High variability of plasma drug concentrations in dual protease inhibitor regimens

Enhancing Repair of Oxidative DNA Damage with Small-Molecule Activators of MTH1

Impaired DNA repair activity has been shown to greatly increase rates of cancer clinically. It has been hypothesized that upregulating repair activity in susceptible individuals may be a useful strategy for inhibiting tumorigenesis. Here, we report that selected tyrosine kinase (TK) inhibitors including nilotinib, employed clinically in the treatment of chronic myeloid leukemia, are activators of the repair enzyme Human MutT Homolog 1 (MTH1). MTH1 cleanses the oxidatively damaged cellular nucleotide pool by hydrolyzing the oxidized nucleotide 8-oxo-2'-deoxyguanosine (8-oxo-dG)TP, which is a highly mutagenic lesion when incorporated into DNA. Structural optimization of analogues of TK inhibitors resulted in compounds such as SU0448, which induces 1000 ± 100% activation of MTH1 at 10 μM and 410 ± 60% at 5 μM. The compounds are found to increase the activity of the endogenous enzyme, and at least one (SU0448) decreases levels of 8-oxo-dG in cellular DNA. The results suggest the possibility of using MTH1 activators to decrease the frequency of mutagenic nucleotides entering DNA, which may be a promising strategy to suppress tumorigenesis in individuals with elevated cancer risks.

Development and Validation of a New LC-MS/MS Analytical Method for Direct-Acting Antivirals and Its Application in End-Stage Renal Disease Patients

BACKGROUND AND OBJECTIVE

The effectiveness of direct-acting antivirals (DAAs) is not well established in end-stage renal disease (ESRD) patients. Assessment of the plasma concentrations may support understanding of their therapeutic outcomes in this population. The aim of this study is to develop a direct, yet matrix-effect tolerant, analytical method for determining DAAs in the plasma of ESRD patients while maintaining a moderate cost per sample and with an improved analyte extraction recovery.

METHODS

In this study, a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for the analysis of ombitasvir (OMB), paritaprevir (PRT) and ritonavir (RIT) in plasma. Sample preparation was performed using the liquid-liquid extraction (LLE) method. Isocratic separation was performed using a mixture of methanol and 10 mM ammonium acetate (79:21, v/v) followed by MS/MS detection. The method was validated and applied to determine DAAs in the plasma of ESRD patients (n = 7).

RESULTS

The developed method was linear (r²> 0.995), accurate (89.4 ± 7.8 to 108.3 ± 3.0) and precise (% CV 0.9-15.0) and showed improved recovery (> 80) over previously published ones in the range 5-250, 30-1,500, 20-1,000 ng/mL for OMB, PRT and RIT, respectively. Relative matrix effect was absent, and the method accurately determined the three DAAs in real-life samples (n = 7).

CONCLUSIONS

An efficient analytical method for the determination of DAAs is presented. The method overcomes the potential analytical response fluctuation in ESRD. The developed method show improved extraction recoveries and is suitable for routine application in developing economies where hepatitis C virus is most prevalent.

Pharmacokinetics and Drug-Drug Interactions of Lopinavir-Ritonavir Administered with First- and Second-Line Antituberculosis Drugs in HIV-Infected Children Treated for Multidrug-Resistant Tuberculosis

Lopinavir-ritonavir forms the backbone of current first-line antiretroviral regimens in young HIV-infected children. As multidrug-resistant (MDR) tuberculosis (TB) frequently occurs in young children in high-burden TB settings, it is important to identify potential interactions between MDR-TB treatment and lopinavir-ritonavir. We describe the pharmacokinetics of and potential drug-drug interactions between lopinavir-ritonavir and drugs routinely used for MDR-TB treatment in HIV-infected children. A combined population pharmacokinetic model was developed to jointly describe the pharmacokinetics of lopinavir and ritonavir in 32 HIV-infected children (16 with MDR-TB receiving treatment with combinations of high-dose isoniazid, pyrazinamide, ethambutol, ethionamide, terizidone, a fluoroquinolone, and amikacin and 16 without TB) who were established on a lopinavir-ritonavir-containing antiretroviral regimen. One-compartment models with first-order absorption and elimination for both lopinavir and ritonavir were combined into an integrated model. The dynamic inhibitory effect of the ritonavir concentration on lopinavir clearance was described using a maximum inhibition model. Even after adjustment for the effect of body weight with allometric scaling, a large variability in lopinavir and ritonavir exposure, together with strong correlations between the pharmacokinetic parameters of lopinavir and ritonavir, was detected. MDR-TB treatment did not have a significant effect on the bioavailability, clearance, or absorption rate constants of lopinavir or ritonavir. Most children (81% of children with MDR-TB, 88% of controls) achieved therapeutic lopinavir trough concentrations (>1 mg/liter). The coadministration of lopinavir-ritonavir with drugs routinely used for the treatment of MDR-TB was found to have no significant effect on the key pharmacokinetic parameters of lopinavir or ritonavir. These findings should be considered in the context of the large interpatient variability found in the present study and the study's modest sample size.

Therapeutic drug monitoring of antiretroviral drugs in HIV-infected patients

INTRODUCTION

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

Biomarkers and biometric measures of adherence to use of ARV-based vaginal rings

Introduction

Poor adherence to product use has been observed in recent trials of antiretroviral (ARV)-based oral and vaginal gel HIV prevention products, resulting in an inability to determine product efficacy. The delivery of microbicides through vaginal rings is widely perceived as a way to achieve better adherence but vaginal rings do not eliminate the adherence challenges exhibited in clinical trials. Improved objective measures of adherence are needed as new ARV-based vaginal ring products enter the clinical trial stage.

Methods

To identify technologies that have potential future application for vaginal ring adherence measurement, a comprehensive literature search was conducted that covered a number of biomedical and public health databases, including PubMed, Embase, POPLINE and the Web of Science. Published patents and patent applications were also searched. Technical experts were also consulted to gather more information and help evaluate identified technologies. Approaches were evaluated as to feasibility of development and clinical trial implementation, cost and technical strength.

Results

Numerous approaches were identified through our landscape analysis and classified as either point measures or cumulative measures of vaginal ring adherence. Point measurements are those that give a measure of adherence at a particular point in time. Cumulative measures attempt to measure ring adherence over a period of time.

Discussion

Approaches that require modifications to an existing ring product are at a significant disadvantage, as this will likely introduce additional regulatory barriers to the development process and increase manufacturing costs. From the point of view of clinical trial implementation, desirable attributes would be high acceptance by trial participants, and little or no additional time or training requirements on the part of participants or clinic staff. We have identified four promising approaches as being high priority for further development based on the following measurements: intracellular drug levels, drug levels in hair, the accumulation of a vaginal analyte that diffuses into the ring, and the depletion of an intrinsic ring constituent.

Conclusions

While some approaches show significant promise over others, it is recommended that a strategy of using complementary biometric and behavioural approaches be adopted to best understand participants’ adherence to ARV-based ring products in clinical trials.

Population-Based Assessments of Clinical Drug-Drug Interactions: Qualitative Indices or Quantitative Measures?

Population-based assessments of drug-drug interactions have become more common since the introduction and acceptance of the population pharmacokinetic approach. Unlike traditional methods, population-based studies provide clinically relevant results that can be applied directly to a target patient population. Furthermore, population-based studies do not demand the traditional requirements of intensive pharmacokinetic sampling, rigorous inpatient stays, or stringent assessment schedules. As such, the population-based approach can effectively be used to confirm known drug-drug interactions and further characterize anticipated interactions. A prospectively designed analysis can also reveal drug-drug interactions that might otherwise have gone undetected with traditional methods. Ultimately, these results could help to alleviate clinicians' concerns about using widely marketed drugs in combination therapies and also reduce patients' risk of experiencing unacceptable side effects. This article intends to provide a balanced overview of the population-based approach and its merits, drawbacks, and potential utility in the assessment of drug-drug interactions during clinical drug development.

Effects of cytochrome P450 3A (CYP3A) and the drug transporters P-glycoprotein (MDR1/ABCB1) and MRP2 (ABCC2) on the pharmacokinetics of lopinavir

BACKGROUND AND PURPOSE

Lopinavir is extensively metabolized by cytochrome P450 3A (CYP3A) and is considered to be a substrate for the drug transporters ABCB1 (P-glycoprotein) and ABCC2 (MRP2). Here, we have assessed the individual and combined effects of CYP3A, ABCB1 and ABCC2 on the pharmacokinetics of lopinavir and the relative importance of intestinal and hepatic metabolism. We also evaluated whether ritonavir increases lopinavir oral bioavailability by inhibition of CYP3A, ABCB1 and/or ABCC2.

EXPERIMENTAL APPROACH

Lopinavir transport was measured in Madin-Darby canine kidney cells expressing ABCB1 or ABCC2. Oral lopinavir kinetics (+/- ritonavir) was studied in mice with genetic deletions of Cyp3a, Abcb1a/b and/or Abcc2, or in transgenic mice expressing human CYP3A4 exclusively in the liver and/or intestine.

KEY RESULTS

Lopinavir was transported by ABCB1 but not by ABCC2 in vitro. Lopinavir area under the plasma concentration - time curve (AUC)(oral) was increased in Abcb1a/b(-/-) mice (approximately ninefold vs. wild-type) but not in Abcc2(-/-) mice. Increased lopinavir AUC(oral) (>2000-fold) was observed in cytochrome P450 3A knockout (Cyp3a(-/-)) mice compared with wild-type mice. No difference in AUC(oral) between Cyp3a(-/-) and Cyp3a/Abcb1a/b/Abcc2(-/-) mice was observed. CYP3A4 activity in intestine or liver, separately, reduced lopinavir AUC(oral) (>100-fold), compared with Cyp3a(-/-) mice. Ritonavir markedly increased lopinavir AUC(oral) in all CYP3A-containing mouse strains.

CONCLUSIONS AND IMPLICATIONS

CYP3A was the major determinant of lopinavir pharmacokinetics, far more than Abcb1a/b. Both intestinal and hepatic CYP3A activity contributed importantly to low oral bioavailability of lopinavir. Ritonavir increased lopinavir bioavailability primarily by inhibiting CYP3A. Effects of Abcb1a/b were only detectable in the presence of CYP3A, suggesting saturation of Abcb1a/b in the absence of CYP3A activity.

Clinical evaluation of a dried blood spot assay for atazanavir

Current procedures for obtaining and measuring plasma concentrations of HIV protease inhibitors (PIs) are technically challenging. Dried blood spot (DBS) assays offer a way to overcome many of the obstacles. We sought to develop a DBS assay for quantitation of the PI atazanavir (ATV) and to compare this method with a previously validated plasma assay. We prospectively enrolled 48 patients with well-controlled HIV disease who had been on ATV for at least 7 days. ATV was quantified from plasma by use of high-performance liquid chromatography (HPLC). A reversed-phase ultrahigh-performance liquid chromatography (UPLC) assay was utilized for DBS samples. The concentrations of ATV quantified in a DBS matrix showed very strong agreement with those measured in plasma (r(2) = 0.988). The mean difference in ATV concentration between the two methods was -10.8% (95% confidence interval [95% CI], -7.65% to -13.95%), indicating that the DBS method has a slight negative bias. A majority (97.8%) of the differences in concentration between the two assays fell within ±2 standard deviations. ATV concentrations were lower in subjects who had detectable HIV RNA in plasma (mean, 543 ng/ml) than in those with HIV RNA of <50 copies/ml (mean, 1,582 ng/ml) (P = 0.03, Wilcoxon rank-sum test). In conclusion, our study demonstrated that ATV quantitation in a DBS matrix is feasible and accurate. DBS use offers a convenient alternative for measuring plasma concentrations of ATV and may have utility in monitoring of drug concentrations in clinical practice and in future studies.

Lopinavir impairs protein synthesis and induces eEF2 phosphorylation via the activation of AMP-activated protein kinase

HIV anti-retroviral drugs decrease protein synthesis, although the underlying regulatory mechanisms of this process are not fully established. Therefore, we investigated the effects of the HIV protease inhibitor lopinavir (LPV) on protein metabolism. We also characterized the mechanisms that mediate the effects of this drug on elongation factor-2 (eEF2), a key component of the translational machinery. Treatment of C2C12 myocytes with LPV produced a dose-dependent inhibitory effect on protein synthesis. This effect was observed at 15 min and was maintained for at least 4 h. Mechanistically, LPV increased the phosphorylation of eEF2 and thereby decreased the activity of this protein. Increased phosphorylation of eEF2 was associated with increased activity of its upstream regulators AMP-activated protein kinase (AMPK) and eEF2 kinase (eEF2K). Both AMPK and eEF2K directly phosphorylated eEF2 in an in vitro kinase assay suggesting two distinct paths lead to eEF2 phosphorylation. To verify this connection, myocytes were treated with the AMPK inhibitor compound C. Compound C blocked eEF2K and eEF2 phosphorylation, demonstrating that LPV affects eEF2 activity via an AMPK-eEF2K dependent pathway. In contrast, incubation of myocytes with rottlerin suppressed eEF2K, but not eEF2 phosphorylation, suggesting that eEF2 can be regulated independent of eEF2K. Finally, LPV did not affect PP2A activity when either eEF2 or peptide was used as the substrate. Collectively, these results indicate that LPV decreases protein synthesis, at least in part, via inhibition of eEF2. This appears regulated by AMPK which can act directly on eEF2 or indirectly via the action of eEF2K.

Clinical and pharmacokinetic data support once-daily low-dose boosted saquinavir (1,200 milligrams saquinavir with 100 milligrams ritonavir) in treatment-naive or limited protease inhibitor-experienced human immunodeficiency virus-infected patients

We evaluated the plasma and intracellular pharmacokinetics, clinical efficacy, and safety of once-daily low-dose boosted saquinavir (SQVr; 1,200 of saquinavir [SQV] with 100 mg of ritonavir) plus two nucleotide reverse transcriptase inhibitors in treatment-naive or limited protease inhibitor (PI)-experienced human immunodeficiency virus (HIV)-infected patients. A prospective study without entry restrictions on the plasma HIV-RNA (VL) or CD4 cell count was carried out. Plasma and intracellular SQV levels were measured by high-performance liquid chromatography. Efficacy was evaluated by an intention-to-treat analysis; treatment failure was defined as virological failure (a VL of >50 copies/ml after 24 weeks or a confirmed rebound to >50 copies/ml) or interruption for any reason. A total of 151 patients were included in the study (106 of them either had never received PI or had no previous virological failure on PIs) and could be characterized as follows: previous C3 stage, 28.9%; injection-drug users, 69.1%; subjects with chronic viral hepatitis, 53%; and subjects with cirrhosis, 10%. The median baseline CD4 level was 184/mul, and the median VL was 4.8 log(10) copies/ml. Median C(max), area under the concentration-time curve from 0 to 24 h, and C(min) plasma and intracellular SQV levels were 3,672 and 10,105 ng/ml, 34,283 and 99,535 ng.h/ml, and 359 and 1,062 ng/ml, respectively. The efficacy as determined by intention to treat at 52 weeks was 69.7% (96% in the on-treatment analysis), with similar results regardless of the baseline VL and CD4 counts. Only five patients had virological failure despite adequate C(min) levels, but with a poor adherence (the only variable related to virological failure). Adverse events caused the withdrawal of the treatment in four patients (2.6%). In conclusion, given the pharmacokinetic profile, efficacy, and tolerability of this regimen, once-daily low-dose SQVr may be considered a treatment option in treatment-naive or limited PI-experienced HIV-infected patients, with the additional benefit of being currently the least-expensive PI-based regimen available.

The use of drug resistance algorithms and genotypic inhibitory quotient in prediction of lopinavir–ritonavir treatment response in human immunodeficiency virus type 1 protease inhibitor-experienced patients

BACKGROUND

Different approaches using genotypic, pharmacokinetic parameters or combination of both have been recently developed to monitor antiretroviral treatment in HIV-1-infected individuals. Their uses in clinical practice may improve the benefit of protease inhibitor-based salvage therapy while reducing treatment toxicity and emergence of viral resistance.

OBJECTIVES

To assess the prediction of genotypic inhibitory quotient (GIQ) using different genotypic drug resistance interpretation's algorithms and lopinavir plasma concentration in PI-experienced patients treated by lopinavir/ritonavir (LPV/r). Genotypic susceptibility score (GSS) was also evaluated.

STUDY DESIGN

Forty-seven HIV-1 PI-experienced, but LPV naïve patients were included in a retrospective cohort study. Plasma HIV-1 viral load (VL), CD4 cell count and LPV plasma concentrations were assessed at weeks (W) 12 and 24. Interpretation of baseline resistance genotype was achieved according to four different algorithms and GSS calculated using two expert systems. GIQ was defined as the ratio of LPV concentration to the number of LPV resistance mutations at day 0 (D0) and patients classified by units of GIQ. The end point of the study was the virological response expressed in HIV VL median decrease from D0 to W24.

RESULTS

The overall median VL decrease from D0 to W24 was -2.42 log(10)copies/mL and 60% of patients had VL below 400 copies/mL. The LPV mutation score was predictive of response for all algorithms whereas plasma concentrations of LPV were not. Mean VL decrease was greater for higher GIQ classes and difference reached statistical significance at W24. When considering virological response at W24, GSS calculated with ANRS and Stanford system were good predictor scores as areas under the receiver operating characteristics (ROC) curves were 0.76 for both.

CONCLUSION

GIQ was found to be a useful drug-monitoring tool which could be helpful in targeting LPV concentrations in order to achieve long-term undetectable viral load, particularly in genotypic resistant patients.

Variability in non-nucleoside reverse transcriptase and protease inhibitors concentrations among HIV-infected adults in routine clinical practice

AIMS

The objective of this study was to assess interindividual variability in plasma trough concentrations of non-nucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI) among HIV-infected adults in an outpatient routine clinical practice setting.

METHODS

The study included 117 patients who attended our clinic for routine outpatient blood tests and who were receiving antiretroviral therapy which included NNRTI or PI. Patients were not informed that drug concentrations were going to be assessed until blood sampling. The time of the last antiretroviral treatment intake and blood sampling were recorded. Drug concentrations were considered optimal if they were above the proposed minimum effective concentration. In addition, efavirenz, nevirapine and atazanavir concentrations were considered potentially toxic if they were higher than 4.0 mg l(-1), 6.0 mg l(-1), and 0.85 mg l(-1), respectively.

RESULTS

Overall, interindividual variability in NNRTI and PI plasma concentrations was approximately 50%, and only 68.4% of the patients had drug concentrations within the proposed therapeutic range. Inappropriate adherence only explained 35% of subtherapeutic drug concentrations.

CONCLUSION

Interindividual variability in trough concentrations of NNRTI and PI among HIV-infected adults is large in routine clinical practice, with drug concentrations being outside the therapeutic window in a significant proportion of patients. Therapeutic drug monitoring may be useful to guide antiretroviral therapy in clinical practice.

High variability of indinavir and nelfinavir pharmacokinetics in HIV-infected patients with a sustained virological response on highly active antiretroviral therapy

OBJECTIVES

To describe plasma concentrations of indinavir alone or combined with ritonavir, and of nelfinavir and its active metabolite M8, and to measure their variabilities in HIV-infected patients treated with a stable antiretroviral regimen and experiencing a sustained virological response for at least 12 months.

PATIENTS AND METHODS

In this prospective trial, blood samples were drawn during a 6-hour time interval between two doses at enrolment to assess protease inhibitor (PI) pharmacokinetic parameters, and 4 months later to assess plasma trough and peak concentrations. Safety and adherence assessments and laboratory data were collected during an 8-month period. PI pharmacokinetic characteristics were analysed using a non-compartmental approach. Inter- and intrapatient variabilities were estimated using a linear mixed-effect model. The impact of different covariates on plasma trough concentrations was investigated. Eighty-eight patients were analysed: 42 treated with indinavir and 46 with nelfinavir.

RESULTS

The interquartile range (IQR) of the plasma trough concentration corrected for the sampling time (Ccalc) was 116-374 microg/L for indinavir alone and 163-508 microg/L for indinavir/ritonavir. Ritonavir significantly increased indinavir elimination half-life and plasma exposure. For nelfinavir, the IQR of Ccalc was 896-2059 microg/L for three-times-daily administration and 998-2124 microg/L for twice-daily administration. Variabilities were high for both PIs. Intrapatient variability for indinavir alone (and indinavir + ritonavir) was 76% (107%) and interpatient variability was 58% (10%) in adherent patients. Intrapatient variability for nelfinavir three times daily (and twice daily) was 41% (74%) and interpatient variability was 62% (50%). Intrapatient variability was lowered in patients with a high adherence level.

CONCLUSION

Although performed in a homogeneous population, this study documented a high interpatient but also intrapatient variability of indinavir and nelfinavir pharmacokinetics, which should be taken into account when interpreting therapeutic drug monitoring. Once patients have reached a sustained virological response, plasma PI monitoring may have a limited impact.

Safety and antiviral response at 12 months of lopinavir/ritonavir therapy in human immunodeficiency virus-1-infected children experienced with three classes of antiretrovirals

INTRODUCTION

Many human immunodeficiency virus type 1 (HIV-1)-infected children have already failed treatment with 2 or even 3 classes of antiretrovirals. Coformulation of lopinavir with low dose ritonavir exhibits a potent antiretroviral effect. However, the data in heavily pretreated children are still scarce. This study evaluated the safety and effectiveness of combination therapy including lopinavir/ritonavir in children with prior exposure to all classes of oral antiretrovirals.

METHODS

This was an open label multicenter observational study, in which data were reviewed according to a standardized protocol. The study population included all HIV-1-infected children with virologic failure (HIV-1 RNA >5000 copies/mL) followed in 12 Spanish hospitals for >12 months, experienced with the 3 classes of oral antiretrovirals, in whom a lopinavir/ritonavir-containing regimen was started.

RESULTS

By March 2003, 45 patients had been treated with lopinavir/ritonavir for a median of 18 months (range, 3-28). The median age at baseline was 9.7 years (range, 4.3-17.1). The median times of prior treatment were 88 months (range, 31-145) with nucleoside reverse transcription inhibitors and 42 months (range, 19-63) with protease inhibitors. Twenty-five patients were classified as Centers for Disease Control and Prevention clinical category C. Median values for absolute and percentage CD4 at baseline were 501 (range, 6-1512) and 19% (range, 0.5-49), respectively, and plasma HIV-RNA was 5.0 log10 copies/mL (range, 4.1-6.1). During follow-up, 11 (24%) children switched from liquid to solid formulation. At 48 weeks, the median values for absolute and percentage CD4 increased by 199 cells/microL and 3%, respectively, and median plasma viral load declined 1.75 log10 copies/mL. Forty-two percent of children achieved a plasma RNA of <400 copies/mL (intent to treat analysis). Baseline genotypic resistance was available in 40 children. Nonresponders had 7.0 +/- 1.6 protease inhibitor-associated mutations at baseline compared with 4.8 +/- 1.7 in children achieving virologic suppression (P = 0.06). Adverse events were described in 18 children. Three children permanently discontinued and 4 transiently withdrew lopinavir/ritonavir. At 12 months, there were mild but not significant increases in plasma cholesterol and triglycerides.

CONCLUSIONS

Lopinavir/ritonavir when given as part of salvage regimen is well-tolerated, although switching to pills is frequently required. The regimen has a potent and durable antiretroviral activity in most heavily pretreated children, despite the presence of multiple mutations to all classes of oral antiretrovirals.

Steady-state pharmacokinetics of atazanavir given alone or in combination with saquinavir hard-gel capsules or amprenavir in HIV-1-infected patients

OBJECTIVE

The aim of this pilot study was to examine the pharmacokinetics of atazanavir (ATV) when given in combination with amprenavir (APV) or saquinavir hard-gel capsules (SQV) to human immunodeficiency virus (HIV)-positive patients.

METHODS

Included in the study were 34 HIV-infected patients enrolled in the ATV Early Access Program, who were treated with unboosted ATV alone (group 1) or with the double protease inhibitor combinations, ATV plus APV (group 2) or ATV plus SQV (group 3). ATV was given at a daily dose of 400 mg q.d. with the morning meal with SQV 1200 mg per day or APV 1200 mg per day. Serial blood samples for steady-state ATV pharmacokinetics were collected before the morning dose and at 1, 2, 3, 6, 8 and 24 h post-dosing. ATV plasma concentrations were measured using a high-performance liquid chromatography method with ultraviolet detection.

RESULTS

Of the patients, 12 received ATV as a single protease inhibitor; 12 received ATV in combination with APV; and 10 in combination with SQV. Geometric mean (coefficient of variation) ATV C(trough) was 110 ng/ml (2.38), 86 ng/ml (0.84) and 149 ng/ml (2.01) in groups 1, 2 and 3, respectively. ATV C(trough) in both double protease inhibitor combination regimens was not significantly different from that as a single protease inhibitor [geometric mean ratio (GMR): 0.77; 95% confidence interval (CI): 0.38-1.58, P=not significant for group 2 versus group 1 and 1.34, 0.40-4.49, P=not significant, for group 3 versus group 1). Patients treated with ATV plus APV had a 40.2% lower ATV C(max) and a 30.8% smaller ATV AUC than the reference group treated with unboosted ATV alone: both these differences were statistically significant (GMR, 95% CI: 0.59, 0.41-0.85, P=0.005 and 0.69, 0.48-0.99, P=0.056, respectively). No difference was observed for either C(max) or AUC between the group treated with ATV plus SQV and the reference group (GMR, 95% CI: 0.78, 0.47-1.30, P=not significant and 1.24, 0.73-2.10, P=not significant, respectively).

CONCLUSION

ATV pharmacokinetics does not seem to be influenced by the concomitant administration of SQV, whereas APV significantly lowers plasma ATV levels.

Development and validation of a population pharmacokinetic model for ritonavir used as a booster or as an antiviral agent in HIV-1-infected patients

AIMS

The aim of this study was to develop and validate a population pharmacokinetic model of ritonavir, used as an antiviral agent or as a booster, in a large patient population and to identify factors influencing its pharmacokinetics.

METHODS

Ambulatory HIV-1-infected patients from the outpatient clinic of the Slotervaart Hospital, Amsterdam, the Netherlands, who were being treated with a ritonavir-containing regimen were included. During regular visits, blood samples were collected for the determination of ritonavir plasma concentrations and several clinical chemistry parameters. Furthermore, complete pharmacokinetic curves were available in some patients. Single and multiple compartment models with zero-order and first-order absorption, with and without absorption lag-time, with linear and nonlinear elimination were tested, using nonlinear mixed effect modelling (NONMEM). Pharmacokinetic parameters and interindividual, interoccasion and residual variability were estimated. In addition, the influence of several factors (e.g. patient characteristics, comedication) on the pharmacokinetics of ritonavir was explored.

RESULTS

From 186 patients 505 ritonavir plasma concentrations at a single time-point and 55 full pharmacokinetic profiles were available, resulting in a database of 1228 plasma ritonavir concentrations. In total 62% of the patients used ritonavir as a booster of their protease inhibitor containing antiretroviral regimen. First order absorption in combination with one-compartment disposition best described the pharmacokinetics of ritonavir. Clearance, volume of distribution and absorption rate constant were 10.5 l h(-1) (95% prediction interval (95% PI) 9.38-11.7), 96.6 l (95% PI 67.2-121) and 0.871 h(-1) (95% PI 0.429-1.47), respectively, with 38.3%, 80.0% and 169% interindividual variability, respectively. The interoccasion variability in the apparent bioavailability was 59.1%. The concomitant use of lopinavir resulted in a 2.7-fold increase in the clearance of ritonavir (P value < 0.001). No patients characteristics influenced the pharmacokinetics of ritonavir.

CONCLUSIONS

The pharmacokinetic parameters of ritonavir were adequately described by our population pharmacokinetic model. Concomitant use of the protease inhibitor lopinavir strongly influenced the pharmacokinetics of ritonavir. The model has been validated and can be used for further investigation of the interaction between ritonavir and other protease inhibitors.

A randomized controlled trial to evaluate antiretroviral salvage therapy guided by rules-based or phenotype-driven HIV-1 genotypic drug-resistance interpretation with or without concentration-controlled intervention: the Resistance and Dosage Adapted Regimens (RADAR) study

BACKGROUND

It is not well defined whether concentration-controlled intervention (CCI) and rules-based human immunodeficiency virus (HIV) type 1 genotype drug-resistance interpretation (GI) or virtual phenotype drug-resistance interpretation (VPI) may improve the outcome of HIV salvage therapy.

METHODS

In a prospective, randomized, controlled trial, patients were randomized (on a factorial basis) to change treatment after either GI or VPI, and they then were further randomized to the control arm (no CCI) or the CCI arm. Protease inhibitor (PI) and nonnucleoside reverse-transcriptase inhibitor (NNRTI) trough concentration (Ctrough) values were determined at weeks 1, 4, 12, and 24 of the study.

RESULTS

Among 230 patients, virological benefit (defined by an HIV RNA load of <400 copies/mL at week 24) was not statistically different, either between patients in the GI and VPI arms or between patients in the CCI and control arms. A virological benefit was found for patients in the CCI arm, compared with patients in the control arm, but this benefit was not statistically significant (56.8% vs. 64.3% at week 4 and 63.6% vs. 74% at week 12). Dosage adaptation was possible for only a fraction of patients, because of low rates of treatment adherence or patient refusal to increase dosages. In the logistic regression analysis, independent predictors of virological response at week 24 were a PI Ctrough value and/or an NNRTI Ctrough value in the higher quartiles (or above cutoff levels) and a low number of PIs previously received. Moreover, receipt of a regimen that contained PIs boosted with ritonavir was an independent predictor of virological response.

CONCLUSIONS

The present study did not support the routine use of CCI for patients undergoing salvage treatment, probably as a result of existing difficulties associated with its clinical application. However, a higher Ctrough value appeared to be correlated with treatment response. No major differences were found between VPI or GI when they are used together with expert advice for the selection of salvage treatment combinations.

Increased Dose of Lopinavir/Ritonavir Compensates for Efavirenz-Induced Drug-Drug Interaction in HIV-1-Infected Children

BACKGROUND

Nucleoside reverse transcriptase inhibitor-sparing regimens have not yet been systematically evaluated in children. The nonnucleoside reverse transcriptase inhibitors nevirapine and efavirenz lower plasma levels of protease inhibitors in adults and children. Therefore, coadministration of lopinavir/ritonavir with nevirapine and efavirenz necessitates a 30% increase in the dose of lopinavir/ritonavir in adults. In children, the extent of the pharmacokinetic interaction between efavirenz and lopinavir/ritonavir has not yet been studied.

OBJECTIVE

To investigate the pharmacokinetics of increased-dose (300/75 mg/m2 twice-daily) lopinavir/ritonavir with normal-dose (14 mg/kg once-daily) efavirenz in HIV-1-infected children.

METHODS

Steady-state pharmacokinetics of lopinavir and efavirenz were determined and compared with historical data.

RESULTS

Fifteen children of median age 11.8 (range, 5.7-16.3) years were included. Area under the plasma concentration-time curve (AUC0-12), peak levels (Cmax), and trough levels (Cmin) of lopinavir were similar to historical data in adults and children. Medians (interquartile range) were 92.3 (43.5-138.5) mg/L.h, 12.5 (6.9-16.7) mg/L, and 5.7 (1.3-8.0) mg/L, respectively. Efavirenz pharmacokinetics approximated previous data in adults and children.

CONCLUSION

The increased dose of 300/75 mg/m2 twice-daily lopinavir/ritonavir compensates for the enzyme-inducing effect of efavirenz in HIV-infected children.

Simple and Simultaneous Determination of the HIV-Protease Inhibitors Amprenavir, Atazanavir, Indinavir, Lopinavir, Nelfinavir, Ritonavir and Saquinavir Plus M8 Nelfinavir Metabolite and the Nonnucleoside Reverse Transcriptase Inhibitors Efavirenz and Nevirapine in Human Plasma by Reversed-Phase Liquid Chromatography

Several studies suggest that therapeutic drug monitoring of protease inhibitors and nonnucleoside reverse transcriptase inhibitors may contribute to the clinical outcome of HIV-infected patients. Because of the growing number of antiretroviral drugs and of drug combinations than can be administered to these patients, an accurate high-performance liquid chromatographic (HPLC) method allowing the simultaneous determination of these drugs may be useful. To date, the authors present the first simultaneous HPLC determination of the new protease inhibitor atazanavir with all the others currently in use (M8 nelfinavir metabolite included) and the 2 widely used nonnucleoside reverse transcriptase inhibitors efavirenz and nevirapine. This simple HPLC method allows the analysis all these drugs at a single ultraviolet wavelength following a 1-step liquid-liquid extraction procedure. A 500-muL plasma sample was spiked with internal standard and subjected to liquid-liquid extraction using by diethyl ether at pH 10. HPLC was performed using a Symmetry Shield RP18 and gradient elution. All the drugs of interest and internal standard were detected with ultraviolet detection at 210 nm. Calibration curves were linear in the range 50-10,000 ng/mL. The observed concentrations of the quality controls at plasma concentrations ranging from 50 to 5000 ng/mL for these drugs showed that the overall accuracy varied from 92% to 104% and 92% to 106% for intraday and day-to-day analysis, respectively. No metabolites of the assayed compounds or other drugs commonly coadministered to HIV-positive patients were found to coelute with the drugs of interest or with the internal standard. This assay was developed for the purpose of therapeutic monitoring (TDM) in HIV-infected patients.

GENOPHAR: a randomized study of plasma drug measurements in association with genotypic resistance testing and expert advice to optimize therapy in patients failing antiretroviral therapy

OBJECTIVES

To evaluate the benefits of therapeutic drug monitoring (TDM) in association with genotypic resistance testing and expert advice to optimize therapy in multiexperienced patients infected with HIV-1.

METHODS

Patients with a viral load>1000 HIV-1 RNA copies/mL and an unchanged antiretroviral therapy regimen over the last 3 months were randomized into two groups: a genotypic group (G) and a geno-pharmacological group (GP). Treatment was selected by an expert committee according to genotypic resistance testing (the G and GP groups) and TDM (the GP group) at week 4. Treatment could be modified at each visit according to toxicity, poor virological response and TDM. Results of TDM were withheld from the G group until week 12. The primary endpoint of the study was the percentage of patients with viral load<200 copies/mL at week 12.

RESULTS

A total of 134 patients were randomized in the study, with 67 in each group, and included in the intent-to-treat (ITT) analysis. At baseline, median values were as follows: viral load (log(10) copies/mL): G=4.1, GP=4.0; CD4 cell count (cells/microL): G=292, GP=294; and number of prior drugs: G=7, GP=8. The median number of resistance mutations was five in the G group [nucleoside reverse transcriptase inhibitors (NRTIs)=three; non-nucleoside reverse transcriptase inhibitors (NNRTIs)=one; protease inhibitors (PI)=one] and seven in the GP group (NRTI=four; NNRTI=two; PI=one). At week 8, treatment was adjusted according to the TDM in 13 of the 67 patients in the GP group (19%). By ITT missing equal failure analysis at week 12, and after only one intervention according to plasma concentration results, a viral load<200 copies/mL was achieved in 30 of the 67 patients (45%) in the G group and in 29 of the 67 patients (43%) in the GP group (not significant). In the multivariate analysis, only prior exposure to at least two PIs at baseline gave a poor response to subsequent antiretroviral therapy. At week 24, a viral load<200 copies/mL was achieved in 35 of the 67 patients (52%) in the G group and in 40 of the 67 patients (60%) in the GP group.

CONCLUSIONS

A statistically significant benefit of using TDM was not found in this short-term study where patients appeared to be adherent. However, combining genotypic resistance testing with the use of an expert committee to monitor subsequent therapy individually in patients with multiple resistance mutations was associated with high antiviral efficacy.

Steady-State Pharmacokinetics of Saquinavir Hard-Gel/Ritonavir/Fosamprenavir in HIV-1???Infected Patients

BACKGROUND

In vitro synergy and complementary resistance profiles provide a strong rationale for combining fosamprenavir with saquinavir as part of a potent double-boosted protease inhibitor regimen. This study evaluated the steady-state pharmacokinetics of saquinavir 1000 mg twice daily (bid) and fosamprenavir 700 mg bid administered with 2 different doses of ritonavir (100 and 200 mg bid) in HIV-1-infected subjects.

METHODS

On day 1, 12-hour pharmacokinetic profiles for saquinavir/ritonavir (1000/100 mg bid) were obtained for 18 subjects. All subjects were receiving ongoing treatment with a saquinavir/ritonavir-containing regimen. Fosamprenavir 700 mg bid was then added to the regimen, and pharmacokinetic sampling was repeated for all 3 agents at day 11. The ritonavir daily dose was then increased to 200 mg bid, and a 3rd pharmacokinetic profile was obtained at day 22.

RESULTS

The coadministration of fosamprenavir 700 mg bid with saquinavir/ritonavir 1000/100 mg bid resulted in a statistically nonsignificant decrease in saquinavir concentrations (by 14, 9, and 24%, for saquinavir area under the concentration-time curve [AUC]0-12, C(max), and C(trough), respectively). This was compensated for by an increased ritonavir dose of 200 mg bid, which resulted in a statistically nonsignificant increase in saquinavir exposure compared with baseline. Amprenavir levels did not appear to be significantly influenced by coadministration of saquinavir with fosamprenavir. Fosamprenavir significantly reduced ritonavir exposure, but the increased ritonavir dose compensated for this interaction.

CONCLUSIONS

Our findings showed that saquinavir/ritonavir/fosamprenavir was well tolerated over the study period. Saquinavir plasma concentrations were slightly lowered by the addition of fosamprenavir to the regimen. However, the addition of a further 100 mg ritonavir bid restored the small and insignificant decrease.

The Plasma and Intracellular Steady-State Pharmacokinetics of Lopinavir/Ritonavir in HIV-1-Infected Patients

Therapeutic drug monitoring of protease inhibitors (PIs) is usually performed on plasma samples although their antiretroviral effect takes place inside cells. Little is known, however, about the intracellular accumulation and related plasma pharmacokinetics of PIs such as lopinavir/ritonavir (LPV/RTV). Therefore, we studied the plasma and intracellular (cell-associated) steady-state pharmacokinetics of this PI combination in a dosage of 400/100 mg twice daily in a non-randomized cohort of HIV-1-infected individuals. Plasma (0–12 h) and peripheral blood mononuclear cell (PBMC; 0–8 h) samples were drawn during a 12-h dosing interval in 11 subjects.

The plasma concentrations versus time curves of LPV and RTV were characterized by an irregular absorption phase showing double-peaks (Cmax) in most subjects and single-peaks in the remaining patients between 1 and 3 h after drug intake. Pre-dose concentrations of both agents in plasma were significantly higher than the concentrations at the end of the dosing interval indicating the presence of a circadian rhythm in their pharmacokinetics. The course of the intracellular concentrations versus time curves appeared to be similar to the plasma concentration curves, with the highest intracellular concentration measured 3 h after drug intake. The intracellular RTV concentrations were higher than reported in vitro EC50 values and might therefore contribute to the antiretroviral effect of LPV/RTV. The median intracellular-to-plasma concentration ratios (interquartile range) were 1.18 (0.74–2.06) and 4.59 (3.20–7.70) for LPV and RTV, respectively.

In conclusion, both LPV and RTV accumulate to potential therapeutic concentrations in PBMCs. Irregular absorption and circadian plasma clearance patterns were observed for the PI combination LPV/RTV.

Long-term suppression of plasma viremia with highly active antiretroviral therapy despite virus evolution and very limited selection of drug-resistant genotypes

HIV-1 evolution and the possible emergence of mutations associated with resistance to antiretroviral inhibitors have been evaluated in a cohort of sixty-three patients successfully treated with highly active antiretroviral therapy (HAART). The patients under effective HAART were recruited in three different hospitals in Spain, and none of them had been treated (naïve) before entering this study. HIV-1 RNA levels, CD4+, and CD8+ T-cell counts were determined, and nucleotide sequences of proviral regions encoding protease and reverse transcriptase (RT) were obtained for longitudinal blood samples spanning a mean follow-up period of 88 weeks. Phylogenetic reconstructions and calculations of genetic distances among the different sequences of each patient were performed. All except one of the patients under study showed an early and sustained decrease in plasma HIV-1 RNA to levels that were below 200 copies/ml. The plasma viral decline paralleled a significant increase in the CD4+ T-lymphocyte counts. Amino acid sequence analyses revealed the occurrence of mutations associated with antiretroviral resistance in nine patients (14.3%) during HAART treatment, that in some cases could be attributed to excess G to A transitions. In six of the nine patients, the mutations conferred resistance to inhibitors administered in the treatment regime, although the mutations did not result in treatment failure. Sequence comparisons revealed viral evolution during the period of treatment in 47.5% of the patients. The results indicate successful suppression of HIV-1 under HAART for extended time periods, indistinguishable for patients in which evidence of virus evolution could or could not be documented.

Pharmacodynamics and clinical use of anti-HIV drugs

Antiretroviral drug exposure has been linked to both antiviral efficacy and the development of toxicity and further research in this area is ongoing and necessary. Use of these data may have important implications for TDM of HAART regimens in clinical practice. TDM, in conjunction with an assessment of the patient's viral resistance in the form of an IQ, needs to be examined and validated in large clinical trials.