Results of a phase 2 clinical trial at 48 weeks (AI424-007): a dose-ranging, safety, and efficacy comparative trial of atazanavir at three doses in combination with didanosine and stavudine in antiretroviral-naive subjects

[Clinical utility of atazanavir]

Atazanavir (ATV) is a protease inhibitor (PI) in which its main qualities, compared to other PI are dosing convenience, good tolerability and excellent metabolic profile. These characteristics makes it more like a nonnucleoside than a PI, but with the increased genetic barrier common to PI. It is indicated in initial treatment, simplification treatment or a change due to toxicity and in first line rescue treatment. The administering of ATV boosted with ritonavir (300/100 mg/d) has been approved in Europe in all clinical situations. In naïve patients it has been combined with practically all the nucleoside analogue pairs and has shown to be as effective as lopinavir/ritonavir and even efavirenz. In the USA, this indication has been approved for almost 5 years and ATV has become the most prescribed PI, while the EMEA has approved it this year. ATV is an optimal drug to replace other antiretrovirals in simplification strategies or changes due to toxicity. In several studies it has been shown that, in patients with good virological control, it can LPV/r or another PI, the therapeutic efficacy being maintained, with excellent tolerance and an improved lipid profile, and decreasing the cardiovascular risk. This strategy is widely used in Spain. In this scenario some patients could benefit from non-boosted ATV treatment (400 mg/d). ATV is an effective and very attractive option in first line rescue treatments in which the virus shows little or no resistance to PI, as its simplicity and tolerability can improve problems with compliance, the main cause of therapeutic failure. In patients with moderate resistance to PI, ATV is as effective as LPV/r. The survival of patients with HIV infection is increasingly longer and factors such as tolerability, cardiovascular risk and the adaptability of the treatment to the lifestyle of the patient, become more important, therefore ATV must play an important role in the treatment of HIV-infection.

No impairment of endothelial function or insulin sensitivity with 4 weeks of the HIV protease inhibitors atazanavir or lopinavir-ritonavir in healthy subjects without HIV infection: a placebo-controlled trial

BACKGROUND

Dyslipidemia alone does not fully explain the increase in cardiovascular events among patients receiving protease inhibitor (PI)-based treatment for human immunodeficiency virus infection. Some PIs, such as indinavir, directly induce endothelial dysfunction, an effect that may mediate that portion of the increase in cardiovascular events that is not attributable to dyslipidemia.

METHODS

Endothelium-dependent vasodilation, insulin-mediated vasodilation, and whole-body and leg glucose uptake during use of a 1-h euglycemic hyperinsulinemic clamp (insulin infusion, 40 mU/m(2)/min) were measured in healthy men before and after 4 weeks of treatment with placebo (12 men), with 400 mg atazanavir per day (9 men), or with 400 mg lopinavir and 100 mg ritonavir twice per day (9 men).

RESULTS

Median age (36 years) and mean body mass index SD (23.4+/-2.6; calculated as weight in kilograms divided by the square of height in meters) did not differ between groups. Endothelium-dependent vasodilation, expressed as the percentage change in the leg blood flow response to intrafemoral artery infusion of 15 microg/min of the endothelium-dependent vasodilator methacholine, did not change after 4 weeks of treatment in any group:mean percentage change +/- SD, 154+/-102 from baseline and 242+/-254 at week 4 with atazanavir (P=.36), 76+/-62 and 86+/-79, respectively, with lopinavir-ritonavir (P=.68), and 111+/-86 and 127+/-153, respectively,with placebo (P=.63; for between-group differences, P=.55). The response to the endothelium-independent vasodilator nitroprusside was not different at week 4 for any group, nor was insulin-mediated vasodilation or leg or whole-body insulin-mediated glucose uptake (all within-group P values were 1.1).

CONCLUSIONS

Unlike the dramatic impairment seen with indinavir, the newer PIs atazanavir and lopinavir-ritonavir do not induce endothelial dysfunction in healthy subjects. Thus, endothelial dysfunction does not appear to be a PI drug class effect. The cause of the non-lipid-mediated increase in cardiovascular events that are reported with PIs remains unclear.

Fosamprenavir or atazanavir once daily boosted with ritonavir 100 mg, plus tenofovir/emtricitabine, for the initial treatment of HIV infection: 48-week results of ALERT

BACKGROUND

Once-daily (QD) ritonavir 100 mg-boosted fosamprenavir 1400 mg (FPV/r100) or atazanavir 300 mg (ATV/r100), plus tenofovir/emtricitabine (TDF/FTC) 300 mg/200 mg, have not been compared as initial antiretroviral treatment. To address this data gap, we conducted an open-label, multicenter 48-week study (ALERT) in 106 antiretroviral-naïve, HIV-infected patients (median HIV-1 RNA 4.9 log10 copies/mL; CD4+ count 191 cells/mm3) randomly assigned to the FPV/r100 or ATV/r100 regimens.

RESULTS

At baseline, the FPV/r100 or ATV/r100 arms were well-matched for HIV-1 RNA (median, 4.9 log10 copies/mL [both]), CD4+ count (mean, 176 vs 205 cells/mm3). At week 48, intent-to-treat: missing/discontinuation = failure analysis showed similar responses to FPV/r100 and ATV/r100 (HIV-1 RNA < 50 copies/mL: 75% (40/53) vs 83% (44/53), p = 0.34 [Cochran-Mantel-Haenszel test]); mean CD4+ count change-from-baseline: +170 vs +183 cells/mm3, p = 0.398 [Wilcoxon rank sum test]). Fasting total/LDL/HDL-cholesterol changes-from-baseline were also similar, although week 48 median fasting triglycerides were higher with FPV/r100 (150 vs 131 mg/dL). FPV/r100-treated patients experienced fewer treatment-related grade 2-4 adverse events (15% vs 57%), with differences driven by ATV-related hyperbilirubinemia. Three patients discontinued TDF/FTC because their GFR decreased to <50 mL/min.

CONCLUSION

The all-QD regimens of FPV/r100 and ATV/r100, plus TDF/FTC, provided similar virologic, CD4+ response, and fasting total/LDL/HDL-cholesterol changes through 48 weeks. Fewer FPV/r100-treated patients experienced treatment-related grade 2-4 adverse events.

HIV lipodystrophy and its metabolic consequences: implications for clinical practice

BACKGROUND

The introduction of highly active antiretroviral therapy (HAART) around 1996 markedly reduced mortality and morbidity from human immunodeficiency virus (HIV) infection. As life expectancy has improved, the chronic complications of HIV and HAART have become increasingly relevant.

SCOPE

This article provides an overview of the HIV-associated lipodystrophy, its pathogenesis and its clinical consequences (based on a search strategy in PubMed including literature published to November 2007).

FINDINGS

Lipodystrophy syndrome is characterized by abnormal fat distribution syndrome associated with metabolic disturbances and includes insulin resistance, deranged glucose and lipid metabolism. It is associated with increased risks of progression to type 2 diabetes and cardiovascular disease. Robust diagnostic criteria are required for lipodystrophy, and subsequent prospective cohort studies and randomized controlled trials are then required to determine the etiology and prognosis of lipodystrophy, and to evaluate therapeutic interventions for this consequence of HAART. Therapies to improve insulin resistance have been tried but they are frequently ineffective, and are limited by potential toxicity in this population. Hence, current management options for HIV associated lipodystrophy are limited and are mostly based on avoidance of risk factors and switching of antiretroviral drugs.

CONCLUSION

As the '3 by 5 strategy' of providing HIV drugs to the developing world is implemented worldwide, the numbers of patients adhering to antiretroviral medicines is dramatically increasing. One must be aware that in reducing the burden of acute retroviral disease, the treatments proposed might lead to significant rates of metabolic complications and further exacerbation of the epidemic of diabetes and cardiovascular disease.

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.

Cardiovascular risk and choice of HIV drug regimen

Since the introduction of combination antiretroviral therapy (cART), there have been many conflicting reports linking its use to the development of cardiovascular disease (CVD). Most antiretroviral drugs have been associated with the development of lipid abnormalities to some degree. However, whereas several large observational studies have reported a link between the use of cART (particularly protease inhibitors) and CVD, evidence linking specific antiretroviral drugs to CVD is limited. Much of the evidence linking cART to the development of dyslipidemia derives from randomized trials. However, given the relative infrequency of CVD in most HIV-positive populations, these may be inadequately powered to demonstrate a link with clinical events. In contrast, large observational studies have greater power to describe the development of clinical events but may be affected by bias. This review will describe the current literature linking cART to CVD as well as the limitations of some of the published studies.

Pharmacokinetics of antiretroviral regimens containing tenofovir disoproxil fumarate and atazanavir-ritonavir in adolescents and young adults with human immunodeficiency virus infection

The primary objective of this study was to measure atazanavir-ritonavir and tenofovir pharmacokinetics when the drugs were used in combination in young adults with human immunodeficiency virus (HIV). HIV-infected subjects > or =18 to <25 years old receiving (> or =28 days) 300/100 mg atazanavir-ritonavir plus 300 mg tenofovir disoproxil fumarate (TDF) plus one or more other nucleoside analogs underwent intensive 24-h pharmacokinetic studies following a light meal. Peripheral blood mononuclear cells were obtained at 1, 4, and 24 h postdose for quantification of intracellular tenofovir diphosphate (TFV-DP) concentrations. Twenty-two subjects were eligible for analyses. The geometric mean (95% confidence interval [CI]) atazanavir area under the concentration-time curve from 0 to 24 h (AUC(0-24)), maximum concentration of drug in serum (C(max)), concentration at 24 h postdose (C(24)), and total apparent oral clearance (CL/F) values were 35,971 ng x hr/ml (30,853 to 41,898), 3,504 ng/ml (2,978 to 4,105), 578 ng/ml (474 to 704), and 8.3 liter/hr (7.2 to 9.7), respectively. The geometric mean (95% CI) tenofovir AUC(0-24), C(max), C(24), and CL/F values were 2,762 ng.hr/ml (2,392 to 3,041), 254 ng/ml (221 to 292), 60 ng/ml (52 to 68), and 49.2 liter/hr (43.8 to 55.3), respectively. Body weight was significantly predictive of CL/F for all three drugs. For every 10-kg increase in weight, there was a 10%, 14.8%, and 6.8% increase in the atazanavir, ritonavir, and tenofovir CL/F, respectively (P < or = 0.01). Renal function was predictive of tenofovir CL/F. For every 10 ml/min increase in creatinine clearance, there was a 4.6% increase in tenofovir CL/F (P < 0.0001). The geometric mean (95% CI) TFV-DP concentrations at 1, 4, and 24 h postdose were 96.4 (71.5 to 130), 93.3 (68 to 130), and 92.7 (70 to 123) fmol/million cells. There was an association between renal function, tenofovir AUC, and tenofovir C(max) and intracellular TFV-DP concentrations, although none of these associations reached statistical significance. In these HIV-infected young adults treated with atazanavir-ritonavir plus TDF, the atazanavir AUC was similar to those of older adults treated with the combination. Based on data for healthy volunteers, a higher tenofovir AUC may have been expected, but was not seen in these subjects. This might be due to faster tenofovir CL/F because of higher creatinine clearance in this age group. Additional studies of the exposure-response relationships of this regimen in children, adolescents, and adults would advance our knowledge of its pharmacodynamic properties.

Evolution of antiretroviral drug costs in Brazil in the context of free and universal access to AIDS treatment

BACKGROUND

Little is known about the long-term drug costs associated with treating AIDS in developing countries. Brazil's AIDS treatment program has been cited widely as the developing world's largest and most successful AIDS treatment program. The program guarantees free access to highly active antiretroviral therapy (HAART) for all people living with HIV/AIDS in need of treatment. Brazil produces non-patented generic antiretroviral drugs (ARVs), procures many patented ARVs with negotiated price reductions, and recently issued a compulsory license to import one patented ARV. In this study, we investigate the drivers of recent ARV cost trends in Brazil through analysis of drug-specific prices and expenditures between 2001 and 2005.

METHODS AND FINDINGS

We compared Brazil's ARV prices to those in other low- and middle-income countries. We analyzed trends in drug expenditures for HAART in Brazil from 2001 to 2005 on the basis of cost data disaggregated by each ARV purchased by the Brazilian program. We decomposed the overall changes in expenditures to compare the relative impacts of changes in drug prices and drug purchase quantities. We also estimated the excess costs attributable to the difference between prices for generics in Brazil and the lowest global prices for these drugs. Finally, we estimated the savings attributable to Brazil's reduced prices for patented drugs. Negotiated drug prices in Brazil are lowest for patented ARVs for which generic competition is emerging. In recent years, the prices for efavirenz and lopinavir-ritonavir (lopinavir/r) have been lower in Brazil than in other middle-income countries. In contrast, the price of tenofovir is US$200 higher per patient per year than that reported in other middle-income countries. Despite precipitous price declines for four patented ARVs, total Brazilian drug expenditures doubled, to reach US$414 million in 2005. We find that the major driver of cost increases was increased purchase quantities of six specific drugs: patented lopinavir/r, efavirenz, tenofovir, atazanavir, enfuvirtide, and a locally produced generic, fixed-dose combination of zidovudine and lamivudine (AZT/3TC). Because prices declined for many of the patented drugs that constitute the largest share of drug costs, nearly the entire increase in overall drug expenditures between 2001 and 2005 is attributable to increases in drug quantities. Had all drug quantities been held constant from 2001 until 2005 (or for those drugs entering treatment guidelines after 2001, held constant between the year of introduction and 2005), total costs would have increased by only an estimated US$7 million. We estimate that in the absence of price declines for patented drugs, Brazil would have spent a cumulative total of US$2 billion on drugs for HAART between 2001 and 2005, implying a savings of US$1.2 billion from price declines. Finally, in comparing Brazilian prices for locally produced generic ARVs to the lowest international prices meeting global pharmaceutical quality standards, we find that current prices for Brazil's locally produced generics are generally much higher than corresponding global prices, and note that these prices have risen in Brazil while declining globally. We estimate the excess costs of Brazil's locally produced generics totaled US$110 million from 2001 to 2005.

CONCLUSIONS

Despite Brazil's more costly generic ARVs, the net result of ARV price changes has been a cost savings of approximately US$1 billion since 2001. HAART costs have nevertheless risen steeply as Brazil has scaled up treatment. These trends may foreshadow future AIDS treatment cost trends in other developing countries as more people start treatment, AIDS patients live longer and move from first-line to second and third-line treatment, AIDS treatment becomes more complex, generic competition emerges, and newer patented drugs become available. The specific application of the Brazilian model to other countries will depend, however, on the strength of their health systems, intellectual property regulations, epidemiological profiles, AIDS treatment guidelines, and differing capacities to produce drugs locally.

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.

Use of metabolic drugs and fish oil in HIV-positive patients with metabolic complications and associations with dyslipidaemia and treatment targets

BACKGROUND

Highly active antiretroviral therapy (HAART) with protease inhibitors (PI) is successful in suppressing viral replication, but may lead to a range of metabolic abnormalities associated with cardiovascular disease (CVD).

OBJECTIVES

The first objective of the study was to compare baseline demographic and clinical characteristics between PI users and non-PI users referred to a specialized metabolic clinic during 1999-2003. The second objective was to assess the associations of prescription drugs and fish oil with dyslipidaemia and to determine whether or not patients achieved treatment targets during 6 months of treatment.

METHODS

A retrospective analysis was performed using two sets of charts based on standardized forms with entries for personal data, drug treatment and clinical history. Anonymous linkage with the British Columbia HIV/AIDS Drug Treatment Program and the hospital laboratory was performed to gather information about HAART prescriptions and blood work.

RESULTS

In total, 237 patients were included in the study. There were few differences in any demographic or clinical factors between PI users and non-PI users. Compared with controls not taking lipid-lowering drugs or fish oil (n=48), statins appeared to be the only agent that was significantly associated with a reduced total cholesterol concentration (-15.6%; P=0.009). Fibrate treatment was associated with the largest reduction of triglyceride concentration (-37.4%; P=0.012), closely followed by fish oil (n=18;-32%; P=0.027). Six-month treatment success rates ranged between 17 and 43% of patients for total cholesterol (<5.2 mmol/L) and between 15 and 44% of patients for triglycerides (<2.3 mmol/L).

CONCLUSIONS

Despite the apparent lowering of blood lipids with drug and fish oil treatments, a majority of patients in these treatment groups (56.5-83.3%) still had elevated concentrations after 6 months.

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

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

Second-line combination antiretroviral therapy in resource-limited settings: facing the challenges through clinical research

Combination antiretroviral therapy (ART) has dramatically altered the prognosis of individuals infected with HIV. In the past 5 years there has been a concerted effort to increase access to ART in the developing world. The evidence to date suggests that adherence to therapy and clinical outcomes in developing world programmes are at least the equal of those observed in developed countries. Although access to first-line therapy is reasonably well established, there is a substantial and unacceptable mortality rate in the first 6 months after initiation of ART, particularly in those with low CD4 cell counts and late-stage disease. Failure of first-line ART is inevitable in a proportion of patients. Access to second-line ART regimens in developing countries is problematic, mainly because of the expense of HIV protease inhibitors (PIs). Access to second-line ART may be facilitated by novel strategies using the existing recommended agents or by the use of new agents or classes. Refinement of programmes in the developing world must be underpinned by the same rigorous scientific research effort that has characterized the success of the effort in the developed world. Therefore, the funding bodies responsible for the roll-out of antiretroviral access across the globe must mandate, incorporate and fund clinical research as an intrinsic aspect of combination ART roll-out programmes.

Antiviral activity, pharmacokinetics and safety of vicriviroc, an oral CCR5 antagonist, during 14-day monotherapy in HIV-infected adults

OBJECTIVE

To determine antiviral activity, pharmacokinetic properties, and safety of vicriviroc, an orally available CCR5 antagonist, as monotherapy in HIV-infected patients.

DESIGN AND METHODS

An ascending, multiple dose, placebo-controlled study randomized within treatment group. Forty-eight HIV-infected individuals were enrolled sequentially to dose groups of vicriviroc: 10, 25 and 50 mg twice a day, and were randomly assigned within group to receive vicriviroc or placebo (16 total patients/group) for 14 days.

RESULTS

Significant reductions from baseline HIV RNA after 14 days were achieved in all active treatment groups. Suppression of viral RNA persisted 2-3 days beyond the end of treatment. Reductions of 1.0 log10 HIV RNA or greater were achieved in 45, 77 and 82% of patients in the three groups, respectively. Eighteen, 46 and 45% of subjects achieved declines of 1.5 log10 or greater in HIV RNA in the three groups, respectively. Vicriviroc was rapidly absorbed with a half-life of 28-33 h, supporting once-daily dosing. Pharmacokinetic parameters were dose linear; steady state was achieved by day 12. Two subjects experienced a transient detectable X4-tropic virus. Vicriviroc was well tolerated in all dose groups. The frequency of adverse events was similar in the vicriviroc and placebo groups: 72 and 62%, respectively. The most frequently reported adverse events included headache, pharyngitis, nausea and abdominal pain, which were not dose related.

CONCLUSION

Whereas all doses were well tolerated and produced significant declines in plasma HIV RNA, total oral daily doses of 50 or 100 mg vicriviroc monotherapy for 14 days appeared to provide the most potent antiviral effect in this study.

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.

Protease Inhibitor-Based Regimens for HIV Therapy

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

X-ray crystal structures of human immunodeficiency virus type 1 protease mutants complexed with atazanavir

Atazanavir, which is marketed as REYATAZ, is the first human immunodeficiency virus type 1 (HIV-1) protease inhibitor approved for once-daily administration. As previously reported, atazanavir offers improved inhibitory profiles against several common variants of HIV-1 protease over those of the other peptidomimetic inhibitors currently on the market. This work describes the X-ray crystal structures of complexes of atazanavir with two HIV-1 protease variants, namely, (i) an enzyme optimized for resistance to autolysis and oxidation, referred to as the cleavage-resistant mutant (CRM); and (ii) the M46I/V82F/I84V/L90M mutant of the CRM enzyme, which is resistant to all approved HIV-1 protease inhibitors, referred to as the inhibitor-resistant mutant. In these two complexes, atazanavir adopts distinct bound conformations in response to the V82F substitution, which may explain why this substitution, at least in isolation, has yet to be selected in vitro or in the clinic. Because of its nearly symmetrical chemical structure, atazanavir is able to make several analogous contacts with each monomer of the biological dimer.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Atazanavir: simplicity and convenience in different scenarios

HIV protease inhibitors (PI) have undergone the most significant evolution when considering the different families of antiretrovirals. Marketed in 2003, atazanavir (ATV) is the first azapeptide PI, and is considered a member of the second generation of PIs. Important characteristics make ATV different from other drugs in the same family of antiretrovirals. It is administered once daily, either as two capsules (200 mg) or boosted with ritonavir (100 mg) two capsules (150 mg) or one capsule (300 mg). No elevations in serum levels of total cholesterol, low-density lipoprotein cholesterol or triglycerides have been observed with unboosted ATV. Although some increases in these levels are found with boosted ATV, these were lower when compared with other PIs. Elevation in unconjugated bilirubin levels, which is usually not dose limiting, is the most frequent adverse event. Naive patients receiving ATV boosted with ritonavir do not develop PI mutations at failure, whereas unboosted ATV in the same scenario induces the I50L mutation, which does not confer cross-resistance to other PIs. The best scenario for unboosted ATV is simplification. In PI treatment-experienced patients with PI mutations, susceptibility to ATV is usually reduced, so it should be administered with ritonavir. As with other PIs, careful attention must be given to pharmacokinetic drug interactions; the coadministration of certain commonly used drugs among HIV-infected patients, tenofovir and members of the proton pump inhibitor family, leads to significantly lower plasma levels of ATV.

Pharmacy care perspectives on problems with HIV antiretroviral therapy in Sweden

OBJECTIVE

This study has three main objectives (1) to identify the major problems or difficulties pharmacy staff in Sweden experience regarding pharmacy care of patients receiving antiretroviral therapy, (2) to identify the perceptions of pharmacy staff regarding what are patient-related concerns with antiretroviral therapy and (3) to compare the extent to which pharmacy staff awareness matches patient perceptions regarding what are the major problems or difficulties associated with antiretroviral therapy.

METHODS

A problem detection study (PDS) containing two questionnaires was conducted: one to be completed by pharmacy staff and another to be completed by both pharmacy staff and patients. In the latter survey, staff were asked about what they thought that patients would have responded. Staff and patient responses were then matched and compared with one another.

RESULTS

The pharmacy staff expressed their need for continuous education so as to assist the patients with their complex regimens. The staff were aware that patients were worried about therapy failure and viral resistance, medication-related problems and negative attitudes from the public. The staff however were less aware of the extent to which patients worried about not having their HIV infection under control. The staff also valued written patient information to a much higher extent than the patients.

CONCLUSIONS

The pharmacy staff' awareness of the major problems HIV patients are experiencing seems incomplete and may lead to lack of concordance between the patients and pharmacy staff. This in turn may lead to non-adherence and poor therapy outcomes. Pharmacy staff should be encouraged to improve and systematically assess patient issues regarding antiretroviral therapy. Through assessing patient needs and concerns, the pharmacists can better identify patient needs and thus better tailor their educational and behavioural interventions to improve therapy outcomes.

Common problems with antiretroviral therapy among three Swedish groups of HIV infected individuals

OBJECTIVE

The main objective of this study was to identify and compare the common problems and difficulties associated with combination antiretroviral therapy (CART) as experienced by three major groups of HIV infected individuals (homo- or bisexuals, former injecting drug users and origins of Sub-Saharan Africa) in Sweden.

METHODS

Based on the results from in-depth interviews with 15 representatives from the three major groups, a questionnaire was designed for use in a problem detection study (PDS). The study was conducted with 195 HIV-positive patients residing in the major cities of Sweden.

RESULTS

The overall response rate was 79%. The problems identified in all three groups were negative attitudes from the public, worries about disease progression or therapy failure, medication or drug-related problems and problems in connection to pharmacy visits. A specific problem in the homo- or bisexual group was drug-related problems such as adverse effects, drug interactions and pill burden. For former injecting drug users, the specific problem was disease-related conflicts with relatives and the problem of coping with the social and psychological burden caused by the HIV infection. The African group termed the risk of exposing their medication at the pharmacy as a specific problem, as this could reveal their HIV status.

CONCLUSIONS

Our findings regarding problems with CART in three patient groups in Sweden may be of use to tailor pharmacy care to HIV infected individuals. General strategies to improve adherence need to be complemented with approaches that will address the specific needs for the different patient groups affected by HIV. Further studies on group-specific interventions that promote concordance and adherence to CART will be necessary to minimize therapy failure and viral resistance.

Efavirenz/emtricitabine/tenofovir disoproxil fumarate fixed-dose combination: first-line therapy for all?

ATRIPLA (Bristol-Myers Squibb and Gilead Sciences) is a complete regimen in a single, fixed-dose combination tablet that contains: efavirenz 600 mg, emtricitabine 200 mg and tenofovir disoproxil fumarate 300 mg. Current treatment guidelines recommend this triple combination for initial therapy because of its excellent potency, tolerability and favorable safety profile. Individually, these agents have long half-lifes that allow for once-daily dosing and may provide a pharmacologic bridge for the occasional missed dose. Although several options for once-daily regimens are available, comparative clinical trials are still in progress. This article reviews relevant efficacy and safety data of efavirenz, emtricitabine and tenofovir disoproxil fumarate, compared with other once-daily agents or certain common alternate drugs presently used as initial therapy in treatment-naive patients.

Strategies for management and treatment of dyslipidemia in HIV/AIDS

With the improved survival of HIV-infected patients, there are increased concerns about the long-term effects of treatment, including protease inhibitor (PI)-related dyslipidemia. Some 50-70% of patients receiving combination antiretroviral therapy (ART) involving PIs develop lipid abnormalities consisting of elevated levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides that are well-known risk factors for cardiovascular disease. Treatment of HIV dyslipidemia should include lifestyle modifications such as a low-fat diet, increased exercise, reduced alcohol consumption and smoking cessation. In many patients, however, these changes alone will not correct lipid levels. In some patients, changing the PI component of ART to another PI or non-PI and/or lipid-lowering drugs has proven successful. Each approach is associated with advantages and limitations and the need to maintain viral suppression must be balanced with the need to treat abnormal lipid levels.

A single centre cohort experience with a new once daily antiretroviral drug

BACKGROUND

Atazanavir, an azadipeptide protease inhibitor (PI) with once daily dosing, a lack of insulin resistance, lipid increase, and gastrointestinal toxicities, is approved in combination with other antiretrovirals for the treatment of patients infected with HIV. Unboosted atazanavir is also used in highly active antiretroviral therapy (HAART) naive patients.

METHODS

The study prospectively followed up an established cohort of patients who received atazanavir, and for whom one year of follow up data were available.

RESULTS

It was found that use of atazanavir in intent to treat and on treatment analyses, maintained and led to virological suppression and increases in CD4 count in both PI naive and experienced patients. Virological failure occurred in 7% of patients and the main toxicity was hyperbilirubinaemia, which led to treatment withdrawal in 2%. Its efficacy and safety profile was similar to that seen in previous randomised studies investigating its use.

CONCLUSIONS

These data should provide reassurance for clinicians wishing to introduce a new antiretroviral into an established cohort.

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

OBJECTIVE

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

DESIGN AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Antiviral Activity, Pharmacokinetics, and Dose Response of the HIV-1 Integrase Inhibitor GS-9137 (JTK-303) in Treatment-Naive and Treatment-Experienced Patients

BACKGROUND

GS-9137 is a potent low-nanomolar strand transfer inhibitor of HIV-1 integrase.

METHODS

The antiviral activity, tolerability, pharmacokinetics, and pharmacodynamics of GS-9137 were evaluated in a randomized, double-blind, placebo-controlled monotherapy study in 40 HIV-1- infected patients not receiving antiretroviral therapy with an HIV-1 RNA between 10,000 and 300,000 copies/mL and a CD4 count of 200 cells/microL or greater. GS-9137 or matching placebo was administered with food for 10 days at 5 dosage regimens (200, 400, or 800 mg BID, 800 mg QD, or 50 mg+100 mg ritonavir QD; 6 active, 2 placebo per dose level). The primary end point was the maximum reduction from baseline in log10 HIV-1 RNA.

RESULTS

Forty patients were enrolled, with a mean baseline viral load of 4.75 log10 copies/mL and a CD4 count of 442 cells/microL. Each GS-9137 dosing regimen exhibited significant, exposure-dependent (mean reductions, -0.98 to -1.99 log10 copies/mL) antiviral activity compared with placebo (P<0.01). Twice-daily administrations of GS-9137 at doses of 400 or 800 mg or once-daily dosing of 50 mg with ritonavir demonstrated mean reductions from baseline in HIV-1 RNA of 1.91 log10 copies/mL or greater, with all patients exhibiting 1 log10 or greater and 50% having 2 log10 or greater reductions. No patient developed evidence of integrase resistance. GS-9137 showed an adverse event profile similar to placebo, and there were no study drug discontinuations.

CONCLUSIONS

GS-9137 demonstrated substantial short-term antiviral activity and was well tolerated as monotherapy, thus warranting further study.

Initiation of antiretroviral therapy

PURPOSE OF REVIEW

Until there is a therapy or a vaccine that can eradicate HIV infection, it is important to continue debating the issues of when and how to use the many antiviral agents licensed as initial treatment since there remain many areas of uncertainty.

RECENT FINDINGS

Early initiation of treatment may be beneficial in terms of HIV progression but it has to be weighed against the risks of adverse drug side effects and complications. In first-line treatment the choice of nucleoside backbones has become limited due to the availability of once a day combined formulations which have excellent short and long-term side-effect profiles. Whether to use protease inhibitors or nonnucleosides as initial agents still awaits definitive data, but again once a day therapy appears to be the preferred option.

SUMMARY

There are only a few initial treatment regimens which are convenient and well tolerated. Starting treatment early will only become a possibility if the agents used cause no long-term problems and no significant resistance. New agents are emerging but it is unlikely that they will manage to reach these exacting standards. There is a need for authoritative adherence research with the results being translated into general care.

Population pharmacokinetics of atazanavir in patients with human immunodeficiency virus infection

Atazanavir (ATV) is a new azapeptide protease inhibitor recently approved and currently used at a fixed dose of either 300 mg once per day (q.d.) in combination with 100 mg ritonavir (RTV) or 400 mg q.d. without boosting. ATV is highly bound to plasma proteins and extensively metabolized by CYP3A4. Since ATV plasma levels are highly variable and seem to be correlated with both viral response and toxicity, dosage individualization based on plasma concentration monitoring might be indicated. This study aimed to assess the ATV pharmacokinetic profile in a target population of HIV patients, to characterize interpatient and intrapatient variability, and to identify covariates that might influence ATV disposition. A population analysis was performed with NONMEM with 574 plasma samples from a cohort of 214 randomly selected patients receiving ATV. A total of 346 randomly collected ATV plasma levels and 19 full concentration-time profiles at steady state were available. The pharmacokinetic parameter estimates were an oral clearance (CL) of 12.9 liters/h (coefficient of variation [CV], 26%), a volume of distribution of 88.3 liters (CV, 29%), an absorption rate constant of 0.405 h(-1) (CV, 122%), and a lag time of 0.88 h. A relative bioavailability value was introduced to account for undercompliance due to infrequent follow-ups (0.81; CV, 45%). Among the covariates tested, only RTV significantly reduced CL by 46%, thereby increasing the ATV elimination half-life from 4.6 h to 8.8 h. The pharmacokinetic parameters of ATV were adequately described by a one-compartment population model. The concomitant use of RTV improved the pharmacokinetic profile. However, the remaining high interpatient variability suggests the possibility of an impact of unmeasured covariates, such as genetic traits or environmental influences. This population pharmacokinetic model, together with therapeutic drug monitoring and Bayesian dosage adaptation, can be helpful in the selection and adaptation of ATV doses.

Pharmacokinetics of saquinavir hard-gel/ritonavir and atazanavir when combined once daily in HIV Type 1-infected individuals administered different atazanavir doses

The pharmacokinetics and short-term safety of atazanavir 150 and 200 mg, when coadministered with saquinavir/ritonavir 1600/100 mg once daily, were evaluated. On day 1, atazanavir 150 mg once daily, was added to saquinavir/ritonavir regimens and sampling was performed to evaluate saquinavir, ritonavir, and atazanavir pharmacokinetics (day 11). Atazanavir was increased to 200 mg and pharmacokinetic assessment repeated (day 30). Geometric mean ratios (GMR) and 95% confidence intervals (CI) were used to compare saquinavir, ritonavir, and atazanavir pharmacokinetic parameters in the present study and for 14 of the subjects treated with saquinavir/ritonavir 1600/100 mg once daily without and with atazanavir 300 mg who participated in a previous trial. Geometric mean (GM) saquinavir AUC0-24, Ctrough, and Cmax were 30,589 and 32,312 ng . h/ml, 166 and 182 ng/ml, and 4267 and 4261 ng/ml when coadministered with atazanavir 150 and 200 mg (n = 18). On days 11 and 30, saquinavir and atazanavir Ctrough remained >100 ng/ml in 13/18, 14/18, 18/18, and 17/18 patients. Among the above mentioned 14 subjects, significant increases in saquinavir Ctrough (87%, 92%, 99%), Cmax (40%, 55%, 44%), and AUC0-24 (51%, 60%, 63%) were observed with atazanavir 300, 150, and 200 mg. Ritonavir AUC0-24 and Cmax were significantly increased with the addition of atazanavir 300 mg only. Atazanavir enhances saquinavir and ritonavir by a mechanism that requires elucidation. While saquinavir enhancement was apparently independent of atazanavir dose, atazanavir 300 mg produced an increase in ritonavir Cmax, which is not observed with lower atazanavir doses. Atazanavir-related hyperbilirubinemia was dose dependent. However, higher saquinavir and atazanavir exposure may be required to suppress HIV-resistant strain replication.

Cerebrovascular disease in highly active antiretroviral therapy-treated individuals: incidence and risk factors

The occurrence of cerebrovascular events in patients infected by human immunodeficiency virus (HIV) has been traditionally associated with opportunistic infections and tumors, and/or advanced stages of immunosuppression. The current use in the clinical practice of antiretroviral treatment (ART) has been associated with a dramatic reduction of HIV-related mortality. Due to the increase of median age of HIV-infected subjects and to the ART-induced lipid abnormalities, an increasing incidence of vascular complications has been reported in this population. The potential contribution of these novel mechanisms should be considered and added to the classic vascular risk factors in the HIV-infected population and the cardiac abnormalities frequently observed in these patients. Large-scale epidemiological studies are needed to better define the incidence of cerebrovascular events in HIV-infected patients and the factors associated with their occurrence.

Review of atazanavir: a novel HIV protease inhibitor

Atazanavir is a novel and potent protease inhibitor that differs from other protease inhibitors because of its good gastrointestinal tolerability, once-daily dosing, low pill burden and it does not seem to cause insulin resistance or lipid elevations in short-term use. Atazanavir produces an increase in indirect bilirubin levels, which is not related to hepatotoxicity. The incidence of atazanavir-related hyperbilirubinaemia does not seem to be increased in hepatitis B or C coinfection. I50L is atazanavir's signature mutation. It has been shown in previously treated patients that resistance is likely when three or more protease inhibitor resistance-related primary mutations are present.

Biological characterization of human immunodeficiency virus type 1 subtype C protease carrying indinavir drug-resistance mutations

Human immunodeficiency virus type 1 subtype C isolates belong to one of the most prevalent strains circulating worldwide and are responsible for the majority of new infections in the sub-Saharan region and other highly populated areas of the globe. In this work, the impact of drug-resistance mutations in the protease gene of subtype C viruses was analysed and compared with that of subtype B counterparts. A series of recombinant subtype C and B viruses was constructed carrying indinavir (IDV)-resistance mutations (M46V, I54V, V82A and L90M) and their susceptibility to six FDA-approved protease inhibitor compounds (amprenavir, indinavir, lopinavir, ritonavir, saquinavir and nelfinavir) was determined. A different impact of these mutations was found when nelfinavir and lopinavir were tested. The IDV drug-resistance mutations in the subtype C protease backbone were retained for a long period in culture without selective pressure when compared with those in subtype B counterparts in washout experiments.

Atazanavir and lopinavir/ritonavir: pharmacokinetics, safety and efficacy of a promising double-boosted protease inhibitor regimen

OBJECTIVE

To assess the pharmacokinetics and tolerability of lopinavir (LPV), ritonavir (RTV) and atazanavir (ATV) as a double-boosted protease inhibitor regimen in HIV-infected adults.

METHODS

Sixteen patients who started LPV/RTV (400/100 mg b.i.d.) and ATV (300 mg q.d.) were enrolled in the study group (arm A). LPV pharmacokinetics were compared to those of two historical groups: arm B, 15 patients who received LPV/RTV (400/100 mg b.i.d.); and arm C, 25 patients who received LPV/RTV/saquinavir (SQV) (400/100/1000 mg b.i.d.). ATV pharmacokinetics were compared to those of 15 consecutive patients who received ATV and RTV (300/100 mg q.d.) (arm D). Drug concentrations were measured by HPLC.

RESULTS

LPV concentrations were significantly higher in arm A than in arms B and C. Median (interquartile range) LPV area under the curve (AUC)0-12 values were 115.7 (99.8-136.5), 85.2 (68.3-109.2) and 85.1 (60.6-110.1) microg/h/ml, respectively. C(max) values were 12.2 (10.7-14.5), 9.5 (6.8-13.9) and 10.0 (6.9-13.6) microg/ml, respectively. C(min) values were 9.1 (7.1-10.4), 5.6 (4.7-8.2) and 5.5 (4.2-7.5) microg/ml, respectively. No difference was observed for ATV AUC0-24 or C(max) between arms A and D. ATV C(min) values were 1.07 (0.61-1.79) in arm A and 0.58 (0.32-0.83) in arm D (P = 0.001). Treatment was not discontinued in any patient because of adverse effects. At 24 weeks, viral load was < 50 copies/ml in 13 of 16 patients.

CONCLUSIONS

The combination of ATV and LPV/RTV provided high plasma concentrations of both PI, which seemed to be appropriate for patients with multiple prior therapeutic failures, yielding good tolerability and substantial antiviral efficacy.

New antiretroviral drugs in clinical use

The advent of combination antiretroviral therapy for the treatment of human immunodeficiency virus (HIV) infection has dramatically changed the prognosis and quality of life of HIV-infected adults and children. To date, there are 21 antiretroviral agents available with only 11 agents being approved for the use in young children less than 6 years of age. The currently available antiretroviral agents belong to four different classes; nucleoside/nucleotide reverse transcriptase inhibitors (NRTI, NtRTI), non-nucleoside reverse transcriptase inhibitors (NNRTI), protease inhibitors (PI), and a new class of fusion inhibitors (FI). It is recommended that the treatment regimen should be a combination of at least 3 drugs from different drug classes as this has been shown to slow disease progression, improve survival, and result in better virologic and immunologic responses. Treatment with antiretroviral agents is frequently complicated by the issues of adherence, tolerability, long term toxicity and drug resistance. Many efforts have been made to develop new antiretroviral agents with greater potency, higher tolerability profiles and better convenience. Some new agents are also effective against drug-resistant strains of HIV. Since 2001, there were 7 new antiretroviral agents and 2 fixed-dose multidrug formulations being approved for the treatment of HIV infection, most are approved only for use in adults. In this article, we will review new antiretroviral agents including emtricitabine, tenofovir disoproxil fumarate, atazanavir, fosamprenavir, tipranavir and enfuvirtide. Pediatric information on these drugs will be provided when available.

[Metabolic alterations in HIV-associated lipodystrophy syndrome]

The introduction of highly active antiretroviral therapy (HAART) has reduced morbidity and mortality in patients infected with the human immunodeficiency virus (HIV). However, prolonged treatment with combination regimens can be difficult to sustain because of problems with adherence and toxic effects. Treatment with antiretroviral agents--protease inhibitors in particular--has uncovered a syndrome of abnormal fat redistribution, impaired glucose metabolism, insulin resistance and dyslipidemia, collectively termed lipodystrophy syndrome (SLHIV). Nowadays, no clinical guidelines are available for the prevention or treatment of SLHIV, and its cause have yet to be totally elucidated. This review emphasizes the clinical features and the data from previous studies about the SLHIV taking into account that a better understanding of this syndrome for HIV specialists, cardiologists and endocrinologists is fundamental for the disease control.

Metabolic Abnormalities Associated with the Use of Protease Inhibitors and Non-nucleoside Reverse Transcriptase Inhibitors

The use of protease inhibitors and non-nucleoside reverse transcriptase inhibitors for the treatment of HIV infection and AIDS has been associated with multiple abnormalities in glucose and lipid metabolism. Specifically, these abnormalities include insulin resistance, increased triglycerides and increased LDL cholesterol levels. The metabolic disturbances are due to a combination of factors, including the direct effect of medications, restoration to health and HIV disease, as well as individual genetic predisposition. Of the available anti-retroviral medications, indinavir has been associated with causing the most insulin resistance and ritonavir with causing the most hypertriglyceridemia.

Nelfinavir: a review of its use in the management of HIV infection

Nelfinavir (Viracept) is an orally administered protease inhibitor. In combination with other antiretroviral drugs (usually nucleoside reverse transcriptase inhibitors [NRTIs]), nelfinavir produces substantial and sustained reductions in viral load in patients with HIV infection. Nelfinavir may be used in the treatment of adults, adolescents and children aged >or=2 years with HIV infection. It can also be used in pregnancy. Resistance to nelfinavir may develop, but the most common mutation (D30N, appearing mainly in HIV-1 subtype B) does not confer resistance to other protease inhibitors, thereby conserving these agents for later use. Although less effective than lopinavir/ritonavir, the preferred first-line treatment in US guidelines, nelfinavir is positioned as an alternative agent for the treatment of adults and adolescents with HIV infection and is an option for those unable to tolerate other protease inhibitors. Nelfinavir also has a role in the management of pregnant patients as well as paediatric patients with HIV infection.

Salvage Therapy with Atazanavir/Ritonavir Combined to Tenofovir in HIV-Infected Patients with Multiple Treatment Failures: Randomized Anrs 107 Trial

Background

Ritonavir (RTV)-boosted atazanavir (ATV) and tenofovir disoproxil fumarate (TDF-DF) are promising in highly experienced patients because of their pharmacokinetic profile, activity, safety and resistance properties.

Methods

A 26-week study of the safety and efficacy of RTV-boosted ATV plus TDF-DF was conducted in 53 HIV-infected patients who were failing their current highly active antiretroviral therapy (HAART) regimen. Patients with history of failure to at least two protease inhibitors (PIs) and one non-nucleoside reverse transcriptase inhibitor (NNRTI) were randomized to either continue their current regimen (group 1) or replace the PI by ATV (300 mg once daily) boosted by RTV (100 mg; group 2) for 2 weeks. Then, all patients received the same combination of ATV, RTV and TDF-DF (300 mg) plus optimized NRTIs regimen.

Results

At baseline, median CD4+ T-cell count was 206/mm3, median viral load (VL) 5.0 log10/ml and median numbers of NRTI, NNRTI and PI resistance mutations were 7, 1 and 8, respectively. At week 2, median VL remained unchanged from baseline in group 2 as compared with group 1 (-0.1 vs -0.1 log10/ml). At week 26, a mild decrease in median VL from baseline of 0.2 log10/ml was observed, with 16 (31%) and 9 (17%) patients exhibiting a decrease in viral load of at least 0.5 and 1.0 log10/ml, respectively. Baseline phenotypic and genotypic resistance to ATV were the most predictive independent factors of virological response. The regimen was well tolerated.

Conclusion

In these very advanced patients failing highly HAART, the combination of boosted ATV plus TDF-DF yielded low antiretroviral activity.

Body Fat and Other Metabolic Effects of Atazanavir and Efavirenz, Each Administered in Combination with Zidovudine plus Lamivudine, in Antiretroviral- Naive HIV-Infected Patients

BACKGROUND

Protease inhibitor treatment of human immunodeficiency virus (HIV)-infected individuals has been linked to the development of lipodystrophy. The effects of atazanavir on body fat distribution and related metabolic parameters were examined in antiretroviral-naive patients.

METHODS

HIV-positive patients with CD4 cell counts > or = 100 cells/mm3 were randomized to 1 of 2 treatment arms: (1) atazanavir, 400 mg given once daily, plus efavirenz placebo; or (2) efavirenz, 600 mg given once daily, plus atazanavir placebo; each drug was administered with fixed-dose zidovudine (300 mg) and lamivudine (150 mg) given twice daily, and patients were treated for at least 48 weeks. Fat distribution measurements (visceral adipose tissue [VAT], subcutaneous adipose tissue [SAT], and total adipose tissue [TAT], as measured by computed tomography; and appendicular fat, truncal fat, and total fat levels, as measured by dual-energy x-ray absorptiometry), metabolic measurements (cholesterol and fasting triglyceride levels), and measurements of insulin resistance (fasting glucose and fasting insulin levels) were made at baseline and at week 48 of treatment for a subgroup of 111 atazanavir recipients and 100 efavirenz recipients.

RESULTS

Atazanavir and efavirenz treatments resulted in minimal to modest increases in fat accumulation, as measured by VAT, SAT, TAT, appendicular fat, truncal fat, and total fat levels; results were comparable in both arms. In addition, atazanavir was associated with none of the metabolic abnormalities seen with many other protease inhibitors.

CONCLUSIONS

Use of atazanavir for 48 weeks neither resulted in abnormal fat redistribution in antiretroviral-naive patients nor induced other metabolic disturbances commonly associated with HIV-related lipodystrophy. Longer-term assessments (e.g., at 96 weeks) will be important to confirm these findings.

Clinical validation of atazanavir/ritonavir genotypic resistance score in protease inhibitor-experienced patients

OBJECTIVE

To develop a clinically relevant genotypic resistance score for boosted atazanavir (ATV) in protease inhibitor-experienced patients.

METHODS

At baseline, 62 patients with HIV-1 RNA > 1000 copies/ml switched to a boosted ATV regimen (300 mg ATV, 100 mg ritonavir once daily); two were excluded from analysis at 3 months as they had undetectable plasma ATV. The impact of baseline protease mutations on virological response (> 1 log10 copies/ml plasma HIV RNA decrease) at 3 months was analysed using Fisher's exact test. Mutations with prevalence > 8% and P < 0.2 were retained. Cochran-Armitage's test was used to select the combination of mutations most strongly associated with reduced virological response. Robustness of the score was investigated using bootstrap resampling.

RESULTS

At 3 months, 82% of patients had a virological response and 56% had RNA < 50 copies/ml. Eight mutations (10F/I/V, 16E, 33I/F/V, 46I/L, 60E, 84V, 85V and 90M) were retained in the genotypic resistance score (P = 8.67 x 10) and virological response was observed in 100%, 100%, 80%, 42%, and 0% of patients with none, one, two, three, and four/five mutations, respectively. There was 100% response in patients with a score < 2 independently of the number of active drugs, whereas in patients with a score > or = 3 there was a gradient of response according to the number of active drugs (0%, 29% and 60% with none, one and two/three active drugs, respectively).

CONCLUSIONS

The occurrence of three of the eight mutations in the ATV/RTV genotypic resistance score predicted a clinically identifiable reduced response in patients.

Early clinical experience with atazanavir in treatment-experienced patients

Background: Atazanavir (ATV) is a newly approved protease inhibitor following successful clinical trials in naive and treatment-experienced patients. We describe early experience with ATV in treatment-experienced patients attending a single ambulatory care clinic in Sydney. Methods: Patients commencing ATV between February 2003 and May 2004 in an expanded access program were identified from the clinic pharmacy’s database. Data were retrospectively collected from patients’ medical records. Results: Data from 30 patients were analysed. Reasons for commencing ATV were: virological failure in six patients (20%); toxicity to previous regimen in 13 patients (43%); simplification strategy in two patients (7%); and recommencing therapy in nine patients (30%) following treatment interruption. Six patients (20%) discontinued ATV. One patient discontinued ATV due to virological failure, two patients discontinued due to toxicity to concomitant antiretrovirals, two as a result of the patient’s choice and one as a result of the physician’s decision. Eighteen patients commenced ATV in combination therapy with a detectable viral load (VL). From a baseline VL of 4.3 ± 1.1 log10 copies mL–1, 15 (83%) had >1.0 log decrease in VL with 11 (61%) achieving viral suppression (<50 copies mL–1). Three (16%) failures were recorded in this group. Twelve subjects commenced ATV with an undetectable VL. One failure was recorded in this group. Bilirubin increased by 22.7 μmol L–1 (P < 0.001), with significant decreases in cholesterol (1.4 mmol L–1, P = 0.01) and triglycerides (1.5 mmol L–1, P = 0.01) in 12 patients on ritonavir-boosted ATV. Conclusion: This audit found ATV to be safe, well tolerated and had good potency in treatment-experienced patients. However caution should be exercised in switching to ATV in heavily pre-treated patients.

What a Cardiologist Needs to Know About Patients With Human Immunodeficiency Virus Infection

Patient case: A 48-year-old man with human immunodeficiency virus (HIV) infection developed chronic chest pain that started after a bout of pneumonia. He has hypertension and has smoked cigarettes in the past. His current medications include Kaletra and Combivir. His total cholesterol was 331 mg/L, his HDL cholesterol was 27 mg/L, his triglycerides were 935 mg/L, and his LDL cholesterol could not be calculated. How should this patient be evaluated and managed?