Pooled Pharyngeal, Rectal, and Urine Specimens for the Point-of-Care Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Lay Providers in Key Population-Led Health Services in Thailand.

Routine testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) in people with heightened risk is lacking in Thailand. This study aimed to assess the performance of the Cepheid Xpert CT/NG assay, conducted by key population (KP) lay providers, for CT and NG detection on single-site and pooled specimens from the pharynx, rectum, and urine. Between August and October 2019, 188 men who have sex with men and 11 transgender women were enrolled. Participants collected urine specimens while trained KP lay providers obtained pharyngeal and rectal swabs. Compared to single-site testing with the Abbott RealTime CT/NG assay by medical technologists, the Xpert assay missed one pharyngeal NG infection out of 199 single-site specimens, giving a 93.3% sensitivity for pharyngeal NG and one missed pharyngeal NG infection out of fifty pooled specimens, giving an 88.9% sensitivity for pharyngeal NG. There was no discrepancy between the two assays for CT detection. The Cohen's Kappa coefficient of pooled specimen testing by the Xpert was 0.93 for NG and 1 for CT when compared to single-site testing by Abbott. Implementing pooled specimen testing by KP lay providers can be a cost-saving strategy to enhance the uptake of CT/NG services for populations facing increased risk.

Pharmacogenetics-based population pharmacokinetic analysis for dose optimization of ritonavir-boosted atazanavir in Thai adult HIV-infected patients.

BACKGROUND: This population pharmacokinetic-pharmacogenetic study aimed to investigate the optimal dose of RTV-boosted ATV (ATV/RTV) for Thai adult HIV-infected patients. METHODS: A total of 1460 concentrations of ATV and RTV from 544 patients receiving an ATV/RTV-based regimen were analyzed. The CYP3A5 6986 A > G, ABCB1 3435 C > T, ABCB1 2677 G > T, SLCO1B1 521 T > C, and NR1I2 63396 C > T were genotyped. A population pharmacokinetic model was performed using a nonlinear mixed-effect model (NONMEM®). Monte Carlo simulations were conducted to compare the percentages of patients achieving the therapeutic range of ATV through concentrations (Ctrough). RESULTS: The apparent oral clearance of ATV (CL/FATV) without RTV was 7.69 L/h with interindividual variability (IIV) of 28.7%. Patients with CYP3A5 6986 GG had a 7.1% lower CL/FATV than those with AA or AG genotype. The CL/FATV decreased by 10.8% for females compared with males. Simulation results showed higher percentages (~70%) of patient receiving doses of 200/100 or 200/50 mg achieved the target ATV Ctrough, while more patients (~40%) receiving a standard dose (300/100 mg) had ATV Ctrough above this target. CONCLUSIONS: Both CYP3A5 6986 A > G and female decreased CL/FATV in Thai HIV-infected patients. Simulations supported that the reduced dose of ATV/RTV was sufficient to achieve the target concentration for Thai population.

Acceptability and satisfaction towards self-collection for chlamydia and gonorrhoea testing among transgender women in Tangerine Clinic, Thailand: shifting towards the new normal.

INTRODUCTION: Provider-collected swabs are an unappealing procedure for many transgender women and may have led to suboptimal rates of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) testing. Self-collection for CT/NG testing is recommended for men who have sex with men. However, the information on acceptability and clinical performance to support a recommendation for transgender women is lacking. We aimed to determine the acceptability and satisfaction towards self-collection for CT/NG testing among Thai transgender women. METHODS: Thai transgender women who attended Tangerine Clinic (a transgender-led, integrated, gender-affirming care and sexual health services clinic in Bangkok, Thailand) between May and July 2020 and had condomless sexual intercourse within the past six months were offered to collect urine and perform self-swabs of pharyngeal, rectal, and if applicable, neovaginal compartments for pooled nucleic acid amplification testing for CT/NG infections. Participants received a diagram, video and oral instructions about how to perform self-collection procedure. Those who accepted self-collection were also offered to receive provider collection to evaluate the performance between the two methods. Self-administered questionnaires were used to assess satisfaction. RESULTS: Among 216 transgender women enrolled, 142 (65.7%) accepted self-collection. All who accepted had pharyngeal, rectal and urine samples collected. Of 31 transgender women who had undergone genital surgery, 28 (90.3%) accepted neovaginal self-swab. The acceptance rate increased from 46.2% in May to 84.5% in July 2020. One participant had an invalid result. All transgender women who accepted self-collection could perform it without assistance, and 82.8% were highly satisfied with the method. None reported dissatisfaction. Due to the COVID-19 pandemic, provider collection services were discontinued early, and only eight transgender women were able to perform both methods for performance evaluation. The performance agreement was 100%. CONCLUSIONS: Thai transgender women had high acceptability and satisfaction towards self-collection for CT/NG testing. The performance was promising compared to provider collection. Our results support the implementation of self-collection to the sexually transmitted infection services, particularly during the COVID-19 pandemic where physical distancing is the new normal. A larger study is warranted to determine the performance of self-collection for CT/NG testing in each anatomical compartment and confirm the performance between self-collection and provider collection.

Determinants of Viral Resuppression or Persistent Virologic Failure After Initial Failure With Second-Line Antiretroviral Treatment Among Asian Children and Adolescents With HIV.

Of 56 children with perinatally acquired human immunodeficiency virus (HIV) who had been prescribed second-line protease inhibitor-based antiretroviral therapy and had ≥1 previous episode of viral failure (HIV RNA, ≥1000 copies/mL), 46% had ≥1, 34% had ≥2, and 23% had ≥3 consecutive episodes of viral failure during the 2 years of follow-up. Two of these children experienced a major protease inhibitor mutation.

Drug-drug interactions between feminizing hormone therapy and pre-exposure prophylaxis among transgender women: the iFACT study.

INTRODUCTION: Concerns over potential drug-drug interactions (DDI) between feminizing hormone therapy (FHT) and pre-exposure prophylaxis (PrEP) have hampered uptake and adherence of PrEP among transgender women (TGW). To determine DDI between FHT and PrEP, we measured the pharmacokinetic (PK) parameters of blood plasma estradiol (E2) and tenofovir (TFV) in Thai TGW. METHODS: Twenty TGW who never underwent orchiectomy and had not received injectable FHT within six months were enrolled between January and March 2018. FHT (E2 valerate and cyproterone acetate) were prescribed to participants at baseline until week 5, and then from week 8 until the end of study. Daily PrEP (tenofovir disoproxil fumarate/emtricitabine) was initiated at week 3 and continued without interruption. Intensive E2 PK parameters and testosterone concentration at 24 hours (C24 ) were measured at weeks 3 (without PrEP) and 5 (with PrEP), and intensive TFV PK parameters were measured at weeks 5 (with FHT) and 8 (without FHT). RESULTS: Median (interquartile range) age, body mass index, and creatinine clearance were 21.5 (21-26) years, 20.6 (19.0-22.4) kg/m2 , and 116 (101-126.5) mL/min, respectively. The geometric mean (%CV) of area under curve from time zero to 24 hours (AUC0-24 ), maximum concentration (Cmax ), and C24 of E2 at weeks 3 and 5 were 775.13 (26.2) pg h/mL, 51.47 (26.9) pg/mL, and 15.15 (42.0) pg/mL; and 782.84 (39.6), 55.76 (32.9), and 14.32 (67.4), respectively. The geometric mean (%CV) of TFV AUC0-24 , Cmax , and C24 at weeks 5 and 8 were 2242.1 (26.5) ng h/mL, 353.9 (34.0) ng/mL, and 40.9 (31.4) ng/mL; and 2530.2 (31.3), 311.4 (30.0), and 49.8 (29.6), respectively. The geometric mean of TFV AUC0-24 and C24 at week 5 were significantly less than that at week 8 by 12% (p = 0.03) and 18% (p < 0.001), respectively. There were no significant changes in E2 PK parameters and median C24 of bioavailable testosterone between week 3 and week 5. CONCLUSIONS: Our study demonstrated lower blood plasma TFV exposure in the presence of FHT, suggesting that FHT may potentially affect PrEP efficacy among TGW; but E2 exposure was not affected by PrEP. Further studies are warranted to determine whether these reductions in TFV are clinically significant. Clinical Trial Number: NCT03620734.

Influence of CYP3A5 and SLCO1B1 polymorphisms on atazanavir/r concentrations in Thai HIV-infected patients.

Aim: To evaluate the influence of genetic polymorphisms on plasma trough concentrations of atazanavir (ATV) and ritonavir (RTV). Patients & methods: The concentration-to-dose ratios were compared between different genotype groups of CYP3A5, ABCB1, SLCO1B1 and NR1I2 in 490 patients. Multiple regression analysis was used to examine the association between genetic and clinical factors and log-transformed concentration-to-dose ratio of ATV and RTV. Results: Higher concentrations of ATV and RTV were significantly associated with CYP3A5 6986 GG and SLCO1B1 521 TC or CC. Female patients had significantly higher ATV plasma concentration than male patients. Conclusion: Genetic polymorphisms and gender are factors affecting the variability of ATV and RTV concentrations in the Thai population. Thus, genetic testing is worth considering when atazanavir + low dose ritonavir is prescribed.

Pharmacokinetics and 48-week safety and efficacy of generic ritonavir tablet-boosted atazanavir in HIV-1-infected Thai adults.

BACKGROUND: Ritonavir (RTV) tablets were not available in Thailand until they were manufactured by the Government Pharmaceutical Organization of Thailand. We assessed pharmacokinetics (PK), safety and efficacy of generic RTV-boosted atazanavir (ATV) in virologically suppressed HIV-1-infected Thai adults. METHODS: Virologically suppressed HIV-1-infected Thai adults who currently use ATV (either 200 or 300 mg) with Norvir® soft gel capsule (SGC) 100-mg-based regimen were enrolled into this prospective, 48-week single-arm study. Participants switched from Norvir® SGC to generic RTV. Plasma trough concentration (Ctrough) was assessed at baseline before switching to generic RTV and week 24 in all participants, with the target ATV Ctrough of 0.15 mg/l. Plasma HIV-1 RNA and other laboratory safety parameters were assessed until week 48. RESULTS: Of 100 participants (51% male) enrolled, 50% was using ATV 200 mg and 50% was using 300 mg at the time RTV SGC were changed into generic tablets. All participants used two nucleoside reverse transcriptase inhibitors (NRTIs) as backbone. There were no significant changes in mean (sd) Ctrough of RTV (0.20 [0.33] versus 0.23 [0.39]; P=0.21) and ATV (0.83 [0.93] versus 0.88 [0.95]; P=0.62) between baseline and week 24. From entry to week 48, median alanine aminotransferase significantly increased from 25 to 30 IU/l (P=0.001) and total bilirubin significantly decreased from 1.7 to 1.3 (P=0.04). One study drug related grade 3 adverse event was reported. All but one participant maintained plasma HIV-1 RNA <50 copies/ml after 48 weeks. CONCLUSIONS: Generic RTV-boosted ATV showed adequate levels, good tolerability and great efficacy after 48 weeks.

Pharmacokinetics of rilpivirine and 24-week outcomes after switching from efavirenz in virologically suppressed HIV-1-infected adolescents.

BACKGROUND: Rilpivirine (RPV), a non-nucleoside reverse transcriptase inhibitor drug, could be a favourable drug for maintenance therapy in HIV-infected adolescents because it has few long-term side effects. However, data among adolescents switching from efavirenz (EFV) to RPV are limited. This study investigated the pharmacokinetics (PK), safety and efficacy of RPV in virologically suppressed HIV-1-infected adolescents after switching from EFV. METHODS: Adolescents aged 12-18 years on EFV-based antiretroviral therapy (ART) were switched from EFV to RPV (25 mg, once daily). Intensive 24-h blood samplings at 0 (pre-dose), 1, 2, 4, 5, 6, 9, 12 and 24 h were performed 4 weeks after switching. PK parameters were calculated using a non-compartmental method and compared with published data from the PAINT and pooled ECHO/THRIVE substudies. HIV RNA level was measured at weeks 12 and 24. Biochemical profiles were measured at baseline and week 24. RESULTS: From January to June 2016, 20 adolescents (12 male) were enrolled. Median (IQR) age was 16 (15-17) years and weight was 49 (42-59) kg. Mean (sd) AUC24 h, C24 h and Cmax of RPV were 2,041 (745) ng•h/ml, 69 (29) ng/ml and 143 (65) ng/ml, respectively. Median (IQR) Tmax was 5 (2-9) h. Four adolescents had C24 h <40 ng/ml. All PK parameters were comparable with published data. All adolescents remained virologically suppressed at week 24. Significant decreases in fasting total cholesterol, triglyceride and low-density lipoprotein were observed (P-value <0.05). CONCLUSIONS: Virologically suppressed HIV-infected adolescents had adequate RPV exposure and remained virologically suppressed after switching from EFV. RPV can be used as long-term maintenance ART in HIV-infected adolescents.

Pharmacogenetics-based population pharmacokinetic analysis of tenofovir in Thai HIV-infected patients.

AIM: To develop a population pharmacokinetic model and identify sources of variability, genetic and nongenetic factors, of tenofovir. METHODS: The ABCC2 and ABCC4 polymorphisms were genotyped in 342 patients. A nonlinear mixed effects model was used to develop the population pharmacokinetic model and investigate the influence of these polymorphisms and other patient specific covariates on the pharmacokinetics of tenofovir. RESULTS: The estimated glomerular filtration rate calculated by the Cockcroft and Gault equation, concomitant use of lopinavir/ritonavir and ABCC4 3463A>G polymorphism were associated with tenofovir apparent oral clearance (CL/F). The use of lopinavir/ritonavir decreased tenofovir CL/F by 25%. Patients carrying ABCC4 3463 AG or GG had a tenofovir CL/F 11% higher than those with genotype AA. CONCLUSION: Renal function, co-medication and genetic variation impact the pharmacokinetics of tenofovir. These factors should be taken into consideration to guide the individual tenofovir disoproxil fumarate dosage regimen in Thai HIV-infected patients.

Carbohydrate, lipid, bone and inflammatory markers in HIV-positive adolescents on antiretroviral therapy and hormonal contraception.

BACKGROUND: Little is known about the cumulative effect of HIV antiretroviral therapy (ART) and hormonal contraception (HC) on metabolism and inflammation in HIV-positive women. METHODS: We conducted a cross-sectional assessment of markers for carbohydrate, lipid, bone metabolism, inflammation and coagulation in HIV-positive adolescents on ART and HC (n=37) versus on ART only (n=51) in Thailand. The Wilcoxon rank-sum test was used to assess differences between groups. RESULTS: The median age was 19.5 years. Most adolescents (95%) were perinatally infected. All were on ART for a median of 9 years. HC used was progestin only (n=21); combined oral contraceptive (COC) tablets (n=6) for the whole study period or alternating between progestin only and COC (n=10). Prevalence of any metabolic abnormalities was 99%. Four biomarkers were significantly higher with HC vs no HC: insulin (10.3 vs 6.2 µU/mL, P=0.002), insulin resistance (1.89 vs 1.19 mass units, P=0.005), 25-OH vitamin D (33.2 vs 20.2 ng/mL, P<0.0001) and C-terminal telopeptide (690 vs 530 ng/L, P=0.011). Triglycerides and D-dimer were significantly lower with HC (103 vs 139 mg/dL, P=0.014 and 140 vs 155 ng/mL, P=0.003, respectively). There was no relationship between the type of HC or ART and the above differences. CONCLUSION: Perinatally infected HIV-positive adolescents on ART in this pilot study had a high prevalence of metabolic abnormalities. Bone turnover markers and insulin resistance were significantly higher with HC. Research on the cumulative effect of HIV, ART and HC on metabolism and inflammation in adolescents with HIV is important in order to devise strategies for preventing and mitigating long-term comorbidities.

Population pharmacokinetics and dose optimisation of ritonavir-boosted atazanavir in Thai HIV-infected patients.

There is evidence that Thai patients receiving standard doses of ritonavir (RTV)-boosted atazanavir (ATV/r) have high exposure to atazanavir (ATV) leading to a higher risk of toxicity. A lower dose of ATV/r may provide adequate exposure in this population. However, pharmacokinetic data on ATV/r in Thai patients required for dose adjustment are limited. This study aimed to develop a population pharmacokinetic model of ATV/r and to determine the influence of patient characteristics on ATV pharmacokinetics. Monte Carlo simulations were performed to estimate the proportion of patients achieving target ATV trough concentration (Ctrough) with the standard ATV/r dose of 300/100 mg and a low dose of 200/100 mg once daily (OD). A total of 127 Thai HIV-infected patients were included in this study. One random blood sample was collected to determine ATV and RTV concentrations at each clinic visit from 100 patients. Intensive data from 27 patients enrolled in previous studies were also included. Data were analysed using the non-linear mixed-effects modelling approach. A one-compartment model with first-order absorption and elimination and absorption lag time best described the data. The population mean clearance of ATV/r was 4.93 L/h in female patients and was 28.7% higher in male patients. Simulation results showed a higher proportion of patients achieving ATV Ctrough within the target range with ATV/r 200/100 mg compared with 300/100 mg. The 200/100 mg OD dose of ATV/r provides adequate ATV exposure in Thai HIV-infected patients. Therefore, a lower dose of ATV/r should be considered for Thai and Asian populations.

Therapeutic drug monitoring of antiretroviral drugs in HIV-infected patients.

INTRODUCTION: Therapeutic drug monitoring (TDM) may be beneficial when applied to antiretroviral (ARV). Even though TDM can be a valuable strategy in HIV management, its role remains controversial. Areas covered: This review provides a comprehensive update on important issues relating to TDM of ARV drugs in HIV-infected patients. Articles from PubMed with keywords relevant to each topic section were reviewed. Search strategies limited to articles published in English. Expert commentary: There is evidence supporting the use of TDM in HIV treatment. However, some limitations need to be considered. The evidence supporting the use of routine TDM for all patients is limited, as it is not clear that this strategy offers any advantages over TDM for selected indications. Selected groups of patients including patients with physiological changes, patients with drug-drug interactions or toxicity, and the elderly could potentially benefit from TDM, as optimized dosing is challenging in these populations.

Pharmaceutical Equivalence of Distributed Generic Antiretroviral (ARV) in Asian Settings: The Cross-Sectional Surveillance Study - PEDA Study.

OBJECTIVES: Ensuring that medicines meet quality standards is mandatory for ensuring safety and efficacy. There have been occasional reports of substandard generic medicines, especially in resource-limiting settings where policies to control quality may be less rigorous. As HIV treatment in Thailand depends mostly on affordable generic antiretrovirals (ARV), we performed quality assurance testing of several generic ARV available from different sources in Thailand and a source from Vietnam. METHODS: We sampled Tenofovir 300mg, Efavirenz 600mg and Lopinavir/ritonavir 200/50mg from 10 primary hospitals randomly selected from those participating in the National AIDS Program, 2 non-government organization ARV clinics, and 3 private drug stores. Quality of ARV was analyzed by blinded investigators at the Faculty of Pharmaceutical Science, Chulalongkorn University. The analysis included an identification test for drug molecules, a chemical composition assay to quantitate the active ingredients, a uniformity of mass test and a dissolution test to assess in-vitro drug release. Comparisons were made against the standards described in the WHO international pharmacopeia. RESULTS: A total of 42 batches of ARV from 15 sources were sampled from January-March 2015. Among those generics, 23, 17, 1, and 1 were Thai-made, Indian-made, Vietnamese-made and Chinese-made, respectively. All sampled products, regardless of manufacturers or sources, met the International Pharmacopeia standards for composition assay, mass uniformity and dissolution. Although local regulations restrict ARV supply to hospitals and clinics, samples of ARV could be bought from private drug stores even without formal prescription. CONCLUSION: Sampled generic ARVs distributed within Thailand and 1 Vietnamese pharmacy showed consistent quality. However some products were illegally supplied without prescription, highlighting the importance of dispensing ARV for treatment or prevention in facilities where continuity along the HIV treatment and care cascade is available.

High Variability of Hormonal Levels and No Clinically Relevant Interaction Between Ethinyl Estradiol, Desogestrel and Lopinavir/Ritonavir in a Small Sample of HIV-positive Adolescents.

BACKGROUND: We report the pharmacokinetic interactions of combined oral contraceptive (COC) containing ethinyl estradiol (EE2)/desogestrel (DSG) with lopinavir/ritonavir (LPV/r) in 16 HIV-positive adolescents. METHODS: We measured Ctrough of EE2 and etonogestrel (ENG), the active metabolite of DSG, in HIV-positives on LPV/r-based ART; Ctrough of LPV/r with and without COC; endogenous progesterone. EE2/ENG levels were compared with our own historical data of HIV-negative controls. RESULTS: Ctrough of EE2 and ENG varied from 3 to 57 pg/mL and from 1051 to 5000 pg/mL, respectively. The geometric mean ratios (GMR) of Ctrough in HIV-positives on LPV/r with COC versus HIV-negative controls with COC only were 0.68 (95% CI: 0.42 to 1.08) or 32% decreased (P = 0.10) for EE2; and 1.08 (95% CI: 0.73 to 1.60) or 8% increased (P = 0.68) for ENG. Endogenous progesterone was <1.0 ng/mL in all participants, consistent with anovulation. Ctrough of LPV decreased statistically insignificantly with COC and remained above the desired therapeutic minimum of 1.0 mg/L in all. CONCLUSIONS: The study found no clinically relevant interaction between EE2/DSG and LPV/r. This was supported by suppressed ovulation, assessed by low endogenous progesterone levels in all participants; and preserved antiretroviral activity, assessed by LPV/r levels above the desired therapeutic minimum in all participants. However, the high variability of hormonal levels warrants individual monitoring and further investigation. Condom use should always be encouraged for infection prevention.

Population pharmacokinetics of tenofovir in HIV/HBV co-infected patients.

OBJECTIVE: Tenofovir is an efficacious drug with a long half-life and high activity against both HIV and HBV. However, the pharmacokinetics of tenofovir have not been studied in HIV/HBV co-infected patients. Data from HIV mono-infected patients may not be transferable to HIV/HBV co-infected population because the nature and consequences of the co-infection are different. This study developed a population pharmacokinetic model of tenofovir in patients with HIV/HBV co-infection and identified pathophysiologic factors that affect the pharmacokinetics of the drug. METHODS: Sparse and intensive blood samples were collected from patients with HIV/HVB coinfection. The population pharmacokinetic model of tenofovir was developed by a nonlinear mixed-effects modeling approach (NONMEM®). RESULTS: A total of 332 tenofovir plasma concentrations from 146 patients were obtained. A two-compartment model best described the pharmacokinetics of tenofovir. Creatinine clearance (estimated by Cockcroft and Gault equation) affected the tenofovir apparent clearance (CL/F). Tenofovir CL/F decreased by 23.5% when concomitantly used with atazanavir/ritonavir. CONCLUSIONS: Based on the results from our study, it was shown that the pharmacokinetics of tenofovir in HIV/HBV co-infected patients are comparable to those with HIVmonoinfection. This study confirmed that patients with kidney impairment and the concurrent use of atazanavir/ritonavir will require the dosage of tenofovir to be adjusted to ensure efficacy and prevent unwanted toxicities. The developed model can reliably be used to adjust for the dosage of tenofovir in this population, especially when therapeutic drug monitoring services are unavailable.

Using Lopinavir Concentrations in Hair Samples to Assess Treatment Outcomes on Second-Line Regimens Among Asian Children.

We conducted a prospective monitoring study to determine whether antiretroviral (ARV) levels in hair of Asian children on second-line protease inhibitor-based ARV therapy (ART) are associated with virologic failure (VF), compared to plasma drug levels and self-reported adherence. HIV-infected Asian children on second-line ART regimens were enrolled into a longitudinal cohort. Traditional adherence measures, plasma, and hair samples were collected 24 weeks after study enrollment. Hair ARV levels were determined via liquid chromatography/tandem mass spectrometry. Among 149 children on lopinavir/ritonavir-based regimens, 47% were female; the median [interquartile range (IQR)] age was 10.3 (7.9-13.3) years. The median CD4% was 26% (IQR 21.7-32.1%) and the median CD4 cell count 754 (IQR 596-1,013) cells/mm(3). The median duration of lopinavir-based ART prior to week 24 of the study was 2.9 (IQR 1.6-4.2) years. Adherence was >95% in 91% (135/148) by visual analogue scale and 89% (129/145) by pill count. The median lopinavir hair concentrations were 5.43 (IQR 3.21-9.01) ng/mg in children with HIV RNA >1,000 copies/ml and 9.96 (IQR 6.51-12.31) ng/mg in children with HIV RNA <1,000 copies/ml (p = 0.003). Plasma trough and lopinavir hair concentrations were not statistically significantly correlated (Pearson's correlation coefficient 0.20; p = 0.13). Increasing lopinavir hair concentrations in quartiles were strongly associated with virologic success (odds ratios ≥4.0, overall p = 0.02), while self-reported adherence, pill count, and plasma lopinavir levels were not. Based on this first report of hair ARV concentrations and virologic outcomes in children, ARV hair concentrations, representing longer-term adherence, may be useful to identify children at risk for VF.

Influence of ABCC2 and ABCC4 polymorphisms on tenofovir plasma concentrations in Thai HIV-infected patients.

Tenofovir (TFV) is eliminated by renal excretion, which is mediated through multidrug-resistant protein 2 (MRP2) and MRP4, encoded by ABCC2 and ABCC4, respectively. Genetic polymorphisms of these transporters may affect the plasma concentrations of tenofovir. Therefore, the aim of this study was to investigate the influence of genetic and nongenetic factors on tenofovir plasma concentrations. A cross-sectional study was performed in Thai HIV-infected patients aged ≥18 years who had been receiving tenofovir disoproxil fumarate at 300 mg once daily for at least 6 months. A middose tenofovir plasma concentration was obtained. Multivariate analysis was performed to investigate whether there was an association between tenofovir plasma concentrations and demographic data, including age, sex, body weight, estimated glomerular filtration rate (eGFR), hepatitis B virus coinfection, hepatitis C virus coinfection, duration of tenofovir treatment, concomitant use of ritonavir-boosted protease inhibitors, and polymorphisms of ABCC2 and ABCC4. A total of 150 Thai HIV-infected patients were included. The mean age of the patients was 43.9 ± 7.2 years. The mean tenofovir plasma concentration was 100.3 ± 52.7 ng/ml. In multivariate analysis, a low body weight, a low eGFR, the concomitant use of ritonavir-boosted protease inhibitors, and the ABCC4 4131T → G variation (genotype TG or GG) were independently associated with higher tenofovir plasma concentrations. After adjusting for weight, eGFR, and the concomitant use of ritonavir-boosted protease inhibitors, a 30% increase in the mean tenofovir plasma concentration was observed in patients having the ABCC4 4131 TG or GG genotype. Both genetic and nongenetic factors affect tenofovir plasma concentrations. These factors should be considered when adjusting tenofovir dosage regimens to ensure the efficacy and safety of a drug. (This study has been registered at ClinicalTrials.gov under registration no. NCT01138241.).

Plasma pharmacokinetics of once-daily abacavir- and lamivudine-containing regimens and week 96 efficacy in HIV-infected Thai children.

BACKGROUND: Abacavir and lamivudine are approved for once-daily use in HIV-infected adults. Limited pharmacokinetic (PK) data for abacavir and lamivudine in children are available. METHODS: A crossover study to compare PK of once- versus twice-daily abacavir and lamivudine was conducted in virologically suppressed HIV-infected Thai children aged <18years, with bodyweight of at least 14 kg, HIV RNA <50 copies/mL and HLA-B*5701 negative. Abacavir and lamivudine daily doses by bodyweight were 300 and 150 mg for 14-<20 kg, 450 and 300 mg for 20-<25 kg, and 600 and 300 mg for ≥25 kg, respectively. Originator abacavir and lamivudine scored tablets were administered. Intensive PK sampling was performed after 14 days of each dose. PK parameters were determined using non-compartmental analysis. RESULTS: Thirty children (57% male) were enrolled, 10 per weight band. Median (IQR) age was 8.8 (6.6-11.3) years and bodyweight was 21.9 (19.2-30.6) kg. The geometric means (GM) AUC0-24 of once- and twice-daily abacavir were 14.43 and 10.65 mg.h/L, respectively. The geometric mean ratio (GMR) of AUC0-24 for once- versus twice-daily abacavir dosing was 1.36 [90% confidence interval (CI) 1.11-1.66]. The GM AUC0-24 of once- and twice-daily lamivudine were 17.70 and 18.11 mg.h/L, respectively. The GMR of AUC0-24 for once- versus twice-daily lamivudine dosing was 0.98 (90% CI 0.84-1.14). At 96 weeks, 90% had HIV RNA <50 copies/mL and there were no serious adverse events. CONCLUSION: Abacavir exposure was greater with once-daily dosing, while lamivudine once- and twice-daily exposures were bioequivalent. Once-daily abacavir and lamivudine using weight-band dosing is a treatment option for children.

Factors associated with daily tenofovir exposure in Thai subjects taking combination antiretroviral therapy.

Tenofovir (TFV) exposure is associated with antiretroviral efficacy and risk of kidney disease. There is evidence of high interindividual variability of the pharmacokinetics of TFV. The effect of several clinical conditions on the pharmacokinetics of TFV has been observed and may partly explain its variability. We assessed factors influencing the pharmacokinetics of TFV in Thai patients. Thirty participants (50% female) taking efavirenz- or ritonavir-boosted protease inhibitor-based regimens were investigated. Intensive pharmacokinetic sampling was performed over 24 h. Multivariate geometric mean regression models adjusted for covariates with p ≤ 0.2 in univariate analysis were developed. The median age was 41 years. Five participants [three taking a protease inhibitor (PI) and two taking efavirenz (EFV)] had mild renal dysfunction [estimated glomerular filtration rate (eGFR) 60-90 ml/min/1.73 m(2); range 72-89]. TFV AUC0-24 was 23% (95% CI 1-49%; p=0.04) higher in those taking PI vs. EFV, 39% (95% CI 5-84%; p=0.02) higher in those with mild renal dysfunction, and reduced by 16% (95% CI 5-26%; p=0.008) with each 10 kg body weight increase, after adjusting for sex and duration of TFV exposure. In PI-treated subjects TFV AUC0-24 increased by 3% (0.3-6%; p=0.03) for each mg·h/liter increase in ritonavir (RTV) AUC0-24 after adjusting for sex, weight, mild renal impairment, and proximal renal tubular dysfunction. Significantly higher TFV exposures were independently associated with PI regimens, mild renal impairment, lower body weight, and increasing RTV AUC0-24. Clinicians should be aware of the effect of these factors on TFV exposure when this drug is prescribed.

Pharmacokinetics of atazanavir/ritonavir among HIV-infected Thai children concomitantly taking tenofovir disoproxil fumarate.

BACKGROUND: Atazanavir/ritonavir (ATV/r) is a recommended once-daily protease inhibitor. Tenofovir disoproxil fumarate (TDF) can reduce ATV exposure. The authors studied ATV pharmacokinetic (PK) parameters among children who received atazanavir/ritonavir co-administered with TDF. METHODS: HIV-infected children aged 6-18 years with a body weight of 25-50 kg were eligible. Branded ATV 200 mg/capsule was taken with generic ritonavir 100 mg/tablet once daily plus TDF and lamivudine. A 24-hour PK study was performed at week 4 at t = 0 (pre-dose), 2, 4, 6, 8, 10, 12 and 24 hours. PK parameters were calculated using non-compartmental methods with WinNonlin software. Targeted ATV AUC 0-24 was 15 mg h/L and C trough was 0.15 mg/L. Comparisons of geometric means of ATV PK parameters between different weight bands were made using regression models. RESULTS: Eighteen HIV-infected children with a median (IQR) age of 13 (11-14) years were enrolled. Median (range) body weight and body surface area were 35 (25-42) kg and 1.21 (0.96-1.35) m2, respectively. Median (IQR) CD4 cell count was 735 (540-1233) cells/mm3. Median (range) of ATV was 164 (145-209) mg/m2. Geometric mean (SD) ATV AUC 0-24 was 35.05 (1.06) mg h/L, and ATV C trough was 0.31 (1.13) mg/L. No child had ATV AUC 0-24 or C trough below target levels. There were no significant differences in PK parameters among weight bands. CONCLUSION: Atazanavir/ritonavir 200/100 mg dosing provided adequate ATV AUC 0-24 when used with TDF in HIV-infected Thai children weighing between 25 and 50 kg.