Impact of Obesity on the Drug-Drug Interaction Between Dolutegravir and Rifampicin or Any Other Strong Inducers

Background

Obesity is increasingly prevalent among people with HIV. Obesity can impact drug pharmacokinetics and consequently the magnitude of drug-drug interactions (DDIs) and, thus, the related recommendations for dose adjustment. Virtual clinical DDI studies were conducted using physiologically based pharmacokinetic (PBPK) modeling to compare the magnitude of the DDI between dolutegravir and rifampicin in nonobese, obese, and morbidly obese individuals.

Methods

Each DDI scenario included a cohort of virtual individuals (50% female) between 20 and 50 years of age. Drug models for dolutegravir and rifampicin were verified against clinical observed data. The verified models were used to simulate the concurrent administration of rifampicin (600 mg) at steady state with dolutegravir (50 mg) administered twice daily in normal-weight (BMI 18.5-30 kg/m²), obese (BMI 30-40 kg/m²), and morbidly obese (BMI 40-50 kg/m²) individuals.

Results

Rifampicin was predicted to decrease dolutegravir area under the curve (AUC) by 72% in obese and 77% in morbidly obese vs 68% in nonobese individuals; however, dolutegravir trough concentrations were reduced to a similar extent (83% and 85% vs 85%). Twice-daily dolutegravir with rifampicin resulted in trough concentrations always above the protein-adjusted 90% inhibitory concentration for all BMI groups and above the 300 ng/mL threshold in a similar proportion for all BMI groups.

Conclusions

The combined effect of obesity and induction by rifampicin was predicted to further decrease dolutegravir exposure but not the minimal concentration at the end of the dosing interval. Thus, dolutegravir 50 mg twice daily with rifampicin can be used in individuals with a high BMI up to 50 kg/m².

Outcomes of modern antiretroviral therapy in obese individuals living with HIV

Obesity is a global epidemic and people living with HIV (PLWH) are showing similar obesity trends to those in the general population. Obesity is manifested by several physiological features that can alter volume of distribution, elimination and metabolism of various medications including ART. Some drugs are increasingly prone to pharmacokinetic alteration during obesity depending on their physicochemical properties and clearance mechanism. These considerations raise concerns of hampered efficacy, development of resistance or increased toxicity of ART in PLWH. Here, we summarize available literature on the exposure and antiviral outcomes of currently available antiretroviral drugs in the context of obesity and provide a panel of recommendations for the clinical management and follow-up in this growing patient population.

Antiretroviral Concentration in Hair as a Measure for Antiretroviral Medication Adherence: A Systematic Review of Global Literature

This review aims to validate hair antiretroviral concentration (HAC) as a measure for antiretroviral medication adherence. This review included 31 studies that analyzed a total of 11 ARV drugs in four different drug classes. The associations between HAC and non-pharmacokinetic measures were generally lower than the association between HAC and other pharmacokinetic measures: the correlation coefficients (r) ranged from - 0.20 to 0.38 for self-report or pill counts and 0.20 to 0.85 for electronic drug monitoring; HAC and other pharmacokinetic measures were positively correlated with the correlation coefficients (r) ranging from 0.20 to 0.72, 0.34 to 0.86, 0.50 to 0.85 for antiretroviral concentration in plasma, peripheral blood mononuclear cells, and dried blood spots, respectively. HAC was one of the strongest independent predictors of virologic responses. HAC of tenofovir was significantly associated with renal toxicity in large sample studies. This review suggests that HAC is a valid biomarker of antiretroviral medication adherence.

A Review of Clinical Pharmacokinetic and Pharmacodynamic Profiles of Select Antiretrovirals: Focus on Differences among Chinese Patients

OBJECTIVE

To identify the pharmacokinetic differences of antiretroviral drugs between HIV-infected Chinese patients and patients of other race/ethnicities.

STUDY DESIGN

Results from prospective, open-label pharmacokinetic studies among Chinese and historical data from other race/ethnicities.

PATIENTS

Pharmacokinetics of six commonly used antiretroviral drugs, including zidovudine, lamivudine, tenofovir disoproxil fumarate, nevirapine, efavirenz and lopinavir/ritonavir, was evaluated in HIV-infected Chinese patients and compared with historical data from other race/ethnicities.

ANALYSIS

Pharmacokinetic analyses were performed at the steady state among HIV-infected Chinese patients. Safety data were collected during the follow-up. The pharmacokinetic parameters including maximal concentrations (Cmax), area-under-curve (AUC) and clearance (Cl/F) from the Chinese patients were compared to the historic data from other race/ethnicities.

RESULTS

Current evidence, though limited, suggested that these antiretroviral agents were generally safe and effective among HIV-infected Chinese patients. However, compared with other racial groups, Chinese patients exhibited higher C_max , AUC and lower Cl/F for most of the agents, and the incidences of adverse reactions, for example, liver toxicity, rash, and bone health, were more frequent.

CONCLUSIONS

These pharmacokinetic differences suggest that lower dosages for commonly prescribed antiretroviral drugs in China might be appropriate to reduce drug-related adverse reactions, while maintain the antiviral efficacy.

High prevalence and long duration of nervous system and psychiatric adverse drug reactions in Ugandan patients taking efavirenz 600 mg daily

Background

Efavirenz-related nervous system or psychiatric adverse drug reactions (ADRs) are conventionally reported to resolve soon after initiation, with incidence of dizziness at 8.5% in large clinical trials. Patients of black ethnicity are genetically at greater risk of elevated efavirenz exposure, which has been linked to nervous system toxicity.

Patients and methods

The current data derive from a prospective longitudinal observational study of adult HIV-positive outpatients taking current antiretrovirals, at three diverse clinics in central Uganda. As part of an interview about medicine use, patients were asked by trained pharmacy technicians to detail current side effects and to rate their severity on a simple visual analogue scale (1–10). Details of the reported ADRs were verified by case note review. Severity and causality of ADRs were rated by the study team using validated tools.

Results

A total of 300 patients taking efavirenz were analysed. Of these, 108 (36%, 95% CI 30.6%–41.7%) were affected by persisting nervous system/psychiatric ADRs (median duration 22 months). Dizziness affected 27.3% (95% CI 22.4%–32.8%) of patients taking efavirenz. Severity of the ADRs was rated by patients at ≥5/10 in 76 (58.5%) cases. In 95 (86%) cases, there was no record of the ADRs in the clinical notes.

Conclusions

Strategies are needed to identify and prioritize patients urgently with persisting efavirenz neurotoxicity for a switch to newer regimens as they become available.

Pharmacogenetics of artemether-lumefantrine influence on nevirapine disposition: Clinically significant drug-drug interaction?

AIMS

In this study the influence of first-line antimalarial drug artemether-lumefantrine on the pharmacokinetics of the antiretroviral drug nevirapine was investigated in the context of selected single nucleotide polymorphisms (SNPs) in a cohort of adult HIV-infected Nigerian patients.

METHODS

This was a two-period, single sequence crossover study. In stage 1, 150 HIV-infected patients receiving nevirapine-based antiretroviral regimens were enrolled and genotyped for seven SNPs. Sparse pharmacokinetic sampling was conducted to identify SNPs independently associated with nevirapine plasma concentration. Patients were categorized as poor, intermediate and extensive metabolizers based on the numbers of alleles of significantly associated SNPs. Intensive sampling was conducted in selected patients from each group. In stage 2, patients received standard artemether-lumefantrine treatment with nevirapine, and intensive pharmacokinetic sampling was conducted on day 3.

RESULTS

No clinically significant changes were observed in key nevirapine pharmacokinetic parameters, the 90% confidence interval for the measured changes falling completely within the 0.80-1.25 no-effect boundaries. However, the number of patients with trough plasma nevirapine concentration below the 3400 ng ml^-1 minimum effective concentration increased from 10% without artemether-lumefantrine (all extensive metabolizers) to 21% with artemether-lumefantrine (14% extensive, 4% intermediate, and 3% poor metabolizers).

CONCLUSIONS

This approach highlights additional increase in the already existing risk of suboptimal trough plasma concentration, especially in extensive metabolizers when nevirapine is co-administered with artemether-lumefantrine.

Daily 800 mg versus 600 mg Efavirenz for HIV Patients Treating Tuberculosis with a Rifampicin-Based Regimen: An Open Label Randomized Controlled Trial

Objectives

Pharmacokinetics studies recommend increasing efavirenz dosage in tuberculosis/HIV patients using rifampicin. We aimed to evaluate efficacy and safety of 600 versus 800 mg of efavirenz in tuberculosis/HIV patients using rifampicin.

Design

We conducted an open label, multicentre, randomized trial from 2006 to 2012. The primary outcome was the proportion of undetectable viral load (HIV-VL) within six months. Secondary outcomes were time to achieve primary endpoint, trajectories of HIV-VL, proportion of any adverse events (AE), proportion of severe and serious AE (SSAE), and time to treatment interruption due to SSAE.

Methods

Efavirenz-naïve patients were randomized 30 days after rifampicin-containing regimens initiation to receive 600 (comparison arm) or 800 mg (intervention arm) efavirenz-based regimens and followed-up for 180 days.

Results

Sixty-five and 67 participants were respectively included in the comparison and intervention arms with 64.6% (52.5%-65.1%) and 62.7% (50.7%-73.3%) attaining undetectable HIV-VL in six months. Median time to attain undetectable HIV-VL was 70 days in both arms, with HIV-VL overlapping trajectories during follow-up. Cough, acne, and dizziness were more frequent in the intervention arm. SSAE were observed in 19.1% (13.8%-25.8%) and 25.0% (18.9%-33.2%), respectively. Survival curves up to the first SSAE-attributed treatment interruption were similar. None of the differences were statistically significant.

Conclusion

Efficacy of efavirenz was similar regardless of dosage. Differences regarding safety occurred as mild and transient events, which did not interfere with treatment. Similar efficacy and safety (SSAE) and lower tolerance (minor AE) in the intervention group favour the use of 600 mg efavirenz in patients using rifampicin.

Pharmacokinetic analysis of nevirapine extended release 400 mg once daily vs nevirapine immediate release 200 mg twice daily formulation in treatment-naïve patients with HIV-1 infection

BACKGROUND

VERxVE data showed non-inferior virologic efficacy with extended release nevirapine (NVP-XR) dosed 400 mg once daily (QD) versus immediate release nevirapine (NVP-IR) 200 mg twice daily in a double-blind, non-inferiority study in treatment-naïve HIV-1-positive patients.

OBJECTIVE

To study the pharmacokinetics (PK) of the NVP formulations and identify possible associations with demographic factors.

METHODS

Patients with viral load ≥1000 copies/mL and CD4+ count > 50- <400 cells/mm³ (males) and >50- <250 cells/mm³ (females) at screening received NVP-IR 200 mg QD during a 14-day lead-in and were then stratified by baseline viral load and randomized to NVP-XR or -IR. NVP trough concentrations at steady state (SS) (C_pre,ss,N) were measured up to week 48 for all participating patients. In a PK sub-study, SS parameters - AUC_0-24, C_max, C_min, and peak-to-trough fluctuation were obtained and analyzed with relative bioavailability assessed at week 4 by plasma collection over 24 h.

RESULTS

Trough concentrations were stable from week 4 to week 48 for all patients (n = 1011) with both formulations, with NVP-XR/IR ratios of 0.77-0.82. Overall, 49 patients completed the PK sub-study: 24 XR and 25 IR. NVP-XR showed less peak-to-trough fluctuation (34.5%) than IR (55.2%), and lower AUC_0-24, C_min, C_max, and trough concentrations than IR. However, no effect of SS trough concentrations was found on the virologic response proportion at least up to 1000 ng/mL. No significant association was found between NVP PK and gender, race, and viral load.

CONCLUSION

These data suggest NVP-XR achieves lower but effective NVP exposure compared with NVP-IR.

Prospective plasma efavirenz concentration assessment in Chinese HIV-infected adults enrolled in a large multicentre study

OBJECTIVES

Few studies have explored the optimal dosing for efavirenz in individuals from China. We investigated plasma efavirenz concentrations and their association with efficacy and tolerance of efavirenz 600 mg daily in Chinese HIV-infected adults.

METHODS

An analysis was performed using plasma samples from 455 patients enrolled in a prospective multicentre trial in China. A total of 1198 plasma samples collected at weeks 4, 24 and 48 following antiretroviral therapy initiation were analysed. The mid-dose interval efavirenz concentrations (C12 ) were determined using high-performance liquid chromatography.

RESULTS

The median efavirenz concentration (interquartile range) steadily increased over time from 3.02 (2.28-4.23) to 3.71 (2.91-4.91) mg/L from week 4 to 48 (P < 0.001). The proportion of patients with C12 > 4.0 mg/L also rose from 28.0% to 34.2% and 43.8%, measured at 4, 24 and 48 weeks, respectively (P < 0.001). Five patients had efavirenz concentrations < 1.0 mg/L at week 4, 24 or 48. In the multivariable regression analysis, lower body weight and non-Han ethnicities were associated with higher efavirenz concentrations over time. At each time-point, patients with a body weight < 60 kg had significantly higher efavirenz C12 compared with those with body weight ≥ 60 kg (P < 0.05).

CONCLUSIONS

Efavirenz concentrations increased steadily over 48 weeks, and a substantial proportion of participants had efavirenz C12 above the upper limit of the proposed therapeutic window, especially those with low body weight (< 60 kg). Based upon these findings, a dosage reduction of efavirenz to 400 mg daily may warrant consideration in this population, especially for those with lower body weight.

Simultaneous determination of antiretroviral drugs in human hair with liquid chromatography-electrospray ionization-tandem mass spectrometry

The determination of the concentrations of antiretroviral drugs in hair is believed to be an important means for the assessment of the long-term adherence to highly active antiretroviral therapy. At present, the combination of tenofovir, lamivudine and nevirapine is widely used in China. However, there was no research reporting simultaneous determination of the three drugs in hair. The present study aimed to develop a sensitive method for simultaneous determination of the three drugs in 2-mg and 10-mg natural hair (Method 1 and Method 2). Hair samples were incubated in methanol at 37 °C for 16 h after being rinsed with methanol twice. The analysis was performed on high performance liquid chromatography tandem mass spectrometry with electronic spray ionization in positive mode and multiple reactions monitoring. Method 1 and Method 2 showed the limits of detection at 160 and 30 pg/mg for tenofovir, at 5 and 6 pg/mg for lamivudine and at 15 and 3 pg/mg for nevirapine. The two methods showed good linearity with the square of correlation coefficient >0.99 at the ranges of 416-5000 and 77-5000 pg/mg for tenofovir, 12-5000 and 15-5000 pg/mg for lamivudine and 39-50,000 and 6-50,000 pg/mg for nevirapine. They gave intra-day and inter-day coefficient of variation <15% and the recoveries ranging from 80.6 to 122.3% and from 83.1 to 114.4%. Method 2 showed LOD and LOQ better than Method 1 for tenofovir and nevirapine and matched Method 1 for lamivudine, but there was high consistency between them in the determination of the three drugs in hair. The population analysis with Method 2 revealed that the concentrations in hair were decreased with the distance of hair segment away from the scalp for the three antiretroviral drugs.

Prediction of plasma efavirenz concentrations among HIV-positive patients taking efavirenz-containing combination antiretroviral therapy

We investigated the predictors of plasma mid-dose concentrations (C12) of efavirenz by enrolling 456 HIV-positive patients who had received 2 nucleos(t)ide reverse-transcriptase inhibitors plus efavirenz (600 mg daily) for 2 weeks or longer and had their CYP2B6 516G>T polymorphism and efavirenz C12 determined. The median efavirenz C12 was 2.41 mg/L (IQR, 1.93–3.14). In analysis of covariance models, patients with CYP2B6 516GT and TT genotypes compared to those with GG genotype had higher efavirenz C12 (for GT genotype, an increase by 0.976 mg/L [95%CI, 0.765–1.188], and TT genotype, 4.871 mg/L [95%CI, 4.126–5.616]), while per 10-kg increment in weight decreased C12 by 0.199 mg/L (95%CI, 0.111–0.287). Models incorporating CYP2B6 516G>T polymorphism and weight had moderate predictive values in predicting efavirenz C12 ≥ 2 mg/L (ROC area under curve = 0.706 [95%CI, 0.656–0.756]). In the absence of CYP2B6 516G>T polymorphism, weight ≤58 kg provided better predictabilities for efavirenz C12 ≥ 2 mg/L (probability, 77.1% [95%CI, 69.0–83.5%] for weight = 50 kg and 70.6% [95%CI, 64.1–76.4%] for weight = 58 kg).

Drug interactions and the role of pharmacokinetic trials in guiding choices in first-line HIV therapy in low-income and middle-income countries

PURPOSE OF REVIEW

Low- and middle-income countries (LMICs) face specific challenges in the treatment of people living with HIV. Drug-drug interactions (DDIs) involving antiretrovirals (ARVs) are prevalent in all settings and have considerable potential to cause clinical harm to patients via toxicity or reduced efficacy of treatment. Differing comorbidities, endemic infections and traditional medicines may complicate ARV therapy (ART) in LMICs, which usually takes a public health approach in these settings, with fewer alternative regimens available. This review discusses the issues surrounding pharmacokinetic DDI studies and their application to ART in LMICs, with particular reference to first-line ART regimens.

RECENT FINDINGS

Pharmacokinetic studies with clinical endpoints are the gold standard for informing management of DDIs; however, data relevant to LMICs are sparse and of low quality. There is significant potential for clinically relevant DDIs between ARVs and antimalarials, antimycobacterials and drugs used in the treatment of neglected tropical diseases.

SUMMARY

Many pharmacokinetic studies are difficult to interpret in LMICs due to differences in patient factors including weight, disease state and genetic polymorphisms. DDI studies relevant to LMICs may also be lacking due to the neglected nature of relevant comorbidities. The ARVs currently available as first-line ART in LMICs are among those with highest propensity for DDIs.

Impact of obesity on antiretroviral pharmacokinetics and immuno-virological response in HIV-infected patients: a case-control study

Background

Obesity has high prevalence among HIV-infected patients. Increased adipose tissue mass affects the pharmacokinetics of numerous drugs, but few data are available for antiretroviral drugs.

Objectives

In this study we aimed to explore the pharmacokinetics of antiretroviral drugs and the immuno-virological response in obese patients with HIV infection.

Patients and methods

We examined data from 2009 to 2012 in our hospital's database for HIV-1-infected patients who received an antiretroviral drug (abacavir, emtricitabine, lamivudine, tenofovir, efavirenz, etravirine, nevirapine, atazanavir/ritonavir, darunavir/ritonavir, lopinavir/ritonavir or raltegravir). Obese patients were defined as those with BMI ≥30 kg/m 2 and normal-weight patients as those with BMI 19-25 kg/m 2 . Plasma concentrations ( C 12/24 ) were compared for each antiretroviral drug using a Mann-Whitney test. Suboptimal dosing and virological outcome were assessed by logistic regression, adjusting on covariates.

Results

We enrolled 291 obese and 196 normal-weight patients. Among the 12 analysed antiretroviral drugs, tenofovir, efavirenz and lopinavir C 12 values were significantly lower in obese than normal-weight patients: 66 versus 86 ng/mL, 1498 versus 2034 ng/mL and 4595 versus 6420 ng/mL, respectively ( P  <   0.001). Antiretroviral drug C 12/24 values were more frequently below efficacy thresholds for obese than for normal-weight patients after adjustment for other covariates ( P  <   0.001). Although obese patients showed a higher CD4 count than normal-weight patients (510 versus 444 cells/mm 3 , P  <   0.001), the groups did not differ in virological failure rate.

Conclusions

This study highlights the impact of obesity on antiretroviral drug plasma exposure, but identifies no consequence of this suboptimal exposure on the immuno-virological control in this population.

Addressing Antiretroviral Therapy-Associated Drug-Drug Interactions in Patients Requiring Treatment for Opportunistic Infections in Low-Income and Resource-Limited Settings

An increasing number of human immunodeficiency virus (HIV)-infected patients are achieving virologic suppression on antiretroviral therapy (ART) limiting the use of primary and secondary antimicrobial prophylaxis. However, in low-income and resource-limited settings, half of those infected with HIV are unaware of their diagnosis, and fewer than 50% of patients on ART achieve virologic suppression. Management of comorbidities and opportunistic infections among patients on ART may lead to inevitable drug-drug interactions (DDIs) and even toxicities. Elderly patients, individuals with multiple comorbidities, those receiving complex ART, and patients living in low-income settings experience higher rates of DDIs. Management of these cytochrome P450-mediated, nonmediated, and drug transport system DDIs is critical in HIV-infected patients, particularly those in resource-limited settings with few options for ART. This article critically analyzes and provides recommendations to manage significant DDIs and drug toxicities in HIV-infected patients receiving ART.

Genetic variants in CYP2B6 and CYP2A6 explain interindividual variation in efavirenz plasma concentrations of HIV-infected children with diverse ethnic origin

Background

Approximately 2.6 million children live with HIV globally, and efavirenz (EFV) is one of the most widely used antiretroviral agents for HIV treatment in children and adults. There are concerns about the appropriateness of current EFV dosing and it has been discussed whether EFV dosing should be adapted according to genotype in children as suggested for adults.

Aim

To investigate if pediatric EFV dosing should be guided by genetic variation in drug metabolizing enzymes rather than by body weight.

Method

EFV plasma concentrations measured for clinical purposes from all children less than 18 years old at Karolinska University Hospital, Stockholm, Sweden, treated with EFV were collected retrospectively. They were genotyped for eleven polymorphisms in genes coding for drug-metabolizing enzymes and P-glycoprotein, of potential importance for EFV disposition. Data on country of origin, sex, age, weight, HIV RNA, viral resistance patterns, CD4 cells, adherence to treatment, subjective health status and adverse events were collected from their medical records.

Results

Thirty-six patients and 182 (mean 5 samples/patient) EFV plasma concentration measurements from children of African, Asian and Latin American origin were included. EFV plasma concentration varied 21-fold between measurements (n = 182) (0.85–19.3 mg/L) and 9-fold measured as mean EFV plasma concentration across the subjects (1.55–13.4 mg/L). A multivariate mixed-effects restricted maximum likelihood regression model, including multiple gene polymorphisms, identified CYP2B6*6 T/T (p < 0.0005), CYP2B6*11 G/G (p < 0.0005), CYP2A6*9 A/C (p = 0.001) genotypes, age at treatment initiation (p = 0.002) and time from treatment initiation (p < 0.0005) as independent factors significantly related to log_e concentration/(dose/weight). The contribution of the model to the intra- and interindividual variation were 6 and 75%, respectively (Bryk/Raudenbush R-squared level).

Conclusion

Genetic polymorphisms in CYP2B6 and CYP2A6 explained a significant proportion of variability in EFV plasma concentration in HIV-infected children in a multi-ethnic outpatient clinic. Knowledge about individual variants in key drug metabolizing enzyme genes could improve clinical safety and genotype directed dosing could achieve more predictable EFV plasma concentrations in HIV-infected children.

Efficacy and safety of switching from nevirapine immediate-release twice daily to nevirapine extended-release once daily in virologically suppressed HIV-infected patients: a retrospective cohort study in Taiwan

Background

Whether the non-inferior efficacy and safety results of switching virologically suppressed HIV-1-infected patients from nevirapine immediate-release (NVP-IR) to NVP extended-release (NVP-XR) demonstrated in the TRANxITION study conducted in Europe and North America are also applicable to virologically suppressed HIV-infected Taiwanese patients remains unknown. We evaluated the comparative safety and efficacy of continuing NVP-IR versus switching to NVP-XR in virologically suppressed HIV-infected Taiwanese adults receiving combined antiretroviral therapy (cART) regimens.

Methods

We conducted a retrospective cohort study at Kaohsiung Veterans General Hospital from April 1, 2013, to March 31, 2015. Eighty-four virologically suppressed HIV-infected adults receiving NVP-IR cART were split into two groups: those continuing with NVP-IR (n = 49) and those being switched to NVP-XR (n = 35). Demographic characteristics, clinical variables, and laboratory findings were compared. Therapeutic drug monitoring of steady-state plasma NVP concentrations and genotype analysis of CYP2B6 516 were also performed in 22 participants. The primary endpoint was continued virological suppression at the end of the study. Secondary endpoints were time to loss of virological response and adverse events.

Results

During a mean follow-up of 18.4 months, the NVP-XR group demonstrated similar success at maintaining virological response compared with the NVP-IR group (82.9% vs. 85.7%; P = 0.72). Cox regression analysis indicated that there were no significant differences between NVP regimens for time to loss of virological response (hazard ratio: 0.940; P = 0.754). Furthermore, there were no significant differences in adverse events between these two groups. In the 22 participants, there was a non-significantly lower level of steady-state plasma NVP concentrations in the NVP-XR group than in NVP-IR recipients (5145.0 ng/mL vs. 6775.0 ng/mL; P = 0.267). The prevalence of CYP2B6 516 GT was 86.6%, and there was no significant difference in the distribution of CYP2B6 516 between these two groups.

Conclusions

We found that switching from NVP-IR to NVP-XR appeared to have similar safety and efficacy compared with continuing NVP-IR among virologically suppressed, HIV-infected Taiwanese patients. Our finding of higher C_trough levels in both groups compared with other studies conducted in Caucasian populations and the high prevalence of CYP2B6 516 GT requires further investigation in a larger Taiwanese cohort.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2371-3) contains supplementary material, which is available to authorized users.

The impact of genetic polymorphisms on the pharmacokinetics of efavirenz in African children

Aims

Using a model‐based approach, the efavirenz steady‐state pharmacokinetics in African children is characterized, quantifying demographic and genotypic effects on the drug's disposition. Simulations are also conducted allowing prediction of optimized doses of efavirenz in this population.

Methods

We modelled the steady‐state population pharmacokinetics of efavirenz in Ugandan and Zambian children using nonlinear mixed‐effects modelling. Individual mid‐dose efavirenz concentrations were derived and simulations explored genotype‐based dose optimization strategies.

Results

A two‐compartment model with absorption through transit compartments well described 2086 concentration‐time points in 169 children. The combined effect of single nucleotide polymorphisms (SNPs) 516G>T and 983T>C explained 44.5% and 14.7% of the variability in efavirenz clearance and bioavailability, respectively. The detected frequencies of composite CYP2B6 genotype were 0.33 for 516GG|983TT, 0.35 for 516GT|983TT, 0.06 for 516GG|983TC, 0.18 for 516TT|983TT, 0.07 516GT|983TC and 0.01 for 516GG|983CC. The corresponding estimated clearance rates were 6.94, 4.90, 3.93, 1.92, 1.36, and 0.74 l h⁻¹ for a 15.4 kg child and median (95% CI) observed mid‐dose concentrations 1.55 (0.51–2.94), 2.20 (0.97–4.40), 2.03 (1.19–4.53), 7.55 (2.40–14.74), 7.79 (3.66–24.59) and 18.22 (11.84–22.76) mg l⁻¹, respectively. Simulations showed that wild‐type individuals had exposures at the bottom of therapeutic range, while slower metabolizers were overexposed.

Conclusions

Dosage guidelines for African children should take into consideration the combined effect of SNPs CYP2B6 516G>T and 983T>C.

Impact of Genetic Polymorphisms of ABCB1 (MDR1, P-Glycoprotein) on Drug Disposition and Potential Clinical Implications: Update of the Literature

ATP-binding cassette transporter B1 (ABCB1; P-glycoprotein; multidrug resistance protein 1) is an adenosine triphosphate (ATP)-dependent efflux transporter located in the plasma membrane of many different cell types. Numerous structurally unrelated compounds, including drugs and environmental toxins, have been identified as substrates. ABCB1 limits the absorption of xenobiotics from the gut lumen, protects sensitive tissues (e.g. the brain, fetus and testes) from xenobiotics and is involved in biliary and renal secretion of its substrates. In recent years, a large number of polymorphisms of the ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1] gene have been described. The variants 1236C>T (rs1128503, p.G412G), 2677G>T/A (rs2032582, p.A893S/T) and 3435C>T (rs1045642, p.I1145I) occur at high allele frequencies and create a common haplotype; therefore, they have been most widely studied. This review provides an overview of clinical studies published between 2002 and March 2015. In summary, the effect of ABCB1 variation on P-glycoprotein expression (messenger RNA and protein expression) and/or activity in various tissues (e.g. the liver, gut and heart) appears to be small. Although polymorphisms and haplotypes of ABCB1 have been associated with alterations in drug disposition and drug response, including adverse events with various ABCB1 substrates in different ethnic populations, the results have been majorly conflicting, with limited clinical relevance. Future research activities are warranted, considering a deep-sequencing approach, as well as well-designed clinical studies with appropriate sample sizes to elucidate the impact of rare ABCB1 variants and their potential consequences for effect sizes.

An Expanded Analysis of Pharmacogenetics Determinants of Efavirenz Response that Includes 3'-UTR Single Nucleotide Polymorphisms among Black South African HIV/AIDS Patients

Introduction: Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor prescribed as part of first-line highly active antiretroviral therapy (HAART) in South Africa. Despite administration of fixed doses of EFV, inter-individual variability in plasma concentrations has been reported. Poor treatment outcomes such as development of adverse drug reactions or treatment failure have been linked to EFV plasma concentrations outside the therapeutic range (1–4 μg/mL) in some studies. The drug metabolizing enzyme (DME), CYP2B6, is primarily responsible for EFV metabolism with minor contributions by CYP1A2, CYP2A6, CYP3A4, CYP3A5, and UGT2B7. DME coding genes are also regulated by microRNAs through targeting the 3′-untranslated region. Expanded analysis of 30 single nucleotide polymorphisms (SNPs), including those in the 3′-UTR, was performed to identify pharmacogenetics determinants of EFV plasma concentrations in addition to CYP2B6 c.516G>T and c.983T>C SNPs.

Methods: SNPs in CYP1A2, CYP2B6, UGT2B7, and NR1I2 (PXR) were selected for genotyping among 222 Bantu-speaking South African HIV-infected patients receiving EFV-containing HAART. This study is a continuation of earlier pharmacogenetics studies emphasizing the role of genetic variation in the 3′-UTR of genes which products are either pharmacokinetic or pharmacodynamic targets of EFV.

Results: Despite evaluating thirty SNPs, CYP2B6 c.516G>T and c.983T>C SNPs remain the most prominent predictors of EFV plasma concentration.

Conclusion: We have shown that CYP2B6 c.516G>T and c.983T>C SNPs are the most important predictors of EFV plasma concentration after taking into account all other SNPs, including genetic variation in the 3′-UTR, and variables affecting EFV metabolism.

Tenofovir DF/emtricitabine and efavirenz combination therapy for HIV infection in patients treated for tuberculosis: the ANRS 129 BKVIR trial

BACKGROUND

HIV-infected patients with TB need simplified, effective and well-tolerated antiretroviral regimens.

METHODS

The French ANRS 129 BKVIR open trial evaluated the once-daily tenofovir DF/emtricitabine and efavirenz combination, started within 12 weeks after TB treatment initiation, in antiretroviral-naive HIV-1-infected patients. Success was defined as an HIV-1 RNA <50 copies/mL and TB cure at 48 weeks.

RESULTS

TB was confirmed microbiologically (90%) or histologically (10%) in 69 patients (71% male; median age 43 years; 54% born in Africa). The median time between TB treatment initiation and antiretroviral therapy was 8 weeks (range 1-22 weeks). At baseline, median HIV-1 RNA was 5.4 log10 copies/mL and median CD4 cell count 74 cells/mm(3). In the ITT analysis, combined success at week 48 was achieved in 57/69 patients (83%, 95% CI 74-92). Twelve patients did not achieve virological success, and TB was not cured in one of them. Among the 47 patients who fully adhered to the strategy, the success rate was 96% (95% CI 90-100) and was not affected by low rifampicin and isoniazid serum concentrations. Forty-nine serious adverse events were reported in 31 patients (45%), and 11 led to antiretroviral drug interruption. All adverse events resolved. The immune reconstitution inflammatory syndrome occurred in 23 patients (33%, 95% CI 22-44), and was associated with a low baseline BMI (P = 0.03) and a low haemoglobin level (P = 0.02).

CONCLUSION

These results support the use of tenofovir DF/emtricitabine and efavirenz combination therapy for HIV infection in patients with TB.

CYP2B6 genotype, but not rifampicin-based anti-TB cotreatments, explains variability in long-term efavirenz plasma exposure

AIM

We investigated the effects of rifampicin-based anti-TB treatment on plasma efavirenz exposure and the implications of CYP2B6 genotype.

PATIENTS & METHODS

Antiretroviral therapy-naive Ugandan HIV patients without (n = 157) or with TB coinfection (n = 106) were enrolled and treated with efavirenz-based highly active antiretroviral therapy alone or with rifampicin-based anti-TB therapy, respectively. Efavirenz plasma concentration was determined on day 3 and weeks 1, 2, 8, 12, 16, 20, 24, 28 and 32.

RESULTS

Rifampicin-based anti-TB cotreatment reduced plasma efavirenz exposure during the first 2 weeks (p < 0.05), but no significant effect was observed afterwards. Although not significant, rifampicin-based anti-TB cotreatment inconsistently increased efavirenz exposure over time, which was reduced immediately after completing anti-TB therapy. CYP2B6*6, *11 and ABCB1 c.4036A>G genotypes were significant predictors of efavirenz plasma exposure.

CONCLUSION

Plasma efavirenz exposure is mainly influenced by CYP2B6 genotype, but not by rifampicin cotreatment. Therefore, no efavirenz dosage adjustment during rifampicin cotreatment is required in Ugandans.

CYP2B6*6, CYP2B6*18, Body weight and sex are predictors of efavirenz pharmacokinetics and treatment response: population pharmacokinetic modeling in an HIV/AIDS and TB cohort in Zimbabwe

Background

Efavirenz (EFV) therapeutic response and toxicity are associated with high inter-individual variability attributed to variation in its pharmacokinetics. Plasma concentrations below 1 μg/ml may result in virologic failure and above 4 μg/ml, may result in central nervous system adverse effects. This study used population pharmacokinetics modeling to explore the influence of demographic and pharmacogenetic factors including efavirenz-rifampicin interaction on EFV pharmacokinetics, towards safer dosing of EFV.

Methods

Patients receiving an EFV-based regimen for their antiretroviral therapy and a rifampicin-containing anti-TB regimen were recruited. EFV plasma concentrations were measured by HPLC and genomic DNA genotyped for variants in the CYP2B6, CYP2A6 and ABCB1 genes. All patients were evaluated for central nervous system adverse effects characterised as sleep disorders, hallucinations and headaches using the WHO ADR grading system. A pharmacokinetic model was built in a forward and reverse procedure using nonlinear mixed effect modeling in NONMEM VI followed by model-based simulations for optimal doses.

Results

CYP2B6*6 and *18 variant alleles, weight and sex were the most significant covariates explaining 55% of inter-individual variability in EFV clearance. Patients with the CYP2B6*6TT genotype had a 63% decrease in EFV clearance despite their CYP2B6*18 genotypes with females having 22% higher clearance compared to males. There was a 21% increase in clearance for every 10 kg increase in weight. The effect of TB/HIV co-treatment versus HIV treatment only was not statistically significant. No clinically relevant association between CYP2B6 genotypes and CNS adverse effects was seen, but patients with CNS adverse effects had a 27% lower clearance compared to those without. Model- based simulations indicated that all carriers of CYP2B6*6 TT genotype would be recommended a dose reduction to 200 mg/day, while the majority of extensive metabolisers may be given 400 mg/day and still maintain therapeutic levels.

Conclusion

This study showed that screening for CYP2B6 functional variants has a high predictability for efavirenz plasma levels and could be used in prescribing optimal and safe EFV doses.

Impact of body weight on virological and immunological responses to efavirenz-containing regimens in HIV-infected, treatment-naive adults

OBJECTIVE

The prevalence of overweight and obesity is increasing among HIV-infected patients. Whether standard antiretroviral drug dosage is adequate in heavy individuals remains unresolved. We assessed the virological and immunological responses to initial efavirenz (EFV)-containing regimens in heavy compared to normal-weight HIV-infected patients.

DESIGN

Observational European cohort collaboration study.

METHODS

Eligible patients were antiretroviral-naïve with documented weight prior to EFV start and follow-up viral loads after treatment initiation. Cox regression analyses evaluated the association between weight and time to first undetectable viral load (<50 copies/ml) after treatment initiation, and time to viral load rebound (two consecutive viral load >50 copies/ml) after initial suppression over 5 years of follow-up. Recovery of CD4 cell count was evaluated 6 and 12 months after EFV initiation. Analyses were stratified by weight (kg) group (I - <55; II - >55, <80 (reference); III - >80, <85; IV - >85, <90; V - >90, <95; VI - >95).

RESULTS

The study included 19,968 patients, of whom 9.1, 68.3, 9.1, 5.8, 3.5, and 4.3% were in weight groups I-VI, respectively. Overall, 81.1% patients attained virological suppression, of whom 34.1% subsequently experienced viral load rebound. After multiple adjustments, no statistical difference was observed in time to undetectable viral load and virological rebound for heavier individuals compared to their normal-weight counterparts. Although heaviest individuals had significantly higher CD4 cell count at baseline, CD4 cell recovery at 6 and 12 months after EFV initiation was comparable to normal-weight individuals.

CONCLUSION

Virological and immunological responses to initial EFV-containing regimens were not impaired in heavy individuals, suggesting that the standard 600 mg EFV dosage is appropriate across a wide weight range.

Sex, age, race and intervention type in clinical studies of HIV cure: a systematic review

This systematic review was undertaken to determine the extent to which adult subjects representing sex (female), race (nonwhite), and age (>50 years) categories are included in clinical studies of HIV curative interventions and thus, by extension, the potential for data to be analyzed that may shed light on the influence of such demographic variables on safety and/or efficacy. English-language publications retrieved from PubMed and from references of retrieved papers describing clinical studies of curative interventions were read and demographic, recruitment year, and intervention-type details were noted. Variables of interest included participation by sex, age, and race; changes in participation rates by recruitment year; and differences in participation by intervention type. Of 151 publications, 23% reported full demographic data of study enrollees, and only 6% reported conducting efficacy analyses by demographic variables. Included studies recruited participants from 1991 to 2011. No study conducted safety analyses by demographic variables. The representation of women, older people, and nonwhites did not reflect national or international burdens of HIV infection. Participation of demographic subgroups differed by intervention type and study location. Rates of participation of demographic groups of interest did not vary with time. Limited data suggest efficacy, particularly of early therapy initiation followed by treatment interruption, may vary by demographic variables, in this case sex. More data are needed to determine associations between demographic characteristics and safety/efficacy of curative interventions. Studies should be powered to conduct such analyses and cure-relevant measures should be standardized.

Gender inequalities in the response to combination antiretroviral therapy over time: the Swiss HIV Cohort Study

OBJECTIVES

Gender-specific data on the outcome of combination antiretroviral therapy (cART) are a subject of controversy. We aimed to compare treatment responses between genders in a setting of equal access to cART over a 14-year period.

METHODS

Analyses included treatment-naïve participants in the Swiss HIV Cohort Study starting cART between 1998 and 2011 and were restricted to patients infected by heterosexual contacts or injecting drug use, excluding men who have sex with men.

RESULTS

A total of 3925 patients (1984 men and 1941 women) were included in the analysis. Women were younger and had higher CD4 cell counts and lower HIV RNA at baseline than men. Women were less likely to achieve virological suppression < 50 HIV-1 RNA copies/mL at 1 year (75.2% versus 78.1% of men; P = 0.029) and at 2 years (77.5% versus 81.1%, respectively; P = 0.008), whereas no difference between sexes was observed at 5 years (81.3% versus 80.5%, respectively; P = 0.635). The probability of virological suppression increased in both genders over time (test for trend, P < 0.001). The median increase in CD4 cell count at 1, 2 and 5 years was generally higher in women during the whole study period, but it gradually improved over time in both sexes (P < 0.001). Women also were more likely to switch or stop treatment during the first year of cART, and stops were only partly driven by pregnancy. In multivariate analysis, after adjustment for sociodemographic factors, HIV-related factors, cART and calendar period, female gender was no longer associated with lower odds of virological suppression.

CONCLUSIONS

Gender inequalities in the response to cART are mainly explained by the different prevalence of socioeconomic characteristics in women compared with men.