Factors predictive of virological failure on atazanavir in 310 HIV-infected patients

Optimizing Pediatric Dosing Recommendations and Treatment Management of Antiretroviral Drugs Using Therapeutic Drug Monitoring Data in Children Living With HIV

INTRODUCTION

This review summarizes the current dosing recommendations for antiretroviral (ARV) drugs in the international pediatric guidelines of the World Health Organization (WHO), US Department of Health and Human Services (DHHS), and Pediatric European Network for Treatment of AIDS (PENTA), and evaluates the research that informed these approaches. We further explore the role of data generated through therapeutic drug monitoring in optimizing the dosing of ARVs in children.

METHODS

A PubMed search was conducted for the literature on ARV dosing published in English. In addition, the registration documentation of European Medicines Agency and the US Food and Drug Administration for currently used ARVs and studies referenced by the WHO, DHHS, and EMA guidelines were screened. Resulting publications were screened for papers containing data on the area under the concentration-time curve, trough concentration, and peak concentration. Studies with enrolled participants with a median or mean age of ≥18 years were excluded. No restriction on publishing date was applied.

DISCUSSION AND CONCLUSION

Pediatric ARV dosing is frequently based on data obtained from small studies and is often simplified to facilitate dosing in the context of a public health approach. Pharmacokinetic parameters of pediatric ARVs are subject to high interpatient variation and this leads to a potential risk of underdosing or overdosing when drugs are used in real life. To ensure optimal use of ARVs and validate dosing recommendations for children, it is essential to monitor ARV dosing more thoroughly with larger sample sizes and to include diverse subpopulations. Therapeutic drug monitoring data generated in children, where available and affordable, have the potential to enhance our understanding of the appropriateness of simplified pediatric dosing strategies recommended using a public health approach and to uncover suboptimal dosing or other unanticipated issues postmarketing, further facilitating the ultimate goal of optimizing pediatric ARV treatment.

Efficacy and safety of once-daily ritonavir-boosted atazanavir or darunavir in combination with a dual nucleos(t)ide analogue backbone in HIV-1-infected combined ART (cART)-naive patients with severe immunosuppression: a 48 week, non-comparative, randomized, multicentre trial (IMEA 040 DATA trial)

OBJECTIVES

Boosted PIs are commonly prescribed in patients presenting with advanced HIV infection. We assessed the efficacy and tolerability of once-daily ritonavir-boosted atazanavir or darunavir plus two NRTIs in HIV-1-infected ART-naive patients with severe immunosuppression, targeting at least an 85% success rate at week 48.

METHODS

This 48 week, open-label, non-comparative, randomized, multicentre trial included ART-naive patients with CD4 cell counts <200 cells/mm(3), with plasma HIV-1 RNA >1000 copies/mL and without genotypic mutations conferring resistance to the study drugs. Patients were randomized (1:1) to receive once-daily atazanavir/ritonavir (300/100 mg) or darunavir/ritonavir (800/100 mg) plus tenofovir disoproxil fumarate/emtricitabine or abacavir/lamivudine. The primary endpoint was treatment success, defined as plasma HIV-1 RNA ≤50 copies/mL at week 48 and no permanent PI/ritonavir discontinuation. The study was registered with ClinicalTrials.gov (NCT01928407).

RESULTS

One hundred and twenty patients were enrolled: 77% were men, 30% were born in Africa and 39% had AIDS. The median baseline CD4 and plasma HIV-RNA values were 69 cells/mm(3) and 5.4 log10 copies/mL. All but four patients received tenofovir disoproxil fumarate/emtricitabine. The week 48 treatment success rate was 66% (95% CI 54%-78%) with atazanavir/ritonavir and 80% (95% CI 68%-89%) with darunavir/ritonavir. The median CD4 cell count increased similarly in the two groups (Δweek 48 to week 0: +194 cells/mm(3)). Adverse events occurred in 23 and 18 patients, respectively.

CONCLUSIONS

Despite good adherence, neither study regimen reached the predefined objective, suggesting a need for more potent regimens for patients with advanced HIV infection.

Successful pharmacogenetics-based optimization of unboosted atazanavir plasma exposure in HIV-positive patients: a randomized, controlled, pilot study (the REYAGEN study)

BACKGROUND

Atazanavir without ritonavir, despite efficacy and tolerability, shows low plasma concentrations that warrant optimization.

METHODS

In a randomized, controlled, pilot trial, stable HIV-positive patients on atazanavir/ritonavir (with tenofovir/emtricitabine) were switched to atazanavir. In the standard-dose arm, atazanavir was administered as 400 mg once daily, while according to patients' genetics (PXR, ABCB1 and SLCO1B1), in the pharmacogenetic arm: patients with unfavourable genotypes received 200 mg of atazanavir twice daily. EudraCT number: 2009-014216-35.

RESULTS

Eighty patients were enrolled with balanced baseline characteristics. The average atazanavir exposure was 253 ng/mL (150-542) in the pharmacogenetic arm versus 111 ng/mL (64-190) in the standard-dose arm (P < 0.001); 28 patients in the pharmacogenetic arm (75.7%) had atazanavir exposure >150 ng/mL versus 14 patients (38.9%) in the standard-dose arm (P = 0.001). Immunovirological and laboratory parameters had a favourable outcome throughout the study with non-significant differences between study arms.

CONCLUSIONS

Atazanavir plasma exposure is higher when the schedule is chosen according to the patient's genetic profile.

Atazanavir: in pediatric patients with HIV-1 infection

Atazanavir is a selective and potent inhibitor of the HIV-1 protease. The drug is administered in combination with low-dose ritonavir, to boost atazanavir pharmacokinetics (i.e. ritonavir-boosted atazanavir), and other antiretroviral agents. The efficacy of once-daily ritonavir-boosted atazanavir plus background therapy (BT) in establishing virologic suppression in treatment-naive pediatric patients (aged 6 to <18 years) infected with HIV-1 was demonstrated in an ongoing, open-label, multicenter, phase I/II trial (PACTG 1020A). HIV-1 RNA levels of <50 or <400 copies/mL were achieved by the majority of patients (>70%) after 24 weeks' therapy, with these benefits maintained at week 48. Some treatment-experienced pediatric patients (aged 6 to <18 years) also achieved HIV-1 RNA levels of <50 or <400 copies/mL in the PACTG 1020A trial after 24 (≤45% of patients) and 48 (≤32%) weeks of treatment with ritonavir-boosted atazanavir plus BT, although the benefits of the regimen in this patient population appeared to be limited by as few as one or two protease inhibitor resistance mutations. Treatment-experienced pediatric patients (aged 10-19 years) infected with HIV-1 had mixed success in establishing/maintaining virologic suppression when they were switched from their current antiretroviral treatment regimen to once-daily ritonavir-boosted atazanavir plus BT in a small, single-center, observational study. However, some patients may have received atazanavir at a suboptimal dosage or had suboptimal susceptibility to BT agents. In the PACTG 1020A trial, use of atazanavir (with or without ritonavir) in pediatric patients aged 6 to <18 years was associated with a similar safety profile to that reported in adults.

Atazanavir concentration in hair is the strongest predictor of outcomes on antiretroviral therapy

BACKGROUND

Adequate exposure to antiretrovirals is important to maintain durable responses, but methods to assess exposure (eg, querying adherence and single plasma drug level measurements) are limited. Hair concentrations of antiretrovirals can integrate adherence and pharmacokinetics into a single assay.

METHODS

Small hair samples were collected from participants in the Women's Interagency HIV Study (WIHS), a large cohort of human immunodeficiency virus (HIV)-infected (and at-risk noninfected) women. From 2003 through 2008, we analyzed atazanavir hair concentrations longitudinally for women reporting receipt of atazanavir-based therapy. Multivariate random effects logistic regression models for repeated measures were used to estimate the association of hair drug levels with the primary outcome of virologic suppression (HIV RNA level, <80 copies/mL).

RESULTS

424 WIHS participants (51% African-American, 31% Hispanic) contributed 1443 person-visits to the analysis. After adjusting for age, race, treatment experience, pretreatment viral load, CD4 count and AIDS status, and self-reported adherence, hair levels were the strongest predictor of suppression. Categorized hair antiretroviral levels revealed a monotonic relationship to suppression; women with atazanavir levels in the highest quintile had odds ratios (ORs) of 59.8 (95% confidence ratio, 29.0-123.2) for virologic suppression. Hair atazanavir concentrations were even more strongly associated with resuppression of viral loads in subgroups in which there had been previous lapses in adherence (OR, 210.2 [95% CI, 46.0-961.1]), low hair levels (OR, 132.8 [95% CI, 26.5-666.0]), or detectable viremia (OR, 400.7 [95% CI, 52.3-3069.7]).

CONCLUSIONS

Antiretroviral hair levels surpassed any other predictor of virologic outcomes to HIV treatment in a large cohort. Low antiretroviral exposure in hair may trigger interventions prior to failure or herald virologic failure in settings where measurement of viral loads is unavailable. Monitoring hair antiretroviral concentrations may be useful for prolonging regimen durability.