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

Applications of the hollow-fibre infection model (HFIM) in viral infection studies

Conventional cell culture systems involve growing cells in stationary cultures in the presence of growth medium containing various types of supplements. At confluency, the cells are divided and further expanded in new culture dishes. This passage from confluent monolayer to sparse cultures does not reflect normal physiological conditions and represents quite a drastic physiological change that may affect the natural cell physiobiology. Hollow-fibre bioreactors were in part developed to overcome these limitations and since their inception, they have widely been used in production of monoclonal antibodies and recombinant proteins. These bioreactors are increasingly used to study antibacterial drug effects via simulation of in vivo pharmacokinetic profiles. The use of the hollow-fibre infection model (HFIM) in viral infection studies is less well developed and in this review we have analysed and summarized the current available literature on the use of these bioreactors, with an emphasis on viruses. Our work has demonstrated that this system can be applied for viral expansion, studies of drug resistance mechanisms, and studies of pharmacokinetic/pharmacodynamic (PK/PD) of antiviral compounds. These platforms could therefore have great applications in large-scale vaccine development, and in studies of mechanisms driving antiviral resistance, since the HFIM could recapitulate the same resistance mechanisms and mutations observed in vivo in clinic. Furthermore, some dosage and spacing regimens evaluated in the HFIM system, as allowing maximal viral suppression, are in line with clinical practice and highlight this 'in vivo-like' system as a powerful tool for experimental validation of in vitro-predicted antiviral activities.

GII.4 Norovirus Protease Shows pH-Sensitive Proteolysis with a Unique Arg-His Pairing in the Catalytic Site

Human noroviruses (NoVs) are the main cause of epidemic and sporadic gastroenteritis. Phylogenetically, noroviruses are divided into seven genogroups, with each divided into multiple genotypes. NoVs belonging to genogroup II and genotype 4 (GII.4) are globally most prevalent. Genetic diversity among the NoVs and the periodic emergence of novel strains present a challenge for the development of vaccines and antivirals to treat NoV infection. NoV protease is essential for viral replication and is an attractive target for the development of antivirals. The available structure of GI.1 protease provided a basis for the design of inhibitors targeting the active site of the protease. These inhibitors, although potent against the GI proteases, poorly inhibit the GII proteases, for which structural information is lacking. To elucidate the structural basis for this difference in the inhibitor efficiency, we determined the crystal structure of a GII.4 protease. The structure revealed significant changes in the S2 substrate-binding pocket, making it noticeably smaller, and in the active site, with the catalytic triad residues showing conformational changes. Furthermore, a conserved arginine is found inserted into the active site, interacting with the catalytic histidine and restricting substrate/inhibitor access to the S2 pocket. This interaction alters the relationships between the catalytic residues and may allow for a pH-dependent regulation of protease activity. The changes we observed in the GII.4 protease structure may explain the reduced potency of the GI-specific inhibitors against the GII protease and therefore must be taken into account when designing broadly cross-reactive antivirals against NoVs.IMPORTANCE Human noroviruses (NoVs) cause sporadic and epidemic gastroenteritis worldwide. They are divided into seven genogroups (GI to GVII), with each genogroup further divided into several genotypes. Human NoVs belonging to genogroup II and genotype 4 (GII.4) are the most prevalent. Currently, there are no vaccines or antiviral drugs available for NoV infection. The protease encoded by NoV is considered a valuable target because of its essential role in replication. NoV protease structures have only been determined for the GI genogroup. We show here that the structure of the GII.4 protease exhibits several significant changes from GI proteases, including a unique pairing of an arginine with the catalytic histidine that makes the proteolytic activity of GII.4 protease pH sensitive. A comparative analysis of NoV protease structures may provide a rational framework for structure-based drug design of broadly cross-reactive inhibitors targeting NoVs.

A first-in-human, randomized, double-blind, placebo-controlled, single and multiple ascending oral dose study to assess the safety, tolerability, and pharmacokinetics of BZF961 with and without ritonavir in healthy adult volunteers

Objective: Infection with hepatitis C virus is the leading indication for liver transplantation and most common cause of infectious disease-related mortality in the United States. BZF961 is a novel inhibitor of the hepatitis C virus NS3-4A protease. Methods: This sequential, three part exploratory first-in-human study investigated the safety and pharmacokinetics of single and multiple ascending oral doses of BZF961 in healthy subjects. The first two parts were randomized, double-blind, placebo-controlled, time-lagged, single and multiple ascending oral dose segments. The third part analyzed the effect of ritonavir on BZF961 pharmacokinetics. Results: BZF961 was generally safe and well-tolerated in single and multiple oral doses in healthy subjects. There were no deaths and no serious adverse events. The most common adverse events were nausea and other gastrointestinal symptoms. Co-administration of ritonavir with BZF961 was well tolerated and increased BZF961 exposure by up to 60-fold, as well as reduced the overall exposure variability. Conclusions: BZF961 was generally safe and well-tolerated and its exposure was boosted by the co-administration of ritonavir.

Excess Clinical Comorbidity Among HIV-Infected Patients Accessing Primary Care in US Community Health Centers

OBJECTIVES

As the life expectancy of people infected with human immunodeficiency virus (HIV) infection has increased, the spectrum of illness has evolved. We evaluated whether people living with HIV accessing primary care in US community health centers had higher morbidity compared with HIV-uninfected patients receiving care at the same sites.

METHODS

We compared data from electronic health records for 12 837 HIV-infected and 227 012 HIV-uninfected patients to evaluate the relative prevalence of diabetes mellitus, hypertension, chronic kidney disease, dyslipidemia, and malignancies by HIV serostatus. We used multivariable logistic regression to evaluate differences. Participants were patients aged ≥18 who were followed for ≥3 years (from January 2006 to December 2016) in 1 of 17 community health centers belonging to the Community Health Applied Research Network.

RESULTS

Nearly two-thirds of HIV-infected and HIV-uninfected patients lived in poverty. Compared with HIV-uninfected patients, HIV-infected patients were significantly more likely to be diagnosed and/or treated for diabetes (odds ratio [OR] = 1.18; 95% confidence interval [CI], 1.22-1.41), hypertension (OR = 1.38; 95% CI, 1.31-1.46), dyslipidemia (OR = 2.30; 95% CI, 2.17-2.43), chronic kidney disease (OR = 4.75; 95% CI, 4.23-5.34), lymphomas (OR = 4.02; 95% CI, 2.86-5.67), cancers related to human papillomavirus (OR = 5.05; 95% CI, 3.77-6.78), or other cancers (OR = 1.25; 95% CI, 1.10-1.42). The prevalence of stroke was higher among HIV-infected patients (OR = 1.32; 95% CI, 1.06-1.63) than among HIV-uninfected patients, but the prevalence of myocardial infarction or coronary artery disease did not differ between the 2 groups.

CONCLUSIONS

As HIV-infected patients live longer, the increasing burden of noncommunicable diseases may complicate their clinical management, requiring primary care providers to be trained in chronic disease management for this population.

Incidence of atazanavir- associated adverse drug reactions in second -line drugs treated south Indian HIV-1 infected patients

Background:

Ritonavir-boosted atazanavir (ATV/r) is the preferred second-line protease inhibitor (PI) option for HIV patients in resource-limited settings; its pattern of adverse drug reactions (ADRs) has not been much reported from India; hence, in this study, we have analyzed the incidence of ATV/r-associated ADRs in Southern Indian HIV-1-infected patients.

Methods:

In this prospective study, 111 HIV patients treated with ATV/r were included with at least 2 years follow-up visits for the emergence of hyperbilirubinemia, hypertransaminasemia, and serum creatinine elevation. The causality assessment was done based on the WHO scale for the causality assessment of suspected ADR.

Results:

The incidence of severe hyperbilirubinemia, hypertransaminasemia, and creatinine elevation was 28.6, 0.76, and 1.62 cases/100 person years, respectively. 3TC/FTC + TDF (odds ratio [OR]: 6.07, confidence interval [CI]: 1.31–27.98, P = 0.015) nucleos (t) ide reverse transcriptase inhibitor backbone and male sex (OR: 18.64, CI: 2.13–162.93, P = 0.0082) were found to be significantly associated with hypertransaminasemia and creatinine elevation, respectively. The causality assessment of ADR was “possible” for all the participants. Kaplan–Meier analysis showed hyperbilirubinemia to emerge earlier (mean duration: 32.18 months, CI: 24.9–39.4 months) followed by hypertransaminasemia and creatinine elevation. Hyperbilirubinemia is an expected side effect associated with ATV/r which is benign, transient, and does not predispose to hypertransaminasemia.

Conclusion:

Our study results show that patients starting ATV/r should be counseled for a good adherence in spite of the emergence of hyperbilirubinemia which generally reverts to normal range.

Population pharmacokinetic modelling of the changes in atazanavir plasma clearance caused by ritonavir plasma concentrations in HIV-1 infected patients

AIMS

The aim of the present study was to develop a simultaneous population pharmacokinetic model for atazanavir (ATV) incorporating the effect of ritonavir (RTV) on clearance to predict ATV concentrations under different dosing regimens in HIV-1-infected patients.

METHODS

A Cross-sectional study was carried out in 83 HIV-1-infected adults taking ATV 400 mg or ATV 300 mg/RTV 100 mg once daily. Demographic and clinical characteristics were registered and blood samples collected to measure drug concentrations. A population pharmacokinetic model was constructed using nonlinear mixed-effects modelling and used to simulate six dosing scenarios.

RESULTS

The selected one-compartmental model described the pharmacokinetics of RTV and ATV simultaneously, showing exponential, direct inhibition of ATV clearance according to the RTV plasma concentration, which explained 17.5% of the variability. A mean RTV plasma concentration of 0.63 mg l-1 predicted an 18% decrease in ATV clearance. The percentages of patients with an end-of-dose-interval concentration of ATV below or above the minimum and maximum target concentrations of 0.15 mg l-1 and 0.85 mg l-1 favoured the selection of the simulated ATV/RTV once-daily regimens (ATV 400 mg, ATV 300 mg/RTV 100 mg, ATV 300 mg/RTV 50 mg, ATV 200/RTV 100 mg) over the unboosted twice-daily regimens (ATV 300 mg, ATV 200 mg).

CONCLUSIONS

A one-compartment simultaneous model can describe the pharmacokinetics of RTV and ATV, including the effect of RTV plasma concentrations on ATV clearance. This model is promising for predicting individuals' ATV concentrations in clinical scenarios, and supports further clinical trials of once-daily doses of ATV 300 mg/RTV 50 mg or ATV 200 mg/RTV 100 mg to confirm efficacy and safety.

Brief Report: A Phase 1b/Pharmacokinetic Trial of PTC299, a Novel PostTranscriptional VEGF Inhibitor, for AIDS-Related Kaposi's Sarcoma: AIDS Malignancy Consortium Trial 059

Vascular endothelial growth factor (VEGF) plays an important role in Kaposi's sarcoma (KS). We administered PTC299, a post-transcriptional inhibitor of pathogenic VEGF, to persons with HIV-related KS. Seventeen participants received 3 different doses of PTC299. Adverse events typically observed with VEGF inhibition were absent. Three participants had partial tumor responses and 11 had stable disease. There were no differences in exposure to PTC299 by antiretroviral regimen. Serum VEGF, but not KS-associated herpesvirus DNA, decreased on treatment. Given redundancies in the VEGF feedback loop, future trials should consider combining PTC299 with agents that inhibit different pathways implicated in KS and KS-associated herpesvirus proliferation.

Pharmacogenetics of unboosted atazanavir in HIV-infected individuals in resource-limited settings: a sub-study of the AIDS Clinical Trials Group (ACTG) PEARLS study (NWCS 342)

OBJECTIVES

The multinational PEARLS (ACTG A5175) study, conducted mainly in resource-limited settings, identified an increased treatment failure rate among HIV-infected individuals randomized to once-daily unboosted atazanavir, didanosine-EC, and emtricitabine compared with efavirenz-based regimens. We evaluated associations between selected human genetic polymorphisms and atazanavir pharmacokinetics in PEARLS.

METHODS

Polymorphisms in CYP3A5, ABCB1, SLCO1B1 and NR1I2 were genotyped in PEARLS participants randomized to atazanavir plus didanosine-EC plus emtricitabine in Peru, South Africa and the USA, who also consented to genetic analysis. Non-linear mixed-effects population pharmacokinetic modelling was used to predict atazanavir oral clearance (CL/F) and concentration at 24 h (C24). Atazanavir mono-oxidation metabolites M1 and M2 were quantified from the same single-point plasma sample used to quantify the parent drug. Data were log10 transformed for statistical analysis using unpaired t-tests and one-way ANOVA and are presented as geometric mean (95% CI).

RESULTS

Eighty-four HIV-infected participants were genotyped, including 44 Black Africans or African Americans and 28 women. Median age was 34 years. We identified 56 CYP3A5 expressers and 28 non-expressers. Atazanavir CL/F and C24 did not differ between CYP3A5 expressers and non-expressers: 13.2 (12.1-14.4) versus 12.7 L/h (11.7-13.9), P = 0.61, and 75.3 (46.1-123.0) versus 130.9 ng/mL (86.9-197.2), P = 0.14, respectively. M1/atazanavir and M2/atazanavir ratios were higher in expressers than in non-expressers: 0.0083 (0.0074-0.0094) versus 0.0063 (0.0053-0.0075), P = 0.008, and 0.0065 (0.0057-0.0073) versus 0.0050 (0.0042-0.0061), P = 0.02, respectively.

CONCLUSIONS

Expression of CYP3A5 appears to be associated with increased M1 and M2 atazanavir metabolite formation, without significantly affecting parent compound pharmacokinetics.

Treatment response to unboosted atazanavir in combination with tenofovir disoproxil fumarate and lamivudine in human immunodeficiency virus-1-infected patients who have achieved virological suppression: A therapeutic drug monitoring and pharmacogenetic study

BACKGROUND/PURPOSE

Treatment response to switch regimens containing unboosted atazanavir and tenofovir disoproxil fumarate (TDF)/lamivudine guided by therapeutic drug monitoring in human immunodeficiency virus-infected patients is rarely investigated.

METHODS

Consecutive patients with plasma human immunodeficiency virus RNA load < 200 copies/mL switching to unboosted atazanavir plus zidovudine-lamivudine (coformulated), abacavir-lamivudine (coformulated), or TDF/lamivudine > 3 months were included for determinations of treatment response, plasma atazanavir concentrations, and single-nucleotide polymorphisms of MDR1, PXR, and UGT1A1 genes from 2010 to 2014. Treatment failure was defined as either discontinuation of atazanavir for any reason or plasma viral load ≥ 200 copies/mL within 96 weeks.

RESULTS

During the study period, 128 patients switched to unboosted atazanavir with TDF/lamivudine (TDF group) and 186 patients switched to unboosted atazanavir with two other nucleoside reverse-transcriptase inhibitors (non-TDF group). There were no statistically significant differences in the distributions of single-nucleotide polymorphisms of MDR1 (2677 and 3435), PXR genotypes (63396), and UGT1A1*28 between the two groups. Recommended plasma atazanavir concentrations were achieved in 83.5% and 64.9% of the TDF group and non-TDF group, respectively (p < 0.01). After a median follow-up duration of 96.0 weeks, treatment failure occurred in 19 (14.9%) and 34 (18.3%) patients in the TDF group and non-TDF group, respectively (p = 0.60). Low-level viremia (40-200 copies/mL) before switch (adjusted hazard ratio, 2.12; 95% confidence interval, 1.12-4.01) and without therapeutic drug monitoring (adjusted hazard ratio, 2.08; 95% confidence interval, 1.16-3.73) were risk factors for treatment failure.

CONCLUSION

Switch to unboosted atazanavir with TDF/lamivudine achieves a similar treatment response to that with two other nucleoside reverse-transcriptase inhibitors in patients achieving virological suppression with the guidance of therapeutic drug monitoring.

Initial Therapy for Human Immunodeficiency Virus: Broadening the Options

The goal of investigation into new therapeutic options for HIV/AIDS is to further the achievements of highly active antiretroviral therapy by developing new drugs with improved efficacy. Although several therapies are currently available for initial therapy in HIV-infected patients, ongoing research focuses on additions to existing and novel drug classes that might have improved pharmacokinetic and tolerability profiles, as well as on new therapeutic combinations that might result in synergistic activity. To retain activity against resistant strains, novel drugs need to target the numerous critical points in the life cycle of HIV, inhibiting different enzyme subsites than those affected by antiretroviral agents currently in use. An improvement in patient adherence to therapy is another key objective of efforts in HIV treatment, as suboptimal drug levels are a main determinant of antiretroviral regimen failure. This article reviews the current classes of antiretroviral agents in development, describing the clinical data obtained to date. These agents may have potential use as initial therapy in HIV patients.

Coronary Heart Disease Risk, Dyslipidemia, and Management in HIV-Infected Persons

Dyslipidemia and coronary heart disease (CHD) are of increasing concern in persons with human immunodeficiency virus (HIV) infection who are living longer because of the benefits of highly active antiretroviral therapy (HAART). All classes of drugs used in HAART have been associated with atherogenic changes in lipid profiles. The management of HIV-infected persons with dyslipidemia and/or CHD currently emphasizes the importance of monitoring and optimizing lipid levels through lifestyle changes, switching antiretrovirals (ARVs), and lipid-lowering treatments utilizing guidelines developed for persons without HIV infection. In HIV-infected persons, the use of lipid-lowering drugs may result in pharmacokinetic interactions with ARVs, complicating the management of patients. Recent advances in our understanding of the differential effects of specific ARVs on lipids is beginning to alter the clinical approach to management. In the absence of randomized clinical trials, clinicians should aggressively treat atherogenic dyslipidemia by primarily utilizing or switching to ARVs with the lowest potential to induce CHD or, when this is not possible or is ineffective, secondarily by the addition of lipid-lowering therapy. The current optimal management of HIV infection requires careful selection of ARVs with consideration given to the potential development of CHD and an understanding of how to manage dyslipidemia.

Impact of Various Antiretroviral Drugs and Their Plasma Concentrations on Plasma Lipids in Heavily Pretreated HIV-Infected Patients

OBJECTIVE

To evaluate the frequency and the magnitude of lipid abnormalities (LA) in respect to the nature of the antiretroviral drug and its plasma concentrations.

PATIENTS/METHOD

Trough concentrations (C(trough)) of protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) were assessed at Weeks 4, 8, 24, 28, and 32. Fasting triglycerides (TG) and total cholesterol (CH) were sampled at Weeks 0, 12, 20, and 32. We analyzed the probability of occurrence of grade 3-4 CH (> 7.8 mmol/L) and TG (> 8.4 mmol/L) during a 24-week period according to the drug taken using a Kaplan-Meier analysis and log rank test. Relation between Week 8 PI or NNRTI C(trough) and Week 12 lipid levels was assessed using the Kendall correlation measure.

RESULTS

The PharmAdapt study included 252 patients (mean age 41 years, 83% males); the patients received a PI (73%), an NNRTI (50%), and/or a ritonavir (RTV) booster-containing (46%) regimen. Compared to any other regimen, use of lopinavir (LPV)/RTV or efavirenz (EFV) was associated with a higher risk of grade 3-4 CH. Use of LPV/RTV and RTV booster was associated with a higher risk of grade 3-4 TG. Use of any PI-containing regimen was associated with a higher risk for grade 3-4 CH and TG compared to non PI-based regimens. Kendall correlation coefficients for PI or NNRTI C(trough) and blood lipid levels were close to zero for all drugs and CH or TG, showing the absence of relation between drug concentrations and lipid levels.

CONCLUSION

Severity of lipid abnormalities is related to the nature of the antiretroviral drug. There is no short-term relation between PI or NNRTI trough concentrations and blood lipid levels in heavily pretreated patients.

Comparison of Two Once-Daily Regimens with a Regimen Consisting of Nelfinavir, Didanosine, and Stavudine in Antiretroviral Therapy-Naïve Adults: 48-Week Results from the Antiretroviral Regimen Evaluation Study (ARES)

BACKGROUND

To improve the dosing frequency and pill burden of antiretroviral therapy, we compared two once-daily dosed regimens to a twice-daily dosed regimen.

METHOD

HIV-1-infected, antiretroviral drug-naïve adults were randomized to either twice-daily nelfinavir and stavudine and once-daily didanosine (regimen A) or simplified once-daily dosed antiretroviral regimens consisting of nevirapine, didanosine, and lamivudine (regimen B) or saquinavir, ritonavir, didanosine, and lamivudine (regimen C).

RESULTS

At 48 weeks of therapy, the proportion of patients with a blood plasma HIV-1 RNA concentration (pVL) <50 copies/mL by intention-to treat analysis was 42.3%, 50.0%, and 56.5% for regimens A (n = 26), B (n = 22), and C (n = 23), respectively. The time to a pVL <50 copies/mL for the first time was significantly shorter in regimen C, and there was significantly more progression to CDC events in regimen B. These differences are possibly due to differences in baseline characteristics. Adverse events were lowest for regimen C; more signs associated with mitochondrial toxicity occurred in regimen A. Increase in CD4 count was comparable between arms.

CONCLUSION

No statistically significant difference in efficacy was found between the two investigated once-daily dosed treatment regimens (B and C) and the reference (A). Regimen C possibly had a better virological response and less toxicity than regimens A and B.

Atazanavir: The Advent of a New Generation of More Convenient Protease Inhibitors

Protease inhibitors (PIs) have created a new future for many HIV-infected patients. After the initial enthusiasm following its first approval, complex drug schedules and frequent toxicities of PIs prompted researchers to find alternative drugs. However, it is now clear that not all triple combinations are equally valid. Certain regimens based on the association of only reverse transcriptase inhibitors have shown high rates of virological failure, with the selection of cross-resistance mutations. The availability of new generation PIs, such as atazanavir, with improved safety profiles and more convenient administration schedules returns this drug family to the front of the HIV therapeutic armamentarium. Recent clinical studies support the assertion that atazanavir may display excellent behavior as part of first-line regimens in rescue interventions or in simplification strategies.

Predictors of Virological Response to Atazanavir in Protease Inhibitor-Experienced Patients

BACKGROUND

Atazanavir (ATV) is the latest approved HIV protease inhibitor (PI). Even though it is very convenient (only two capsules once a day), concerns have risen about its potency.

METHOD

The clinical performance of ATV 400 mg once a day was examined in all PI-experienced patients who were included in the ATV expanded access program conducted in a single institution. The predictive value of baseline drug resistance HIV genotypes, ATV plasma trough levels, and the genotypic inhibitory quotient (GIQ) on the virological response at week 24 was assessed.

RESULTS

Data from 92 patients were analyzed. ATV was prescribed as part of a rescue intervention (45%), a simplification strategy (11%), or an attempt to ameliorate hyperlipidemias (23%) or other toxicities (16%). Tenofovir (TDF) was concomitantly used with ATV in 78% of patients. None received ritonavir boosting. In patients with detectable viremia at baseline (65%), the median HIV RNA drop was 0.7 logs. The median ATV Cmin was 0.12 microg/mL (IQR, 0.05-0.22 microg/mL), which is clearly above the IC90 (90% inhibitory concentration) for ATV in wild-type viruses. The virological response did not correlate significantly with ATV Cmin. The median number of protease resistance mutations was lower in patients showing virological response than in nonresponders (1 vs. 5; p=.07). A higher HIV RNA drop was associated with a higher GIQ (p=.02; beta=-5.4; 95% CI, -10 to -1). Only 4 patients (4%) discontinued treatment due to ATV-related toxicities (hyperbilirubinemia in 1). Bilirubin levels were associated with ATV plasma concentrations (p=.05; beta=3.2; 95% CI, -0.1 to 6.5). The rate of hypertriglyceridemia and hypercholesterolemia declined significantly with respect to baseline.

CONCLUSION

ATV is relatively safe and provides significant virological response in PI-experienced patients, mainly among those with a low number of protease resistance mutations. The GIQ predicts accurately the virological response in patients receiving ATV. Hyperbilirubinemia is associated with higher ATV plasma levels.

Association between Medication Adherence Outcomes and Adverse Drug Reactions to Highly Active Antiretroviral Therapy in Indian Human Immunodeficiency Virus-Positive Patients

In India, interruptions to highly active antiretroviral therapy (HAART) are due to adverse drug reactions. This study was aimed to assess the association between HAART adherence and adverse drug reactions (ADRs) in human immunodeficiency virus (HIV) patients. This prospective study was conducted at a Medicine department in a South Indian tertiary care teaching hospital. HIV-positive patients were interviewed for adherence using ACTG adherence questionnaire and intensively monitored for ADRs to HAART. The percentage of adherence was calculated based on missed doses, and graded as less than 80%, 80-95%, and >95%. The World Health Organization (WHO) probability scale was used for causality assessment. Logistic regression analysis as well as univariate analysis was used to assess the association (P value < 0.05). A total of 105 HIV-positive patients had been taking HAART out of whom 50 (47.6%) patients agreed for adherence assessment, and 23 (21.9%) refused due to social stigma. Upon evaluation of the patient characteristics in the reported adherence, 78% were in males (53.8%) and 22% were in females (46.2%) with the level of adherence greater than 95%. Six (12%) patients had a regular alcoholic intake with adherence less than 80% compared to 31 (62%) patients who never had any alcoholic intake (P < 0.05). A significant association between ADRs and adherence was found (P < 0.05). Causality found by the WHO scale was "probable." Clinicians must focus on education regarding the need for adherence, possible adverse effects, and early detection and prevention of ADRs to HAART.

Short communication: fasting increases serum concentrations of bilirubin in patients receiving atazanavir: results from a pilot study

Unconjugated hyperbilirubinemia resulting from therapy with atazanavir is physiologically related to hyperbilirubinemia in Gilbert's syndrome (GS). In patients with GS, changes in diet have a significant impact on bilirubinemia. Our aim was to investigate whether changes in diet affect the level of serum bilirubin in patients receiving atazanavir. Thirty patients on stable therapy with ritonavir-boosted atazanavir without evidence of GS were enrolled. Hemolysis and chronic hepatitis were excluded. After a baseline period of normal intake of calories, the patients were randomized to follow a 24-h 400-calorie diet (fasting), then a 48-h period of normal calorie intake and, afterward, a 24-h period of a high-calorie diet, or the same interventions in inverse order. Serum bilirubin concentrations were measured before and after each intervention. A high adherence to the recommended diet was observed. The mean unconjugated bilirubin concentration before the high-calorie diet was 2.79±1.53 mg/dl and after such intervention it was 2.70±1.40 mg/dl. The mean difference between preintervention and postintervention was -0.08±0.69 mg/dl (p=NS). The mean unconjugated bilirubin concentration before the fasting diet was 2.31±1.23 mg/dl and it was 3.84±1.90 mg/dl after. The mean difference between prefasting and postfasting was 1.53±1.17 mg/dl (p=0.001). According to these results, short periods of fasting seem to increase the unconjugated bilirubin concentration in patients on atazanavir. A high-calorie diet did not have any impact in bilirubin probably because most patients follow similar diets in their everyday life.

Differences in implementation of HIV/AIDS clinical research in developed versus developing world: an evidence-based review on protease inhibitor use among women and minorities

The aim of this revision is to evaluate ethnicity and gender rate of enrolment in registrative clinical trials of the protease inhibitors (Pis) from 1996 to 2009. Company-sponsored, phase II or III registrative clinical trials of PIs were evaluated. Forty-nine clinical trials were included. Clinical trials were conducted in centres in North America ( n = 39), Central-South America ( n = 22), Europe ( n = 22), Africa ( n = 8), Asia ( n = 5), Australia ( n = 10). Overall mean age was 39.6 years; median proportion of women was 16.3%. The most represented ethnic group was Caucasian. A test for trend over time (1996-2009) shows a significant increase in the proportion of women included ( P = 0.012), and a decrease in the proportion of Caucasians included, reaching borderline significance ( P = 0.061). An inverse correlation was observed between the proportion of Caucasians and that of women enrolled in each study ( r = 0.65, P < 0.0001). Women were less likely to be included in double-blind studies (11.2% versus 17%, P = 0.019). Clinical trials for treatment-naive subjects were more likely to enrol ethnicities other than Caucasian compared with Caucasian (44.7% versus 27.1 %, respectively, P = 0.04). Rates of enrolment of minorities in registrative clinical trials for PIs show a positive trend since 1996, mirroring the growing number of people of different ethnic groups accessing ART.

HIV antiretroviral medications and hepatotoxicity

PURPOSE OF REVIEW

This review considers the differential diagnosis, pathophysiology and risk of hepatotoxicity of specific antiretroviral medications.

RECENT FINDINGS

Currently prescribed antiretroviral medications are associated with an incidence of grade 3/4 liver enzyme elevation of less than 5%. Clinically apparent hepatotoxicity rates are much lower. The risk of adverse events with combination HIV and hepatitis C virus treatments is low, assuming that several nucleosides including didanosine and stavudine are avoided.

SUMMARY

Irrespective of the HIV antiretroviral regimen prescribed, careful observation of liver function and enzymes is advised, especially in those with comorbid liver disease. The majority of patients do not experience treatment-limiting liver toxicities, achieve virological suppression, and realize immunological restoration.

Efficacy and safety of three antiretroviral regimens for initial treatment of HIV-1: a randomized clinical trial in diverse multinational settings

BACKGROUND

Antiretroviral regimens with simplified dosing and better safety are needed to maximize the efficiency of antiretroviral delivery in resource-limited settings. We investigated the efficacy and safety of antiretroviral regimens with once-daily compared to twice-daily dosing in diverse areas of the world.

METHODS AND FINDINGS

1,571 HIV-1-infected persons (47% women) from nine countries in four continents were assigned with equal probability to open-label antiretroviral therapy with efavirenz plus lamivudine-zidovudine (EFV+3TC-ZDV), atazanavir plus didanosine-EC plus emtricitabine (ATV+DDI+FTC), or efavirenz plus emtricitabine-tenofovir-disoproxil fumarate (DF) (EFV+FTC-TDF). ATV+DDI+FTC and EFV+FTC-TDF were hypothesized to be non-inferior to EFV+3TC-ZDV if the upper one-sided 95% confidence bound for the hazard ratio (HR) was ≤1.35 when 30% of participants had treatment failure. An independent monitoring board recommended stopping study follow-up prior to accumulation of 472 treatment failures. Comparing EFV+FTC-TDF to EFV+3TC-ZDV, during a median 184 wk of follow-up there were 95 treatment failures (18%) among 526 participants versus 98 failures among 519 participants (19%; HR 0.95, 95% CI 0.72-1.27; p = 0.74). Safety endpoints occurred in 243 (46%) participants assigned to EFV+FTC-TDF versus 313 (60%) assigned to EFV+3TC-ZDV (HR 0.64, CI 0.54-0.76; p<0.001) and there was a significant interaction between sex and regimen safety (HR 0.50, CI 0.39-0.64 for women; HR 0.79, CI 0.62-1.00 for men; p = 0.01). Comparing ATV+DDI+FTC to EFV+3TC-ZDV, during a median follow-up of 81 wk there were 108 failures (21%) among 526 participants assigned to ATV+DDI+FTC and 76 (15%) among 519 participants assigned to EFV+3TC-ZDV (HR 1.51, CI 1.12-2.04; p = 0.007).

CONCLUSION

EFV+FTC-TDF had similar high efficacy compared to EFV+3TC-ZDV in this trial population, recruited in diverse multinational settings. Superior safety, especially in HIV-1-infected women, and once-daily dosing of EFV+FTC-TDF are advantageous for use of this regimen for initial treatment of HIV-1 infection in resource-limited countries. ATV+DDI+FTC had inferior efficacy and is not recommended as an initial antiretroviral regimen.

TRIAL REGISTRATION

www.ClinicalTrials.gov NCT00084136. Please see later in the article for the Editors' Summary.

Ritonavir boosting dose reduction from 100 to 50 mg does not change the atazanavir steady-state exposure in healthy volunteers

OBJECTIVES

To evaluate the pharmacokinetics, tolerability and safety of 300 mg of atazanavir boosted with 100 or 50 mg of ritonavir, both once daily, at steady state.

METHODS

This was a single-blind, multiple-dose, crossover, sequence-randomized trial. Thirteen healthy HIV-1-negative men received witnessed once-daily doses of atazanavir (300 mg) and 100 or 50 mg of ritonavir for 10 days (15 day washout). Atazanavir and ritonavir plasma concentrations were determined for 24 h on day 10. Log-transformed individual pharmacokinetic parameters were compared between treatments (analysis of variance); the difference between treatments on the log scale and 95% CIs were calculated. Fasting cholesterol, triglycerides, glucose and bilirubin plasma levels were measured at the beginning and end of each period and compared (Wilcoxon signed rank test). Gastrointestinal symptoms and other events were recorded.

RESULTS

Ritonavir C(max) and the AUC₀₋₂₄ were lower after the 50 mg booster dose than after 100 mg [geometric mean ratio (GMR) (95% CI), 0.40 (0.31-0.51) and 0.35 (0.29-0.42), respectively]. No differences were observed in atazanavir exposure with 50 or 100 mg of ritonavir [GMR C(max) (95% CI), 1.00 (0.79-1.28); GMR AUC₀₋₂₄ (95% CI), 0.98 (0.79-1.21)]. Atazanavir trough concentration was >0.15 mg/L in all volunteers. Total and low-density lipoprotein cholesterol increased 0.40 mM (P = 0.01) and 0.37 mM (P = 0.003) from their corresponding baseline value during the 100 mg dosing period; there were no significant changes on 50 mg. Mild increases in bilirubin were detected on day 10 after both treatments without differences between treatments.

CONCLUSIONS

In spite of higher exposure to ritonavir with 100 mg, atazanavir exposure was equivalent; the lipid profile was better under the lower booster dose (50 mg).

Antiretroviral drugs: critical issues and recent advances

Human immunodeficiency virus (HIV) infection is now recognized as a chronic illness. Although the success of highly active antiretroviral therapy is beyond question, several issues still persist. Since the drugs cannot eradicate the virus, cure is not yet possible, and patients have to maintain a lifelong adherence with the risk of toxic effects, drug-drug interactions and drug resistance. A clear understanding of the viral replication and its interaction with host cell factors has led to the development of a large number of effective antiretroviral drugs (ARVs). New drugs in the existing class such as apricitabine, elvucitabine and etravirine have shown promising results against HIV isolates resistant to first line drugs. These drugs have offered a new choice for patients with drug resistant disease. However, the impact of their long term use on safety is yet to be assessed. Novel drugs with unique mechanism of action such as CD4 receptor attachment inhibitors, maturation inhibitors, pharmacokinetic enhancers, capsid assembly inhibitors and lens epithelium derived growth factor inhibitors are still under development. Currently, ARVs, especially tenofovir and emtricitabine, are also being evaluated for prevention of sexual transmission of HIV-1. The initial results of an HIV prevention trial network are encouraging and have recommended the use of ARVs for pre-exposure prophylaxis. Thus, ARVs form the key component of HIV prevention and treatment strategy. This article discusses the challenges associated with HIV-1 treatment and updates several major advances in the development of ARVs.

Clinical significance of hyperbilirubinemia among HIV-1-infected patients treated with atazanavir/ritonavir through 96 weeks in the CASTLE study

CASTLE was a randomized 96-week study that demonstrated that atazanavir/ritonavir (ATV/r) was noninferior to lopinavir/ritonavir (LPV/r) in treatment-naïve HIV-infected patients. Analyses were carried out among patients who received ATV/r in the CASTLE study to better understand the clinical significance of unconjugated hyperbilirubinemia associated with administration of boosted ATV. Hyperbilirubinemia was defined as total bilirubin (conjugated and unconjugated) elevation greater than 2.5 times the upper limit of normal (grade 3-4). Patients in the ATV/r arm were assessed based on the presence or absence of hyperbilirubinemia through week 96. Analyses included number of confirmed virologic responders (CVR; HIV RNA<50 copies per milliliter), impact of hyperbilirubinemia on symptoms, elevations in liver enzymes, patient quality of life, and medication adherence. Through 96 weeks in the CASTLE study, 44% of patients who received ATV/r had hyperbilirubinemia at any time point, and between 12.5% and 21.6% had hyperbilirubinemia at any single study visit. At 96 weeks, 74% of patients overall and 84% and 69% of patients with and without hyperbilirubinemia, respectively, achieved CVR. Symptoms of jaundice or scleral icterus occurred in 5% of patients overall and in 11% with hyperbilirubinemia and 0% without hyperbilirubinemia. Four percent of patients with and 3% of patients without hyperbilirubinemia had grade 3-4 elevations in liver transaminases. Less than 1% of patients discontinued treatment due to hyperbilirubinemia. There were no differences in quality of life or adherence between patients with or without hyperbilirubinemia. In the CASTLE study, hyperbilirubinemia observed in the ATV/r group did not negatively impact clinical outcomes in HIV-infected patients.

Symptomatic hyperbilirubinemia secondary to dapsone-induced hemolysis and atazanavir therapy

The antiretroviral agent atazanavir is associated with mild asymptomatic hyperbilirubinemia. We report two cases of symptomatic hyperbilirubinemia attributed to atazanavir in conjunction with the Pneumocystis jirovecii pneumonia prophylaxis agent dapsone. Symptoms and laboratory evidence of hemolysis resolved upon discontinuation of dapsone, enabling successful antiretroviral therapy. Symptomatic hyperbilirubinemia due to hemolytic anemia is a potential adverse event when using the combination of atazanavir and dapsone in the treatment of patients with the human immunodeficiency virus.

Ritonavir-boosted protease inhibitors in HIV therapy

The advent of combination antiretroviral therapy has led to significant improvement in the care of HIV-infected patients. Originally designed as a protease inhibitor (PI), ritonavir is currently exclusively used as a pharmacokinetic enhancer of other protease inhibitors, predominantly due to ritonavir's potent inhibition of the cytochrome P450 3A4 isoenzyme. Ritonavir-boosting of PIs decrease pill burden and frequency of dosing. Boosted PIs are recommended for first-line therapy in treatment and play a key role in the management of treatment-experienced patients. Potential problems associated with PIs include metabolic abnormalities (e.g. dyslipidemia), increased cardiovascular risk, and drug interactions.

Antiviral pharmacodynamics in hollow fibre bioreactors

Pharmacodynamic investigation of antiviral compounds studies the relationship between drug exposure and the virological response. These studies are usually performed in animals and, eventually, in humans and are a very expensive proposition. To find a more efficient and less expensive method for determining pharmacodynamics of antiviral and antimicrobial compounds, the hollow fibre infection model (HFIM) system was developed to perform pharmacodynamic studies in vitro. This review covers the authors' studies on the use of in vitro hollow fibre bioreactor technologies for determining the pharmacodynamics of antiviral compounds for viruses grown in cultured cells, including HIV grown in CD4+ lymphoblastoid cells, vaccinia viruses grown in HeLa-S3 cells and influenza viruses grown in Madin-Darby canine kidney cells. Where possible, correlations between the pharmacodynamic index derived from the in vitro HFIM systems and clinical pharmacodynamic studies are made.

Premature onset of cardiovascular disease in HIV-infected individuals: the drugs and the virus

Life expectancy in HIV-infected individuals has been greatly enhanced through immunologic restoration and virologic suppression resulting from antiretroviral therapy. Current clinical HIV care in Western countries focuses on treatment of drug toxicities and prevention of comorbidities. These non-AIDS HIV-related comorbidities, such as cardiovascular disease, occur even in individuals with virologic suppression and manifest at an earlier age than when normally presenting in the general population. While traditional risk factors are present in many HIV-infected individuals who develop cardiovascular disease, the additional roles of HIV-related chronic inflammation and immune activation as well as chronic HIV viremia may be significant. This review provides current evidence for the contributions of the virus, in terms of both chronic viremia and its contribution via chronic low-level inflammation, immune activation, premature immune senescence and dyslipidemia, to the pathogenesis of HIV-related cardiovascular disease, and balances this against the propensity of specific antiretroviral therapies to cause cardiovascular disease, in particular through altered cholesterol metabolism.

Management of antiretroviral failure and resistance in developing countries

PURPOSE OF REVIEW

As scale-up of antiretroviral therapy in developing countries continues, an increasing number of patients developing antiretroviral failure and resistance are being identified. This review focuses on the identification and management of these complex patients in settings with limited antiretroviral drug options and resources.

RECENT FINDINGS

The number of patients receiving second-line and salvage therapies remains lower than the number of patients who are eligible for these therapies. This situation is a result of delays in the recognition and management of antiretroviral failure caused by a lack of sensitive diagnostic techniques, and effective and tolerable alternative antiretroviral drugs. Alternative treatment options using currently available therapies in developing countries are suggested for the management of patients with antiretroviral failure and resistance. Strategies to enhance the durability of antiretroviral regimens to minimize the risk of failure are also discussed.

SUMMARY

The development of antiretroviral failure and drug resistance among HIV-infected patients in developing countries is of increasing concern. Intensive efforts by HIV care and treatment programs are required to ensure the timely and effective diagnosis and management of these patients. Efforts to minimize the risk of failure are also needed given the significant cost and resource limitations in these settings.

96-Week Efficacy and Safety of Atazanavir, With and Without Ritonavir, in a HAART Regimen in Treatment-Naive Patients

This study assesses virologic response, safety, tolerability, and changes in health-related quality of life (HRQoL) in antiretroviral (ARV)-naive patients treated with 2 atazanavir (ATV)-based regimens over 96 weeks. Treatment-naive adult patients (n = 200) were randomized to receive either ATV 300 mg with ritonavir (RTV) 100 mg (ATV300/r, n = 95) or ATV 400 mg (ATV400; n = 105). At week 96, 75% of ATV300/r-treated and 70% of ATV400-treated patients achieved viral loads <400 copies/mL (difference estimate [95% confidence interval, CI] = 5.1 [-7.1 to 17.2]). Five and 20 patients, respectively, experienced virologic failure. Adverse event-related discontinuations occurred among 8% receiving ATV300/r and 3% receiving ATV400. Plasma lipid elevations were generally low. Both regimens were well tolerated and associated with sustained improvements in HRQoL. These findings demonstrate long-term efficacy, tolerability, and safety of both ATV300/r and ATV400 in ARV-naive patients through 96 weeks with improvements in HRQoL.

Protease inhibitor therapy in resource-limited settings

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

The relation between treatment outcome and efavirenz, atazanavir or lopinavir exposure in the NORTHIV trial of treatment-naïve HIV-1 infected patients

PURPOSE

The relation between treatment outcome and trough plasma concentrations of efavirenz (EFV), atazanavir (ATV) and lopinavir (LPV) was studied in a pharmacokinetic/pharmacodynamic substudy of the NORTHIV trial-a randomised phase IV efficacy trial comparing antiretroviral-naïve human immunodeficiency virus-1-infected patients treated with (1) EFV + 2 nucleoside reverse transcriptase inhibitors (2NRTI) once daily, (2) ritonavir-boosted ATV + 2NRTI once daily or (3) ritonavir-boosted LPV + 2NRTI twice daily. The findings were related to the generally cited minimum effective concentration levels for the respective drugs (EFV 1,000 ng/ml, ATV 150 ng/ml, LPV 1,000 ng/ml). The relation between atazanavir-induced hyperbilirubinemia and virological efficacy was also studied.

METHODS

Drug concentrations were sampled at weeks 4 and 48 and optionally at week 12 and analysed by high-performance liquid chromatography with UV detector. When necessary, trough values were imputed by assuming the reported average half-lives for the respective drugs. Outcomes up to week 48 are reported.

RESULTS

No relation between plasma concentrations of EFV, ATV or LPV and virological failure, treatment withdrawal due to adverse effects or antiviral potency (viral load decline from baseline to week 4) was demonstrated. Very few samples were below the suggested minimum efficacy cut-offs, and their predictive value for treatment failure could not be validated. There was a trend toward an increased risk of virological failure in patients on ATV who had an average increase of serum bilirubin from baseline of <25 micromol/l.

CONCLUSIONS

The great majority of treatment-naïve and adherent patients on standard doses of EFV, ritonavir-boosted ATV and ritonavir-boosted LPV have drug concentrations above that considered to deliver the maximum effect for the respective drug. The results do not support the use of routine therapeutic drug monitoring (TDM) for efficacy optimisation in treatment-naïve patients on these drugs, although TDM may still be of value in some cases of altered pharmacokinetics, adverse events or drug interactions. Serum bilirubin may be a useful marker of adherence to ATV therapy.

Atazanavir: a review of its use in the management of HIV-1 infection

Atazanavir (Reyataz), a protease inhibitor (PI), is approved in many countries for use as a component of antiretroviral therapy (ART) regimens for the treatment of adult, and in some countries in paediatric, patients with HIV-1 infection. ART regimens containing ritonavir-boosted atazanavir improved virological and immunological markers in adult patients with HIV-1 infection, and had similar efficacy to regimens containing lopinavir/ritonavir in treatment-naive and treatment-experienced patients. In addition, unboosted atazanavir was noninferior to ritonavir-boosted atazanavir in treatment-naive patients. Atazanavir is administered once daily and has a low capsule burden. Atazanavir, whether unboosted or boosted, was generally well tolerated and appeared to be associated with less marked metabolic effects, including less alteration of lipid levels, than other PIs. These properties mean that boosted atazanavir, and unboosted atazanavir in patients unable to tolerate ritonavir, continues to have a role as a component of ART regimens in patients with HIV-1 infection.

HIV protease inhibitors: recent clinical trials and recommendations on use

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

Hyperbilirubinemia during atazanavir treatment in 2,404 patients in the Italian atazanavir expanded access program and MASTER Cohorts

BACKGROUND

Although the mechanism of atazanavir (ATV)-related hyperbilirubinemia is well identified, its prevalence, risk factors, and association with transaminase flares have rarely been assessed in a large population from the "real life" setting.

METHODS

Prospectively collected data on 2,404 patients from the Italian MASTER Cohort and the Italian ATV expanded access program database were examined. Uni- and multivariable Cox proportional hazards regression models were conducted to identify risk factors for grade >or= III hyperbilirubinemia during the administration of ATV. The risk of increased levels of serum alanine aminotransferase (ALT) was compared between patients with or without grade >or= III hyperbilirubinemia in a Cox regression analysis stratified by hepatitis C virus (HCV) serostatus.

RESULTS

Grade III and IV hyperbilirubinemia were observed in 1,072 (44.6%) and 174 (7.2%) of the patients, respectively. Higher CD4+ T-cell counts, abnormal bilirubinemia at baseline, and ritonavir co-administration were associated with a higher risk of developing grade >or= III hyperbilirubinemia. In contrast, female gender, clinical class C, and non-nucleoside reverse transcriptase co-administration appeared to be protective. Higher bilirubinemia at baseline and the use of ritonavir were associated with a higher risk of grade IV hyperbilirubinemia. The occurrence of grade >or= III hyperbilirubinemia was not associated with severe hepatotoxicity (hazard ratio 1.00, 95% confidence interval 0.64-1.57; p = 0.997).

CONCLUSIONS

Hyperbilirubinemia is a common side effect of an ATV pharmacotherapeutic regimen. However, grade IV increase in bilirubin was rarely found. In most cases, ATV hyperbilirubinemia appeared to be an innocent phenomenon as far as the risk of a subsequent increase in liver enzyme level is concerned.

A randomized, controlled trial of initial anti-retroviral therapy with abacavir/lamivudine/zidovudine twice-daily compared to atazanavir once-daily with lamivudine/zidovudine twice-daily in HIV-infected patients over 48 weeks (ESS100327, the ACTION Study)

Background

Traditional first line regimens containing a non-nucleoside reverse transcriptase inhibitor or protease inhibitor may not be suitable for a subset of antiretroviral-naïve patients such as those with certain co-morbidities, women of child-bearing potential, and intolerability to components of standard first line therapy. This study was conducted to determine if alternate treatment options may meet the needs of both general and special patient populations. The ACTION study was a randomized, open-label, multicenter, 48-week trial that compared the safety and efficacy of a triple nucleoside regimen versus a protease inhibitor plus a dual nucleoside regimen in HIV-1 treatment-naïve subjects.

Results

279 HIV-infected subjects with HIV-1 RNA (VL) >5000 but < 200,000 copies/mL (c/mL) and CD4+ count ≥ 100 cells/mm³ were randomized (1:1) to receive abacavir sulfate/lamivudine/zidovudine (ABC/3TC/ZDV) twice-daily or atazanavir (ATV) once-daily plus lamivudine/zidovudine (3TC/ZDV) twice-daily. Protocol-defined virologic failure was based on multiple failure criteria.

Non-inferiority of ABC/3TC/ZDV to ATV+3TC/ZDV was established with 62% vs. 59% of subjects achieving a VL < 50 c/mL at week 48, [ITT(E), M/S = F, 95% CI: -5.9, 10.4]. Similar results were observed in the 230 (82%) subjects with baseline VL<100,000 c/mL (ABC/3TC/ZDV vs. ATV+3TC/ZDV), 66% vs. 59%; 95% CI: -5.6, 19.5. However, ABC/3TC/ZDV did not meet the non-inferiority criterion compared to ATV+3TC/ZDV in the 48 subjects with baseline VL ≥ 100,000 c/mL, 39% vs. 60%; 95% CI: -49.2, 7.4, respectively. Protocol-defined virologic failure was similar between groups.

Conclusion

ABC/3TC/ZDV demonstrated comparable virologic efficacy to ATV+3TC/ZDV in this population over 48 weeks. In those with a baseline VL ≥ 100,000 c/mL, subjects in the ATV+3TC/ZDV showed better virologic efficacy. Both regimens offer benefits in select therapy-naïve subjects.

Trial Registration

[Clinical Trials Identifier, NCT00082394].

Viral protease inhibitors

This review provides an overview of the development of viral protease inhibitors as antiviral drugs. We concentrate on HIV-1 protease inhibitors, as these have made the most significant advances in the recent past. Thus, we discuss the biochemistry of HIV-1 protease, inhibitor development, clinical use of inhibitors, and evolution of resistance. Since many different viruses encode essential proteases, it is possible to envision the development of a potent protease inhibitor for other viruses if the processing site sequence and the catalytic mechanism are known. At this time, interest in developing inhibitors is limited to viruses that cause chronic disease, viruses that have the potential to cause large-scale epidemics, or viruses that are sufficiently ubiquitous that treating an acute infection would be beneficial even if the infection was ultimately self-limiting. Protease inhibitor development is most advanced for hepatitis C virus (HCV), and we also provide a review of HCV NS3/4A serine protease inhibitor development, including combination therapy and resistance. Finally, we discuss other viral proteases as potential drug targets, including those from Dengue virus, cytomegalovirus, rhinovirus, and coronavirus.

Simplification Strategies to Reduce Antiretroviral drug Exposure: Progress and Prospects

Current US guidelines for initial therapy of HIV type-1 (HIV-1) infection recommend daily, lifelong treatment with a combination of three antiretroviral drugs consisting of two nucleoside analogue reverse transcriptase inhibitors and a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor. Although this approach has been successful in reducing morbidity and mortality from HIV-1 infection, concerns remain about adverse events from chronic drug exposure, the requirement for daily medication adherence, the risk of HIV-1 drug resistance and high treatment costs. The availability of antiretrovirals that are coformulated and dosed once daily have reduced pill burden and have simplified dosing schedules, but have not lowered drug exposure or cost. These limitations have stimulated research into drug-sparing strategies including intermittent therapy and simplified maintenance regimens. Randomized clinical trials have shown greater mortality with intermittent therapy compared with continuous therapy leading to rejection of this strategy. Pilot studies of simplified maintenance therapy with a ritonavir-boosted protease inhibitor alone have shown more promise, although concerns remain. This article reviews progress in the simplification of antiretroviral therapy, recent clinical trial results and prospects for the future.

[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.