Pilot pharmacokinetic study of human immunodeficiency virus-infected patients receiving tenofovir disoproxil fumarate (TDF): investigation of systemic and intracellular interactions between TDF and abacavir, lamivudine, or lopinavir-ritonavir

Concordance between daily diary reported pre-exposure prophylaxis intake and intraerythrocytic tenofovir diphosphate in the Amsterdam Pre-exposure Prophylaxis demonstration project

OBJECTIVE

We assessed the association and concordance between self-reported oral pre-exposure prophylaxis (PrEP) intake in a diary app and intraerythrocytic drug metabolite concentrations.

DESIGN

AMPrEP was a prospective demonstration study providing daily and event-driven PrEP to MSM in Amsterdam, the Netherlands (2015-2020).

METHODS

Participants could record their PrEP intake in a diary app. Dried blood spots (DBS) were taken at 6, 12, 24, and 48 months and analysed for tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP) concentrations. We included TFV-DP measurements preceded by diary completion on at least 90% of days in the 6 weeks prior. We examined the association between self-reported PrEP intake (i.e. number of pills) and TFV-DP concentrations using tobit regression with a random intercept per participant. We also calculated concordance between categorized PrEP intake (i.e. <2, 2-3, 4-6 or 7 pills per week) and categorized TFV-DP concentrations (i.e. <350, 350-699,700-1249 or ≥1250 fmol/punch) using weighted Cohen's kappa. Last, we calculated concordance between self-reported recent PrEP intake (yes/no, in past 2 days) and quantifiability of FTC-TP (yes/no) using Cohen's kappa.

RESULTS

Seven hundred and fifty-nine DBS measurements from 282 MSM were included. Self-reported PrEP intake was strongly and positively associated with TFV-DP concentration ( β  = 0.77, 95% CI = 0.70-0.84, P  < 0.0001). Concordance between categorized PrEP intake and TFV-DP concentration was moderate ( κ  = 0.44, 95% CI = 0.39-0.50). Concordance between self-reported recent PrEP intake and FTC-TP quantifiability was perfect ( κ  = 0.83, 95% CI 0.76-0.90).

CONCLUSION

Self-reported PrEP intake in a diary app is strongly correlated with actual use, and therefore reliable for comparing PrEP adherence between groups. Still, suboptimal criterion validity according to clinically relevant categories warrants caution when assessing 6-week reported adherence for individuals.

Tenofovir and emtricitabine concentrations in hair are comparable between individuals on tenofovir disoproxil fumarate versus tenofovir alafenamide-based ART

Tenofovir disoproxil fumarate (TDF) in combination with emtricitabine (FTC) is the backbone for both human immunodeficiency virus (HIV) treatment and pre-exposure prophylaxis (PrEP) worldwide. Tenofovir alafenamide (TAF) with FTC is increasingly used in HIV treatment and was recently approved for PrEP among men-who-have-sex-with-men. TDF and TAF are both metabolized into tenofovir (TFV). Antiretrovirals in plasma are taken up into hair over time, with hair levels providing a long-term measure of adherence. Here, we report a simple, robust, highly sensitive, and validated high-performance liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS)-based analytical method for analyzing TFV and FTC from individuals on either TDF/FTC or TAF/FTC in small hair samples. TFV/FTC are extracted from ~5 mg hair and separated on a column using a gradient elution. The lower quantification limits are 0.00200 (TFV) and 0.0200 (FTC) ng/mg hair; the assay is linear up to 0.400 (TFV) and 4.00 (FTC) ng/mg hair. The intra-day and inter-day coefficients of variance (CVs) are 5.39-12.6% and 6.40-13.5% for TFV and 0.571-2.45% and 2.45-5.16% for FTC. TFV concentrations from participants on TDF/FTC-based regimens with undetectable plasma HIV RNA were 0.0525 ± 0.0295 ng/mg, whereas those from individuals on TAF/FTC-based regimens were 0.0426 ± 0.0246 ng/mg. Despite the dose of TFV in TDF being 10 times that of TAF, hair concentrations of TFV were not significantly different for those on TDF versus TAF regimens. Pharmacological enhancers (ritonavir and cobicistat) did not boost TFV concentrations in hair. In summary, we developed and validated a sensitive analytical method to analyze TFV and FTC in hair and found that hair concentrations of TFV were essentially equivalent among those on TDF and TAF.

Factors associated with tenofovir diphosphate concentrations in dried blood spots in persons living with HIV

OBJECTIVES

To determine factors associated with interindividual variability in tenofovir diphosphate (TFV-DP) concentrations in dried blood spots (DBSs) among persons living with HIV (PLWH).

METHODS

PLWH who were at least 18 years old and taking tenofovir disoproxil fumarate-containing ART were prospectively recruited and enrolled from a clinical cohort and followed longitudinally (up to three visits over 48 weeks). With log-transformed TFV-DP concentrations in DBSs as the outcome, mixed-model regression analyses were used to assess associations between self-reported 3 month ART adherence, race and other clinical covariates (gender, age, BMI, CD4+ T cell count, estimated glomerular filtration rate, haematocrit, duration on current ART and anchor drug class) on TFV-DP in DBSs.

RESULTS

Five hundred and twenty-seven participants (1150 person-visits) were analysed. Adjusting for race and other clinical covariates, every 10% increase in self-reported 3 month ART adherence was associated with an average TFV-DP concentration increase in DBSs of 28% (95% CI: 24%-32%; P < 0.0001). In the same model, female participants had 20% (95% CI: 3%-40%; P = 0.02) higher TFV-DP concentrations in DBSs, compared with male participants, and every 1 kg/m2 increase in BMI was associated with a decrease in TFV-DP concentration in DBSs by 2% (95% CI: -3% to -1%; P < 0.0001).

CONCLUSIONS

Individual patient characteristics were predictive of TFV-DP concentration in DBSs in PLWH receiving tenofovir disoproxil fumarate-based ART. Future research to incorporate these predictors into the interpretation of this ART adherence biomarker, and to establish whether these associations extend to PLWH taking tenofovir alafenamide-containing ART, is needed.

Efficacy and safety of lower dose tenofovir disoproxil fumarate and efavirenz versus standard dose in HIV-infected, antiretroviral-naive adults: a multicentre, randomized, noninferiority trial

Reduced doses of antiretroviral (ARV) drugs may lower toxicity while preserving efficacy. We aimed to evaluate the efficacy of reduced doses of both tenofovir disoproxil fumarate (TDF) and efavirenz for the treatment of HIV-1 infection. In this open-label, non-inferiority trial, HIV-1-infected antiretroviral-naive adults were randomly assigned to receive either a lower dose anti-retroviral regimen comprised of TDF (200 mg), efavirenz (400 mg), and standard dose lamivudine (300 mg) or the standard dose regimen. The primary endpoint was the proportion of participants with HIV-1 RNA≤ 50 copies/mL at week 48 using a non-inferiority margin of –10%. At week 48, 79 of 92 (85.9%) participants in the lower dose regimen group and 78 of 92 (84.8%) in the standard dose regimen group achieved HIV-1 RNA≤ 50 copies/mL (treatment difference 1.1%, 95% CI −9.1 to 11.3) in the intention-to-treat analysis. Drug-related adverse events occurred more frequently in the participants receiving the standard dose regimen compared with the lower dose one (63.0% vs 80.4%). Changes in estimated glomerular filtration rate and bone mineral density were comparable between the two groups. The non-inferior efficacy and better safety profile of the lower dose ARV regimen support its use as alternative initial therapy for HIV-1 infected patients.

Intracellular Tenofovir and Emtricitabine Concentrations in Younger and Older Women with HIV Receiving Tenofovir Disoproxil Fumarate/Emtricitabine

The altered immune states of aging and HIV infection may affect intracellular metabolism of tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC); increased cellular senescence decreases FTC-triphosphate (FTCtp) concentrations. The effects of age and inflammation on the ratio of intracellular metabolites (IMs; tenofovir diphosphate [TFVdp] and FTCtp) to their endogenous nucleotides (ENs; dATP and dCTP), a potential treatment efficacy marker, were assessed among participants of the Women's Interagency HIV Study (WIHS), who ranged from 25 to 75 years. Samples from women receiving TDF-FTC with viral loads of <200 copies/ml were dichotomized by age at collection into two groups (≤45 years and ≥60 years). IM/EN concentrations were measured in peripheral blood mononuclear cell (PBMC) pellets; interleukin-6 (IL-6) and sCD163 were measured in plasma; senescent CD8⁺ T cells were measured in viable PBMCs. The TFVdp:dATP and FTCtp:dCTP ratios had statistically significantly different distributions in older and younger women (log-rank test, P = 0.0023 and P = 0.032, respectively); in general, IM and EN concentrations were higher in the older women. After adjusting for potential confounders, these findings were not significant. In women aged ≤45 years, TFVdp was negatively associated with IL-6 and sCD163, while FTCtp was positively associated with sCD163 and IL-6 in women aged ≥60 years. Body mass index (BMI) was positively associated with IL-6 in both age groups and negatively associated with TFVdp in women aged ≤45 years. After adjustment, age remained significant for sCD163, while black race, BMI, and renal function remained significant for several IMs and ENs, suggesting that factors associated with aging, but not age itself, govern intracellular TDF-FTC pharmacology.

The Lymphoid Tissue Pharmacokinetics of Tenofovir Disoproxil Fumarate and Tenofovir Alafenamide in HIV-Infected Persons

The secondary lymphoid tissues (LT), lymph nodes (LN) and gut-associated lymphoid tissue are the primary sites of HIV replication and where the latent pool of virus is maintained. We compared the pharmacokinetics of tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) in LT of 13 HIV-infected persons receiving a TDF-containing antiretroviral regimen who subsequently switched to a TAF-containing regimen. Study participants were on stable antiretroviral therapy for ≥12 months with plasma HIV-RNA < 48 copies/mL for 6 months before enrollment and entry CD4 cell counts > 300 cells/µL. Intracellular concentrations of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) were quantified in PBMCs and in mononuclear cells obtained from LN, ileum and rectal tissues. With TAF, the TFV-DP concentrations in PBMCs and LN were 7.3-fold and 6.4-fold higher (ratios of geometric means of TAF to TDF), respectively, compared with TDF; ileal and rectal concentrations, however, were lower with geometric mean ratios of 0.14 and 0.18, respectively. A statistically significant relationship was observed between PBMC and LN concentrations of TFV-DP. During TDF-containing therapy, the expected effect of cobicistat to increase TFV plasma concentrations was observed, as were higher TFV-DP concentrations in PBMCs and mononuclear cells from LN, ileum and rectal tissues. The higher TFV-DP concentrations achieved with TAF in the LN provides the first human correlate of the observation in animals that TAF produced higher tenofovir LN concentrations. The ability to increase LN concentrations allows investigations of whether antiretroviral regimens with improved LN pharmacokinetics elicit a more complete virologic response in that compartment.

Brief Report: Relationship Between ABCC4 SNPs and Hepatitis B Virus Suppression During Tenofovir-Containing Antiretroviral Therapy in Patients With HIV/HBV Coinfection

BACKGROUND

Incomplete hepatitis B virus (HBV) suppression during antiretroviral therapy (ART) in HIV and HBV coinfected patients is common, but underlying factors are not fully elucidated. We hypothesize that genetic factors that influence nucleoside analog pharmacokinetics will affect HBV treatment response.

METHODS

HIV/HBV coinfected patients on tenofovir disoproxil fumarate/lamivudine (TDF/3TC)-containing ART were enrolled. Selected ABCC4 single nucleotide polymorphisms (SNPs) with known effects on nucleoside pharmacokinetics were genotyped using TaqMan assays. Relationship between ABCC4 SNPs and unsuppressed HBV DNA (HBV DNA ≥20 IU/mL) were examined.

RESULTS

Of the 50 participants on TDF/3TC-containing ART for a median (range) of 1.5 (1-7.4) years, 20 (40%) had unsuppressed HBV DNA. Participants with unsuppressed compared with those with suppressed HBV DNA were more likely to have negative HBe antibody, lower body mass index, and lower CD4 count at enrollment. Carriers of ABCC4 rs11568695 (G3724A) variant allele were more likely than noncarriers to have unsuppressed HBV (61.1% vs. 29.0%, P = 0.038). Among 36 patients with suppressed HIV RNA (presumed good ART adherence), ABCC4 rs11568695 variant carriers were more likely than noncarriers to have unsuppressed HBV (58.8% vs. 20.0% P = 0.021). Logistic regression analysis that included genetic and nongenetic factors identified ABCC4 rs11568695 variant allele, body mass index, and male sex as predictors of unsuppressed HBV DNA.

CONCLUSIONS

We identified a novel association between ABCC4 rs11568695 SNP and poor HBV treatment response. If confirmed in further studies, ABCC4 genotyping could be used to identify individuals who may need intensified HBV therapy.

Antenatal Intracellular Concentrations of Tenofovir Diphosphate and Emtricitabine Triphosphate and Associations Between Tenofovir Diphosphate and Severe Adverse Pregnancy Outcomes: IMPAACT-PROMISE (1077BF) Trial

BACKGROUND

In the Promoting Maternal and Infant Survival Everywhere (PROMISE) trial, tenofovir disoproxil fumarate (TDF) use was associated with moderate or severe adverse pregnancy/neonatal outcomes. This study characterized tenofovir diphosphate (TFV-DP) and emtricitabine triphosphate (FTC-TP) concentrations in dried blood spots (DBS) and assessed association between severe adverse pregnancy/neonatal outcomes and TFV-DP concentration.

METHODS

Retrospective case-control study of PROMISE trial arm-C women randomized to receive TDF, FTC, and ritonavir-boosted lopinavir (LPV/r), who took at least 1 dose of TDF + FTC and had week-4 postrandomization DBS drawn before delivery. Cases, defined as severe adverse pregnancy/neonatal outcomes (very preterm delivery before 34 weeks of gestation, stillbirth ≥20 weeks of gestation, or infant death before 14 days-of-age), were matched to controls (1:2 ratio) by site and gestational age at entry. Week 4 and week 8 DBS samples were assayed for TFV-DP and FTC-TP by liquid chromatography and tandem mass spectrometry. Associations were tested using Wilcoxon rank test and conditional logistic regression.

RESULTS

Of 447 PROMISE arm-C women, 33 met case definitions, and overall, 22 cases and 44 controls were analyzed. Median (interquartile range) concentrations of TFV-DP at weeks 4 and 8 were 706 (375-1023) fmol/punch and 806 (414-1265) fmol/punch, respectively. Odds ratio (95% confidence interval) for severe adverse pregnancy/neonatal outcome with natural log of TFV-DP concentrations as the predictor were 1.27 (0.74 to 2.18) and 1.74 (0.66 to 4.60) at weeks 4 and 8, respectively. Median (interquartile range) concentrations of FTC-TP at weeks 4 and 8 were 0.27 (0.05-0.36) pmol/punch and 0.29 (0.05-0.40) pmol/punch, respectively.

CONCLUSIONS

TFV-DP concentrations in DBS appeared not to be associated with severe adverse pregnancy/neonatal outcomes, although sample size was limited.

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.

Long term renal function in Asian HIV-1 infected adults receiving tenofovir disoproxil fumarate without protease inhibitors

OBJECTIVES

The risk of kidney dysfunction on the WHO recommended first line regimens containing tenofovir disoproxil fumarate (TDF) without protease inhibitors (PI) remains unclear in Asian patients, especially those with low body weight.

METHODS

Using data collected in a multicenter clinical trial in Thailand and proportional hazard regression models, we compared the risk of a >25% estimated glomerular filtration rate (eGFR) reduction in HIV naïve patients initiating TDF or zidovudine (AZT) containing non-PI regimen.

RESULTS

Of 640 patients included in the analysis, 461 (72%) received a TDF-containing regimen for a median 6.7 years and 179 (28%) an AZT-containing regimen for 6.5 years. The risk of a >25% eGFR reduction was not associated with treatment (HR 1.11, 95% CI 0.84-1.47, P = 0.46). In multivariate analysis, the risk of >25% eGFR reduction form baseline was associated with body weight at baseline (HR 2.12, 95% CI 1.48-3.02 for <48 kg patients and HR 1.64, 95% CI 1.20-2.25 for 48-59.9 kg patients, compared to those with >60 kg, P < 0.001) and hypertension (HR 4.03, 95% CI 2.0-8.0, P < 0.001). The effect of baseline weight on >25% eGFR reduction did not significantly vary with treatment (P = 0.27).

CONCLUSIONS

The risk of eGFR reduction was not higher on TDF- versus AZT-based non-PI regimens. Although the risk of eGFR reduction was greater for patients of lower body weight, this risk was not significantly increased by TDF.

Predictive Value of Tenofovir Diphosphate in Dried Blood Spots for Future Viremia in Persons Living With HIV

BACKGROUND

Tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is associated with viral suppression in persons living with HIV (PLWH) taking tenofovir disoproxil fumarate (TDF). However, its value as a predictor of future viremia remained unknown.

METHODS

Blood for plasma viral load (VL) and TFV-DP in DBS were collected (up to 3 visits within 48 weeks) in PLWH on TDF. TFV-DP cut points were selected using logistic prediction models maximizing the area under the receiver operation characteristic curve, and estimated adjusted odds ratio (aOR) of future viremia (≥20 copies/mL) were compared to the highest TFV-DP category.

RESULTS

Among all 451 participants in the analysis, aOR of future viremia for participants with TFV-DP <800 and 800 to <1650 fmol/punch were 4.7 (95% CI, 2.6-8.7; P < .0001) and 2.1 (95% CI, 1.3-3.3; P = .002) versus ≥1650 fmol/punch, respectively. These remained significant for participants who were virologically suppressed at the time of the study visit (4.2; 95% CI, 1.5-12.0; P = .007 and 2.2; 95% CI, 1.2-4.0; P = .01).

CONCLUSIONS

TFV-DP in DBS predicts future viremia in PLWH on TDF, even in those who are virologically suppressed. This highlights the utility of this biomarker to inform about adherence beyond VL. Clinical Trials Registration. NCT02012621.

Tenofovir Diphosphate in Dried Blood Spots Is Strongly Associated With Viral Suppression in Individuals With Human Immunodeficiency Virus Infections

BACKGROUND

Although tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a predictor of adherence and pre-exposure prophylaxis efficacy, its utility in human immunodeficiency virus (HIV) treatment remains unknown.

METHODS

DBS for TFV-DP were collected up to 3 times over 48 weeks in persons living with HIV (PLWH) who were receiving TFV disoproxil fumarate (TDF)-based therapy. Log-transformed baseline TFV-DP was compared using t-tests or analyses of variance; generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression (<20 copies/mL) based on the TFV-DP concentration at the study visit.

RESULTS

We analyzed 1199 DBS from 532 participants (76 female; 101 Black, 101 Hispanic). Among the virologically-suppressed participants at baseline (n = 347), TFV-DP was lower in Blacks (geometric mean 1453, 95% confidence interval [CI] 1291-1635) vs Whites (1793, 95% CI 1678-1916; P = .002) and Hispanics (1760, 95% CI 1563-1982; P = .025); in non-boosted (1610, 95% CI 1505-1723) vs. boosted (1888, 95% CI 1749-2037; P = .002) regimens; and in non-nucleoside reverse transcription inhibitor-based (1563, 95% CI 1432-1707) vs. boosted protease inhibitor-based (1890, 95% CI 1704-2095; P = .006) and multiclass-based (1927, 95% CI 1650-2252; P = .022) regimens. The aOR of virologic suppression, after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4+ T-cell count, antiretroviral drug class and duration of therapy, was 73.5 (95% CI 25.7-210.5; P < .0001) for a TFV-DP concentration ≥1850 fmol/punch compared to <350 fmol/punch.

CONCLUSIONS

TFV-DP in DBS is strongly associated with virologic suppression in PLWH on TDF-based therapy and is associated with certain participant characteristics. Further research is required to evaluate this drug adherence and exposure measure in clinical practice.

CLINICAL TRIALS REGISTRATION

NCT02012621.

Improving the clinical relevance of a mouse pregnancy model of antiretroviral toxicity; a pharmacokinetic dosing-optimization study of current HIV antiretroviral regimens

Animal models can be useful tools for the study of HIV antiretroviral (ARV) safety/toxicity in pregnancy and the mechanisms that underlie ARV-associated adverse events. The utility and translatability of animal model-based ARV safety/toxicity data is improved if ARVs are tested in clinically relevant concentrations. The objective of this work was to improve the clinical relevance of our mouse pregnancy model of ARV toxicity, by determining the doses of currently prescribed ARV regimens that would yield human therapeutic plasma concentrations. Pregnant mice were administered increasing doses of ARV combinations by oral gavage, followed by measurement of drug concentrations in the maternal plasma and amniotic fluid. Concentrations of ten different ARVs in maternal plasma and amniotic fluid samples of pregnant mice are presented, with dosing optimization to yield human pregnancy-relevant plasma drug concentrations. We have proposed optimal dosing for different regimen component drugs to achieve human therapeutic plasma levels, so that a clinically relevant standard dosing is established. A review of related ARV pharmacokinetic studies in (pregnant/non-pregnant) rodents and human pregnancy is also shown. We hope these data will inform and encourage the use of mouse pregnancy models in the study of ARV safety/toxicity.

Intracellular Tenofovir-Diphosphate and Emtricitabine-Triphosphate in Dried Blood Spots following Directly Observed Therapy

Studies of daily emtricitabine-tenofovir disoproxil fumarate (FTC-TDF) for HIV preexposure prophylaxis (PrEP) in men who have sex with men (MSM) modeled intracellular tenofovir-diphosphate (TFV-DP) in dried blood spots (DBS) to assess adherence and corresponding PrEP outcomes. We conducted a prospective, randomized, crossover pharmacokinetic study of TFV-DP in DBS during 33%, 67%, or 100% of daily dosing under directly observed therapy (DOT). Participants were assigned to two 12-week dosing regimens, separated by a 12-week washout. Forty-eight adults (25 women) from Denver and San Francisco were included. TFV-DP exhibited a median half-life of 17 days, reaching steady state in 8 weeks. TFV-DP was dose proportional with mean (SD) steady-state concentrations of 530 (159), 997 (267), and 1,605 (405) fmol/punch for the 33%, 67%, and 100% arms, respectively. Prior work in MSM demonstrated clinically meaningful TFV-DP thresholds of 350, 700, and 1,250 fmol/punch, which were estimated 25th percentiles for 2, 4, and 7 doses/week. In the present study, corresponding TFV-DP was within 3% of the prior estimates, and subgroups by site, race, and sex were within 14% of prior estimates, although males had 17.6% (95% confidence intervals [CIs], 6.5, 27.4%) lower TFV-DP than females. The thresholds of 350, 700, and 1,250 fmol/punch were achieved by 75% of men taking ≥1.2, 3.2, and 6 doses/week and 75% of women taking ≥0.6, 2.0, and 5.3 doses/week, indicating that lower dosing reached these thresholds for both sexes. In conclusion, TFV-DP arising from DOT was similar to previous estimates and is useful for interpreting PrEP adherence and study outcomes. (This study has been registered at ClinicalTrials.gov under identifier NCT02022657.).

Effect of Antiretroviral Therapy on Bone and Renal Health in Young Adults Infected With HIV in Early Life

Context

HIV antiretroviral (ARV) therapy is associated with renal and bone toxicity, but little is known about the potential cumulative effects in adults exposed to ARVs from birth.

Objective

To prospectively evaluate renal and bone health in young adults with lifelong HIV and extensive ARV exposure.

Design

Cross-sectional comparison of bone mineral density (BMD) by dual-energy X-ray absorptiometry, bone turnover, and renal function in young adults infected with HIV in early life (n = 65) to matched healthy controls (n = 23) and longitudinal evaluation (mean follow-up = 4.4 years) within a subset of the HIV cohort (n = 33).

Setting

Government outpatient research clinic.

Results

Albumin/creatinine ratio, protein/creatinine ratio, anion gap, N-terminal telopeptides, and osteocalcin were significantly increased in persons with HIV compared with controls, whereas whole-body BMD and BMD z scores were lower. Within the HIV group, duration of tenofovir disoproxil fumarate (TDF) correlated with higher anion gap but did not correlate with bone parameters. Longer duration of didanosine and stavudine use correlated with lower BMD and BMD z scores. Longitudinal analyses revealed that BMD and bone metabolism significantly improved over time. No subject had an estimated glomerular filtration rate (eGFR) <60, but decline in eGFR correlated with increasing years of TDF exposure.

Conclusions

Subclinical markers of renal dysfunction were increased in HIV-infected young adults and associated with TDF exposure, whereas lower bone density was associated with didanosine and stavudine exposure. The tendency for improvement in markers of bone health over time and the availability of less toxic ARV alternatives may herald improvements in renal and bone health for perinatally infected patients in adulthood.

Steady-state pharmacokinetics of tenofovir disoproxil fumarate in human immunodeficiency virus-infected Chinese patients

BACKGROUND

The pharmacokinetic (PK) profile of tenofovir disoproxil fumarate in Chinese adults infected with HIV is unknown.

METHODS

A pilot, prospective, open-label study was performed to investigate the steady-state PK profile of tenofovir disoproxil fumarate in 15 Chinese HIV-infected patients among whom eight patients were treated with 300 mg tenofovir disoproxil fumarate, 300 mg lamivudine and 400/100 mg lopinavir/ritonavir, and seven with 300 mg tenofovir disoproxil fumarate, 300 mg lamivudine and 400 mg nevirapine. The plasma concentrations of tenofovir over the 24-h dosing interval were determined by HPLC. The PK parameters were calculated using the non-compartmental model in WinNonlin software.

RESULTS

The PK parameters of tenofovir in the 15 patients were determined as follows (mean ± SD): AUC_{(0-24 h)}, 4074.7 ± 1551.9 ng•h/mL; C_max,ss, 447.1 ± 217.4 ng/mL; C_trough,ss, 98.7 ± 36.7 ng/mL; t_max,ss, 1.3 ± 0.4 h; plasma t_1/2, 21.8 ± 7.6 h; and CL_ss/F, 45.8 ± 13.0 L/h.

CONCLUSION

Tenofovir demonstrated slower elimination rate and increased plasma concentration in Chinese patients compared to previously published data from Caucasian or African subjects, which may be associated with the higher incidences of renal and bone resorption dysfunction observed in our patient population. Clinicians should be cautious of the differing PK characteristics of tenofovir among people of different races.

Tenofovir alafenamide (TAF) does not deplete mitochondrial DNA in human T-cell lines at intracellular concentrations exceeding clinically relevant drug exposures

HIV-infected patients treated with certain nucleoside reverse transcriptase inhibitors (NRTIs) have experienced adverse effects due to drug-related mitochondrial toxicity. Tenofovir alafenamide (TAF) is a novel prodrug of the NRTI tenofovir (TFV) with an improved safety profile compared to tenofovir disoproxil fumarate (TDF). Prior in vitro studies have demonstrated that the parent nucleotide TFV has no significant effects on mtDNA synthesis. This study investigated whether clinically relevant TAF and TDF exposures affect mtDNA content in human lymphocytes. First, activated or resting peripheral blood mononuclear cells (PBMCs), as well as MT-2 and Jurkat T-cell lines, were continuously treated with ddC for 10 days to establish their susceptibility to mtDNA depletion. PBMCs had low sensitivity to NRTI-mediated mtDNA depletion in vitro. In contrast, ddC treatment of rapidly dividing MT-2 and Jurkat cells resulted in a dose-dependent decrease in mtDNA. Therefore, these two T-cell lines were selected for evaluating TAF and TDF treatment effects. MT-2 and Jurkat cells were pulse-treated with TAF or TDF every 24 h for 10 days to mimic pharmacologically relevant drug exposures. Pulse treatment of cells with 3.3 μM TAF or 1.1 μM TDF for 10 days resulted in 2- to 7-fold greater steady-state intracellular TFV-diphosphate (TFV-DP) levels than those observed clinically in TAF- or TDF-treated patients. At these concentrations, no significant TAF- (106.7% and 84.1% of control; p = 0.77 and 0.12 for MT-2 and Jurkat, respectively) or TDF- (100.6% and 91.0% of control; p = 0.91 and 0.37, respectively) associated reduction in mtDNA content was observed compared with untreated control cells. This study demonstrates that, despite delivering higher intracellular levels of TFV-DP than TDF, TAF does not inhibit mtDNA synthesis in vitro at concentrations exceeding the clinically relevant intracellular drug exposures. Thus, TAF has a low potential for mitochondrial toxicity in T-cells of HIV-infected patients.

Benefits and Risks of Antiretroviral Therapy for Perinatal HIV Prevention

BACKGROUND

Randomized-trial data on the risks and benefits of antiretroviral therapy (ART) as compared with zidovudine and single-dose nevirapine to prevent transmission of the human immunodeficiency virus (HIV) in HIV-infected pregnant women with high CD4 counts are lacking.

METHODS

We randomly assigned HIV-infected women at 14 or more weeks of gestation with CD4 counts of at least 350 cells per cubic millimeter to zidovudine and single-dose nevirapine plus a 1-to-2-week postpartum "tail" of tenofovir and emtricitabine (zidovudine alone); zidovudine, lamivudine, and lopinavir-ritonavir (zidovudine-based ART); or tenofovir, emtricitabine, and lopinavir-ritonavir (tenofovir-based ART). The primary outcomes were HIV transmission at 1 week of age in the infant and maternal and infant safety.

RESULTS

The median CD4 count was 530 cells per cubic millimeter among 3490 primarily black African HIV-infected women enrolled at a median of 26 weeks of gestation (interquartile range, 21 to 30). The rate of transmission was significantly lower with ART than with zidovudine alone (0.5% in the combined ART groups vs. 1.8%; difference, -1.3 percentage points; repeated confidence interval, -2.1 to -0.4). However, the rate of maternal grade 2 to 4 adverse events was significantly higher with zidovudine-based ART than with zidovudine alone (21.1% vs. 17.3%, P=0.008), and the rate of grade 2 to 4 abnormal blood chemical values was higher with tenofovir-based ART than with zidovudine alone (2.9% vs. 0.8%, P=0.03). Adverse events did not differ significantly between the ART groups (P>0.99). A birth weight of less than 2500 g was more frequent with zidovudine-based ART than with zidovudine alone (23.0% vs. 12.0%, P<0.001) and was more frequent with tenofovir-based ART than with zidovudine alone (16.9% vs. 8.9%, P=0.004); preterm delivery before 37 weeks was more frequent with zidovudine-based ART than with zidovudine alone (20.5% vs. 13.1%, P<0.001). Tenofovir-based ART was associated with higher rates than zidovudine-based ART of very preterm delivery before 34 weeks (6.0% vs. 2.6%, P=0.04) and early infant death (4.4% vs. 0.6%, P=0.001), but there were no significant differences between tenofovir-based ART and zidovudine alone (P=0.10 and P=0.43). The rate of HIV-free survival was highest among infants whose mothers received zidovudine-based ART.

CONCLUSIONS

Antenatal ART resulted in significantly lower rates of early HIV transmission than zidovudine alone but a higher risk of adverse maternal and neonatal outcomes. (Funded by the National Institutes of Health; PROMISE ClinicalTrials.gov numbers, NCT01061151 and NCT01253538 .).

Tenofovir-Associated Nephrotoxicity in Children with Perinatally-Acquired HIV Infection: A Single-Centre Cohort Study

BACKGROUND AND OBJECTIVE

In 2012, tenofovir disoproxil fumarate (TDF) was approved for use in children over 2 years of age at a dose of 8 mg/kg/day, and is the WHO recommended first-line therapy for children over 10 years of age or 35 kg in weight, at 300 mg daily. Whilst postmarketing experience of paediatric TDF is limited, prior off-licence use has occurred at our centre due to its tolerability, efficacy and resistance profiles. In this article we describe a single-centre experience of TDF nephrotoxicity in children aged <16 years.

METHODS

We conducted a retrospective case-note audit of children with perinatally-acquired HIV who ever received TDF-based antiretroviral therapy.

RESULTS

From 2001 to December 2013, 70 children [39 (56 %) females] ever received TDF. Median age at the start of TDF treatment was 12 years (interquartile range 10-14). Seven (10 %) children developed asymptomatic renal tubular leak with associated hypophosphataemia (3) and hypokalaemia (1), all resulting in TDF withdrawal and biochemical resolution. Comparison of the nephrotoxic group versus the rest of the cohort showed no significant differences for age, sex, antiretroviral regimen or CD4 count. Lower weight (p = 0.05) and initial dose of TDF received (p = 0.0048) were significantly associated with TDF-induced nephrotoxicity: median dose of TDF (7.8 mg/kg/day) compared with the remainder of the cohort (6.5 mg/kg/day). Concurrent use of protease inhibitors (PIs) with TDF may be a contributing factor to the development of nephrotoxicity (odds ratio 6; 95 % CI 0.7-54; p = 0.111).

CONCLUSION

Although all children with TDF-associated nephrotoxicity had biochemical resolution on drug withdrawal, renal monitoring of children receiving TDF is important, especially with the co-administration of PIs. Postmarketing surveillance is essential in the paediatric setting.

Estimated Glomerular Filtration Rate Trajectories in HIV-Infected Subjects Treated With Different Ritonavir-Boosted Protease Inhibitors and Tenofovir Disoproxil Fumarate or Abacavir

The aim of the study was to evaluate in human immunodeficiency virus (HIV)-infected patients estimated glomerular filtration rate (eGFR) trajectories during treatment with different protease inhibitors (PIs) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus tenofovir (TDF) or abacavir (ABC) and lamivudine or emtricitabine (xTC).Retrospective study of patients followed at a single clinical center; all patients who started TDF or ABC for the first time with a NNRTI or lopinavir/r (LPV/r) or atazanavir/r (ATV/r) or darunavir/r (DRV/r), for whom at least 1 eGFR value before the start and during the studied treatment was known, were included in this analysis. eGFR was calculated by means of the CKD-EPI formula. Univariate and multivariate mixed linear model (MLM) was applied to estimate eGFR slope with the considered antiretroviral treatment.In the 1658 patients treated with TDF/xTC (aged 43 [37-48] years, with an eGFR of 105 [96; 113] mL/min/1.73 m, 80% males, 92% Caucasians, 10% coinfected with HCV, 4% with diabetes, 11% with hypertension, 38% naive for antiretroviral therapy (ART), 37% with HIV-RNA <50 copies/mL) the median follow-up was 2.5 (1.2-4.6) years. Their adjusted eGFR slopes (95% CI) were -1.26 (-1.58; -0.95), -0.43 (-1.20; +0.33), -0.86 (-1.28; -0.44), and -0.20 (-0.42; +0.02) mL/min/1.73 m per year in patients treated with ATV/r, DRV/r, LPV/r, and NNRTI, respectively. Patients receiving ATV/r or LPV/r had a greater adjusted decline in eGFR compared with those receiving NNRTIs (difference -1.06 [-1.44; -0.69] mL/min/1.73 m per year, P <0.001; and -0.66 [-1.13; -0.20] mL/min/1.73 m per year, P = 0.005, respectively); adjusted eGFR slopes were similar in patients receiving DRV/r and in those receiving NNRTIs. Patients receiving ATV/r had a greater adjusted eGFR decline than those treated with DRV/r (difference -0.83 [-1.65; -0.02] mL/min/1.73 m per year; P = 0.04), but not than those receiving LPV/r; no significant difference was observed in adjusted eGFR slopes between patients receiving DRV/r and those receiving LPV/r. In the 286 patients treated with ABC and lamivudine, eGFR slopes were similar, independent of the PI.In patients receiving TDF/xTC, eGFR trajectories were small for all regimens and declined less in patients receiving DRV/r or NNRTIs than in those treated with ATV/r or LPV/r.

The protease inhibitors and HIV-associated bone loss

PURPOSE OF REVIEW

HIV infection is an established risk factor for osteoporosis and bone fracture. Combination antiretroviral therapy (cART) increases bone resorption leading to an additional 2-6% bone mineral density (BMD) loss within the first 1-2 years of therapy. Although tenofovir disoproxil fumarate is often blamed for antiretroviral drug-associated bone loss, evidence abounds to suggest that other agents, including the protease inhibitors (PIs), have adverse bone effects. In the current review, we examine bone loss associated with protease inhibitor use, describing the relative magnitude of bone loss reported for individual protease inhibitors. We also review the potential mechanisms associated with protease inhibitor-induced bone loss.

RECENT FINDINGS

As a class, protease inhibitors contribute to a greater degree of bone loss than other anchor drugs. HIV disease reversal and the associated immune reconstitution following cART initiation play an important role in protease inhibitor-mediated bone loss in addition to plausible direct effects of protease inhibitors on bone cells.

SUMMARY

Protease inhibitors remain an important component of cART despite their adverse effects on bone. A better understanding of factors that drive HIV/cART-induced bone loss is needed to stem the rising rate of fracture in the HIV-infected population.

Reassuring Birth Outcomes With Tenofovir/Emtricitabine/Efavirenz Used for Prevention of Mother-to-Child Transmission of HIV in Botswana

BACKGROUND

Before introduction of tenofovir/emtricitabine/efavirenz (TDF/FTC/EFV), 3-drug antiretroviral therapy (ART) was associated with increased adverse birth outcomes when used for prevention of mother-to-child HIV transmission (PMTCT) in Botswana.

METHODS

We extracted obstetric records from all women at the 2 largest maternities in Botswana from 2009-2011 when Botswana National Guidelines recommended zidovudine (ZDV) from 28 weeks gestational age (GA) for CD4 ≥350 and ART for CD4 <350, and again in 2013-2014 after implementation of TDF/FTC/EFV for prevention of mother-to-child HIV transmission regardless of CD4 or GA. We compared the use of TDF/FTC/EFV in pregnancy with other 3-drug ART regimens, and with initiation of ZDV, among women with similar CD4 cell counts. Outcomes included small for gestational age (SGA), preterm delivery (PTD) (<37 weeks GA), and stillbirths (SB).

RESULTS

Among 9445 HIV-infected women delivering during the study period, 170 were on TDF/FTC/EFV at conception and 1468 initiated TDF/FTC/EFV during pregnancy. Adverse birth outcomes were high overall (3% SB, 21% PTD, and 18% SGA) and among women receiving TDF/FTC/EFV (3% SB, 22% PTD, and 12% SGA). There was no difference in PTD or SB among women initiating TDF/FTC/EFV compared with ZDV or other 3-drug ART, but initiating TDF/FTC/EFV was associated with fewer SGA infants than other 3-drug ART (adjusted odds ratio: 0.4, 95% confidence interval: 0.2 to 0.7).

CONCLUSIONS

Adverse birth outcomes remain high among HIV-infected women. TDF/FTC/EFV was at least as safe as other ART and associated with fewer SGA infants when initiated during pregnancy. Larger studies are needed to evaluate birth outcomes and congenital abnormalities among women on TDF/FTC/EFV at conception.

Proportion and factors associated with Hepatitis B viremia in antiretroviral treatment naïve and experienced HIV co-infected Ghanaian patients

BACKGROUND

The global burden of Hepatitis B virus (HBV) and HIV co-infection is enormous. The risk of developing cirrhosis and hepatocellular cancer is associated with HBV DNA levels. The main objective of the study was to determine proportion of Hepatitis B viremia in ART-naïve and ART-experienced co-infected Ghanaian patients and factors associated with HBV viremia after at least 36 weeks of lamivudine with or without tenofovir containing ART.

METHODS

Hepatitis B and HIV co-infected patients who were ART-naïve or had received at least 9 months of lamivudine-containing ART were enrolled in a cross-sectional study at Korle-Bu Teaching Hospital. Demographic and clinical data were collected and samples obtained for Hepatitis B serology, liver function tests and HBV DNA. Factors associated with viremia were determined using univariate and multivariate logistic regression analysis.

RESULTS

Of 3108 HIV-infected patients screened, 257 (8.3%) were HBsAg-positive, of which 235 enrolled. Overall, 152 (64.7%) were ART-experienced and 83 (35.3%) were ART-naïve. Eighty-nine-percent of ART-naïve and 42.1% of ART-experienced patients had HBV DNA > 20 IU/mL. In multivariate analysis of all patients, being ART-naïve (OR 10.1, 95% CI 4.6-21.9) and elevated ALT (OR 3.7, 95% CI 1.8-7.9) were associated with Hepatitis B viremia. In treatment experienced patients, elevated ALT (OR 4.8 CI 2.0-12.1) and male sex (OR 2.1, 95% CI 1.0-4.2) were associated with Hepatitis B viremia.

CONCLUSIONS

Majority of ART-naïve (89%) and 42% of ART-experienced patients had detectable hepatitis B viremia > 20 IU/mL. An abnormal serum ALT was significantly associated with hepatitis B viremia in HBV and HIV co-infected patients irrespective of treatment status. Baseline and on-treatment ALT may be a useful non-invasive predictor of Hepatitis B viremia in resource-constrained countries in sub-Saharan Africa where infection is endemic and viral load tests are not widely available.

Dose Frequency Ranging Pharmacokinetic Study of Tenofovir-Emtricitabine After Directly Observed Dosing in Healthy Volunteers to Establish Adherence Benchmarks (HPTN 066)

Oral preexposure prophylaxis (PrEP) trials report disparate efficacy attributed to variable adherence. HPTN 066 was conducted to establish objective, quantitative benchmarks for discrete, regular levels of adherence using directly observed dosing of tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC). Healthy, HIV-uninfected men and women were randomized to one of four oral regimens of fixed-dose TDF 300 mg/FTC 200 mg tablet for 5 weeks with all doses observed: one tablet weekly (one/week), one tablet twice weekly (two/week), two tablets twice weekly (four/week), or one tablet daily (seven/week). Trough serum TFV and FTC, peripheral blood mononuclear cell (PBMC), and CD4(+) TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) concentrations were determined throughout dosing and 2 weeks after the last dose. Rectosigmoidal, semen, and cervicovaginal samples were collected for drug assessment at end of dosing and 2 weeks later in a subset of participants. The 49 enrolled participants tolerated the regimens well. All regimens achieved steady-state concentrations by the second dose for serum TFV/FTC and by 7 days for PBMC TFV-DP/FTC-TP. Steady-state median TFV-DP predose concentrations demonstrated dose proportionality: one/week 1.6 fmol/10(6) PBMCs, two/week 9.1, four/week 18.8, seven/week, 36.3. Further, TFV-DP was consistently quantifiable 2 weeks after the last dose for the ≥4/week regimens. Adherence benchmarks were identified using receiver operating characteristic curves, which had areas under the curve ≥0.93 for all analytes in serum and PBMCs. Intersubject and intrasubject coefficients of variation (%CV) ranged from 33% to 63% and 14% to 34%, respectively, for all analytes in serum and PBMCs. Steady-state PBMC TFV-DP was established earlier and at lower concentrations than predicted and was the only analyte demonstrating predose concentration dose proportionality. Steady-state daily dosing serum TFV and PBMC TFV-DP was consistent with highly effective PrEP clinical trials. HPTN 066 provides adherence benchmarks for oral TFV/FTC regimens to assist interpreting study outcomes.

Impact of protease inhibitors on intracellular concentration of tenofovir-diphosphate among HIV-1 infected patients

Intracellular nucleoside reverse transcriptase inhibitor (NRTI) concentrations are associated with plasma HIV-1 response. Coadministration of protease inhibitors with NRTIs can affect intracellular concentrations due to protease inhibitor inhibition of efflux transporters. Tenofovir-diphosphate (TFV-DP) concentrations within peripheral blood mononuclear cells were compared among individuals receiving either atazanavir or darunavir-based regimens. There was a trend towards higher TFV-DP concentrations among women and among participants receiving atazanavir. TFV-DP intracellular concentrations were positively associated with undetectable plasma HIV-1 RNA.

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.

Detection of Simian Immunodeficiency Virus in Semen, Urethra, and Male Reproductive Organs during Efficient Highly Active Antiretroviral Therapy

A number of men receiving prolonged suppressive highly active antiretroviral therapy (HAART) still shed human immunodeficiency virus (HIV) in semen. To investigate whether this seminal shedding may be due to poor drug penetration and/or viral production by long-lived cells within male genital tissues, we analyzed semen and reproductive tissues from macaques chronically infected with simian immunodeficiency virus mac251 (SIVmac251) who were treated for 4 months with HAART, which was intensified over the last 7 weeks with an integrase inhibitor. We showed that a subset of treated animals continued shedding SIV in semen despite efficient HAART. This shedding was not associated with low antiretroviral drug concentrations in semen or in testis, epididymis, seminal vesicles, and prostate. HAART had no significant impact on SIV RNA in the urethra, whereas it drastically reduced SIV RNA levels in the prostate and vas deferens and to a lesser extent in the epididymis and seminal vesicle. The only detectable SIV RNA-positive cells within the male genital tract after HAART were urethral macrophages. SIV DNA levels in genital tissues were not decreased by HAART, suggesting the presence throughout the male genital tract of nonproductively infected cells. In conclusion, our results demonstrate that 4 months of HAART induced variable and limited control of viral infection in the male reproductive organs, particularly in the urethra, and suggest that infected long-lived cells in the male genital tract may be involved in persistent seminal shedding during HAART. These results pave the way for further investigations of male genital organ infection in long-term-treated infected individuals.

IMPORTANCE

A substantial subset of men receiving prolonged HAART suppressing viral loads in the blood still harbor HIV in semen, and cases of sexual transmission have been reported. To understand the origin of this persistence, we analyzed the semen and male reproductive tissues from SIV-infected macaques treated with HAART. We demonstrated that persistent seminal shedding was not linked to poor drug penetration in semen or semen-producing prostate, seminal vesicle, epididymis, and testis. We revealed that HAART decreased SIV RNA to various extents in all male genital organs, with the exception of the urethra, in which SIV RNA(+) macrophages were observed despite HAART. Importantly, HAART did not impact SIV DNA levels in the male genital organs. These results suggest that infection of male genital organs, and particularly the urethra, could be involved in the release of virus in semen during HAART.

Review of tenofovir use in HIV-infected children

Tenofovir disoproxil fumarate (TDF) is approved by the Food and Drug Administration for use in children ages 2 years and older and is recommended by the World Health Organization for use as a preferred first-line nucleotide reverse transcriptase inhibitor in adults and adolescents ages 10 years and older. The simplicity of once daily dosing, few metabolic side effects and efficacy against hepatitis B virus make TDF suitable for use in a large scale program. Unlike thymidine analoge nucleoside reverse transcriptase inhibitors (NRTIs); tenofovir does not induce multi-NRTI resistance mutations, so more NRTI options are available for future second-line-regimens. Fixed-dose combinations of TDF with other ARVs as a single tablet regimen are now widely available for adults and adolescents, but none are available for young children. Current information on TDF including the pharmacokinetics, safety and tolerability in children and adolescents was reviewed. A dosing regimen according to body-weight-band has been established for pediatric use. Safety concerns of TDF mainly relate to its effects on renal function and bone mineral density. Regular monitoring of renal function in high-risk patients, including those on other nephrotoxic drugs, may be warranted to detect adverse renal effects. Long-term-data on renal and bone outcomes among HIV-infected children is needed. Lessons learned from clinical studies will help clinicians balance the risks and benefits of TDF and design appropriate antiretroviral regimens for children in different circumstances.

Drug interactions and antiretroviral drug monitoring

Owing to the improved longevity afforded by combination antiretroviral therapy (cART), HIV-infected individuals are developing several non-AIDS-related comorbid conditions. Consequently, medical management of the HIV-infected population is increasingly complex, with a growing list of potential drug-drug interactions (DDIs). This article reviews some of the most relevant and emerging potential interactions between antiretroviral medications and other agents. The most common DDIs are those involving protease inhibitors or non-nucleoside reverse transcriptase inhibitors, which alter the cytochrome P450 enzyme system and/or drug transporters such as p-glycoprotein. Of note are the new agents for the treatment of chronic hepatitis C virus infection. These new classes of drugs and others drugs that are increasingly used in this patient population represent a significant challenge with regard to achieving the goals of effective HIV suppression and minimization of drug-related toxicities. Awareness of DDIs and a multidisciplinary approach are imperative in reaching these goals.

Antiretroviral drugs for prevention of mother-to-child transmission: pharmacologic considerations for a public health approach

OBJECTIVE

Efavirenz-based antiretroviral therapy is recommended for prevention of mother-to-child transmission of HIV with two programmatic options: lifelong therapy for all women or treatment until cessation of breastfeeding. However, the risk of HIV resistance emerging after discontinuing efavirenz-based antiretroviral therapy is unclear. We review present knowledge surrounding the emergence of resistance after stopping efavirenz-based antiretroviral regimens.

DESIGN

An expert review.

METHODS

A literature review was conducted to identify studies assessing risk for emergence of efavirenz-related resistance following discontinuation of efavirenz-based antiretroviral regimens containing either lamivudine and zidovudine or tenofovir disoproxil fumarate and lamivudine. Discontinuation strategies including the use of 'pharmacologic tails' are discussed in the light of what is known about the pharmacology of the drugs.

RESULTS

We found no head-to-head comparisons between zidovudine, lamivudine and efavirenz and tenofovir disoproxil fumarate, lamivudine and efavirenz. The risk for HIV resistance exists, even with a 5-7 day tail of zidovudine and lamivudine. For tenofovir disoproxil fumarate, lamivudine and efavirenz, we found no clinical data to inform a recommendation for a tail.

CONCLUSION

In order to prevent emergence of resistance, a tail of at least 2 weeks in duration may be required when discontinuing efavirenz in a regimen containing zidovudine and lamivudine. Studies are needed to characterize the risk of resistance among women who discontinue tenofovir disoproxil fumarate, lamivudine and efavirenz.

Novel liquid chromatography-tandem mass spectrometry method for simultaneous detection of anti-HIV drugs Lopinavir, Ritonavir, and Tenofovir in plasma

For HIV infection, anti-HIV drug combinations are typically used as highly active antiretroviral therapy (HAART), intended to maximize viral suppression. Three drugs used frequently in combination are the protease inhibitors lopinavir and ritonavir and the nucleotide reverse transcriptase inhibitor tenofovir. We have successfully developed a simple, efficient, and sensitive method to simultaneously extract and determine the concentrations of lopinavir, ritonavir, and tenofovir in plasma samples. The plasma extractions were performed using a liquid-liquid extraction followed by protein precipitation of the remaining aqueous layer. The collected fractions were combined, dried, and reconstituted in the mobile phase. The drugs were quantified using liquid chromatography coupled with tandem mass spectrometry. The assay was applied to a study of plasma drug levels in two primates (Macaca nemestrina). The bioanalytical assay was optimized and validated to exhibit a high extraction efficiency and good sensitivity and reproducibility. When the assay was applied in a primate study, all three drugs could be detected in plasma within minutes of subcutaneous dosing. This validated assay will be useful for evaluation of drug concentrations in an efficient, selective, and sensitive manner.

Common clinical conditions - age, low BMI, ritonavir use, mild renal impairment - affect tenofovir pharmacokinetics in a large cohort of HIV-infected women

OBJECTIVE

Tenofovir is used commonly in HIV treatment and prevention settings, but factors that correlate with tenofovir exposure in real-world settings are unknown.

DESIGN

Intensive pharmacokinetic studies of tenofovir in a large, diverse cohort of HIV-infected women over 24 h at steady state were performed and factors that influenced exposure [assessed by areas under the concentration-time curves (AUCs)] identified.

METHODS

HIV-infected women (n = 101) on tenofovir-based therapy underwent intensive 24-h pharmacokinetic sampling. Data on race/ethnicity, age, exogenous steroid use, menstrual cycle phase, concomitant medications, recreational drugs and/or tobacco, hepatic and renal function, weight, and BMI were collected. Multivariable models using forward stepwise selection identified factors associated with effects on AUC. Glomerular filtration rates (GFRs) prior to starting tenofovir were estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation using both creatinine and cystatin-C measures.

RESULTS

The median (range) of tenofovir AUCs was 3350 (1031-13 911) ng × h/ml. Higher AUCs were associated with concomitant ritonavir use (1.33-fold increase, P = 0.002), increasing age (1.21-fold increase per decade, P = 0.0007), and decreasing BMI (1.04-fold increase per 10% decrease in BMI). When GFR was calculated using cystatin-C measures, mild renal insufficiency prior to tenofovir initiation was associated with higher subsequent exposure (1.35-fold increase when pre-tenofovir GFR <70 ml/min, P = 0.0075).

CONCLUSION

Concomitant ritonavir use, increasing age, decreasing BMI, and lower GFR prior to tenofovir initiation as estimated by cystatin C were all associated with elevated tenofovir exposure in a diverse cohort of HIV-infected women. Clinicians treating HIV-infected women should be aware of common clinical conditions that affect tenofovir exposure when prescribing this medication.

Single dose pharmacokinetics of oral tenofovir in plasma, peripheral blood mononuclear cells, colonic tissue, and vaginal tissue

HIV seroconversion outcomes in preexposure prophylaxis (PrEP) trials of oral tenofovir (TFV)-containing regimens are highly sensitive to drug concentration, yet less-than-daily dosing regimens are under study. Description of TFV and its active moiety, TFV diphosphate (TFV-DP), in blood, vaginal tissue, and colon tissue may guide the design and interpretation of PrEP clinical trials. Six healthy women were administered a single oral dose of 300 mg tenofovir disoproxil fumarate (TDF) and 4.3 mg (12.31 MBq, 333 μCi) (14)C-TDF slurry. Blood was collected every 4 h for the first 24 h, then at 4, 8, 11, and 15 days postdosing. Colonic and vaginal samples (tissue, total and CD4(+) cells, luminal fluid and cells) were collected 1, 8 and 15 days postdose. Samples were analyzed for TFV and TFV-DP. Plasma TFV demonstrated triphasic decay with terminal elimination half-life median [interquartile range (IQR)] 69 h (58-77). Peripheral blood mononuclear cell (PBMC) TFV-DP demonstrated biphasic peaks (median 12 h and 96 h) followed by a terminal 48 h (38-76) half-life; Cmax was 20 fmol/million cells (2-63). One day postdose, the TFV-DP paired colon:vaginal tissue concentration ratio was 1 or greater in all subjects' tissue homogenates, median 124 (range 1-281), but was not sustained. The ratio was lower and more variable in cells extracted from tissue. Among all sample types, TFV and TFV-DP half-life ranged from 23 to 139 h. PBMC TFV-DP rose slowly in the hours after dosing indicating that success with exposure-driven dosing regimens may be sensitive to timing of the dose prior to exposure. Colonic tissue homogenate TFV-DP concentrations were greater than in vaginal homogenate at 24 h, but not in cells extracted from tissue. These and the other pharmacokinetic findings will guide the interpretation and design of future PrEP trials.

[Consensus statement on assistance to women with human immunodeficiency virus infection in the health care sector. National AIDS Plan (PNS) and AIDS Study Group (GeSIDA)]

OBJECTIVE

To develop a consensus document on clinical recommendations for the health care of women with human immunodeficiency virus (HIV) infection.

METHODS

We assembled a panel of experts appointed by the Secretariat of the National AIDS Plan and GeSIDA that included internal medicine physicians with expertise in the field of HIV infection, gynecologists, pediatricians and psychologists, and two panel members acting as coordinators. Scientific information was reviewed in publications and conference reports up to October 2012. In keeping with the criteria of the Infectious Disease Society of America, two levels of evidence were applied to support the proposed recommendations: the strength of the recommendation according to expert opinion (A, B, C), and the level of empirical evidence (i, ii, iii), already used in previous documents from SPNS/GeSIDA.

RESULTS

We provide multiple recommendations for the clinical management of women with HIV infection, considering both the diagnostic and possible therapeutic strategies. The consensus recommends gender mainstreaming in health care, and promoting training for healthcare professionals in order to avoid gender bias. With currently available data it seems that the effectiveness of the treatment is the same in both men and women, there being no limitation as to the use of any antiretroviral for this reason. Women have more treatments suspended for reasons other than virological failure, thus they require better monitoring.

CONCLUSIONS

This document presents recommendations for addressing women with HIV infection. This must be multidisciplinary, taking into account the differences that can be found in the diagnosis, disease development, and treatment between men and women.

Interactions between tenofovir and nevirapine in CD4+ T cells and monocyte-derived macrophages restrict their intracellular accumulation

OBJECTIVES

There is no pharmacokinetic interaction between tenofovir and nevirapine, but a higher emergence rate of resistance mutations has been reported when these drugs are coadministered. We sought to examine if there is a potential intracellular interaction that may account for the emergence of resistant virus.

METHODS

Primary CD4+ and CD14+ cells were isolated from healthy volunteer blood. Monocyte-derived macrophages were differentiated from CD14+ cells. Accumulation of radiolabelled tenofovir and nevirapine was then assessed in these cells.

RESULTS

We show here that tenofovir and nevirapine immune cell intracellular concentrations are lower when coincubated in CD4+ cells and monocyte-derived macrophages, but not in CD14+ cells.

CONCLUSIONS

These data indicate a potential intracellular drug-drug interaction between these drugs that warrants further investigation.

Long-term lopinavir/ritonavir monotherapy in HIV-infected children

BACKGROUND

Long-term data are limited on lopinavir/ritonavir monotherapy (mLPV/r) as a treatment simplification strategy in virologically suppressed children.

METHODS

Children with confirmed plasma HIV viral load (VL) <50 copies/mL while receiving double protease inhibitors (dPI) were switched to mLPV/r therapy. Virologic failure (VF) was defined as 2 consecutive VL ≥ 500 or 3 consecutive VL ≥ 50 copies/mL. dPI was resumed within 4 weeks in children with VF. Primary endpoint was the proportion of children with VL < 50 copies/mL while still receiving mLPV/r at week 144.

RESULTS

Forty children were enrolled; 90% were receiving LPV/r + saquinavir and 10% LPV/r + indinavir before simplifying to mLPV/r. Median age was 11.7 years; 50% were female. Median CD4% was 27%. Four (10%) had VL > 50 copies/mL at entry. At week 144, the proportion of children still receiving mLPV/r who had VL < 50 copies/mL was 22 of 40 (55%). The proportion of all children with VL < 50 copies/mL at week 144 was 33 of 40 (82.5%). Among 16 children who had VF and resumed dPI, 11 (69%) achieved VL < 50 copies/mL at week 144. No children with VF had major LPV/r mutations. Having detectable VL at entry and adherence by pill count <95% for >3 times at any visits during the study period significantly predicted VF on mLPV/r (both P = 0.025). The proportion of children with elevated total cholesterol (>200 mg/dL) decreased from 65% at baseline to 40% at week 144 (P = 0.007).

CONCLUSIONS

About half of children maintained virologic suppression on mLPV/r for almost 3 years. VF was common but the majority achieved suppression after resuming dPI and none had major LPV/r mutations. mLPV/r should only be considered for simplified maintenance therapy if frequent VL monitoring to detect VF is available.

Tenofovir, emtricitabine, and tenofovir diphosphate in dried blood spots for determining recent and cumulative drug exposure

Tenofovir (TFV) disoproxil fumarate (TDF)±emtricitabine (FTC) are widely used for HIV treatment and chemoprophylaxis, but variable adherence may lead to suboptimal responses. Methods that quantify adherence would allow for interventions to improve treatment and prevention outcomes. Our objective was to characterize the pharmacokinetics of TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) in red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs); to extend the RBC analysis to dried blood spots (DBSs); and to model how RBC/DBS monitoring could inform recent and cumulative drug exposure/adherence. Blood samples were collected from 17 HIV-negative adults at 5 visits over a 30-day pharmacokinetics study of daily oral TDF/FTC. Dosing was discontinued on day 30 and blood was collected on days 35, 45, and 60 during the washout period. Plasma/RBCs/PBMCs/DBSs were all quantified by liquid chromatography/tandem mass spectrometry. DBSs were paired with RBCs and plasma for comparisons. The median (interquartile range) RBC TFV-DP half-life was 17.1 (15.7-20.2) versus 4.2 (3.7-5.2) days in PBMCs. At steady state, TFV-DP was 130 fmol/10(6) RBCs versus 98 fmol/10(6) PBMCs. FTC-TP was not quantifiable in most RBC samples. TFV-DP in RBCs versus DBSs yielded an r(2)=0.83. TFV-DP in DBSs was stable at -20°C. Simulations of TFV-DP in RBCs/DBSs, when dosed from one to seven times per week, demonstrated that each dose per week resulted in an average change of approximately 19 fmol/10(6) RBCs and 230 fmol/punch. TFV and FTC in plasma versus DBSs was defined by y=1.4x; r(2)=0.96 and y=0.8x; r(2)=0.99, respectively. We conclude that DBSs offer a convenient measure of recent (TFV/FTC) and cumulative (TFV-DP in RBCs) drug exposure with potential application to adherence monitoring.

MTN-001: randomized pharmacokinetic cross-over study comparing tenofovir vaginal gel and oral tablets in vaginal tissue and other compartments

Background

Oral and vaginal preparations of tenofovir as pre-exposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection have demonstrated variable efficacy in men and women prompting assessment of variation in drug concentration as an explanation. Knowledge of tenofovir concentration and its active form, tenofovir diphosphate, at the putative vaginal and rectal site of action and its relationship to concentrations at multiple other anatomic locations may provide key information for both interpreting PrEP study outcomes and planning future PrEP drug development.

Objective

MTN-001 was designed to directly compare oral to vaginal steady-state tenofovir pharmacokinetics in blood, vaginal tissue, and vaginal and rectal fluid in a paired cross-over design.

Methods and Findings

We enrolled 144 HIV-uninfected women at 4 US and 3 African clinical research sites in an open label, 3-period crossover study of three different daily tenofovir regimens, each for 6 weeks (oral 300 mg tenofovir disoproxil fumarate, vaginal 1% tenofovir gel [40 mg], or both). Serum concentrations after vaginal dosing were 56-fold lower than after oral dosing (p<0.001). Vaginal tissue tenofovir diphosphate was quantifiable in ≥90% of women with vaginal dosing and only 19% of women with oral dosing. Vaginal tissue tenofovir diphosphate was ≥130-fold higher with vaginal compared to oral dosing (p<0.001). Rectal fluid tenofovir concentrations in vaginal dosing periods were higher than concentrations measured in the oral only dosing period (p<0.03).

Conclusions

Compared to oral dosing, vaginal dosing achieved much lower serum concentrations and much higher vaginal tissue concentrations. Even allowing for 100-fold concentration differences due to poor adherence or less frequent prescribed dosing, vaginal dosing of tenofovir should provide higher active site concentrations and theoretically greater PrEP efficacy than oral dosing; randomized topical dosing PrEP trials to the contrary indicates that factors beyond tenofovir’s antiviral effect substantially influence PrEP efficacy.

Trial Registration

ClinicalTrials.gov NCT00592124

The clinical pharmacology of antiretrovirals for HIV prevention

PURPOSE OF REVIEW

Pre-exposure prophylaxis (PrEP) clinical trial results using antiretrovirals can seem confusing, if not conflicting. We review recent antiretroviral pharmacokinetic studies to help explain PrEP trial results.

RECENT FINDINGS

Pharmacokinetic studies indicate that topical dosing, compared with oral dosing, achieves far higher colon and vaginal tissue drug concentrations, and far lower drug concentrations in blood. After oral dosing, higher tenofovir diphosphate concentrations are found in colon tissue than cervico-vaginal tissue, but the reverse is the case for emtricitabine triphosphate, although it does not persist as long. Vaginal dosing achieves measurable tenofovir concentrations in the rectum and vice versa. Within and among oral PrEP trials, increased drug concentration is associated with increased HIV protection, with drug concentration differences best explained by adherence, rather than pharmacokinetics. The poor level of protection in topical studies is not consistent with concentration-response in oral studies indicating unknown variables in need of further investigation.

SUMMARY

Sparse pharmacokinetic sampling in large trials combined with more intensive sampling in smaller pharmacokinetic-focused studies help explain trial outcome differences due largely to differences in adherence, tissue pharmacokinetics, and type of HIV exposure. Pharmacokinetic analysis can identify protective drug concentration targets, guide dose optimization, and inform future trials.

Pharmacokinetics and pharmacodynamics of the reverse transcriptase inhibitor tenofovir and prophylactic efficacy against HIV-1 infection

Antiviral pre-exposure prophylaxis (PrEP) through daily drug administration can protect healthy individuals from HIV-1 infection. While PrEP was recently approved by the FDA, the potential long-term consequences of PrEP implementation remain entirely unclear. The aim of this study is to predict the efficacy of different prophylactic strategies with the pro-drug tenofovir-disoproxil-fumarate (TDF) and to assess the sensitivity towards timing- and mode of TDF administration (daily- vs. single dose), adherence and the number of transmitted viruses. We developed a pharmacokinetic model for TDF and its active anabolite tenofovir-diphosphate (TFV-DP) and validated it with data from 4 different trials, including 4 distinct dosing regimes. Pharmacokinetics were coupled to an HIV model and viral decay following TDF mono-therapy was predicted, consistent with available data. Subsequently, a stochastic approach was used to estimate the % infections prevented by (i) daily TDF-based PrEP, (ii) one week TDF started either shortly before, or -after viral exposure and (iii) a single dose oral TDF before viral challenge (sd-PrEP). Analytical solutions were derived to assess the relation between intracellular TFV-DP concentrations and prophylactic efficacy. The predicted efficacy of TDF was limited by a slow accumulation of active compound (TFV-DP) and variable TFV-DP half-life and decreased with increasing numbers of transmitted viruses. Once daily TDF-based PrEP yielded [Formula: see text]80% protection, if at least 40% of pills were taken. Sd-PrEP with 300 mg or 600 mg TDF could prevent [Formula: see text]50% infections, when given at least before virus exposure. The efficacy dropped to [Formula: see text]10%, when given 1 h before 24 h exposure. Efficacy could not be increased with increasing dosage or prolonged administration. Post-exposure prophylaxis poorly prevented infection. The use of drugs that accumulate more rapidly, or local application of tenofovir gel may overcome the need for drug administration long before virus exposure.

Effect of HIV-1 infection and sex on the cellular pharmacology of the antiretroviral drugs zidovudine and lamivudine

The cellular pharmacology of zidovudine (ZDV) and lamivudine (3TC) in vivo is not completely understood. This prospective longitudinal study investigated the relationship between HIV-1 serostatus, sex, race, and time on therapy with intracellular and plasma ZDV and 3TC concentrations. Of 20 HIV-seronegative and 23 HIV-seropositive volunteers enrolled, 16 (8 women) and 21 (5 women) completed all 12 study days, respectively. Volunteers began ZDV-3TC therapy (plus a third active drug in HIV-seropositive volunteers), and steady-state concentrations (C(ss)) were determined after days 1, 3, 7, and 12. A repeated-measures mixed model was utilized. HIV-seronegative status was associated with 22% (95% confidence interval [CI], 0%, 50%) and 37% (15%, 67%) higher C(ss) estimates compared to those of HIV-seropositive individuals for intracellular ZDV-TP and 3TC-TP levels, respectively. African-Americans had 36% (8%, 72%) higher ZDV-TP estimates than non-African-Americans. Sex was not associated with ZDV-TP or 3TC-TP (P > 0.19). Women had 36% (4%, 78%) higher plasma ZDV, but the effect was lessened when normalized by lean body weight (5% [-19%, 38%]; P = 0.68). Plasma 3TC was 19% (0%, 41%) higher in HIV-seropositive volunteers and 22% (0%, 48%) higher in African American volunteers, but these effects were not significant when corrected for creatinine clearance (7% [-9%, 20%] and -5% [-26%, 12%] for HIV serostatus and race, respectively; P > 0.35). These results suggest that HIV-seropositive status decreases and African American race elevates the cellular triphosphates of ZDV and 3TC. This information extends knowledge of ZDV and 3TC cellular pharmacology in vivo and provides new leads for future cellular pharmacology studies aimed at optimizing HIV prevention/treatment with these agents.

Pharmacokinetics of lamivudine and lamivudine-triphosphate after administration of 300 milligrams and 150 milligrams once daily to healthy volunteers: results of the ENCORE 2 study

There is interest in evaluating the efficacy of lower doses of certain antiretrovirals for clinical care. We determined here the bioequivalence of plasma lamivudine (3TC) and intracellular 3TC-triphosphate (3TC-TP) concentrations after the administration of two different doses. ENCORE 2 was a randomized crossover study. Subjects received 3TC at 300 and 150 mg once daily for 10 days (arm 1; n = 13) or vice versa (arm 2; n = 11), separated by a 10-day washout. Pharmacokinetic (PK) profiles (0 to 24 h) were assessed on days 10 and 30. Plasma 3TC and 3TC-TP levels in peripheral blood mononuclear cells were quantified by high-performance liquid chromatography-tandem mass spectrometry. Within-subject changes in PK parameters (the area under the concentration-time curve from 0 to 24 h [AUC(0-24)], the trough concentration of drug in plasma at 24 h [C(24)], and the maximum concentration of drug in plasma [C(max)]) were evaluated by determining the geometric mean ratios (GMRs) adjusted for study arm, period, and intra-individual variation. Regimens were considered bioequivalent if the 90% confidence interval (90% CI) fell within the range of 0.8 to 1.25. A total of 24 subjects completed the study. The GM (90% CI) 3TC AUC(0-24)), expressed as ng·h/ml, for the 300- and 150-mg doses were 8,354 (7,609 to 9,172) and 4,773 (4,408 to 5,169), respectively. Bioequivalence in 3TC PK following the administration of 300 and 150 mg was not demonstrated: the GMRs for AUC(0-24), C(24), and C(max) were 0.57 (0.55 to 0.60), 0.63 (0.59 to 0.67), and 0.56 (0.53 to 0.60), respectively. The GM (90% CI) 3TC-TP AUC(0-24) values (pmol·h/10(6) cells) for the 300- and 150-mg doses were 59.5 (51.8 to 68.3) and 44.0 (38.0 to 51.0), respectively. Bioequivalence in 3TC-TP PK following the administration of 300 and 150 mg was not demonstrated: the GMRs for AUC(0-24), C(24), and C(max) were 0.73 (0.64 to 0.83), 0.82 (0.68 to 0.99), and 0.70 (0.61 to 0.82), respectively. We found that 3TC at 150 mg is not bioequivalent to the standard regimen of 300 mg, indicating that saturation of cytosine phosphorylation pathways is not achieved at a dose of 150 mg.

The role of therapeutic drug monitoring in the management of patients with human immunodeficiency virus infection

Therapeutic drug monitoring (TDM) is a well-established method to optimize dosing regimens in individual patients for drugs that are characterized by a narrow therapeutic range and large interindividual pharmacokinetic variability. For some antiretroviral drugs, mainly nonnucleoside reverse transcriptase inhibitors and protease inhibitors, TDM has been proposed as a means to improve the response in human immunodeficiency virus-infected patients. In contrast, nucleoside reverse transcriptase inhibitors do not show a predictable plasma concentration-response (toxicity, efficacy) relationship, and intracellular analyses are expensive. Therefore, TDM is generally not recommended for this class of drugs. TDM has been successfully applied in the clinical practice for certain antiretroviral drugs, but there are ongoing research efforts on the use and refinement of TDM for human immunodeficiency virus treatment, and convincing data from randomized trials are still needed. The best pharmacokinetic measures of drug exposure such as trough and peak concentrations or concentration ratios have not been unambiguously established.

Plasma and intracellular population pharmacokinetic analysis of tenofovir in HIV-1-infected patients

The relationships among the dose of tenofovir disoproxil fumarate (TDF), tenofovir (TFV) plasma concentrations, and intracellular TFV diphosphate (TFV-DP) concentrations are poorly understood. Our objective was to characterize TFV and TFV-DP relationships. Data were pooled from two studies in HIV-infected persons (n = 55) on stable antiretroviral therapy. TFV and TFV-DP were measured with validated liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods. Nonlinear mixed effects modeling (NONMEM 7) was used to develop the population model and explore the influence of covariates on TFV. A sequential analysis approach was utilized. A two-compartment model with first-order absorption best described TFV PK (FOCEI). An indirect stimulation of response model best described TFV-DP, where formation of TFV-DP was driven by plasma TFV concentration. Final plasma population estimates were as follows: absorption rate constant, 1.03 h(-1); apparent clearance (CL/F), 42 liters/h (33.5% interindividual variability [IIV]); intercompartment clearance, 181 liters/h; apparent central distribution volume (Vc/F), 273 liters (64.8% IIV); and apparent peripheral distribution volume (Vp/F), 440 liters (46.5% IIV). Creatinine clearance was the most significant covariate on CL/F and Vc/F. The correlation between CL/F and Vc/F was 0.553. The indirect response model for TFV-DP resulted in estimates of the maximal intracellular concentration (E(max)), the TFV concentration producing 50% of E(max) (EC(50)), and the intracellular elimination rate constant (k(out)) of 300 fmol/10(6) cells (82% IIV), 100 ng/ml (106% IIV), and 0.008 h(-1), respectively. The estimated k(out) gave an 87-h TFV-DP half-life. A predictive check assessment indicated satisfactory model performance. This model links formation of TFV-DP with plasma TFV concentrations and should facilitate more informed investigations of TFV clinical pharmacology.

Determination of nucleoside analog mono-, di-, and tri-phosphates in cellular matrix by solid phase extraction and ultra-sensitive LC-MS/MS detection

An ultra-sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed and validated to facilitate the assessment of clinical pharmacokinetics of nucleotide analogs from lysed intracellular matrix. The method utilized a strong anion exchange isolation of mono-(MP), di-(DP), and tri-phosphates (TP) from intracellular matrix. Each fraction was then dephosphorylated to the parent moiety yielding a molar equivalent to the original nucleotide analog intracellular concentration. The analytical portion of the methodology was optimized in specific nucleoside analog centric modes (i.e. tenofovir (TFV) centric, zidovudine (ZDV) centric), which included desalting/concentration by solid phase extraction and detection by LC-MS/MS. Nucleotide analog MP-, DP-, and TP-determined on the TFV centric mode of analysis include TFV, lamivudine (3TC), and emtricitibine (FTC). The quantifiable linear range for TFV was 2.5-2000 fmol/sample, and that for 3TC/FTC was 0.1 200 pmol/sample. Nucleoside analog MP-, DP-, and TP-determined on the ZDV centric mode of analysis included 3TC and ZDV. The quantifiable linear range for 3TC was 0.1 100 pmol/sample, and 5-2000 fmol/sample for ZDV. Stable labeled isotopic internal standards facilitated accuracy and precision in alternative cell matrices, which supported the intended use of the method for MP, DP, and TP determinations in various cell types. The method was successfully applied to clinical research samples generating novel intracellular information for TFV, FTC, ZDV, and 3TC nucleotides. This document outlines method development, validation, and application to clinical research.

Plasma and intracellular tenofovir pharmacokinetics in the neonate (ANRS 12109 trial, step 2)

The objective of this study was to investigate for the first time tenofovir (TFV) pharmacokinetics in plasma and peripheral blood mononuclear cells (PBMCs) of the neonate. HIV-1-infected pregnant women received two tablets of tenofovir disoproxil fumarate (TDF; 300 mg) and emtricitabine (FTC; 200 mg) at onset of labor and then one tablet daily for 7 days postpartum. A single dose of 13 mg/kg of body weight of TDF was administered to 36 neonates within 12 h of life after the HIV-1-infected mothers had been administered two tablets of TDF-emtricitabine at delivery. A total of 626 samples collected within the 2 days after the drug administration were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and analyzed by a population approach. In the neonate, the median TFV plasma area under the curve and minimal and maximal concentrations, respectively, were 3.73 mg/liter · h and 0.076 and 0.29 mg/liter. In PBMCs, TFV concentrations were detectable in all fetuses, whereas tenofovir diphosphate (TFV-DP) was quantifiable in only two fetuses, suggesting a lag in appearance of TFV-DP. The median TFV-DP neonatal concentration was 146 fmol/10⁶ cells (interquartile range [IQR], 53 to 430 fmol/10⁶ cells); two neonates had very high TFV-DP concentrations (1,530 and 2963 fmol/10⁶ cells). The 13-mg/kg TDF dose given to neonates produced plasma TFV and intracellular active TFV-DP concentrations similar to those in adults. This dose should be given immediately after birth to reduce the delay before the active compound TFV-DP appears in cells.