it is often associated with the use of specific antiretroviral drugs. The phenotypic profile can include elevated triglycerides or cholesterol alone, or mixed patterns with varying changes in LDL and HDL lipoproteins, which imply different levels of cardiovascular risk. Growing evidence indicates that ART-associated hyperlipidemia accelerates the development of atherosclerosis and coronary heart disease in HIV-infected patients. In recent years, a number of retrospective database reviews and prospective cohort studies have reported a higher incidence of coronary events in patients receiving ART, which seems to be closely related with the presence of dyslipidemia and the duration of exposure to ART. Although the clinical benefit of treating ART-related dyslipidemia remains unproven, most experts recommend a policy of cardiovascular disease prevention and management similar to that used in non-HIV-infected individuals. In addition, the use of antiretrovirals associated with a more favorable lipid profile is considered. Clinical experience with lipid-lowering therapy in HIV-infected patients is still limited, but there is increasing data confirming its efficacy and safety in this setting. Drug interactions should be taken into account when statins are used in patients receiving protease inhibitors.

Successful treatment with atazanavir and lopinavir/ritonavir combination therapy in protease inhibitor-susceptible and protease inhibitor-resistant HIV-infected patients

The combination of atazanavir (ATV) plus lopinavir/ritonavir (LPV/r) has been used in practice. However, clinical data supporting its use are limited. The objective of this study was to evaluate the efficacy and tolerability of regimens with ATV + LPV/r in protease inhibitor (PI)-susceptible and PI-resistant patients. A retrospective review of 2703 charts was performed to identify all patients who received ATV + LPV/r. From June 2003 to January 2005, 33 patients received ATV + LPV/r with nucleoside reverse transcriptase inhibitors (NRTIs) for 3 months or more. Virologic success (HIV-RNA < 400 copies per milliliter) was achieved in 30 patients (91%) in a median of 10 weeks (range, 2-68). Nineteen of the 23 patients (83%) who had ultrasensitive viral load (VL) assays were nondetectable. Among patients with 6 or more protease resistance (PR) mutations (PI-resistant), 11 of 14 (79%) achieved virologic success. Eleven of those received phenotypic testing (10 Virtual Phenotype, VircoLab, Baltimore, MD). Despite predicted phenotypic resistance to ATV (6 patients) and LPV/r (7 patients), virologic success was achieved in 4 of 6 (67%) and 4 of 7 (57%), respectively. The 3 PI-resistant patients who were virologic failures had extensive prior LPV/r use, 8-11 PR mutations, and predicted phenotypic resistance to LPV/r, but 2 of 3 had CD4 increases with ATV + LPV/r. Overall, 28 patients (85%) continue to tolerate ATV + LPV/r for a median of 32 weeks follow-up (range, 12-76). Combination ATV + LPV/r with NRTIs appears safe, tolerable, and efficacious in PI-resistant patients (>/=6 PR mutations) and predicted phenotypic resistance to ATV and LPV/r. Further studies of ATV + LPV/r in HIV-treatment are warranted.

The Lifetime Cost of Current Human Immunodeficiency Virus Care in the United States

OBJECTIVE

We sought to project the lifetime cost of medical care for human immunodefiency virus (HIV)-infected adults using current antiretroviral therapy (ART) standards.

METHODS

Medical visits and hospitalizations for any reason were from the HIV Research Network, a consortium of high-volume HIV primary care sites. HIV treatment drug regimen efficacies were from clinical guidelines and published sources; data on other drugs used were not available. In a computer simulation model, we projected HIV medical care costs in 2004 U.S. dollars.

RESULTS

From the time of entering HIV care, per person projected life expectancy is 24.2 years, discounted lifetime cost is Dollars 385,200, and undiscounted cost is Dollars 618,900 for adults who initiate ART with CD4 cell count < 350/microL. Seventy-three percent of the cost is antiretroviral medications, 13% inpatient care, 9% outpatient care, and 5% other HIV-related medications and laboratory costs. For patients who initiate ART with CD4 cell count < 200/microL, projected life expectancy is 22.5 years, discounted lifetime cost is Dollars 354,100 and undiscounted cost is Dollars 567,000. Results are sensitive to drug manufacturers' discounts, ART efficacy, and use of enfuvirtide for salvage. If costs are discounted to the time of infection, the discounted lifetime cost is Dollars 303,100.

CONCLUSIONS

Effective ART regimens have substantially improved survival and have increased the lifetime cost of HIV-related medical care in the U.S.

Methodological standards in non-inferiority AIDS trials: moving from adherence to compliance

Background

The interpretation of the results of active-control trials regarding the efficacy and safety of a new drug is important for drug registration and following clinical use. It has been suggested that non-inferiority and equivalence studies are not reported with the same quantitative rigor as superiority studies.

Methods

Standard methodological criteria for non-inferiority and equivalence trials including design, analysis and interpretation issues were applied to 18 recently conducted large non-inferiority (15) and equivalence (3) randomized trials in the field of AIDS antiretroviral therapy. We used the continuity-corrected non-inferiority chi-square to test 95% confidence interval treatment difference against the predefined non-inferiority margin.

Results

The pre-specified non-inferiority margin ranged from 10% to 15%. Only 4 studies provided justification for their choice. 39% of the studies (7/18) reported only intent-to-treat (ITT) analysis for the primary endpoint. When on-treatment (OT) and ITT statistical analyses were provided, ITT was favoured over OT for results interpretation for all but one study, inappropriately in this statistical context. All but two of the studies concluded there was "similar" efficacy of the experimental group. However, 9/18 had inconclusive results for non-inferiority.

Conclusion

Conclusions about non-inferiority should be drawn on the basis of the confidence interval analysis of an appropriate primary endpoint, using the predefined criteria for non-inferiority, in both OT and ITT, in compliance with the non-inferiority and equivalence CONSORT statement. We suggest that the use of the non-inferiority chi-square test may provide additional useful information.

Clinical outcomes associated with concomitant use of atazanavir and proton pump inhibitors

BACKGROUND

Pharmacokinetic studies have shown that the concomitant use of atazanavir and proton pump inhibitors (PPIs) decreases atazanavir plasma concentrations. Data describing clinical outcomes associated with this drug interaction are limited.

OBJECTIVE

To describe the clinical outcomes, in terms of viral load (VL) suppression, associated with the concurrent use of ritonavir-boosted or unboosted atazanavir and PPIs.

METHODS

A retrospective chart review of 301 HIV-positive adults attending an Ohio infectious diseases clinic was performed to identify patients prescribed atazanavir, with or without ritonavir, and a PPI. The primary outcome was achievement/maintenance of VL less than 400 copies/mL for 2 or more months during concomitant atazanavir and PPI therapies. Data collected included VL and CD4+ cell count at initiation of coadministered atazanavir and PPIs, genotype/phenotype, prior protease inhibitor experience, length of concurrent atazanavir/PPI therapy, and adherence.

RESULTS

Twelve patients met inclusion criteria. PPIs and dosing regimens varied among subjects. Five of the subjects had a VL less than 400 copies/mL at initiation of atazanavir, with or without ritonavir, which was maintained during concurrent atazanavir and PPI therapy. Four additional subjects initiated protease inhibitor treatment with a VL greater than 400 copies/mL and achieved an undetectable VL while on concurrent PPI therapy. Duration of concurrent therapy ranged from 4 to 23 months in these 9 subjects. Of the 3 patients not maintaining a VL less than 400 copies/mL, 1 achieved that level at 4 months, and all 3 of these subjects showed atazanavir susceptibility during therapy per genotype resistance testing. Subsequently, decreased atazanavir susceptibility was reported in 1 of the 3 patients after 18 months of therapy. Patients not achieving an undetectable VL had known adherence issues.

CONCLUSIONS

In this case series, 9 of 12 subjects achieved successful virologic outcomes while receiving concurrent atazanavir and PPIs in a real-world environment. In our experience, the interaction between atazanavir and once-daily PPIs is not clinically significant for adherent patients. Concurrent use of these medications could be considered in patients with limited treatment options.

Effects of atazanavir/ritonavir and lopinavir/ritonavir on glucose uptake and insulin sensitivity: demonstrable differences in vitro and clinically

BACKGROUND

The HIV protease inhibitor (PI) atazanavir does not impair insulin sensitivity acutely but ritonavir and lopinavir induce insulin resistance at therapeutic concentrations.

OBJECTIVE

To test the hypothesis that atazanavir combined with a lower dose of ritonavir would have significantly less effect on glucose metabolism than lopinavir/ritonavir in vitro and clinically.

METHODS

Glucose uptake was measured following insulin stimulation in differentiated human adipocytes in the presence of ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l). These data were examined clinically using the hyperinsulinemic euglycemic clamp and oral glucose tolerance testing (OGTT) in 26 healthy HIV-negative men treated with atazanavir/ritonavir (300/100 mg once daily) and lopinavir/ritonavir (400/100 mg twice daily) for 10 days in a randomized cross-over study.

RESULTS

Atazanavir inhibited glucose uptake in vitro significantly less than lopinavir and ritonavir at all concentrations. Ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l) did not further inhibit glucose uptake. During euglycemic clamp, there was no significant change from baseline insulin sensitivity with atazanavir/ritonavir (P = 0.132), while insulin sensitivity significantly decreased with lopinavir/ritonavir from the baseline (-25%; P < 0.001) and from that seen with atazanavir/ritonavir (-18%; P = 0.023). During OGTT, the HOMA insulin resistance index significantly increased from baseline at 120 min with atazanavir/ritonavir and at 150 min with lopinavir/ritonavir. The area under the curve of glucose increased significantly with lopinavir/ritonavir but not with atazanavir/ritonavir.

CONCLUSIONS

Both glucose uptake in vitro and clinical insulin sensitivity in healthy volunteers demonstrate differential effects on glucose metabolism by the combination PI atazanavir/ritonavir and lopinavir/ritonavir.

Change to a once-daily combination including boosted atazanavir in HIV-1-infected children

BACKGROUND

Pediatric experience with atazanavir combined with antiretroviral drugs administered once daily is very limited.

OBJECTIVE

The objective of this prospective, single-center observation study was to evaluate efficacy and tolerance of once-a-day ritonavir-boosted atazanavir, including treatment.

RESULTS

Antiretroviral treatment of 23 children and adolescents with a median age of 16 years (range, 10-19 years) was changed to a single daily dose of a combination of ritonavir-boosted atazanavir and 2 other nucleoside or nonnucleoside analogs. The single daily dosing was expected to improve adherence to treatment. The mean follow-up period was 12 months (range, 6-17 months). At the time of the treatment switch, the previous treatment had been effective in 11 children (plasma viral load [pVL] <50 copies/mL) and not effective in 12 (pVL >50 copies/mL). None of the viral genotypes had resistance to atazanavir. The susceptibility score for the drugs used in combination with atazanavir (GSS) was at least 1.5 in 12 of 20 children. The atazanavir dose was 300 mg per day for children weighing more than 50 kg and 200 mg per day for children weighing 30 to 50 kg, in all cases associated with 100 mg ritonavir. During follow up, the mean atazanavir plasma concentration at 12 to 15 hours was 2.18 +/- 1.19 mg/L. Tolerance was good in most patients, but 4 children chose to stop treatment because of icterus (n = 2) or persistent nausea and vomiting (n = 2). In 6 of the 12 children in whom treatment was not virologically effective before the switch, pVL was below 50 copies/mL after 1 to 3 months of treatment. Poor compliance and virologic failure persisted in the other 6 children. Seven of the 11 children with good virologic control before the switch continued to have undetectable pVL but 4 experienced virologic failure after 1, 1, 3 or 12 months of treatment despite good compliance. Insufficient antiviral potency of associated drugs could have been the cause of 2 of these 4 unexpected virologic failures.

CONCLUSION

In these children with extensive previous treatment, the change to a once-daily treatment, including ritonavir-boosted atazanavir, was associated with a significant risk of virologic failure.

Effect of omeprazole on the pharmacokinetics of saquinavir-500 mg formulation with ritonavir in healthy male and female volunteers

INTRODUCTION

Recent studies have described reduced absorption of certain protease inhibitors when administered with agents known to increase gastric pH. No clinically significant interactions between saquinavir absorption and gastric pH have previously been shown. We evaluated the effect of omeprazole, a proton-pump-inhibitor, on the pharmacokinetics of the recently developed saquinavir-500 mg formulation co-administered with ritonavir.

METHODS

Eighteen healthy subjects (n = 6 women and 12 men) received 1000/100 mg saquinavir/ritonavir twice daily in an open-label study for 15 days. On days 11-15, subjects were administered omeprazole 40 mg daily with the morning dose. Serial plasma samples were collected for 12-h pharmacokinetic profiles of saquinavir and ritonavir on days 10 and 15 and safety analysis on days 1, 4, 10, 15 and 29.

RESULTS

The geometric mean and 95% confidence interval (CI), for the area under time-concentration curve (AUC; ng h/ml), trough plasma concentration (C trough; ng/ml) and maximum observed plasma concentration (Cmax; ng/ml) of saquinavir were 20599 (14396-29360) and 37511 (28733-48970); 737 (482-1127) and 1521 (1039-2227); 3227 (2370-4393) and 5611 (4507-7710) on days 10 and 15, respectively, with geometric mean ratios of 1.82, 2.06 and 1.75. No significant changes were observed in saquinavir elimination half life, ritonavir pharmacokinetic parameters or in safety laboratory tests. No unexpected adverse events attributed to study medication were noted.

CONCLUSIONS

In the presence of omeprazole, total saquinavir plasma exposure is significantly increased (82% increase in AUC). The mechanism of this interaction requires elucidation. Despite the significant increase in saquinavir exposure, no short term toxicities were observed.