Efavirenz plasma concentrations at 1, 3, and 6 months post-antiretroviral therapy initiation in HIV type 1-infected South African children

CYP2B6 Haplotype Predicts Efavirenz Plasma Concentration in Black South African HIV-1-Infected Children: A Longitudinal Pediatric Pharmacogenomic Study

South Africa has the highest burden of the human immunodeficiency virus (HIV) infection globally. Efavirenz (EFV), a frequently used drug against HIV infection, displays a relationship between drug concentration and pharmacodynamics effects clinically. However, haplotype-based genetic variation in drug metabolism in a pediatric sample has been little considered in a longitudinal long-term context. CYP2B6 plays a key role in variation of EFV plasma concentration through altered drug metabolism. We report here on a prospective clinical pharmacogenomics/pharmacokinetic study of Bantu-speaking children, importantly, over a period of 24 months post-initiation of EFV-based treatment in South Africa. We characterized the HIV-1-infected children (n = 60) for the CYP2B6 c.516G>T, c.785A>G, c.983T>C, and c.1459C>T single nucleotide polymorphisms (SNPs). These SNPs were determined using polymerase chain reaction/restricted fragment length polymorphism and SNaPshot genotyping. Longitudinal mid-dose EFV plasma concentrations were determined by LC-MS/MS and association analyses with genotypes and haplotypes at 1, 3, and 24 months were performed. The CYP2B6 c.516T/T genotype showed significantly higher EFV plasma concentrations (p < 0.001) compared to non 516T-allele carriers at all three time points. The minor allele frequencies (MAF) for CYP2B6 c.516T, c.785G, c.983C, and c.1459T were 0.410, 0.408, 0.110, and 0.000 respectively. Haplotypes were constructed using CYP2B6 c.516G>T,-c.785A>G and c.983T>C. The haplotype T-G-T presented with significantly increased EFV plasma concentrations compared to the reference G-A-T haplotype at 1, 3, and 24 months (p = 0.009; p = 0.003; p = 0.001), suggesting that the T-G-T haplotype predisposes a risk of EFV plasma concentrations >4 μg/mL. The clinical implications of these pharmacogenomics observations for EFV toxicity and treatment resistance warrant further future research.

Plasma Efavirenz Exposure, Sex, and Age Predict Virological Response in HIV-Infected African Children

BACKGROUND

Owing to insufficient evidence in children, target plasma concentrations of efavirenz are based on studies in adults. Our analysis aimed to evaluate the pediatric therapeutic thresholds and characterize the determinants of virological suppression in African children.

METHODS

We analyzed data from 128 African children (aged 1.7-13.5 years) treated with efavirenz, lamivudine, and one among abacavir, stavudine, or zidovudine, and followed up to 36 months. Individual pharmacokinetic (PK) measures [plasma concentration 12 hours after dose (C12h), plasma concentration 24 hours after dose (C24h), and area under the curve (AUC0-24)] were estimated using population PK modeling. Cox multiple failure regression and multivariable fractional polynomials were used to investigate the risks of unsuppressed viral load associated with efavirenz exposure and other factors among 106 initially treatment-naive children, and likelihood profiling was used to identify the most predictive PK thresholds.

RESULTS

The risk of viral load >100 copies per milliliter decreased by 42% for every 2-fold increase in efavirenz mid-dose concentration [95% confidence interval (CI): 23% to 57%; P < 0.001]. The most predictive PK thresholds for increased risk of unsuppressed viral load were C12h 1.12 mg/L [hazard ratio (HR): 6.14; 95% CI: 2.64 to 14.27], C24h 0.65 mg/L (HR: 6.57; 95% CI: 2.86 to 15.10), and AUC0-24 28 mg·h/L (HR: 5.77; 95% CI: 2.28 to 14.58). Children older than 8 years had a more than 10-fold increased risk of virological nonsuppression (P = 0.005); among children younger than 8 years, boys had a 5.31 times higher risk than girls (P = 0.007). Central nervous system adverse events were infrequently reported.

CONCLUSIONS

Our analysis suggests that the minimum target C24h and AUC0-24 could be lowered in children. Our findings should be confirmed in a prospective pediatric trial.

Concentrations of tenofovir, lamivudine and efavirenz in mothers and children enrolled under the Option B-Plus approach in Malawi

OBJECTIVES

To evaluate antiretroviral drug concentrations in mothers and infants enrolled under the Option B-Plus approach for the prevention of HIV mother-to-child transmission in Malawi and to assess the maternal virological response after 1 year of treatment.

PATIENTS AND METHODS

Forty-seven women and 25 children were studied. Mothers were administered during pregnancy a combination of tenofovir, lamivudine and efavirenz and continued it during breastfeeding (up to 2 years) and thereafter. Drug concentrations were evaluated in mothers (plasma and breast milk) at 1 and 12 months post-partum and in infants (plasma) at 6 and 12 months of age. Drug concentrations were determined using an LC-MS/MS validated methodology.

RESULTS

In breast milk, tenofovir concentrations were very low (breast milk/maternal plasma ratio = 0.08), while lamivudine was concentrated (breast milk/plasma ratio = 3) and efavirenz levels were 80% of those found in plasma. In infants, median levels at 6 months were 24 ng/mL tenofovir, 2.5 ng/mL lamivudine and 86.4 ng/mL efavirenz. At month 12, median levels were below the limit of quantification for the three drugs. No correlation was found between drug concentrations and laboratory parameters or indices of growth. HIV-RNA >1000 copies/mL was seen at month 1 in 15% of the women and at month 12 in 8.5%. Resistance was found in half of the women with detectable viral load.

CONCLUSIONS

Breastfeeding infants under Option B-Plus are exposed to low concentrations of antiretroviral drugs. With this strategy, mothers had a good virological response 1 year after delivery.

The physical and psychological effects of HIV infection and its treatment on perinatally HIV-infected children

INTRODUCTION

As highly active antiretroviral therapy (HAART) transforms human immunodeficiency virus (HIV) into a manageable chronic disease, new challenges are emerging in treating children born with HIV, including a number of risks to their physical and psychological health due to HIV infection and its lifelong treatment.

METHODS

We conducted a literature review to evaluate the evidence on the physical and psychological effects of perinatal HIV (PHIV+) infection and its treatment in the era of HAART, including major chronic comorbidities.

RESULTS AND DISCUSSION

Perinatally infected children face concerning levels of treatment failure and drug resistance, which may hamper their long-term treatment and result in more significant comorbidities. Physical complications from PHIV+ infection and treatment potentially affect all major organ systems. Although treatment with antiretroviral (ARV) therapy has reduced incidence of severe neurocognitive diseases like HIV encephalopathy, perinatally infected children may experience less severe neurocognitive complications related to HIV disease and ARV neurotoxicity. Major metabolic complications include dyslipidaemia and insulin resistance, complications that are associated with both HIV infection and several ARV agents and may significantly affect cardiovascular disease risk with age. Bone abnormalities, particularly amongst children treated with tenofovir, are a concern for perinatally infected children who may be at higher risk for bone fractures and osteoporosis. In many studies, rates of anaemia are significantly higher for HIV-infected children. Renal failure is a significant complication and cause of death amongst perinatally infected children, while new data on sexual and reproductive health suggest that sexually transmitted infections and birth complications may be additional concerns for perinatally infected children in adolescence. Finally, perinatally infected children may face psychological challenges, including higher rates of mental health and behavioural disorders. Existing studies have significant methodological limitations, including small sample sizes, inappropriate control groups and heterogeneous definitions, to name a few.

CONCLUSIONS

Success in treating perinatally HIV-infected children and better understanding of the physical and psychological implications of lifelong HIV infection require that we address a new set of challenges for children. A better understanding of these challenges will guide care providers, researchers and policymakers towards more effective HIV care management for perinatally infected children and their transition to adulthood.

Measuring adherence to antiretroviral therapy in children and adolescents in western Kenya

Introduction

High levels of adherence to antiretroviral therapy (ART) are central to HIV management. The objective of this study was to compare multiple measures of adherence and investigate factors associated with adherence among HIV-infected children in western Kenya.

Methods

We evaluated ART adherence prospectively for six months among HIV-infected children aged ≤14 years attending a large outpatient HIV clinic in Kenya. Adherence was reported using caregiver report, plasma drug concentrations and Medication Event Monitoring Systems (MEMS^®). Kappa statistics were used to compare adherence estimates with MEMS^®. Logistic regression analyses were performed to assess the association between child, caregiver and household characteristics with dichotomized adherence (MEMS^® adherence ≥90% vs. <90%) and MEMS^® treatment interruptions of ≥48 hours. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated.

Results

Among 191 children, mean age at baseline was 8.2 years and 55% were female. Median adherence by MEMS^® was 96.3% and improved over the course of follow-up (p<0.01), although 49.5% of children had at least one MEMS^® treatment interruption of ≥48 hours. Adherence estimates were highest by caregiver report, and there was poor agreement between MEMS^® and other adherence measures (Kappa statistics 0.04–0.37). In multivariable logistic regression, only caregiver-reported missed doses in the past 30 days (OR 1.25, 95% CI 1.14–1.39), late doses in the past seven days (OR 1.14, 95% CI 1.05–1.22) and caregiver-reported problems with getting the child to take ART (OR 1.10, 95% CI 1.01–1.20) were significantly associated with dichotomized MEMS^® adherence. The caregivers reporting that ART made the child sick (OR 1.12, 95% CI 1.01–1.25) and reporting difficulties in the community that made giving ART more difficult (e.g. stigma) (OR 1.14, 95% CI 1.02–1.27) were significantly associated with MEMS^® treatment interruptions in multivariable logistic regression.

Conclusions

Non-adherence in the form of missed and late doses, treatment interruptions of more than 48 hours and sub-therapeutic drug levels were common in this cohort. Adherence varied significantly by adherence measure, suggesting that additional validation of adherence measures is needed. Few factors were consistently associated with non-adherence or treatment interruptions.

Are lopinavir and efavirenz serum concentrations in HIV-infected children in the therapeutic range in clinical practice?

BACKGROUND

In antiretroviral treatment the role of therapeutic drug monitoring via measurement of serum levels remains unclear, especially in children.

AIM

To quantify exposure to LPV and EFV in children receiving therapy in a routine clinical setting in order to identify risk factors associated with inadequate drug exposure.

METHOD

A prospective study was conducted in a routine clinical setting in Tygerberg Children's Hospital, South Africa. A total of 53 random serum levels were analyzed. Serum concentrations were determined by an established high-performance liquid chromatography method.

RESULTS

Of 53 HIV-infected children treated with lopinavir (n = 29, median age 1·83 y) or efavirenz (n = 24, median age 9·3 years), 12 showed serum levels outside the therapeutic range (efavirenz) or below Cmin (lopinavir). Low bodyweight, rifampicin co-treatment, and significant comorbidity were potential risk factors for inadequate drug exposure.

CONCLUSION

These findings, together with previous studies, indicate that therapeutic drug monitoring can improve the management of antiretroviral therapy in children at risk.

Antiretroviral treatment in HIV-1 infected pediatric patients: focus on efavirenz

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI), used for the treatment of human immunodeficiency virus (HIV)-1 infection. Approved by the US Food and Drug Administration in 1998, its indication was recently extended to include children as young as 3 months of age. The World Health Organization and many national guidelines consider efavirenz to be the preferred NNRTI for first-line treatment of children over the age of 3 years. Clinical outcomes of patients on three-drug antiretroviral regimens which include efavirenz are as good as or better than those for patients on all other currently approved HIV medications. Efavirenz is dosed once daily and has pediatric-friendly formulations. It is usually well tolerated, with central nervous system side effects being of greatest concern. Efavirenz increases the risk of neural tube defects in nonhuman primates and therefore its use during the first trimester of pregnancy is limited in some settings. With minimal interactions with antituberculous drugs, efavirenz is preferred for use among patients with HIV/tuberculosis coinfection. Efavirenz can be rendered inactive by a single point mutation in the reverse transcriptase enzyme. Newer NNRTI drugs such as etravirine, not yet approved for use in children under the age of 6 years, may maintain their activity following development of efavirenz resistance. This review highlights key points from the existing literature regarding the use of efavirenz in children and suggests directions for future investigation.

Enhanced oral bioavailability of the antiretroviral efavirenz encapsulated in poly(epsilon-caprolactone) nanoparticles by a spray-drying method

AIM

To encapsulate efavirenz (EFV) within poly(epsilon-caprolactone) (PCL) nanoparticles (NPs) and compare the oral pharmacokinetics with that of EFV-loaded micelles and pure EFV NPs.

MATERIALS & METHODS

EFV-loaded PCL NPs were produced by a double-emulsion/spray-drying method.

RESULTS

NPs displayed a hydrodynamic diameter of 200-250 nm. The encapsulation efficiency was 86-93% and the mass recovery was above 60%. X-ray diffraction indicated that drug and PCL underwent amorphization during the spray-drying process. Encapsulation within NPs significantly increased the maximum concentration in plasma and the bioavailability.

CONCLUSION

EFV-loaded PCL NPs represent a promising platform to develop scalable pharmaceuticals with improved (bio)pharmaceutic performance. Original submitted 2 May 2013; Revised submitted 4 September 2013.

Mid-dosing interval efavirenz plasma concentrations in HIV-1-infected children in Rwanda: treatment efficacy, tolerability, adherence, and the influence of CYP2B6 polymorphisms

This study evaluated mid-dosing interval efavirenz plasma concentrations and the influence of CYP2B6 polymorphisms in relation to efficacy, tolerability, and adherence in 97 Rwandan HIV-infected children (3-16 years). Plasma drug concentrations and CYP2B6 polymorphisms were determined. Ten children were excluded for nonadherence. Large intersubject variability in efavirenz plasma concentrations was found. Of the 87 remaining, efavirenz concentrations were therapeutic, supratherapeutic, and subtherapeutic in 67%, 20%, and 14%, respectively. No associations were found between efavirenz concentrations and central nervous system disturbances or virologic failure. Minor allele frequencies were 0.32 (516G>T), 0.33 (785A>G), and 0.09 (983T>C). Polymorphisms in CYP2B6 were strongly associated with high efavirenz levels.

The glory of guidelines and the twilight of reality: controversies and challenges in the prevention and treatment of HIV in children

Since the discovery of HIV 30 years ago, we have learned much about HIV in children and adolescents. Dramatic declines have occurred in mother-to-child transmission of HIV in resource-rich countries. Resource-poor countries struggle with improving prevention of mother-to-child transmission due to the lack of universal antiretroviral treatment for pregnant and nursing mothers. In children infected with HIV, pharmacokinetic, safety and efficacy data have been determined for many of the older drugs. Data are lacking for the newer, safer and more effective currently available drugs, resulting in the pediatric guidelines lagging behind adult recommendations. Although guidelines for prevention and treatment are helpful, the way they are created causes them to lag behind new scientific evidence, and in some situations they will be confusing or only based on expert opinion. Improving prevention of HIV infection in adolescents and young adults and in treating those who become HIV infected is crucially important. The next 10 years hold tremendous opportunities for improvements in prevention and treatment of HIV in children, adolescents and young adults.

AtriplaR/anti-TB combination in TB/HIV patients. Drug in focus

Background

Co-administration of anti-tuberculosis and antiretroviral therapy is often inevitable in high-burden countries where tuberculosis is the most common opportunistic infection associated with HIV/AIDS. Concurrent use of rifampicin and several antiretroviral drugs is complicated by pharmacokinetic drug-drug interaction.

Method

Pubmed and Google search following the key words tuberculosis, HIV, emtricitabine, tenofovir efavirenz, interaction were used to find relevant information on each drug of the fixed dose combination Atripla^R

Results

Information on generic name, trade name, pharmacokinetic parameter, metabolism and the pharmacokinetic interaction with Anti-TB drugs of emtricitabine, tenofovir, and efavirenz was obtained.

Conclusion

Fixed dose combination of emtricitabine/tenofovir/efavirenz (ATRIPLA^R) which has been approved by Food and Drug Administration shows promising results as far as safety and efficacy is concerned in TB/HIV co-infection patients, hence can be considered effective and safe antiretroviral drug in TB/HIV management for adult and children above 3 years of age.

Influence of CYP2B6 516G>T polymorphism and interoccasion variability (IOV) on the population pharmacokinetics of efavirenz in HIV-infected South African children

OBJECTIVE

To investigate the influence of CYP2B6 516G>T polymorphism, as a covariate, and of interoccasion variability (IOV) on the oral clearance (CL/F) of efavirenz (EFV) in treatment-naïve black South African children over a period of 24 months post-antiretroviral therapy (ART) initiation.

METHODS

HIV-infected black children (n = 60, aged 3-16 years), with no prior exposure to ART, eligible to commence ART and attending an outpatient clinic were enrolled into this study. Blood samples were taken at mid-dose interval at 1, 3, 6, 12, 18 and 24 months post-ART initiation. EFV plasma samples were determined with an adapted and validated LC/MS/MS method. Genotyping of the CYP2B6 G516T single nucleotide polymorphism (SNP) was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). NONMEM was used for the population pharmacokinetic modelling.

RESULTS

EFV concentrations below 1 μg/mL accounted for 18% (116/649), EFV concentrations >4 μg/mL accounted for 29.5% (192/649) and concentrations within the therapeutic range (1-4 μg/mL) represented 52.5% (341/649) of all the samples determined. The covariates age, weight and CYP2B6 G516Tgenotype were included in the final model with population estimates for CL/F determined as 2.46, 4.60 and 7.33 L/h for the T/T, G/T and G/G genotype groups respectively.

CONCLUSIONS

The inclusion of both age and weight to predict accurate EFV CL values for the respective genotype groups within this paediatric population was required, whereas the addition of gender and body surface area did not improve the predictions. The importance of introducing IOV in a PK model for a longitudinal study with sparsely collected data was again highlighted by this investigation.

Absence seizures associated with efavirenz initiation

Efavirenz, used in treating pediatric human immunodeficiency virus infection, has central nervous system side effects. We report on a 5-year-old girl with perinatally acquired human immunodeficiency virus infection, presenting with new onset absence seizures after starting treatment with efavirenz. Plasma efavirenz values were above therapeutic range. The child was homozygous for the CYP2B6-516T/T genotype, which is associated with poor efavirenz clearance. Seizures abated after efavirenz discontinuation.