Discovery of Novel Aryl Triazolone Dihydropyridines (ATDPs) Targeting Highly Conserved Residue W229 as Promising HIV-1 NNRTIs

NNRTI is an important component of the highly active antiretroviral therapy (HAART), but the rapid emergence of drug resistance and poor pharmacokinetics limited their clinical application. Herein, a series of novel aryl triazolone dihydropyridines (ATDPs) were designed by structure-guided design with the aim of improving drug resistance profiles and pharmacokinetic profiles. Compound 10n (EC50 = 0.009-17.7 μM) exhibited the most active potency, being superior to or comparable to that of doravirine (DOR) against the whole tested viral panel. Molecular docking was performed to clarify the reason for its higher resistance profiles. Moreover, 10n demonstrated excellent pharmacokinetic profile (T1/2 = 5.09 h, F = 108.96%) compared that of DOR (T1/2 = 4.4 h, F = 57%). Additionally, 10n was also verified to have no in vivo acute or subacute toxicity (LD50 > 2000 mg/kg), suggesting that 10n is worth further investigation as a novel oral NNRTIs for HIV-1 therapy.

Development of Novel Dihydrofuro[3,4-d]pyrimidine Derivatives as HIV-1 NNRTIs to Overcome the Highly Resistant Mutant Strains F227L/V106A and K103N/Y181C

Here, we report the design, synthesis, structure-activity relationship studies, antiviral activity, enzyme inhibition, and druggability evaluation of dihydrofuro[3,4-d]pyrimidine derivatives as a potent class of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Compounds 14b (EC50 = 5.79-28.3 nM) and 16c (EC50 = 2.85-18.0 nM) exhibited superior potency against a panel of HIV-1-resistant strains. Especially, for the changeling mutations F227L/V106A and K103N/Y181C, both compounds exhibited remarkably improved activity compared to those of etravirine and rilpivirine. Moreover, 14b and 16c showed moderate RT enzyme inhibition (IC50 = 0.14-0.15 μM), which demonstrated that they acted as HIV-1 NNRTIs. Furthermore, 14b and 16c exhibited favorable pharmacokinetic and safety properties, making them excellent leads for further development.

Fluoride Pharmacokinetics in Urine and Plasma Following Multiple Doses of MK-8507, an Investigational, Oral, Once-Weekly Nonnucleoside Reverse Transcriptase Inhibitor

MK-8507 is an investigational HIV-1 nonnucleoside reverse transcriptase inhibitor being developed for the treatment of HIV-1 infection. MK-8507 contains 2 trifluoromethyl groups that may result in fluoride release through metabolism, but the extent of MK-8507-related fluoride release in humans has yet to be determined. This double-blind, placebo-controlled, 2-period, parallel-group, multiple-dose trial in healthy participants without HIV-1 who were administered a fluoride-restricted diet and once-weekly doses of MK-8507 aimed to estimate the relationship between MK-8507 dose and fluoride exposure. A total of 15 adult male and 3 adult female (of non-childbearing potential) participants were randomized to receive MK-8507 200 mg (n = 6), MK-8507 800 mg (n = 6), or placebo (n = 6). Change from baseline in mean daily fluoride excretion averaged over 7 days following the administration of MK-8507 200 mg resulted in a net mean increase of 19.8 μmol (90% confidence interval, 12.2-27.4) relative to placebo and did not exceed 57 μmol, a threshold related to the mean difference between the daily reference dose set by the US Environmental Protection Agency and the average dietary fluoride intake in the United States. However, daily urinary fluoride excretion exceeded the threshold following administration of 800 mg MK-8507 (75.1 μmol [90% confidence interval, 67.5-82.7]). Assuming a linear relationship between MK-8507 dose and estimated mean daily fluoride released at steady-state, data interpolation suggests that the US Environmental Protection Agency reference dose for fluoride would not be exceeded in most patients when administering MK-8507 at doses currently under clinical investigation (≤400 mg once weekly).

Pharmacokinetics and safety of early nevirapine-based antiretroviral therapy for neonates at high risk for perinatal HIV infection: a phase 1/2 proof of concept study

BACKGROUND

With increasing intention to treat HIV as early as possible, evidence to confirm the safety and therapeutic drug concentrations of a nevirapine-based antiretroviral regimen in the early neonatal period is needed. This study aims to establish dosing of nevirapine for very early treatment of HIV-exposed neonates at high risk of HIV acquisition.

METHODS

IMPAACT P1115 is a multinational phase 1/2 proof-of-concept study in which presumptive treatment for in-utero HIV infection is initiated within 48 h of birth in HIV-exposed neonates at high risk of HIV acquisition. Participants were neonates who were at least 34 weeks gestational age at birth and enrolled within 48 h of birth, born to women with presumed or confirmed HIV infection who had not received antiretrovirals during this pregnancy. The regimen consisted of two nucleoside reverse transcriptase inhibitors plus nevirapine dosed at 6 mg/kg twice daily for term neonates (≥37 weeks gestational age) or 4 mg/kg twice daily for 1 week and 6 mg/kg twice daily thereafter for preterm neonates (34 to <37 weeks gestational age). Here, we report the secondary outcomes of the study: nevirapine exposures in study weeks 1 and 2 and treatment-associated grade 3 or 4 adverse events at least possibly related to study treatment up to study week 4. A population pharmacokinetic model to assess nevirapine exposure was developed from dried blood spot and plasma nevirapine concentrations at study weeks 1 and 2. Nevirapine exposure was assessed in all patients with available blood samples and safety was assessed in all participants. This trial is registered at ClinicalTrials.gov (NCT02140255).

FINDINGS

Between Jan 23, 2015, and Sept 4, 2017, 438 neonates were enrolled and included in analyses; 36 had in-utero HIV infection and 389 (89%) were born at term. Neonates without confirmed in-utero HIV infection received nevirapine for a median of 13 days (IQR 7-14). Measured dried blood spot nevirapine concentrations were higher than the minimum HIV treatment target (3 μg/mL) in 314 (90%, 95% CI 86-93) of 349 neonates at week 1 and 174 (87%, 81-91) of 201 at week 2. In Monte-Carlo simulations, week 1 nevirapine concentrations exceeded 3 μg/mL in 80% of term neonates and 82% of preterm neonates. DAIDS grade 3 or 4 adverse events at least possibly related to antiretrovirals occurred in 30 (7%, 95% CI 5-10) of 438 infants but did not lead to nevirapine cessation in any neonates; neutropenia (25 [6%] neonates) and anaemia (six [1%]) were most common.

INTERPRETATION

Nevirapine at the dose studied was confirmed to be safe and provides therapeutic exposure concentrations. These data support nevirapine as a component of presumptive HIV treatment in high-risk neonates.

FUNDING

National Institute of Allergy and Infectious Diseases, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute of Mental Health.

Clinical Pharmacokinetics of the Novel HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitor Doravirine: An Assessment of the Effect of Patient Characteristics and Drug-Drug Interactions

Doravirine (MK-1439) is a novel non-nucleoside reverse transcriptase inhibitor indicated for the combination treatment of human immunodeficiency virus type-1 (HIV-1) infection. The recommended dose is 100 mg once daily. This review summarizes the pharmacokinetics of doravirine, the influence of intrinsic factors, and its drug-drug interaction (DDI) profile. Following oral administration, doravirine is rapidly absorbed (median time to maximum plasma concentration, 1-4 h) and undergoes cytochrome P450 (CYP)3A-mediated oxidative metabolism. Steady-state geometric means for AUC0-24, C24, and Cmax in individuals with HIV-1 following administration of doravirine 100 mg once daily are 37.8 μM·h, 930 nM, and 2260 nM, respectively. Age, gender, severe renal impairment, and moderate hepatic impairment have no clinically meaningful effect on doravirine pharmacokinetics, and there is limited potential for DDIs. No dose adjustment is necessary when doravirine is co-administered with strong CYP3A inhibitors. However, doravirine is contraindicated with strong CYP3A inducers (e.g., rifampin), and dose adjustment of doravirine is recommended for co-administration with the moderate CYP3A inducer, rifabutin. Included in this review are clinical trial data from phase I pharmacokinetic trials, including DDI trials and trials in participants with renal and hepatic disease but without HIV-1 infection (N = 326), as well as phase I, II, and III safety and efficacy trials in participants living with HIV-1 (N = 991). Based on these data, the pharmacokinetic profile of doravirine supports its use in diverse populations living with HIV-1 and allows co-administration with various antiretroviral agents and treatments for commonly occurring co-morbidities.

Meta-analysis of the effect of CYP2B6, CYP2A6, UGT2B7 and CAR polymorphisms on efavirenz plasma concentrations

BACKGROUND

Efavirenz primary metabolism is catalysed by CYP2B6 with minor involvement of CYP2A6. Subsequently, phase I metabolites are conjugated by UGT2B7, and constitutive androstane receptor (CAR) has been shown to transcriptionally regulate many relevant enzymes and transporters. Several polymorphisms occurring in the genes coding for these proteins have been shown to impact efavirenz pharmacokinetics in some but not all studies.

OBJECTIVES

A meta-analysis was performed to assess the overall effect of CYP2B6 rs3745274, CYP2A6 (rs28399454, rs8192726 and rs28399433), UGT2B7 (rs28365062 and rs7439366) and NR1I3 (rs2307424 and rs3003596) polymorphisms on mid-dose efavirenz plasma concentrations.

METHODS

Following a literature review, pharmacokinetic parameters were compiled and a meta-analysis for these variants was performed using Review Manager and OpenMetaAnalyst. A total of 28 studies were included.

RESULTS

Unsurprisingly, the analysis confirmed that individuals homozygous for the T allele for CYP2B6 rs3745274 had significantly higher efavirenz concentrations than those homozygous for the G allele [weighted standard mean difference (WSMD) = 2.98; 95% CI 2.19-3.76; P < 0.00001]. A subgroup analysis confirmed ethnic differences in frequency but with a similar effect size in each ethnic group (P = 0.96). Associations with CYP2A6 and UGT2B7 variants were not statistically significant, but T homozygosity for CAR rs2307424 was associated with significantly lower efavirenz concentrations than in C homozygotes (WSMD = -0.32; 95% CI -0.59 to -0.06; P = 0.02).

CONCLUSIONS

This meta-analysis provides the overall effect size for the impact of CYP2B6 rs3745274 and NR1I3 rs2307424 on efavirenz pharmacokinetics. The analysis also indicates that some previous associations were not significant when interrogated across studies.

Clinical Pharmacodynamics, Pharmacokinetics, and Drug Interaction Profile of Doravirine

Doravirine is a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) that has demonstrated good efficacy, tolerability, and safety for the treatment of patients with human immunodeficiency virus (HIV)-1 infection in phase III clinical trials. Doravirine achieved non-inferiority when compared with efavirenz- and darunavir/ritonavir-based regimens. Fewer adverse effects, including neuropsychiatric effects were observed with doravirine compared with efavirenz. Key pharmacodynamic and pharmacokinetic characteristics as well as drug-drug interactions and the resistance profile were assessed in this clinical review. Doravirine is a pyridinone NNRTI with potent antiviral activity against wild-type HIV-1 virus and common NNRTI variants. Studies in healthy volunteers and HIV-infected individuals have shown that doravirine has a favorable pharmacokinetic profile for once-daily dosing, with an elimination half-life of around 15 h, median time to maximum plasma concentrations of 1-4 h, and time to steady-state concentration of 7 days. The pharmacokinetics of doravirine are not greatly influenced by sex, age, race, or hepatic impairment. Although no dose adjustment is required for doravirine in renal impairment when given as a single tablet, the fixed-dose combination tablet of doravirine/lamivudine/tenofovir disoproxil fumarate is not recommended in patients with a creatinine clearance of < 50 mL/min. Doravirine has a low potential for drug-drug interactions and does not impact on the pharmacokinetics of other drugs. However, it is metabolized via cytochrome P450 (CYP) 3A enzymes and is thus susceptible to interactions with CYP3A inhibitors and inducers. Strong CYP3A inhibitors can significantly increase doravirine exposure; however, this is not considered to be clinically relevant. Conversely, strong CYP3A inducers, such as rifampin, are contraindicated with doravirine owing to a significant reduction in exposure with potential for impaired virological efficacy. Moderate CYP3A inducers, such as rifabutin, may be co-administered if the doravirine dose is increased to 100 mg twice daily. Doravirine has a unique resistance profile and has demonstrated in vitro activity against some of the most common, clinically relevant NNRTI-resistant mutations. Prevalence of baseline NNRTI resistance to doravirine appears to be low in treatment-naïve cohorts. Further data on the efficacy of doravirine in patients with previous treatment experience and/or transmitted NNRTI resistance are required to further inform its place in the current armamentarium of drugs for the treatment of HIV infection.

Discovery and Characterization of Fluorine-Substituted Diarylpyrimidine Derivatives as Novel HIV-1 NNRTIs with Highly Improved Resistance Profiles and Low Activity for the hERG Ion Channel

Our previous efforts have led to the development of two potent NNRTIs, K-5a2 and 25a, exhibiting effective anti-HIV-1 potency and resistance profiles compared with etravirine. However, both inhibitors suffered from potent hERG inhibition and short half-life. In this article, with K-5a2 and etravirine as leads, series of novel fluorine-substituted diarylpyrimidine derivatives were designed via molecular hybridization and bioisosterism strategies. The results indicated 24b was the most active inhibitor, exhibiting broad-spectrum activity (EC50 = 3.60-21.5 nM) against resistant strains, significantly lower cytotoxicity (CC50= 155 μM), and reduced hERG inhibition (IC50 > 30 μM). Crystallographic studies confirmed the binding of 24b and the role of the fluorine atom, as well as optimal contacts of a nitrile group with the main-chain carbonyl group of H235. Furthermore, 24b showed longer half-life and favorable safety properties. All the results demonstrated that 24b has significant promise in circumventing drug resistance as an anti-HIV-1 candidate.

Using PBPK Modeling to Predict Drug Exposure and Support Dosage Adjustments in Patients With Renal Impairment: An Example with Lamivudine

BACKGROUND

Lamivudine is a nucleoside reverse transcriptase inhibitor used to treat HIV and hepatitis B. It is primarily cleared by the kidney with renal secretion mediated by OCT2 and MATE.

OBJECTIVE

To use PBPK modeling to assess the impact of renal impairment on lamivudine pharmacokinetics using the Simcyp® Simulator.

METHODS

The model incorporated the Simcyp® Mechanistic Kidney Model option to predict renal disposition. The model was initially verified using the Simcyp® Healthy Volunteer population. Two discrete patient populations were then created for moderate (GFR 10-40 mL/min) and severe (GFR < 10 mL/min) renal failure (RF), and model simulations were compared to published data. The developed model was then utilized in a clinical study evaluating the clinical experience and plasma exposure of lamivudine when administered at higher than recommended doses to HIV-infected patients with varying degrees of renal impairment.

RESULTS

Predicted systemic exposure metrics (Cmax, AUC) compared favorably to published clinical data for each population, with the following fold errors (FE, ratio of predicted and observed data) for Cmax/AUC: Healthy Volunteers 1.04/1.04, Moderate RF 1.03/0.78, Severe RF 0.89/0.79. The model captured lamivudine plasma concentrations measured pre- and post-dose (0.5-1.5hr) in study participants (n = 34). Model simulations demonstrated comparable systemic profiles across patient cohorts, supporting the proposed dosage adjustment scheme.

CONCLUSION

This study illustrates how PBPK modeling can help verify dosing guidelines for patients with varying levels of renal impairment. This approach may also be useful for predicting potential changes in exposure during renal insufficiency for compounds undergoing clinical development.

Safety and pharmacokinetics of dolutegravir in pregnant mothers with HIV infection and their neonates: A randomised trial (DolPHIN-1 study)

BACKGROUND

The global transition to use of dolutegravir (DTG) in WHO-preferred regimens for HIV treatment is limited by lack of knowledge on use in pregnancy. Here we assessed the relationship between drug concentrations (pharmacokinetics, PK), including in breastmilk, and impact on viral suppression when initiated in the third trimester (T3).

METHODS AND FINDINGS

In DolPHIN-1, HIV-infected treatment-naïve pregnant women (28-36 weeks of gestation, age 26 (19-42), weight 67kg (45-119), all Black African) in Uganda and South Africa were randomised 1:1 to dolutegravir (DTG) or efavirenz (EFV)-containing ART until 2 weeks post-partum (2wPP), between 9th March 2017 and 16th January 2018, with follow-up until six months postpartum. The primary endpoint was pharmacokinetics of DTG in women and breastfed infants; secondary endpoints included maternal and infant safety and viral suppression. Intensive pharmacokinetic sampling of DTG was undertaken at day 14 and 2wPP following administration of a medium-fat breakfast, with additional paired sampling between maternal plasma and cord blood, breastmilk and infant plasma. No differences in median baseline maternal age, gestation (31 vs 30 weeks), weight, obstetric history, viral load (4.5 log10 copies/mL both arms) and CD4 count (343 vs 466 cells/mm3) were observed between DTG (n = 29) and EFV (n = 31) arms. Although DTG Ctrough was below the target 324ng/mL (clinical EC90) in 9/28 (32%) mothers in the third trimester, transfer across the placenta (121% of plasma concentrations) and into breastmilk (3% of plasma concentrations), coupled with slower elimination, led to significant infant plasma exposures (3-8% of maternal exposures). Both regimens were well-tolerated with no significant differences in frequency of adverse events (two on DTG-ART, one on EFV-ART, all considered unrelated to drug). No congenital abnormalities were observed. DTG resulted in significantly faster viral suppression (P = 0.02) at the 2wPP visit, with median time to <50 copies/mL of 32 vs 72 days. Limitations related to the requirement to initiate EFV-ART prior to randomisation, and to continue DTG for only two weeks postpartum.

CONCLUSION

Despite low plasma DTG exposures in the third trimester, transfer across the placenta and through breastfeeding was observed in this study, with persistence in infants likely due to slower metabolic clearance. HIV RNA suppression <50 copies/mL was twice as fast with DTG compared to EFV, suggesting DTG has potential to reduce risk of vertical transmission in mothers who are initiated on treatment late in pregnancy.

TRIAL REGISTRATION

clinicaltrials.gov NCT02245022.

Structural and pharmacological evaluation of a novel non-nucleoside reverse transcriptase inhibitor as a promising long acting nanoformulation for treating HIV

Combination antiretroviral therapy (cART) has been proven effective in inhibiting human immunodeficiency virus type 1 (HIV-1) infection and has significantly improved the health outcomes in acquired immune deficiency syndrome (AIDS) patients. The therapeutic benefits of cART have been challenged because of the toxicity and emergence of drug-resistant HIV-1 strains along with lifelong patient compliance resulting in non-adherence. These issues also hinder the clinical benefits of non-nucleoside reverse transcriptase inhibitors (NNRTIs), which are one of the vital components of cART for the treatment of HIV-1 infection. In this study, using a computational and structural based drug design approach, we have discovered an effective HIV -1 NNRTI, compound I (Cmpd I) that is very potent in biochemical assays and which targets key residues in the allosteric binding pocket of wild-type (WT)-RT as revealed by structural studies. Furthermore, Cmpd I exhibited very potent antiviral activity in HIV-1 infected T cells, lacked cytotoxicity (therapeutic index >100,000), and no significant off-target effects were noted in pharmacological assays. To address the issue of non-adherence, we developed a long-acting nanoformulation of Cmpd I (Cmpd I-NP) using poly (lactide-coglycolide) (PLGA) particles. The pharmacokinetic studies of free and nanoformulated Cmpd I were carried out in BALB/c mice. Intraperitoneal administration of Cmpd I and Cmpd I-NP in BALB/c mice revealed prolonged serum residence time of 48 h and 30 days, respectively. The observed serum concentrations of Cmpd I in both cases were sufficient to provide >97% inhibition in HIV-1 infected T-cells. The significant antiviral activity along with favorable pharmacological and pharmacokinetic profile of Cmpd I, provide compelling and critical support for its further development as an anti-HIV therapeutic agent.

Efavirenz reduces renal excretion of lamivudine in rats by inhibiting organic cation transporters (OCT, Oct) and multidrug and toxin extrusion proteins (MATE, Mate)

Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor used in first-line combination antiretroviral therapy (cART). It is usually administered with nucleoside reverse transcriptase inhibitors (NRTI), many of which are substrates of OCT uptake solute carriers (SLC22A) and MATE (SLC47A), P-gp (MDR1, ABCB1), BCRP (ABCG2), or MRP2 (ABCC2) efflux transporters. The aim of this study was to evaluate the inhibitory potential of efavirenz towards these transporters and investigate its effects on the pharmacokinetics and tissue distribution of a known Oct/Mate substrate, lamivudine, in rats. Accumulation and transport assays showed that efavirenz inhibits the uptake of metformin by OCT1-, OCT2- and MATE1-expressing MDCK cells and reduces transcellular transport of lamivudine across OCT1/OCT2- and MATE1-expressing MDCK monolayers. Only negligible inhibition of MATE2-K was observed in HEK-MATE2-K cells. Efavirenz also reduced the efflux of calcein from MDCK-MRP2 cells, but had a rather weak inhibitory effect on Hoechst 33342 accumulation in MDCK-MDR1 and MDCK-BCRP cells. An in vivo pharmacokinetic interaction study in male Wistar rats revealed that intravenous injection of efavirenz or the control Oct/Mate inhibitor cimetidine significantly reduced the recovery of lamivudine in urine and greatly increased lamivudine retention in the renal tissue. Co-administration with efavirenz or cimetidine also increased the AUC0-∞ value and reduced total body clearance of lamivudine. These data suggest that efavirenz is a potent inhibitor of OCT/Oct and MATE/Mate transporters. Consequently, it can engage in drug-drug interactions that reduce renal excretion of co-administered substrates and enhance their retention in the kidneys, potentially compromising therapeutic safety.

A Two-Way Steady-State Pharmacokinetic Interaction Study of Doravirine (MK-1439) and Dolutegravir

INTRODUCTION

Doravirine, a non-nucleoside reverse-transcriptase inhibitor in development for the treatment of patients with human immunodeficiency virus-1 infection, has potential to be used concomitantly in antiretroviral therapy with dolutegravir, an integrase strand transfer inhibitor. The pharmacokinetic interactions between these drugs were therefore assessed.

METHODS

Oral formulations of doravirine and dolutegravir were dosed both individually and concomitantly once daily in healthy adults. Twelve subjects (six were male), 23-42 years of age, were enrolled and 11 completed this phase I, open-label, three-period, fixed-sequence study per protocol; one subject was discontinued for a positive cotinine test at admission to period 2. In period 1, dolutegravir 50 mg was administered for 7 days. After a 7-day washout, doravirine 200 mg was dosed for 7 days in period 2, followed (without washout) by both doravirine and dolutegravir simultaneously for 7 days in period 3. Plasma samples were taken to determine dolutegravir and doravirine concentrations.

RESULTS

The steady-state concentration 24 h post-dose (C₂₄) of dolutegravir was not substantially altered by co-administration of doravirine multiple doses; area under the plasma concentration-time curve from dosing to 24 h post-dose (AUC_0-24), maximum concentration (C _max), and C₂₄ geometric mean ratios were 1.36, 1.43, and 1.27, respectively. The pharmacokinetics of doravirine was not affected by multiple doses of dolutegravir (geometric mean ratios: 1.00, 0.98, and 1.06 for AUC_0-24, C₂₄, and C _max, respectively). Both drugs were generally well tolerated.

CONCLUSION

The results of this study demonstrate that concomitant administration of doravirine and dolutegravir in healthy subjects causes no clinically significant alteration in the pharmacokinetic and safety profiles of the two drugs, thereby supporting further evaluation of co-administration of these agents for human immunodeficiency virus-1 treatment.

The Effect of Single and Multiple Doses of Rifampin on the Pharmacokinetics of Doravirine in Healthy Subjects

BACKGROUND AND OBJECTIVE

Doravirine is a novel, next-generation, non-nucleoside reverse transcriptase inhibitor in development for the treatment of human immunodeficiency virus-1 infection in combination with other antiretrovirals. Doravirine is a substrate for cytochrome P450 (CYP) 3A and P-glycoprotein. Rifampin (rifampicin) is used for treating tuberculosis in patients who are co-infected with human immunodeficiency virus. Rifampin demonstrates organic anion-transporting polypeptide 1B1 and P-glycoprotein inhibition after single-dose administration and CYP3A and P-glycoprotein induction after multiple-dose administration. The objective of this study was to evaluate the effects of co-administration of single and multiple doses of rifampin on doravirine pharmacokinetics.

METHODS

In period 1 of this open-label, two-period, fixed-sequence study in healthy adults, subjects received single-dose doravirine 100 mg; blood samples for measuring plasma concentration were collected pre-dose and up to 72 h post-dose. In period 2, following a 7-day washout, subjects received doravirine 100 mg and rifampin 600 mg on day 1, rifampin 600 mg daily on days 4-18, with doravirine 100 mg co-administered on day 17; blood samples were collected pre-dose and up to 72 h post-dose on day 1 and up to 48 h post-dose on day 17. Safety assessments included adverse events, physical examinations, vital signs, and clinical laboratory measurements.

RESULTS

Ten subjects completed the study. Doravirine area under the concentration-time curve from time zero extrapolated to infinity and plasma concentration at 24 h post-dose were comparable in the presence and absence of single-dose rifampin [geometric mean ratios (90% confidence intervals)] of 0.91 (0.78-1.06) and 0.90 (0.80-1.01), respectively. Doravirine maximum plasma concentration increased when co-administered with single-dose rifampin vs. doravirine alone, geometric mean ratio (90% confidence interval): 1.40 (1.21-1.63). Reductions in doravirine geometric mean ratios (90% confidence interval), area under the concentration-time curve from time zero extrapolated to infinity: 0.12 (0.10-0.15), plasma concentration at 24 h post-dose: 0.03 (0.02-0.04), maximum plasma concentration: 0.43 (0.35-0.52), and apparent terminal half-life were observed when co-administered with multiple-dose rifampin vs. doravirine administered alone. Doravirine was well tolerated. Adverse events were mild and resolved by study completion.

CONCLUSIONS

Doravirine co-administration with single-dose rifampin indicated that inhibition of organic anion-transporting polypeptide uptake transporters and P-glycoprotein has little impact on doravirine pharmacokinetics. Long-term co-administration of rifampin or other strong CYP3A inducers with doravirine will likely reduce its efficacy.

Nanoparticle-releasing nanofiber composites for enhanced in vivo vaginal retention

Current approaches for topical vaginal administration of nanoparticles result in poor retention and extensive leakage. To overcome these challenges, we developed a nanoparticle-releasing nanofiber delivery platform and evaluated its ability to improve nanoparticle retention in a murine model. We individually tailored two components of this drug delivery system for optimal interaction with mucus, designing (1) mucoadhesive fibers for better retention in the vaginal tract, and (2) PEGylated nanoparticles that diffuse quickly through mucus. We hypothesized that this novel dual-functioning (mucoadhesive/mucus-penetrating) composite material would provide enhanced retention of nanoparticles in the vaginal mucosa. Equivalent doses of fluorescent nanoparticles were vaginally administered to mice in either water (aqueous suspension) or fiber composites, and fluorescent content was quantified in cervicovaginal mucus and vaginal tissue at time points from 24 h to 7d. We also fabricated composite fibers containing etravirine-loaded nanoparticles and evaluated the pharmacokinetics over 7d. We found that our composite materials provided approximately 30-fold greater retention of nanoparticles in the reproductive tract at 24 h compared to aqueous suspensions. Compared to nanoparticles in aqueous suspension, the nanoparticles in fiber composites exhibited sustained and higher etravirine concentrations after 24 h and up to 7d, demonstrating the capabilities of this new delivery platform to sustain nanoparticle release out to 3d and drug retention out to one week after a single administration. This is the first report of nanoparticle-releasing fibers for vaginal drug delivery, as well as the first study of a single delivery system that combines two components uniquely engineered for complementary interactions with mucus.

Development and validation of reversed-phase HPLC gradient method for the estimation of efavirenz in plasma

Efavirenz is an anti-viral agent of non-nucleoside reverse transcriptase inhibitor category used as a part of highly active retroviral therapy for the treatment of infections of human immune deficiency virus type-1. A simple, sensitive and rapid reversed-phase high performance liquid chromatographic gradient method was developed and validated for the determination of efavirenz in plasma. The method was developed with high performance liquid chromatography using Waters X-Terra Shield, RP18 50 x 4.6 mm, 3.5 μm column and a mobile phase consisting of phosphate buffer pH 3.5 and Acetonitrile. The elute was monitored with the UV-Visible detector at 260 nm with a flow rate of 1.5 mL/min. Tenofovir disoproxil fumarate was used as internal standard. The method was validated for linearity, precision, accuracy, specificity, robustness and data obtained were statistically analyzed. Calibration curve was found to be linear over the concentration range of 1-300 μg/mL. The retention times of efavirenz and tenofovir disoproxil fumarate (internal standard) were 5.941 min and 4.356 min respectively. The regression coefficient value was found to be 0.999. The limit of detection and the limit of quantification obtained were 0.03 and 0.1 μg/mL respectively. The developed HPLC method can be useful for quantitative pharmacokinetic parameters determination of efavirenz in plasma.

Multicompartmental Pharmacokinetic Model of Tenofovir Delivery to the Rectal Mucosa by an Enema

Rectal enemas that contain prophylactic levels of anti-HIV microbicides such as tenofovir have emerged as a promising dosage form to prevent sexually transmitted HIV infections. The enema vehicle is promising due to its likely ability to deliver a large amount of drug along the length of the rectal canal. Computational models of microbicide drug delivery by enemas can help their design process by determining key factors governing drug transport and, more specifically, the time history and degree of protection. They can also inform interpretations of experimental pharmacokinetic measures such as drug concentrations in biopsies. The present work begins rectal microbicide PK modeling, for enema vehicles. Results here show that a paramount factor in drug transport is the time of enema retention; direct connectivity between enema fluid and the fluid within rectal crypts is also important. Computations of the percentage of stromal volume protected by a single enema dose indicate that even with only a minute of enema retention, protection of 100% can be achieved after around 14 minutes post dose. Concentrations in biopsies are dependent on biopsy thickness; and control and/or knowledge of thickness could improve accuracy and decrease variability in biopsy measurements. Results here provide evidence that enemas are a promising dosage form for rectal microbicide delivery, and offer insights into their rational design.

Pharmacokinetics of long-acting tenofovir alafenamide (GS-7340) subdermal implant for HIV prophylaxis

Oral or topical daily administration of antiretroviral (ARV) drugs to HIV-1-negative individuals in vulnerable populations is a promising strategy for HIV-1 prevention. Adherence to the dosing regimen has emerged as a critical factor determining efficacy outcomes of clinical trials. Because adherence to therapy is inversely related to the dosing period, sustained release or long-acting ARV formulations hold significant promise for increasing the effectiveness of HIV-1 preexposure prophylaxis (PrEP) by reducing dosing frequency. A novel, subdermal implant delivering the potent prodrug tenofovir alafenamide (TAF) with controlled, sustained, zero-order (linear) release characteristics is described. A candidate device delivering TAF at 0.92 mg day(-1) in vitro was evaluated in beagle dogs over 40 days for pharmacokinetics and preliminary safety. No adverse events related to treatment with the test article were noted during the course of the study, and no significant, unusual abnormalities were observed. The implant maintained a low systemic exposure to TAF (median, 0.85 ng ml(-1); interquartile range [IQR], 0.60 to 1.50 ng ml(-1)) and tenofovir (TFV; median, 15.0 ng ml(-1); IQR, 8.8 to 23.3 ng ml(-1)), the product of in vivo TAF hydrolysis. High concentrations (median, 512 fmol/10(6) cells over the first 35 days) of the pharmacologically active metabolite, TFV diphosphate, were observed in peripheral blood mononuclear cells at levels over 30 times higher than those associated with HIV-1 PrEP efficacy in humans. Our report on the first sustained-release nucleoside reverse transcriptase inhibitor (NRTI) for systemic delivery demonstrates a successful proof of principle and holds significant promise as a candidate for HIV-1 prophylaxis in vulnerable populations.

Efavirenz Has the Highest Anti-Proliferative Effect of Non-Nucleoside Reverse Transcriptase Inhibitors against Pancreatic Cancer Cells

Background

Cancer prevention and therapy in HIV-1-infected patients will play an important role in future. The non-nucleoside reverse transcriptase inhibitors (NNRTI) Efavirenz and Nevirapine are cytotoxic against cancer cells in vitro. As other NNRTIs have not been studied so far, all clinically used NNRTIs were tested and the in vitro toxic concentrations were compared to drug levels in patients to predict possible anti-cancer effects in vivo.

Methods

Cytotoxicity was studied by Annexin-V-APC/7AAD staining and flow cytometry in the pancreatic cancer cell lines BxPC-3 and Panc-1 and confirmed by colony formation assays. The 50% effective cytotoxic concentrations (EC50) were calculated and compared to the blood levels in our patients and published data.

Results

The in vitro EC50 of the different drugs in the BxPC-3 pancreatic cancer cells were: Efavirenz 31.5μmol/l (= 9944ng/ml), Nevirapine 239μmol/l (= 63786ng/ml), Etravirine 89.0μmol/l (= 38740ng/ml), Lersivirine 543μmol/l (= 168523ng/ml), Delavirdine 171μmol/l (= 78072ng/ml), Rilpivirine 24.4μmol/l (= 8941ng/ml). As Efavirenz and Rilpivirine had the highest cytotoxic potential and Nevirapine is frequently used in HIV-1 positive patients, the results of these three drugs were further studied in Panc-1 pancreatic cancer cells and confirmed with colony formation assays. 205 patient blood levels of Efavirenz, 127 of Rilpivirine and 31 of Nevirapine were analyzed. The mean blood level of Efavirenz was 3587ng/ml (range 162–15363ng/ml), of Rilpivirine 144ng/ml (range 0-572ng/ml) and of Nevirapine 4955ng/ml (range 1856–8697ng/ml). Blood levels from our patients and from published data had comparable Efavirenz levels to the in vitro toxic EC50 in about 1 to 5% of all patients.

Conclusion

All studied NNRTIs were toxic against cancer cells. A low percentage of patients taking Efavirenz reached in vitro cytotoxic blood levels. It can be speculated that in HIV-1 positive patients having high Efavirenz blood levels pancreatic cancer incidence might be reduced. Efavirenz might be a new option in the treatment of cancer.

Impact of Various Antiretroviral Drugs and Their Plasma Concentrations on Plasma Lipids in Heavily Pretreated HIV-Infected Patients

OBJECTIVE

To evaluate the frequency and the magnitude of lipid abnormalities (LA) in respect to the nature of the antiretroviral drug and its plasma concentrations.

PATIENTS/METHOD

Trough concentrations (C(trough)) of protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) were assessed at Weeks 4, 8, 24, 28, and 32. Fasting triglycerides (TG) and total cholesterol (CH) were sampled at Weeks 0, 12, 20, and 32. We analyzed the probability of occurrence of grade 3-4 CH (> 7.8 mmol/L) and TG (> 8.4 mmol/L) during a 24-week period according to the drug taken using a Kaplan-Meier analysis and log rank test. Relation between Week 8 PI or NNRTI C(trough) and Week 12 lipid levels was assessed using the Kendall correlation measure.

RESULTS

The PharmAdapt study included 252 patients (mean age 41 years, 83% males); the patients received a PI (73%), an NNRTI (50%), and/or a ritonavir (RTV) booster-containing (46%) regimen. Compared to any other regimen, use of lopinavir (LPV)/RTV or efavirenz (EFV) was associated with a higher risk of grade 3-4 CH. Use of LPV/RTV and RTV booster was associated with a higher risk of grade 3-4 TG. Use of any PI-containing regimen was associated with a higher risk for grade 3-4 CH and TG compared to non PI-based regimens. Kendall correlation coefficients for PI or NNRTI C(trough) and blood lipid levels were close to zero for all drugs and CH or TG, showing the absence of relation between drug concentrations and lipid levels.

CONCLUSION

Severity of lipid abnormalities is related to the nature of the antiretroviral drug. There is no short-term relation between PI or NNRTI trough concentrations and blood lipid levels in heavily pretreated patients.

Pharmacokinetics of Antiretrovirals Administered to HIV-Infected Children via Gastrostomy Tube

BACKGROUND

Surgical placement of a gastrostomy tube (g-tube) directly into a patient's gastrointestinal system to support antiretroviral administration is occasionally used to increase adherence in HIV-infected children. Absorption and distribution characteristics of antiretrovirals after g-tube administration, however, are unknown. The goal of this pilot study was to describe the pharmacokinetic characteristics of protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) when administered to HIV-infected children via g-tube.

METHOD

Nine HIV-infected children who were receiving a PI- or NNRTI-containing regimen via g-tube were enrolled. All antiretrovirals (excluding efavirenz) were administered under direct observation for the pharmacokinetic evaluation. Blood samples were collected at predose and at 1, 2, 4, 8, and 12 hours postdose. Antiretroviral concentrations were measured in plasma using high performance liquid chromatography with ultraviolet detection.

RESULTS

Systemic exposure of PIs and NNRTIs in our 9 patients was similar to data from historical oral administration controls. Due to likely drug interactions, LPV exposure was decreased and one patient had low exposure of all antiretrovirals. When doses were increased, adequate exposure was attained.

CONCLUSION

This pilot study suggests that administration of most PIs and NNRTIs by a g-tube to HIV-infected children provides systemic exposure comparable with that achieved after oral administration.

Usefulness of Therapeutic Drug Monitoring of Antiretrovirals in Routine Clinical Practice

BACKGROUND

Clinical trials have shown that therapeutic drug monitoring (TDM) of antiretrovirals (ARV) improves patient care. However, little is known about the usefulness of TDM in routine practice.

METHOD

We reviewed all the trough concentrations of protease inhibitors and nonnucleoside reverse transcriptase inhibitors that were performed for therapeutic failure, suspected drug toxicity, or routine purposes.

RESULTS

Between 1998 and 2001, 146 TDMs were done in 109 HIV patients. Of the 48 patients with therapeutic failure, 62% had resistance to ARV with adequate ARV concentrations, 16% had insufficient drug exposure without any ARV resistance mutations, and 16% combined both resistance and suboptimal drug concentrations. Subsequent therapeutic interventions (increasing adherence and/or changing HAART) resulted in an undetectable viral load in 37.5% of the patients (14/48). Five (24%) of 21 patients with suspected drug toxicity had high drug concentrations associated with side effects. In all the cases, adverse events regressed after reduction of drug dosage. Of the 77 TDMs done for routine purposes, 26% were outside the therapeutic range.

CONCLUSION

The data show that TDM of ARVs in the clinical setting provides important information that can be used to improve the management of HIV patients receiving antiretroviral therapy.

Plasma concentrations, efficacy and safety of efavirenz in HIV-infected adults treated for tuberculosis in Cambodia (ANRS 1295-CIPRA KH001 CAMELIA trial)

OBJECTIVE

To assess efavirenz plasma concentrations and their association with treatment efficacy and tolerance of efavirenz 600 mg daily in HIV-tuberculosis co-infected patients.

METHODS

HIV-infected adults with CD4+ T cell count ≤ 200/mm(3) received standard 6-month tuberculosis treatment and antiretroviral therapy including a daily-dose of 600 mg of efavirenz, irrespective of their body weight. Mid-dose blood samples were drawn both on tuberculosis treatment (week +2 and week +6 after antiretroviral therapy initiation, and week 22 of follow-up) and off tuberculosis treatment (week 50 of follow-up). Considered therapeutic range was 1,000 to 4,000 ng/mL. Multivariate analysis was performed to evaluate the association between efavirenz concentration below 1,000 ng/mL and virological failure. Linear regression was used to test the association between efavirenz exposure and CD4+ T cell gain. Severe side effects potentially related to efavirenz were described and their association with efavirenz exposure was tested by multivariate analysis.

RESULTS

Efavirenz plasma concentrations were available in 540 patients. Median [interquartile range] efavirenz concentrations were 2,674 ng/mL [1,690-4,533], 2,667 ng/mL [1,753-4,494] and 2,799 ng/mL [1,804-4,744] at week +2, week +6, week 22, respectively, and 2,766 ng/mL [1,941-3,976] at week 50. Efavirenz concentrations were lower at week 50 (off rifampicin) compared to week 22 (on rifampicin) (p<0.001). Late attendance to study visit and low hemoglobinemia were the only factors associated with an increased risk of efavirenz concentration below 1,000 ng/mL. Efavirenz concentration below 1,000 ng/mL was not associated with treatment failure. Efavirenz concentration above 4,000 ng/mL was associated with higher risk of central nervous system side effects (p<0.001) and of hepatotoxicity (p<0.001).

CONCLUSION

Body weight and tuberculosis treatment were not associated with low efavirenz concentrations or treatment failure, supporting the 600 mg daily-dose of efavirenz in HIV-tuberculosis co-infected patients. High efavirenz concentrations were related to a higher risk of central nervous system side effects and hepatotoxicity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01300481.

Nevirapine in the treatment of HIV

Nevirapine (Viramune, Boehringer Ingelheim Ltd) is the first marketed non-nucleoside reverse transcriptase inhibitor. As with any antiretroviral drug, nevirapine should always be used as part of a fully suppressive regimen. Clinical studies have shown that nevirapine-containing regimens may accomplish durable virological and immunological responses in approximately half of all antiretroviral-naive patients. It can also be successfully used as a component of salvage therapies and as a part of a strategy to simplify protease inhibitor-containing regimens. Nevirapine has a beneficial effect on the lipid profile in both treatment-naive and -experienced patients. Nevirapine also has an important role in preventing mother-to-child transmission of HIV. It is usually well-tolerated with rash and liver toxicity being the most frequently reported adverse events. Nevirapine interacts with cytochrome P450 enzymes both as a substrate and as an inducer. For this reason, therapeutic drug monitoring should be recommended whenever nevirapine is used with protease inhibitors, methadone (Methadose, Rosemont Pharmaceuticals Ltd), oral contraceptives, rifampicin (Rifadin, Aventis Pharma) and other potentially interacting drugs. Nevirapine-resistant mutations are common to the non-nucleoside reverse transcriptase inhibitor family and they include K103N, V106A, Y181C, Y188C and G190A. A better understanding of the nevirapine profile will certainly contribute to ensuring that its clinical application becomes more effective and beneficial.

Toxicology and Carcinogenesis Studies of Mixtures of 3'-Azido-3'-Deoxythymidine (AZT), Lamivudine (3TC), and Nevirapine (NVP) (CAS Nos. 30516-87-1, 134678-17-4, 129618-40-2) in Genetically Modified C3B6.129F1-Trp53(tm1Brd) N12 Haploinsufficient Mice (in utero and postnatal gavage studies)

3'-Azido-3'-deoxythymidine (AZT) is the most widely used and evaluated chemotherapeutic agent for the treatment of persons with acquired immune deficiency syndrome (AIDS). Antiviral therapy is essential for treatment and prevention of AIDS in adults and children infected with human immunodeficiency virus (HIV), and to prevent mother-to-child transmission of HIV during pregnancy and labor. The studies described in this report were designed to determine possible long-term sequelae from AZT treatment, often used in combination with other antiviral drugs, such as lamivudine (3TC) and nevirapine (NVP) in preventing mother-to-child transmission of HIV. Male and female heterozygous F1 p53+/- mice were exposed to AZT, 3TC, NVP, or combinations of the chemicals in utero on gestation days (GD) 12 through 18, then administered the same chemical or combination of chemicals by gavage from postnatal day (PND) 1 through PND 28 and then observed until 45 weeks of age. Vehicle control mice received only an aqueous solution containing 0.2% methylcellulose and 0.1% Tween 80. Mice were dosed twice daily until PND 28. Genetic toxicology studies were conducted in mouse peripheral blood erythrocytes. The study compared three combination doses of AZT, 3TC and NVP (AZT/3TC/NVP-L, AZT/3TC/NVP-M, and AZT/3TC/NVP-H) with the vehicle controls, and compared the individual components with each other at the highest dose (AZT-H, 3TC-H, NVP-H, AZT/3TC-H and AZT/3TC/NVP-H). Because exposure to AZT/3TC/NVP-M and AZT/3TC/NVP-H reduced pup survival, additional litters were required to provide sufficient pups to load the 45-week study. 45-WEEK STUDY: In general, survival was relatively high once the pup exposure phase had been completed, with at least 75% of the mice surviving to terminal sacrifice in all groups. For males, survival was significantly greater in the AZT/3TC/NVP-L and AZT/3TC/NVP-M groups relative to the vehicle control group. There were no significant differences in survival between high dose groups of the constituent chemicals in either sex; however, survival of females in the AZT/3TC-H group was significantly less than that in the vehicle control group. Early deaths were predominantly associated with occurrences of malignant lymphoma, mammary gland tumors, and osteosarcomas. In the combination dose comparison, males and females dosed with the AZT/3TC/NVP-H combination had significantly decreased body weights compared to the vehicle control groups from PND 11 when individual monitoring began until 20 (males) or 11 (females) weeks. In addition, mean body weights for the male and female AZT/3TC/NVP-M groups were significantly less than those of the vehicle control groups until 14 weeks. In the high dose comparison, mean body weights of the male and female AZT-H groups were significantly less than those of the vehicle control groups during some of the early weeks of dosing. In male and female mice, absolute brain weights of the combination dose groups decreased with increasing dose and, except in low dose males, the absolute brain weights of the dosed groups were significantly less than those of the vehicle control groups. When the high doses of the constituent chemicals were compared, absolute brain weights of the male and female AZT-H and AZT/3TC/NVP-H groups were significantly less than those of the vehicle control groups. However, relative brain weights were not significantly altered. Relative liver weights of male combination dose groups followed a positive trend with dose. When the high dose groups were compared, increases in relative liver weights of male mice appeared to be associated with AZT exposure. In combination dose groups, the absolute heart weight of AZT/3TC/NVP-H females was significantly greater than that of the vehicle control group, and there was a positive trend in absolute heart weights. There was also a positive trend for relative heart weights in these combination dose groups, though no individual group relative weight was significantly greater than that of the vehicle control group. In females, absolute heart weight was also significantly increased in the AZT/3TC-H group relative to the vehicle control group. A small but statistically significant increase in serum alanine aminotransferase activity was observed in the male AZT/3TC/NVP-H group compared to the vehicle control group. In the combination dose comparison, the incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) in the liver of all groups of males dosed with AZT/3TC/NVP were significantly increased compared to the vehicle control group. In the high dose comparison, the incidences of hepatocellular adenoma in males in the AZT-H group and hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) in males in the AZT/3TC-H and AZT/3TC/NVP-H groups were significantly greater than those in the vehicle control group; the incidences of these lesions in the 3TC-H and NVP-H groups were significantly less than those in the AZT/3TC/NVP-H group. The incidences of malignant lymphoma in males administered AZT-H or AZT/3TC-H and in females administered AZT/3TC/NVP-M, AZT/3TC/NVP-H, NVP-H, or AZT/3TC-H were slightly greater than those in the vehicle control groups. The incidence of mammary gland adenoacanthoma or adenocarcinoma (combined) in females administered 3TC-H was slightly greater than that in the vehicle control group.

GENETIC TOXICOLOGY

In the peripheral blood of 1-day-old male and female mice, the percentage of total reticulocytes (RETs) was significantly decreased in groups exposed to doses that contained AZT. In addition, the percentages of micronucleated normochromatic erythrocytes (NCEs) and micronucleated RETs were generally significantly increased in groups exposed to doses containing AZT, but not in the 3TC-H or NVP-H groups. The percentages of micronucleated NCEs in the AZT/3TC/NVP-H groups were greater than in the AZT-H and the AZT/3TC-H groups. In peripheral blood of male pups evaluated at PND 28, both the percentage of micronucleated RETs and the percentage of micronucleated NCEs were significantly increased in the group where 3TC was coadministered with AZT compared to the group administered only AZT.

CONCLUSIONS

Under the conditions of this gavage study, there was clear evidence of carcinogenic activity of AZT alone in male heterozygous F1 p53+/- mice based on increased incidences of hepatocellular adenoma. There was clear evidence of carcinogenic activity of AZT in combination with 3TC, and AZT in combination with 3TC and NVP in male heterozygous F1 p53+/- mice based on increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). The occurrence of malignant lymphoma may have been related to treatment with AZT alone and with AZT in combination with 3TC. There was no evidence of carcinogenic activity of 3TC alone in male heterozygous F1 p53+/- mice administered 150 mg/kg. There was no evidence of carcinogenic activity of NVP alone in male heterozygous F1 p53+/- mice administered 168 mg/kg. There was equivocal evidence of carcinogenic activity of NVP alone, AZT in combination with 3TC, and AZT in combination with 3TC and NVP in female heterozygous F1 p53+/- mice based on the occurrence of malignant lymphoma. There was equivocal evidence of carcinogenic activity of 3TC alone in female heterozygous F1 p53+/- mice based on the occurrence of mammary gland adenoacanthoma or adenocarcinoma (combined). There was no evidence of carcinogenic activity of AZT alone in female heterozygous F1 p53+/- mice administered 240 mg/kg. Synonyms: (3'-AZIDO-3'-DEOXYTHYMIDINE) 3'-azido-2',3'-dideoxythymidine; azidodeoxythymidine; azidothymidine; 3'-azidothymidine; AZT; BW A509U; Compound S; 3'-deoxy-3'-azidothymidine; 3'-deoxy-(8CI) (9CI); ZDV; zidovudine. Trade name: Retrovir® [Combivir® with 3TC] Synonyms: (2',3'-DIDEOXY-3'-THIACYTIDINE) 3TC; 4-amino-1-[(2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-1,2-dihydropyrimidin-2-one; L-2',3'-dideoxy-3'-thiacytidine; lamivudine Trade name: Epivir® [Combivir® with AZT] Synonyms: (NEVIRAPINE) NVP; 11-cyclopropyl-4-methyl-5,11-dihydro-6H- dipyrido[3,2-b:2',3'-e][1,4]diazepin-6-one Trade name: Viramune®

Plasma concentrations of efavirenz and nevirapine among HIV-infected patients with immunological failure attending a tertiary hospital in North-western Tanzania

BACKGROUND

Sub-therapeutic and supra-therapeutic plasma concentrations of antriretrovirals are the significant causes of treatment failure and toxicity respectively among HIV-infected patients. We conducted this study to determine the pattern of efavirenz and nevirapine plasma drug concentrations among adult HIV-infected patients with immunological failure attending at a tertiary hospital in North-western Tanzania.

MATERIALS AND METHODS

A cross-sectional study was conducted among adult HIV-infected patients with immunological failure who have been on either efavirenz or nevirapine based antiretroviral regimen for more than 6 months. Patients were serially enrolled through routine Care and Treatment Clinic (CTC) activities. Plasma drug concentrations for efavirenz and nevirapine were determined by high performance liquid chromatography (HPLC) and Gas Chromatography (GC) respectively. Demographic, clinical and laboratory data such as viral load and CD4 counts were collected. Data analysis was done using STATA 12.

RESULTS

Of the 152 patients with immunological failure enrolled, the sub-therapeutic, therapeutic and supra-therapeutic plasma antiretroviral drug concentrations were found in 43/152 (28.3%), 76/152 (50.0%) and 33/152 (21.7%) respectively. Half of the patients were outside therapeutic window with either sub-therapeutic or supra-therapeutic plasma ARV drug concentrations. There was a significant difference in distribution of ARV adherence (p-value<0.001), NRTI backbone (p-value = 0.039), HIV stage (p-value = 0.026) and viral load (p-value = 0.007) within sub-therapeutic, therapeutic and supra-therapeutic ARV plasma drug concentrations.

CONCLUSION

There is a wide inter-individual variability of plasma ARV concentrations among HIV patients with immunological failure, with a large proportion of patients being outside therapeutic window. This variability is significant based on ARV adherence, NRTI backbone, viral load and HIV stage. Routine therapeutic drug monitoring (TDM) could assist identifying these patients early and making timely correction to avoid virological failure, poor immunological outcome and prevent associated drug toxicities. Nonetheless, ARV adherence should be strictly emphasized on HIV patients with immunological failure.

Systemic and Renal Pharmacokinetics of Adefovir and Tenofovir Upon Coadministration

Adefovir and tenofovir are nucleotide analogs that undergo renal secretion by the human renal organic anion transporter. The pharmacokinetics of tenofovir and adefovir following the administration of tenofovir disoproxil fumarate and adefovir dipivoxil alone and together were determined in 24 healthy subjects in an 8-day, open-label, fixed-sequence study. Subjects received oral doses of adefovir dipivoxil on days 1 and 8 and oral doses of tenofovir disoproxil fumarate on days 2 to 8. Pharmacokinetic sampling was performed on days 1, 7, and 8. The plasma pharmacokinetics of tenofovir and adefovir were unaltered upon coadministration. Furthermore, the renal clearances (CLrenal) of tenofovir and adefovir were unaffected by their coadministration. The plasma Cmax values of tenofovir and adefovir were 33-fold and 340-fold lower than their Km values for the human renal organic anion transporter. These results demonstrate that coadministration of tenofovir disoproxil fumarate and adefovir dipivoxil does not result in substantial changes to their individual pharmacokinetic profiles.

Drug-Drug and Drug-Food Interactions Between Tenofovir Disoproxil Fumarate and Didanosine

The drug-drug and drug-food interactions between tenofovir DF and didanosine EC were evaluated in 2 pharmacokinetic studies in healthy adult subjects. When 400 mg was dosed with tenofovir DF, mean didanosine AUC was increased by 44% to 60% following fasted or fed administration. Staggered coadministration (2 hour, fasted) of a reduced didanosine dose of 250 mg resulted in equivalent didanosine exposure, while simultaneous administration with tenofovir DF in the fasted and fed state resulted in didanosine AUCs similar to that of the reference treatment of 400 mg alone in the fasted state. These data indicate that a dose reduction of didanosine is warranted when it is used with tenofovir DF. The drug-drug-food interaction of didanosine may offer more flexible dosing of didanosine EC when it is used with tenofovir DF. Patients receiving tenofovir DF and didanosine together should be carefully monitored for safety and efficacy.

The Bioavailability of the Novel Nonnucleoside Reverse Transcriptase Inhibitor GW420867X Is Unaffected by Food in Healthy Male Volunteers

The effect of food on the bioavailability of GW420867X, a novel nonnucleoside reverse transcriptase inhibitor, was investigated in 15 young, healthy, male volunteers. A single oral dose of GW420867X 100 mg was administered in the fasted state, after a high-fat meal, and after a meal of normal fat composition. Tolerability and pharmacokinetic sampling were assessed at baseline and up to 600 hours. The median concentration-time plots for each treatment group were essentially superimposable. Neither the rate nor the extent of absorption of GW420867X was significantly affected by food. The median time to peak plasma concentration was 3 to 4 hours, irrespective of treatment. Pairwise comparisons using the fasted treatment as the comparator showed no impact of food on GW420867X pharmacokinetics. GW420867X was well tolerated. There were no serious or treatment-limiting adverse events; all episodes reported were rated as mild to moderate. The bioavailability of GW420867X was unaffected by food. GW420867X may be administered independently of food and fat intake.

Abacavir Pharmacokinetics in Human Immunodeficiency Virus-Infected Children Ranging in Age From 1 Month to 16 Years: A Population Analysis

Abacavir pharmacokinetics was studied in 105 children by a population approach performed with NONMEM. A 1-compartment open model with linear absorption and elimination adequately described the data. Typical population estimates (percent interindividual variability) of absorption rate constant, apparent distribution volume, and apparent plasma clearance were 1.79 h(-1) (58%), 42.9 L (53%), and 24.3 L/h (30%), respectively. Apparent plasma clearance was positively related to body weight. Individual Bayesian estimates of apparent plasma clearance were used to calculate individual abacavir area under the concentration curve (AUC). For the current weight-based regimen, abacavir exposure was found to be constant throughout the age range of the study, with an overall mean AUC value of 8.5 +/- 2.5 mg x h/L, which is slightly greater than the mean AUC value reported in adults. This study confirms the relevance of the current weight-based abacavir dosage regimen in pediatric patients.

A Combined-Formulation Tablet of Lamivudine/Nevirapine/Stavudine: Bioequivalence Compared With Concurrent Administration of Lamivudine, Nevirapine, and Stavudine in Healthy Indian Subjects

Generic fixed-dose combinations of antiretrovirals are frequently prescribed for the treatment of human immunodeficiency virus infection. A randomized, 2-way study was conducted in 24 fasting, healthy, Indian male subjects to assess bioequivalence between a single combination tablet containing lamivudine, stavudine, and nevirapine (treatment A) with respect to separate marketed tablets administered simultaneously (treatment B). Each subject received treatments A and B separated by 19 days of a drug-free washout period. Plasma concentrations of antiretrovirals, determined by a validated liquid chromatography/tandem mass spectrometry assay, were used to assess pharmacokinetic parameters such as maximum observed plasma concentration and area under the plasma concentration curve. Pharmacokinetic parameters were comparable for either treatment. As geometric mean ratios (% treatment A/treatment B) of log-transformed parameters of area under the plasma concentration curve and plasma concentration, as well as their resultant 90% confidence intervals, were within 80% to 125% and 75% to 133%, respectively, 2 treatments were considered bioequivalent in the extent and rate of absorption. Both treatments exhibited similar tolerability under fasting conditions.

Developmental pharmacokinetic changes of Lamivudine in infants and children

Lamivudine is a nucleoside reverse transcriptase inhibitor widely used in infants and children in combination antiretroviral therapy to treat human immunodeficiency virus (HIV) infection. Developmental changes in lamivudine pharmacokinetic disposition were assessed by combining data from 7 studies of lamivudine (Pediatric AIDS Clinical Trials Group 300, 353, 356, 358, 386, 1056, and 1069) representing subjects across the pediatric age continuum. A population pharmacokinetic model was developed to identify factors that influence lamivudine disposition. Age and Thai race were independent predictors of apparent clearance (CL/F), whereas the use of a fixed drug combination formulation (GPO-VIR) was an independent predictor of bioavailability, with CL/F more than doubling from birth to adolescence. Serum creatinine was not associated with CL/F. Monte Carlo simulations were used to compare the lamivudine exposure achieved with World Health Organization (WHO) weight band and Food and Drug Administration (FDA) label dosing recommendations. WHO dosing yielded higher exposure during the first few months of life, but this difference was less pronounced between 6 months and 14 years of age. Overall, both FDA and WHO dosing provided similar AUC values to those previously reported in HIV-infected adults. Lamivudine WHO weight band dosing results in therapeutic exposure in infants and children and may improve drug dosing in resource-limited countries.

Drug interaction profile for GSK2248761, a next generation non-nucleoside reverse transcriptase inhibitor

AIM

To evaluate potential drug interactions with antiretroviral therapies or supportive therapies for use in conjunction with the once daily, next generation non-nucleoside reverse transcriptase inhibitor GSK2248761 in patients with HIV-1 infection.

METHODS

A series of phase I drug interaction studies was conducted.

RESULTS

GSK2248761 was shown to be a weak CYP3A4 and CYP2D6 inhibitor in a clinical study with a probe cocktail. Mean plasma concentration-time profiles for atazanavir, tenofovir disoproxil fumarate/emtricitabine (TDF/FTC), darunavir (DRV, administered with ritonavir [RTV]), and drospirenone/ethinylestradiol were similar following co-administration of GSK2248761. Plasma raltegravir AUC(0,τ) and C(max) increased by 18% with no change in Cτ when raltegravir was co-administered with GSK2248761. Lopinavir (LPV) plasma AUC(0,τ), C(max) and Cτ decreased by 23%, 14% and 40%, respectively, following administration of lopinavir/ritonavir with GSK2248761. Atorvastatin, rosuvastatin and simvastatin AUC(0,∞) and C(max) increased following co-administration with GSK2248761, with the largest changes observed for simvastatin (3.7-fold and 4.3-fold). Changes in maximum and extent of GSK2248761 exposure were marginal after co-administration with atazanavir, TDF/FTC and raltegravir compared with GSK2248761 administered alone. Co-administration of GSK2248761 with DRV/RTV and LPV/RTV increased plasma GSK2248761 exposures by 1.25- to ≤2-fold compared with GSK2248761 administered alone, and increases in GSK2248761 exposure were higher following single dose co-administration of DRV/RTV or LPV/RTV compared with multiple doses. There were few drug-related AEs, and no treatment-related trends in blood chemistry, haematology, urinalysis, vital signs or ECG findings.

CONCLUSIONS

These studies indicate that GSK2248761 was safe and well tolerated in healthy adults treated in these studies at the doses and duration of therapy evaluated.

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.

Effects of ketoconazole and valproic acid on the pharmacokinetics of the next generation NNRTI, lersivirine (UK-453,061), in healthy adult subjects

AIMS

To investigate the effect of inhibitors of cytochrome P450 (CYP) 3A4 and glucuronidation (UGT2B7) on the pharmacokinetics of lersivirine (UK-453,061), a next generation non-nucleoside reverse transcriptase inhibitor with a unique resistance profile, and to investigate the safety and tolerability of co-administration of lersivirine with these inhibitors.

METHODS

Two open-label, randomized, placebo-controlled, crossover studies were conducted in healthy subjects. Study 1 investigated the effect of ketoconazole (400 mg once daily) on the pharmacokinetics of lersivirine (250 mg once daily). Subjects received ketoconazole 400 mg once daily or placebo on days 1-2 and received lersivirine 250 mg once daily and ketoconazole 400 mg once daily or placebo on days 3-9. Study 2 investigated the effect of valproic acid (VPA, sodium valproate, 1000 mg once daily) on the PK of lersivirine (500 mg once daily). On days 1-7, subjects received lersivirine 500 mg once daily plus either VPA 1000 mg or placebo.

RESULTS

Compared with lersivirine alone, co-administration with ketoconazole increased the lersivirine mean area under the curve (AUC(0,24 h)) and maximum plasma concentration (C(max) ) by 82% (90% CI 74%, 91%) and 61% (90% CI 41%, 83%), respectively. VPA increased the mean lersivirine AUC(0,24 h) by 25% (90% CI 16%, 35%), with little effect on C(max) (2.5%, 90% CI -9%, 16%). There were no serious adverse events and no treatment-related discontinuations from either study.

CONCLUSIONS

Inhibition of CYP3A4 and UGT2B7 by ketoconazole increased lersivirine exposure. Inhibition of UGT2B7-mediated glucuronidation by VPA had a modest effect on lersivirine exposure. Co-administration of lersivirine with either ketoconazole or VPA appeared to be well tolerated.

A drug evaluation of 1% tenofovir gel and tenofovir disoproxil fumarate tablets for the prevention of HIV infection

INTRODUCTION

More than a million people acquire HIV infection annually. Pre-exposure prophylaxis (PrEP) using antiretrovirals is currently being investigated for HIV prevention. Oral and topical formulations of tenofovir have undergone preclinical and clinical testing to assess acceptability, safety and effectiveness in preventing HIV infection.

AREAS COVERED

The tenofovir drug development pathway from compound discovery, preclinical animal model testing and human testing were reviewed for safety, tolerability and efficacy. Tenofovir is well tolerated and safe when used both systemically or applied topically for HIV prevention. High drug concentrations at the site of HIV transmission and concomitant low systemic drug concentrations are achieved with vaginal application. Coitally applied gel may be the favored prevention option for women compared with the tablets, which may be more suitable for prevention in men and sero-discordant couples. However, recent contradictory effectiveness outcomes in women need to be better understood.

EXPERT OPINION

Emerging evidence has brought new hope that antiretrovirals can potentially change the course of the HIV epidemic when used as early treatment for prevention, as topical or oral PrEP. Although some trial results appear conflicting, behavioral factors, adherence to dosing and pharmacokinetic properties of the different tenofovir formulations and dosing approaches offer plausible explanations for most of the variations in effectiveness observed in different trials.

Quantifying the impact of nevirapine-based prophylaxis strategies to prevent mother-to-child transmission of HIV-1: a combined pharmacokinetic, pharmacodynamic, and viral dynamic analysis to predict clinical outcomes

Single-dose nevirapine (sd-NVP) and extended NVP prophylaxis are widely used in resource-constrained settings to prevent vertical HIV-1 transmission. We assessed the pharmacokinetics of sd-NVP in 62 HIV-1-positive pregnant Ugandan woman and their newborns who were receiving sd-NVP prophylaxis to prevent mother-to-child HIV-1 transmission. Based on these data, we developed a mathematical model system to quantify the impact of different sd-NVP regimens at delivery and of extended infant NVP prophylaxis (6, 14, 21, 26, 52, 78, and 102 weeks) on the 2-year risk of HIV-1 transmission and development of drug resistance in mothers and their breast-fed infants. Pharmacokinetic parameter estimates and model-predicted HIV-1 transmission rates were very consistent with other studies. Predicted 2-year HIV-1 transmission risks were 35.8% without prophylaxis, 31.6% for newborn sd-NVP, 19.1% for maternal sd-NVP, and 19.7% for maternal/newborn sd-NVP. Maternal sd-NVP reduced newborn infection predominately by transplacental exchange, providing protective NVP concentrations to the newborn at delivery, rather than by maternal viral load reduction. Drug resistance was frequently selected in HIV-1-positive mothers after maternal sd-NVP. Extended newborn NVP prophylaxis further decreased HIV-1 transmission risks, but an overall decline in cost-effectiveness for increasing durations of newborn prophylaxis was indicated. The total number of infections with resistant virus in newborns was not increased by extended newborn NVP prophylaxis. The developed mathematical modeling framework successfully predicted the risk of HIV-1 transmission and resistance development and can be adapted to other drugs/drug combinations to a priori assess their potential in reducing vertical HIV-1 transmission and resistance spread.

A multi-compartment, single and multiple dose pharmacokinetic study of the vaginal candidate microbicide 1% tenofovir gel

Background

Tenofovir (TFV) gel is being evaluated as a microbicide with pericoital and daily regimens. To inhibit viral replication locally, an adequate concentration in the genital tract is critical.

Methods and Findings

Forty-nine participants entered a two-phase study: single-dose (SD) and multi-dose (MD), were randomized to collection of genital tract samples (endocervical cells [ECC], cervicovaginal aspirate and vaginal biopsies) at one of seven time points [0.5, 1, 2, 4, 6, 8, or 24 hr(s)] post-dose following SD exposure of 4 mL 1% TFV gel and received a single dose. Forty-seven were randomized to once (QD) or twice daily (BID) dosing for 2 weeks and to collection of genital tract samples at 4, 8 or 24 hrs after the final dose, but two discontinued prior to gel application. Blood was collected during both phases at the seven times post-dose. TFV exposure was low in blood plasma for SD and MD; median C_max was 4.0 and 3.4 ng/mL, respectively (C≤29 ng/mL). TFV concentrations were high in aspirates and tissue after SD and MD, ranging from 1.2×10⁴ to 9.9×10⁶ ng/mL and 2.1×10² to 1.4×10⁶ ng/mL, respectively, and did not noticeably differ between proximal and distal tissue. TFV diphosphate (TFV-DP), the intracellular active metabolite, was high in ECC, ranging from 7.1×10³ to 8.8×10⁶ ng/mL. TFV-DP was detectable in approximately 40% of the tissue samples, ranging from 1.8×10² to 3.5×10⁴ ng/mL. AUC for tissue TFV-DP was two logs higher after MD compared to SD, with no noticeable differences when comparing QD and BID.

Conclusions

Single-dose and multiple-dose TFV gel exposure resulted in high genital tract concentrations for at least 24 hours post-dose with minimal systemic absorption. These results support further study of TFV gel for HIV prevention.

Trial registration

ClinicalTrials.gov NCT00561496

Surface modified nevirapine nanosuspensions for viral reservoir targeting: In vitro and in vivo evaluation

Most of the time HIV virus escape immunological burden exerted by antiretroviral drugs and develops resistance against therapy. For complete eradication of virus from body one has to use long term chemotherapies, which results in drug toxicity, drug resistance and eventually poor patient compliance. Nevirapine (NNRTI, non nucleoside reverse transcriptase inhibitor) nanosuspensions were developed and surface modified with serum albumin, polysaccharide and polyethylene glycol to enhance its targeting potential. The biodistribution studies revealed improved antiretroviral drug accumulation in various organs of rat for nanosuspensions as compared to the plain drug solution when administered intravenously. Nanosuspension after surface modification showed further enhancement in accumulation. Higher MRT values of surface coated nanosuspension in brain, liver and spleen as compared to pure drug solution ensured enhanced bioavailability and prolonged residence of the drug at the target site.

Renal excretion of apricitabine in rats: ex vivo and in vivo studies

Apricitabine (ATC) is a novel nucleoside reverse transcriptase inhibitor undergoing phase 2/3 clinical development for the treatment of HIV infection. In this investigation, the renal handling of ATC was evaluated in the isolated perfused rat kidney (IPK) model with follow-up in vivo studies. IPK experiments were performed to characterize the renal excretion of ATC, to probe mechanisms of ATC excretion using known inhibitors of organic cation (cimetidine) and organic anion (probenecid) transport systems, and to screen for potential drug-drug interactions between ATC and clinically relevant medications (dapsone, metformin, pentamidine, stavudine, tenofovir and ritonavir). ATC demonstrated net tubular secretion in the IPK with a baseline excretion ratio (XR) of 2.1 ± 0.56. ATC XR decreased 3.6-fold in the presence of cimetidine and 2-fold in the presence of probenecid. Among the clinically relevant medications, metformin produced the greatest inhibitory effect on ATC excretion. In vivo studies were conducted in rats to evaluate ATC disposition upon co-administration with compounds that showed a significant effect on ATC clearance in the IPK model. Co-administration of cimetidine and trimethoprim significantly reduced ATC renal clearance, but resulted in only a moderate increase in plasma exposure. Metformin had no apparent effect on ATC clearance in rats. These findings indicate that the IPK model is more sensitive to secretory inhibition as compared to in vivo. The medications screened showed minimal effects on ATC renal excretion in the IPK, and should thus be excluded as potential in vivo interactants. Overall, this study generated important information on renal handling of ATC to support its development and commercialization.

Plasma efavirenz in HIV infected children treated with generic antiretroviral drugs in India

We measured plasma concentration of efavirenz (EFV) in 16 HIV-infected Indian children receiving antiretroviral treatment at Government ART centres. The mean 12 hour concentration was 2.39 ug/mL (range: 0.72- 7.82 ug/mL). The majority of children treated with generic EFV at currently recommended doses had blood levels within the therapeutic range.

Comparison of levels of antiretroviral drugs with efficacy in children with HIV infection

OBJECTIVE

To determine the prevalence of low and high antiretroviral (ARV) plasma levels and to analyze correlation between ARV concentrations and the appearance of therapeutic failure and toxicity.

METHODS

The authors present here a study evaluating antiretroviral plasma concentrations in HIV infected children on nonnucleoside reverse transcriptase inhibitors and protease inhibitors based therapy. The authors carried out a multicentre, cross-sectional study, including HIV-infected children from five large Hospitals in Madrid, Spain. Clinical, haematological, biochemical and immuno-virological parameters were assessed. Antiretroviral plasma trough levels were performed using a validated high performance liquid chromatography method.

RESULTS

Between April 2006 and April 2008, 129 children were enrolled in the present study, with median treatment duration of 39.2 months. 25.5% of the non-nucleoside reverse transcriptase inhibitors levels were low and 17.6%, high. 27.9% percent of the protease inhibitors levels were low and 12.5%, high. A correlation was found among adequate or high levels of antiretrovirals and normal CD4 percentage and low viral load. Lopinavir/ritonavir plasma levels were correlated with an increase in lipodystrophy. Patients with Tanner stage 1 presented the lowest ARV plasma levels. Full adherence was reported for all the participants by a questionnaire.

CONCLUSION

Many HIV-infected children show ARV plasma levels out of the therapeutic range which demands a child-adjusted approach. However, larger studies are urgently needed in pediatric populations to define optimal reference values.

[Etravirine in highly treatment-experienced patients]

Etravirine (ETR) has demonstrated efficacy in patients with multiple prior treatments with prior virological failure and resistance mutations to various families of antiretroviral drugs. Most of the evidence concerning this drug has been drawn from the DUET studies, consisting of two multicenter, randomized, double-blind clinical trials with identical designs that included 1,200 patients. These trials showed that ETR obtained a superior virological and immunological response to placebo, reducing the incidence of hospital admissions and progression to AIDS/death. The most frequent adverse effect was rash, which was generally mild to moderate and required treatment discontinuation in only 2%. There were no differences in gastrointestinal, liver or lipid toxicities compared with the placebo arm. Because of the recent development of new drugs, effective regimens are now available for multi-treated patients. The TRIO study evaluated the efficacy and tolerability of one of the regimens most widely used today (ETR/raltegravir/darunavir/r) with excellent virological and immunological response (86% of viral load < 50 copies and CD4 +108 at 48 weeks) and excellent tolerance. ETR is effective and well tolerated and is the first non-nucleoside reverse transcriptase inhibitor (NNRTI) that allows the sequential use of drugs in this family, due to its high genetic barrier compared with firstgeneration NNRTI. Moreover, its long half-life allows once daily administration in patients requiring a QD regimen.

IDX-899, an aryl phosphinate-indole non-nucleoside reverse transcriptase inhibitor for the potential treatment of HIV infection

Antiretroviral drug resistance is one of the complications of highly active antiretroviral therapy (HAART). Second-generation non-nucleoside reverse transcriptase inhibitors (NNRTIs) are being developed for use in patients infected with HIV-1 because of the enhanced activity of these inhibitors against viruses that are resistant to the first-generation NNRTIs. IDX-899 (GSK-2248761), under development by Idenix Pharmaceuticals Inc and ViiV Healthcare, is an aryl phosphinate-indole second-generation NNRTI that potently and selectively inhibits wild-type and NNRTI-resistant HIV-1 in vitro. Preclinical data for IDX-899 suggest a significantly greater barrier to resistance compared with that of the first-generation NNRTI efavirenz. Two pathways of resistance have been identified for IDX-899 in vitro that include Glu138Lys and Val90Ile/Tyr181Cys mutations. Pharmacokinetic studies demonstrated that IDX-899 exhibits linear, dose-proportional and food-dependent pharmacokinetics; Cmin concentrations achieved with this drug allow once-daily dosing. In phase I clinical trials, IDX-899 reduced HIV-1 RNA and increased CD4+ cell counts in treatment-naïve patients infected with HIV-1. At the time of publication, a phase II clinical trial of IDX-899 was being conducted.

N1-Alkyl pyrimidinediones as non-nucleoside inhibitors of HIV-1 reverse transcriptase

A series of N1-alkyl pyrimidinediones were designed, synthesized and evaluated as HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). Our efforts identified compound 10b, which represents the lead compound in this series with pharmacokinetics and antiviral potency that may support once-daily dosing.

Microdetermination of emtricitabine in human plasma by liquid chromatography/tandem mass spectrometry

A simple, precise, and rapid LC/MS/MS method was developed and validated for the quantification of emtricitabine in human plasma using lamivudine as the internal standard (IS). The method involves liquid-liquid extraction of emtricitabine and the IS in diethyl ether-ethyl acetate (50 + 50, v/v) from 0.1 mL human plasma. A Kromasil C18 (150 x 4.6 mm, 5 microm particle size) analytical column was used for the chromatographic separation under isocratic conditions. The parent --> product ion transitions for emtricitabine (m/z 248.0 --> 130.0) and the IS (m/z 230.1 --> 112.0) were monitored on a triple-quadrupole mass spectrometer, operated in the multiple reaction monitoring positive ion mode. The method was validated over the concentration range of 29.2-3110 ng/mL for emtricitabine, with a total chromatographic run time of 1.5 min. Acceptable precision and accuracy were obtained for the concentrations used to prepare the standard curves. The applicability of the method was demonstrated by a pharmacokinetic study conducted with 43 healthy volunteers who were administered a capsule formulation containing 200 mg emtricitabine.

Nonnucleoside reverse transcriptase inhibitor pharmacokinetics in a large unselected cohort of HIV-infected women

BACKGROUND

Small intensive pharmacokinetic (PK) studies of medications in early-phase trials cannot identify the range of factors that influence drug exposure in heterogenous populations. We performed PK studies in large numbers of HIV-infected women on nonnucleoside reverse transcriptase inhibitors (NNRTIs) under conditions of actual use to assess patient characteristics that influence exposure and evaluated the relationship between exposure and response.

METHODS

Two hundred twenty-five women on NNRTI-based antiretroviral regimens from the Women's Interagency HIV Study were enrolled into 12-hour or 24-hour PK studies. Extensive demographic, laboratory, and medication covariate data were collected before and during the visit to be used in multivariate models. Total NNRTI drug exposure was estimated by area under the concentration-time curves.

RESULTS

Hepatic inflammation and renal insufficiency were independently associated with increased nevirapine exposure in multivariate analysis: crack cocaine, high fat diets, and amenorrhea were associated with decreased levels (n = 106). Higher efavirenz exposure was seen with increased transaminase, albumin levels, and orange juice consumption; tenofovir use, increased weight, being African American, and amenorrhea were associated with decreased exposure (n = 119). With every 10-fold increase in nevirapine or efavirenz exposure, participants were 3.3 and 3.6 times likely to exhibit virologic suppression, respectively. Patients with higher drug exposure were also more likely to report side effects on therapy.

CONCLUSIONS

Our study identifies and quantitates previously unrecognized factors modifying NNRTI exposure in the "real-world" setting. Comprehensive PK studies in representative populations are feasible and may ultimately lead to dose optimization strategies in patients at risk for failure or adverse events.

Systematic review: Helicobacter pylori infection and impaired drug absorption

BACKGROUND

Impaired acid secretion may affect drug absorption and may be consequent to corporal Helicobacter pylori-gastritis, which may affect the absorption of orally administered drugs.

AIM

To focus on the evidence of impaired drug absorption associated with H. pylori infection.

METHODS

Data sources were the systematic search of MEDLINE/EMBASE/SCOPUS databases (1980-April 2008) for English articles using the keywords: drug malabsorption/absorption, stomach, Helicobacter pylori, gastritis, gastric acid, gastric pH, hypochlorhydria, gastric hypoacidity. Study selection was made from 2099 retrieved articles, five studies were identified. Data were extracted from selected papers, investigated drugs, study type, main features of subjects, study design, intervention type and results were extracted.

RESULTS

In all, five studies investigated impaired absorption of l-dopa, thyroxine and delavirdine in H. pylori infection. Eradication treatment led to 21-54% increase in l-dopa in Parkinson's disease. Thyroxine requirement was higher in hypochlorhydric goitre with H. pylori-gastritis and thyrotropin levels decreased by 94% after treatment. In H. pylori- and HIV-positive hypochlorhydric subjects, delavirdine absorption increased by 57% with orange juice administration and by 150% after eradication.

CONCLUSIONS

A plausible mechanism of impaired drug absorption is decreased acid secretion in H. pylori-gastritis patients. Helicobacter pylori infection and hypochlorhydria should be considered in prescribing drugs the absorption of which is potentially affected by intragastric pH.