PharmAdapt: a randomized prospective study to evaluate the benefit of therapeutic monitoring of protease inhibitors: 12 week results

Approaches to Objectively Measure Antiretroviral Medication Adherence and Drive Adherence Interventions

PURPOSE OF REVIEW

Traditional methods to assess antiretroviral adherence, such as self-report, pill counts, and pharmacy refill data, may be inaccurate in determining actual pill-taking to both antiretroviral therapy (ART) or pre-exposure prophylaxis (PrEP). HIV viral loads serve as surrogates of adherence on ART, but loss of virologic control may occur well after decreases in adherence and viral loads are not relevant to PrEP.

RECENT FINDINGS

Pharmacologic measures of adherence, electronic adherence monitors, and ingestible electronic pills all serve as more objective metrics of adherence, surpassing self-report in predicting outcomes. Pharmacologic metrics can identify either recent adherence or cumulative adherence. Recent dosing measures include antiretroviral levels in plasma or urine, as well as emtricitabine-triphosphate in dried blood spots (DBS) for those on tenofovir-emtricitabine-based therapy. A urine tenofovir test has recently been developed into a point-of-care test for bedside adherence monitoring. Cumulative adherence metrics assess adherence over weeks to months and include measurement of tenofovir-diphosphate in peripheral blood mononuclear cells or DBS, as well as ART levels in hair. Electronic adherence monitors and ingestible electronic pills can track pill bottle openings or medication ingestion, respectively. New and objective approaches in adherence monitoring can be used to detect nonadherence prior to loss of prevention efficacy or virologic control with PrEP or ART, respectively.

Urine Assay to Measure Tenofovir Concentrations in Patients Taking Tenofovir Alafenamide

Background: HIV pre-exposure prophylaxis (PrEP) with tenofovir/emtricitabine is effective when taken daily. Previously, we developed a urine assay capable of detecting the prodrug tenofovir (TFV) in patients taking tenofovir disoproxil fumarate (TDF)-based PrEP. However, tenofovir alafenamide (TAF) has replaced TDF due to its different safety profile for HIV treatment and was recently approved as PrEP. Given the need to ensure the aforementioned assay remains available for the purpose of objective adherence monitoring, it is critical to ensure its accuracy for detecting TFV in patients taking TAF. Methods: Blood and urine samples were collected from 3 cohorts of patients: (1) 10 participants living with HIV (PLWH) with suppressed virus on a TAF-based regimen, (2) 10 HIV-participants administered 1 dose of TAF/FTC followed by urine and plasma sampling for 7 days starting 1-3 h post-dose, and (3) 10 HIV-participants administered 7 doses of TAF/FTC followed by urine and plasma sampling for 10 days starting 1-3 h after the last dose. Samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with high sensitivity and specificity for TFV. HIV-samples were compared to a historical cohort administered one dose of TDF/FTC. Results: PLWH were 90% male, 40% African American, and 10% Hispanic (mean age = 57 y; SD 8.88 y). HIV-participants were 55% male and 70% Caucasian (mean age = 31.6 y; SD 7.70 y). Samples from PLWH demonstrated TFV concentrations 2 logs higher in urine than plasma (1,000 ng/mL vs ±10 ng/mL) at the time of collection. Urine samples following a single dose of TAF in HIV-participants yielded TFV concentrations ranging from 100 to 1,000 ng/mL 1-3 h post-dose and remained >100 ng/mL for 6 days in 8 of 10 participants. Urine samples collected after 7 consecutive doses of TAF yielded TFV concentrations >1,000 ng/mL 1-3 h after dosing discontinuation, with TFV concentrations >1,00 ng/mL 7 days post discontinuation in 8 of 10 participants. Urine TFV concentrations following TAF administration were comparable to those from a historical cohort administered TDF/FTC. Plasma TFV concentrations were low(±10 ng/mL) in both HIV-cohorts at all time points. Conclusions: TFV persists in urine at detectable concentrations in participants taking TAF/FTC for at least 7 days despite largely undetectable plasma concentrations, with urine TFV concentrations comparable to patients taking TDF/FTC. This study demonstrates the ability of a urine TFV assay to measure recent TAF adherence.

Antiretroviral resistance testing in HIV-positive people

BACKGROUND

Resistance to antiretroviral therapy (ART) among people living with human immunodeficiency virus (HIV) compromises treatment effectiveness, often leading to virological failure and mortality. Antiretroviral drug resistance tests may be used at the time of initiation of therapy, or when treatment failure occurs, to inform the choice of ART regimen. Resistance tests (genotypic or phenotypic) are widely used in high-income countries, but not in resource-limited settings. This systematic review summarizes the relative merits of resistance testing in treatment-naive and treatment-exposed people living with HIV.

OBJECTIVES

To evaluate the effectiveness of antiretroviral resistance testing (genotypic or phenotypic) in reducing mortality and morbidity in HIV-positive people.

SEARCH METHODS

We attempted to identify all relevant studies, regardless of language or publication status, through searches of electronic databases and conference proceedings up to 26 January 2018. We searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), in the Cochrane Library, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and ClinicalTrials.gov to 26 January 2018. We searched Latin American and Caribbean Health Sciences Literature (LILACS) and the Web of Science for publications from 1996 to 26 January 2018.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs) and observational studies that compared resistance testing to no resistance testing in people with HIV irrespective of their exposure to ART.Primary outcomes of interest were mortality and virological failure. Secondary outcomes were change in mean CD4-T-lymphocyte count, clinical progression to AIDS, development of a second or new opportunistic infection, change in viral load, and quality of life.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed each reference for prespecified inclusion criteria. Two review authors then independently extracted data from each included study using a standardized data extraction form. We analysed data on an intention-to-treat basis using a random-effects model. We performed subgroup analyses for the type of resistance test used (phenotypic or genotypic), use of expert advice to interpret resistance tests, and age (children and adolescents versus adults). We followed standard Cochrane methodological procedures.

MAIN RESULTS

Eleven RCTs (published between 1999 and 2006), which included 2531 participants, met our inclusion criteria. All of these trials exclusively enrolled patients who had previous exposure to ART. We found no observational studies. Length of follow-up time, study settings, and types of resistance testing varied greatly. Follow-up ranged from 12 to 150 weeks. All studies were conducted in Europe, USA, or South America. Seven studies used genotypic testing, two used phenotypic testing, and two used both phenotypic and genotypic testing. Only one study was funded by a manufacturer of resistance tests.Resistance testing made little or no difference in mortality (odds ratio (OR) 0.89, 95% confidence interval (CI) 0.36 to 2.22; 5 trials, 1140 participants; moderate-certainty evidence), and may have slightly reduced the number of people with virological failure (OR 0.70, 95% CI 0.56 to 0.87; 10 trials, 1728 participants; low-certainty evidence); and probably made little or no difference in change in CD4 cell count (mean difference (MD) -1.00 cells/mm³, 95% CI -12.49 to 10.50; 7 trials, 1349 participants; moderate-certainty evidence) or progression to AIDS (OR 0.64, 95% CI 0.31 to 1.29; 3 trials, 809 participants; moderate-certainty evidence). Resistance testing made little or no difference in adverse events (OR 0.89, 95% CI 0.51 to 1.55; 4 trials, 808 participants; low-certainty evidence) and probably reduced viral load (MD -0.23, 95% CI -0.35 to -0.11; 10 trials, 1837 participants; moderate-certainty evidence). No studies reported on development of new opportunistic infections or quality of life. We found no statistically significant heterogeneity for any outcomes, and the I² statistic value ranged from 0 to 25%. We found no subgroup effects for types of resistance testing (genotypic versus phenotypic), the addition of expert advice to interpretation of resistance tests, or age. Results for mortality were consistent when we compared studies at high or unclear risk of bias versus studies at low risk of bias.

AUTHORS' CONCLUSIONS

Resistance testing probably improved virological outcomes in people who have had virological failure in trials conducted 12 or more years ago. We found no evidence in treatment-naive people. Resistance testing did not demonstrate important patient benefits in terms of risk of death or progression to AIDS. The trials included very few participants from low- and middle-income countries.

Development and validation of an assay to analyze atazanavir in human hair via liquid chromatography/tandem mass spectrometry

RATIONALE

Assays to quantify antiretrovirals in hair samples are increasingly used to monitor adherence and exposure in both HIV prevention and treatment studies. Atazanavir (ATV) is a protease inhibitor used in combination antiretroviral therapy (ART). We developed and validated a liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based method to quantify ATV in human hair, per the NIH Division of AIDS Clinical Pharmacology Quality Assurance (CPQA) program and the FDA bioanalytical method validation guidelines.

METHODS

ATV was extracted from hair using optimized methods and the extracts were injected onto a BDS C-18 column (5 μm, 4.6 × 100 mm), followed by isocratic elution via a mobile phase composed of 55% acetonitrile, 45% water, 0.15% acetic acid, and 4 mM ammonium acetate, at a flow rate of 0.8 mL/min prior to analysis by MS/MS. Levels were quantified using positive electrospray ionization by multiple reaction monitoring (MRM) for the transitions MH⁺ m/z 705.3 to m/z 168.0 and MH⁺ m/z 710.2 to m/z 168.0 for ATV and ATV-d5 (internal standard), respectively.

RESULTS

Our assay demonstrated a linear standard curve (r = 0.99) over the concentration range of 0.0500 ng ATV/mg hair to 20.0 ng/mg hair. The inter- and intraday accuracy of ATV quality control (QC) samples was -1.33 to 4.00% and precision (% coefficient of variation (%CV)) was 1.75 to 6.31%. The %CV for ATV levels in hair samples from highly adherent patients (incurred samples) was less than 10%. No significant endogenous peaks or crosstalk were observed in the specificity test with other HIV drugs. The overall extraction efficiency of ATV from incurred hair samples was greater than 95%.

CONCLUSIONS

This highly sensitive, highly specific and validated assay can be considered for therapeutic drug monitoring for HIV-infected patients on ATV-based ART.

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.

A single untimed plasma drug concentration measurement during low-level HIV viremia predicts virologic failure

Suboptimal untimed plasma drug levels (UDL) have been associated with lower rates of virologic suppression and the emergence of drug resistance. Our aim was to evaluate whether UDL among patients with low-level viremia (LLV) while receiving highly active antiretroviral therapy (HAART) can predict subsequent virologic failure (plasma viral load ≥1000 copies/mL) and emergence of resistance. The first documented LLV episode of 328 consenting patients was analysed in terms of drug levels, viral load and resistance, which were monitored while patients were on a consistent HAART regimen. UDL of protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), were categorized as 'therapeutic' or 'subtherapeutic' based on predefined target trough concentrations. Drug resistance genotype was assessed using the Stanford algorithm. Time to virologic failure was evaluated by Kaplan-Meier analysis and Cox proportional hazards regression. We found 78 of 328 patients (24%) with subtherapeutic drug levels at time of first detectable LLV, while 19% harboured drug-resistant virus. Both subtherapeutic UDL and drug resistance independently increased the risk of subsequent virologic failure (p <0.001 and p 0.04, respectively). In a multivariable model, variables associated with LLV and virologic failure included subtherapeutic UDL, elevated plasma viral load, and drug resistance. Patients with subtherapeutic UDL accumulated further drug resistance faster during follow-up (p 0.03). Together, resistance and UDL variables can explain a higher proportion of virologic failure than either measure alone. Our results support further prospective evaluation of UDL in the management of low-level viremia.

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.

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.

Strong relationship between oral dose and tenofovir hair levels in a randomized trial: hair as a potential adherence measure for pre-exposure prophylaxis (PrEP)

BACKGROUND

Pre-exposure prophylaxis (PrEP) trials using tenofovir-based regimens have demonstrated that high levels of adherence are required to evaluate efficacy; the incorporation of objective biomarkers of adherence in trial design has been essential to interpretation, given the inaccuracy of self-report. Antiretroviral measurements in scalp hair have been useful as a marker of long-term exposure in the HIV treatment setting, and hair samples are relatively easy and inexpensive to collect, transport, and store for analysis. To evaluate the relationship between dose and tenofovir concentrations in hair, we examined the dose proportionality of tenofovir in hair in healthy, HIV-uninfected adults.

METHODS

A phase I, crossover pharmacokinetic study was performed in 24 HIV-negative adults receiving directly-observed oral tenofovir tablets administered 2, 4, and 7 doses/week for 6 weeks, with a ≥3-week break between periods. Small samples of hair were collected after each six-week period and analyzed for tenofovir concentrations. Geometric-mean-ratios compared levels between each pair of dosing conditions. Intensive plasma pharmacokinetic studies were performed during the daily-dosing period to calculate areas-under-the-time-concentration curves (AUCs).

RESULTS

Over 90% of doses were observed per protocol. Median tenofovir concentrations in hair increased monotonically with dose. A log-linear relationship was seen between dose and hair levels, with an estimated 76% (95% CI 60-93%) increase in hair level per 2-fold dose increase. Tenofovir plasma AUCs modestly predicted drug concentrations in hair.

CONCLUSIONS

This study found a strong linear relationship between frequency of dosing and tenofovir levels in scalp hair. The analysis of quantitative drug levels in hair has the potential to improve adherence measurement in the PrEP field and may be helpful in determining exposure thresholds for protection and explaining failures in PrEP trials. Hair measures for adherence monitoring may also facilitate adherence measurement in real-world settings and merit further investigation in upcoming PrEP implementation studies and programs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00903084.

Short communication: A low-cost method for analyzing nevirapine levels in hair as a marker of adherence in resource-limited settings

The measurement of antiretroviral concentrations in hair is emerging as an important technology to objectively quantify adherence to combination antiretroviral therapy. Hair levels of antiretrovirals are the strongest independent predictor of virologic success in large prospective cohorts of HIV-infected patients and surpass self-report in predicting outcomes. Hair is easy to collect and store, but validated methods to analyze antiretroviral levels in hair using liquid chromatography tandem mass spectrometry (LC-MS/MS) are expensive. We report here on the development of a thin-layer chromatography (TLC) assay for the semiquantitative analysis of nevirapine in hair. TLC assay results from 11 samples were consistent with results using LC-MS/MS [Spearman correlation coefficient 0.99 (95% CI 0.95-0.996)]. This simple, low-cost method of analyzing nevirapine concentrations in hair may provide a novel monitoring tool for antiretroviral adherence in resource-limited settings and merits further study in clinical settings.

Population pharmacokinetics of lopinavir/ritonavir (Kaletra) in HIV-infected patients

BACKGROUND

A relationship between plasma concentrations and viral suppression in patients receiving lopinavir (LPV)/ritonavir (RTV) has been observed. Therefore, it is important to increase our knowledge about factors that determine interpatient variability in LPV pharmacokinetics (PK).

METHODS

The study, designed to develop and validate population PK models for LPV and RTV, involved 263 ambulatory patients treated with 400/100 mg of LPV/RTV twice daily. A database of 1110 concentrations of LPV and RTV (647 from a single time-point and 463 from 73 full PK profiles) was available. Concentrations were determined at steady state using high-performance liquid chromatography with ultraviolet detection. PK analysis was performed with NONMEM software. Age, gender, height, total body weight, body mass index, RTV trough concentration (RTC), hepatitis C virus coinfection, total bilirubin, hospital of origin, formulation and concomitant administration of efavirenz (EFV), saquinavir (SQV), atazanavir (ATV), and tenofovir were analyzed as possible covariates influencing LPV/RTV kinetic behavior.

RESULTS

Population models were developed with 954 drug plasma concentrations from 201 patients, and the validation was conducted in the remaining 62 patients (156 concentrations). A 1-compartment model with first-order absorption (including lag-time) and elimination best described the PK. Proportional error models for interindividual and residual variability were used. The final models for the drugs oral clearance (CL/F) were as follows: CL/F(LPV)(L/h)=0.216·BMI·0.81(RTC)·1.25(EFV)·0.84(ATV); CL/F(RTV)(L/h) = 8.00·1.34(SQV)·1.77(EFV)·1.35(ATV). The predictive performance of the final population PK models was tested using standardized mean prediction errors, showing values of 0.03 ± 0.74 and 0.05 ± 0.91 for LPV and RTV, and normalized prediction distribution error, confirming the suitability of both models.

CONCLUSIONS

These validated models could be implemented in clinical PK software and applied to dose individualization using a Bayesian approach for both drugs.

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

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

Therapeutic drug monitoring of protease inhibitors and efavirenz in HIV-infected individuals with active substance-related disorders

BACKGROUND

Achieving targeted antiretroviral (ARV) plasma concentrations during long-term treatment in human immunodeficiency virus (HIV)-infected patients with substance-related disorders (SRDs) may be challenging due to a number of factors, including medication adherence, coinfection with hepatitis B or C virus, medication intolerance, and drug interactions. One approach to investigate these factors is to conduct therapeutic drug monitoring to measure ARV exposure during treatment. The objective of this study was to utilize therapeutic drug monitoring to compare efavirenz (EFV) and protease inhibitor pharmacokinetics in patients with and without SRDs.

METHODS

This was a multicenter, cross-sectional open-label study in patients with HIV-1 infection receiving antiretroviral therapy (ART), with active (n=129) or without (n=146) SRD according to National Institute on Drug Abuse criteria. Two hundred seventy-five subjects who were receiving either protease inhibitor-based or EFV-based ART regimens for >6 months were enrolled at 4 HIV treatment centers with an equal distribution of SRD and non-SRD at each site. The patients were instructed during enrollment visits with regard to the importance of adherence before and after study visits. Demographics and routine clinical laboratory tests were recorded.

RESULTS

Among the 275 patients, 47% had SRD with at least 1 substance. There were no significant differences between SRD and non-SRD groups for race, gender, age, or CD4 count at entry. A significantly higher proportion of patients with SRD had an entry HIV RNA plasma concentration>75 copies per milliliter compared with patients without SRD (40% vs 28%, P=0.044). Logistic regression modeling revealed an association between HIV RNA plasma concentration and African American race (P=0.017). A significantly higher proportion of SRDs also had an EFV or protease inhibitor trough concentration below the desired range (23% vs 9%, P=0.048). Significantly lower trough concentrations were noted in patients with SRDs receiving atazanavir (0.290 vs 0.976 μg/mL) or lopinavir (3.75 vs 5.30 μg/mL).

CONCLUSIONS

The pharmacokinetic data indicate differences between HIV-infected patients with and without SRDs that may influence viral load suppression during long-term ART. These findings require additional investigation in a randomized design with more intensive pharmacokinetic assessment to identify individual factors that are contributing to suboptimal ARV exposure in patients with SRDs.

Microanalysis of the antiretroviral nevirapine in human hair from HIV-infected patients by liquid chromatography-tandem mass spectrometry

Sufficient drug exposure is crucial for maintaining durable responses to HIV treatments. However, monitoring drug exposure using single blood samples only provides short-term information and is highly subject to intra-individual pharmacokinetic variation. Drugs can accumulate in hair over a long period of time, so hair drug levels can provide drug exposure information over prolonged periods. We now report on a specific, sensitive, and reproducible liquid chromatography-tandem mass spectrometry method for measuring nevirapine (NVP), a widely used antiretroviral drug, levels in human hair using even a single short strand of hair. Hair samples are cut into small segments, and the drug is extracted in methanol/trifluoroacetic acid (v/v, 9:1) shaken at 37 °C in a water bath overnight, followed by liquid-liquid extraction under alkaline conditions. The extracted samples are then separated on a BDS-C(18) column with a mobile phase composed of 50% acetonitrile containing 0.15% acetic acid and 4 mM ammonium acetate with an isocratic elution for a total run time of 3 min and detected by triple quadrupole electrospray multiple reaction mode at precursor/product ion at 267.0 > 225.9 m/z. Deuterated nevirapine-d5 was used as an internal standard. This method was validated from 0.25 to 100 ng/mg using 2 mg hair samples. The accuracies for spiked NVP hair control samples were 98-106% with coefficients of variation (CV) less than 10%. The CV for incurred hair control samples was less than 7%. The extraction efficiency for incurred control hair samples was estimated at more than 95% by repeated extractions. This method has been successfully applied to analyze more than 1,000 hair samples from participants in a large ongoing cohort study of HIV-infected participants. We also showed that NVP in human hair can easily be detected in a single short strand of hair. This method will allow us to identify drug non-adherence using even a single strand of hair.

Minimum effective plasma concentration of efavirenz in treatment-naïve Chinese HIV-infected patients

To assess the relationship between mean efavirenz (EFV) plasma concentration and clinical effect during the first 48 weeks of combination antiretroviral therapy (cART), the baseline CD4 cell count was recorded and plasma EFV concentration and CD4 cell count were measured every 12 weeks. HIV-RNA viral load was determined in the 48th week of cART. In total, 42 subjects were recruited and grouped according to their mean concentration of EFV during the study period: groups A, B and C with EFV concentrations (mean) <2 mg/L (1.8 mg/L), 2-4 mg/L (2.9 mg/L) and >4 mg/L (5.5 mg/L), respectively. The CD4 cell counts in group C increased more quickly than in groups B and A, although this was not statistically significant (211 ± 176/μL versus 151 ± 145/μL and 172 ± 105/μL, respectively; P = 0.799). Groups B and C had higher rates of HIV viral load suppression than group A (P = 0.017). For treatment-naïve Chinese HIV-infected patients, EFV plasma concentrations above 2 mg/L appear to suppress HIV replication more effectively than concentrations below 2 mg/L.

Therapeutic drug monitoring in highly active antiretroviral therapy

IMPORTANCE OF THE FIELD

Despite the efficacy of combination antiretroviral therapy (ART), a large proportion of patients living with HIV/AIDS on ART does not achieve or maintain adequate virological suppression. Therapeutic drug monitoring (TDM) has been utilised to improve treatment outcomes of ART.

AREAS COVERED IN THE REVIEW

The potential incorporation of TDM into the clinical HIV management is supported by the existing relationship between drug exposure and efficacy/toxicity, the high inter-patient variability pharmacokinetics, and the accurate, specific and rapid method for drug level determination. The current status of TDM in ART is reviewed in this article with discussions on its feasibility, potential use and limitations.

WHAT THE READER WILL GAIN

Mounting evidence from clinical trials has indicated the potential use of TDM in reducing the rates of treatment failure and adverse effect, avoiding the drug interactions, and special populations, such as children, pregnant women and patients with co-infections. TDM may play an important role even in resource-limited settings, to safeguard expanded use of bioequivalent generic antiretroviral drugs and avoid drug interactions with traditional Chinese medicines.

TAKE HOME MESSAGE

TDM is still in the centre of controversy in that several critical issues need to be addressed, such as limited adherence assessment, inappropriate response predictors, insufficient validation of target concentration windows and lack of the quality control of assay. The utility of TDM will remain experimental until more data are obtained from large clinical trials showing the benefit of TDM.

Immune activation mediated change in alpha-1-acid glycoprotein: impact on total and free lopinavir plasma exposure

BACKGROUND

Immune mediated changes in circulating α-1-acid glycoprotein (AAG), a type 1 acute phase protein, which binds protease inhibitors (PI), may alter protein binding and contribute to PI's pharmacokinetic (PK) variability.

METHODS

In a prospective, 2-phase intensive PK study on antiretroviral naive human immunodeficiency virus (HIV)-infected subjects treated with a lopinavir-/ritonavir-based regimen, steady state PK sampling and AAG assays were performed at weeks 2 and 16 of treatment.

RESULTS

Median entry age was 43 years (n = 16). Median plasma log(10) HIV-1 RNA, CD4 T-cell counts, and AAG were 5.16 copies/mL, 28 cells/µL, and 143 mg/dL, respectively.The total lopinavir area under the concentration time curve (AUC(12_total)) and maximum concentration (C(max_total)) changed linearly with AAG at mean rates of 16±7 mg*hr/L (slope ± SE); P = .04, and 1.6 ± 0.6 mg/L, P = .02, per 100 mg/dL increase in AAG levels, respectively (n = 15).A 29% drop in AAG levels between week 2 and week 16 was associated with 14% (geometric mean ratio [GMR] = 0.86; 90% confidence interval [CI] = 0.74-0.98) and 13% (GMR = 0.87; 90% CI = 0.79-0.95) reduction in AUC(12_total) and C(max_total), respectively. Neither free lopinavir PK parameters nor antiviral activity (HIV-1 RNA average AUC minus baseline) was affected by change in plasma AAG.

CONCLUSIONS

Changes in plasma AAG levels alter total lopinavir concentrations, but not the free lopinavir exposure or antiviral activity. This observation may have implications in therapeutic drug monitoring.

Quality assessment for therapeutic drug monitoring in AIDS Clinical Trials Group (ACTG 5146): a multicenter clinical trial

In a randomized trial, AIDS Clinical Trials Group (ACTG) protocol 5146 (A5146) investigated the use of therapeutic drug monitoring (TDM) to adjust doses of HIV-1 protease inhibitors (PIs) in patients with prior virologic failure on PI-based therapy who were starting a new PI-based regimen. The overall percentage of "PI trough repeats" such as rescheduled visits or redrawn PI trough specimens increased from 2% to 5% to 10% as the process progressed from the clinical sites, the pharmacology specialty laboratory, and the study team, respectively. Cumulatively, this represents a 17% rate of failure to obtain adequate PI trough sample. While targeting a turnaround of 7 days or less from sample receipt to a drug concentration report, 12% of the received specimens required a longer period to report concentrations. The implementation of dosing changes in the TDM arm were achieved within 7 days or less for 56% of the dose change events and within 14 days or less for 77% of dose change events. This quality assurance analysis provides a valuable summary of the specific points in the TDM process that could be improved during a multicenter clinical trial including: 1) shortening the timeline of sample shipment from clinical site to the laboratory; 2) performing the collection of PI trough specimen within the targeted sampling window by careful monitoring of the last dose times and collection times by the clinicians; 3) increasing patient adherence counseling to reduce the number of samples that are redrawn due to suspecting inconsistent adherence; and 4) decreasing the time to successful TDM-based dose adjustment. The application of some of these findings may also be relevant to single-center studies or clinical TDM programs within a hospital.

Kinetics and determining factors of the virologic response to antiretrovirals during pregnancy

HIV-infected pregnant women with undetectable plasma HIV RNA concentrations at delivery pose a minimal risk of vertical transmission. We studied the kinetics and the determinants of the virologic response to antiretroviral therapy in 117 consecutive pregnancies. Patients who initiated therapy during pregnancy had a VL decrease of 2 and 2.5 log₁₀ after 4 and 24 weeks, respectively. Therapeutic drug monitoring (TDM) of the protease inhibitors administered in doses recommended for nonpregnant adults resulted in below-target concentrations in 29%, 35%, and 44% of 1st, 2nd, and 3rd trimester measurements, respectively, but low drug concentrations did not correlate with virologic failure. Demographic characteristics, antiretroviral experience prior to pregnancy, baseline VL, or use of specific antiretrovirals did not affect the virologic response. Adherence to ≥95% of prescribed doses and utilization of psychosocial services were associated with undetectable plasma HIV RNA at delivery. In conclusion, the virologic responses of pregnant and nonpregnant adults share similar charactersitics.

Inhibitory quotient in HIV pharmacology

PURPOSE OF REVIEW

This review discusses the use of the inhibitory quotient in light of therapeutic drug monitoring of antiretroviral drugs. The inhibitory quotient is a parameter that combines viral resistance data with drug exposure data, and has its main role in therapeutic drug monitoring of protease inhibitors in experienced patients. Data from recent clinical studies investigating inhibitory quotient cutoffs to be used in therapeutic drug monitoring will be reviewed. In addition points for discussion regarding the use and study of inhibitory quotients will be presented.

RECENT FINDINGS

A number of studies generated data on the use of the inhibitory quotient in general and the genotypic inhibitory quotient in particular. Most of these studies define a cutoff inhibitory quotient value, above which the virological response rate is higher. These cutoff values can be used in therapeutic drug monitoring and give guidance to the clinician on dose adjustments. Genotypic inhibitory quotient cutoff values are available for amprenavir, atazanavir, darunavir, lopinavir, saquinavir and tipranavir.

SUMMARY

The inhibitory quotient is becoming a valuable tool in therapeutic drug monitoring. At this moment most data are available for the genotypic inhibitory quotient. Nevertheless, a consensus needs to be reached on a number of items, including the methods to study inhibitory quotient as well as the mathematical and virological background.

Benefit of therapeutic drug monitoring of protease inhibitors in HIV-infected patients depends on PI used in HAART regimen--ANRS 111 trial

As a result of high inter-patient variability, and efficacy-concentration and toxicity-concentration relationships, optimization of HIV-protease inhibitor (PI) doses based on plasma concentrations could be beneficial. During a 48-week open prospective non-randomized interventional study of 115 protease inhibitor-naïve patients initiating an indinavir/ritonavir- or lopinavir/ritonavir-, or nelfinavir-containing therapy, protease inhibitor dose was modified when plasma trough concentrations (C(trough)) at weeks 2, 8, 16 and 24 were outside predefined optimal concentration ranges. Failure of the strategy was defined as the proportions of patients with HIV-RNA above 200 copies/mL from weeks 24 to 48 and/or experiencing grades 2, 3 or 4 PI-related adverse events during the study; proportion of patients with last C(trough) measurement outside the concentration range was determined at each visit. Virological failure and/or occurrence of adverse event were observed in 37/94 assessable patients (39%; 95% CI: 29.4-50.0). In the on-treatment analysis, failure of the strategy was noted in 16% of indinavir/r- or lopinavir/r-treated patients (8/51; 95% CI: 7.0-28.6; virological failure: 2; adverse event: 6) but in 44% of nelfinavir-treated patients (11/25; 95% CI: 24.4-65.1; virological failure: 10; adverse event: 1); C(trough) concentrations outside the range were less frequent at the last measurement than at W2 (41% vs. 66%; P < 0.05), with proportions of 35% for indinavir/r- or lopinavir/r-treated patients, but 57% for nelfinavir-treated patients. The proposed strategy of therapeutic drug monitoring may be beneficial to indinavir/r- and lopinavir/r-treated patients, but failed to move concentrations into the predefined range and to produce the expected virological success for nelfinavir-treated patients.

Therapeutic drug monitoring of antiretrovirals for people with HIV

BACKGROUND

Despite the efficacy of combination antiretroviral therapy (ART) and the improvement in prognosis of those living with HIV/AIDS, a large proportion of individuals on ART does not achieve or maintain adequate virological suppression. Several tools have been proposed to enhance ART outcomes, including therapeutic drug monitoring (TDM) of antiretrovirals (ARVs). The aim of ARV TDM is to identify elevated (potentially toxic) or low (potentially sub-therapeutic) ARV concentrations. ARV TDM may thus optimise efficacy and minimise toxicity of ART.

OBJECTIVES

To evaluate whether ARV TDM reduces mortality and morbidity of adult patients on ART. The primary outcome measures that have been assessed include death (all cause); occurrence of HIV-related events (death or AIDS-defining illness) and the proportion of patients achieving and maintaining an undetectable viral load, as defined by the authors.

SEARCH STRATEGY

We conducted a comprehensive search including both published and unpublished studies in all languages in MEDLINE, EMBASE and The Cochrane Library, between January 1980 and January 2008. Databases listing conference abstracts and reference lists of articles were searched. Additional data were sought from relevant authors; however, no additional data were provided.

SELECTION CRITERIA

Only randomized controlled trials conducted subsequent to the introduction of combination ART were included in this systematic review. Participants could be on either a protease inhibitor (PI)-based regimen or non-nucleoside reverse transcriptase (NNRTI)-based regimen and be either ARV-naive or -experienced.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed and extracted data for analysis. Meta-analysis was conducted where appropriate. Where study outcomes could not be combined, a narrative review was performed. Outcome measures for dichotomous data were reported as a relative risk with 95% confidence intervals. Stratified analyses were conducted by ARV regimen and treatment groups. Heterogeneity between studies was anticipated; therefore, random effects models were chosen to generate pooled effects. Differences in the findings were assessed by the chi square test for heterogeneity (p <0.1) that was quantified by the Higgins I(2) statistic.

MAIN RESULTS

Identified were 1408 records, and eight trials with a total of 1181 participants were included in the review. Trials were conducted in higher income earning countries between 2002 and 2007. Sample sizes ranged between 40 and 230. The methodological quality of the studies was judged to be generally good, although allocation concealment was reported in only three of the eight studies. A meta-analysis including three studies did not show any significant effect on virological suppression below 500 HIV-RNA copies/mL at one year (RR 1.28; [0.86, 1.92] chi(2) = 11.55 (P = 0.003), I(2) = 83%). Two trials including participants predominantly treated with unboosted PI-based regimens reported a 49% increased likelihood of achieving a HIV-RNA viral load below 500 copies/mL at 52 weeks (RR 1.49 [1.20, 1.83] chi(2) = 0.69 (P = 0.4), I(2) = 0%). Safety outcomes were reported in four studies and were similar between TDM and standard of care. Uptake of expert advice based on TDM results was good in two trials (>70%), but low (<35%) in the remaining three studies that reported uptake of the recommendations.

AUTHORS' CONCLUSIONS

Our review does not support routine use of ARV TDM in ARV-naive or -experienced patients on either boosted PI or NNRTI ART regimens. TDM in treatment-naive participants on a PI-based ART regimen, particularly if unboosted by ritonavir, may improve virological outcomes. Trials were underpowered with small sample sizes, short durations of follow-up and generally poor uptake of TDM recommendations. As these trials were conducted in higher income earning countries, results may not be generalisable to resource-limited countries where the burden of HIV is heaviest.

Protease inhibitor levels in hair strongly predict virologic response to treatment

OBJECTIVE

Antiretroviral (ARV) therapies fail when behavioral or biologic factors lead to inadequate medication exposure. The currently available methods to assess ARV exposure are limited. Levels of ARVs in hair reflect plasma concentrations over weeks to months, and may provide a novel method for predicting therapeutic responses.

DESIGN/METHODS

The Women's Interagency HIV Study, a prospective cohort of HIV-infected women, provided the basis for developing and assessing methods to measure commonly prescribed protease inhibitors (lopinavir/ritonavir and atazanavir) in small hair samples. We examined the association between hair protease inhibitor levels and initial virologic responses to therapy in multivariate logistic regression models.

RESULTS

ARV concentrations in hair were strongly and independently associated with treatment response for 224 women starting a new protease inhibitor-based regimen. For participants initiating lopinavir/ritonavir, the odds ratio (OR) for virologic suppression was 39.8 [95% confidence interval (CI) = 2.8-564] for those with lopinavir hair levels in the top tertile (>1.9 ng/mg) compared to the bottom (3.4 ng/mg) compared to the lowest (

CONCLUSION

Protease inhibitor levels in small hair samples were the strongest independent predictor of virologic success in a diverse group of HIV-infected adults. This non-invasive method for determining ARV exposure may have particular relevance for the epidemic in resource-poor settings due to the ease of collecting and storing hair.

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Key Words

• hair levels
• therapeutic drug monitoring
• antiretroviral exposure
• virologic response
• protease inhibitors
• atazanavir
• lopinavir
• wihs cohort

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MESH Headings

• Adult
• Atazanavir Sulfate
• CD4 Lymphocyte Count
• Drug Monitoring/methods
• Epidemiologic Methods
• Female
• HIV Infections/drug therapy
• HIV Infections/metabolism
• HIV Infections/virology
• HIV Protease Inhibitors/pharmacokinetics
• HIV Protease Inhibitors/therapeutic use
• Hair/metabolism
• Humans
• Lopinavir
• Middle Aged
• Oligopeptides/pharmacokinetics
• Oligopeptides/therapeutic use
• Patient Compliance
• Pyridines/pharmacokinetics
• Pyridines/therapeutic use
• Pyrimidinones/pharmacokinetics
• Pyrimidinones/therapeutic use
• Ritonavir/pharmacokinetics
• Ritonavir/therapeutic use
• Specimen Handling/methods
• Treatment Outcome
• Viral Load

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Grants

• M01 RR000079 NCRR NIH HHS
• UO1-AI-34994 NIAID NIH HHS
• UO1-AI-34989 NIAID NIH HHS
• U01 AI035004 NIAID NIH HHS
• K23 AI067065 NIAID NIH HHS
• UO1-CH-32632 OID CDC HHS
• U01 AI034989 NIAID NIH HHS
• M01 RR000071 NCRR NIH HHS
• UO1-AI-34993 NIAID NIH HHS
• U01 AI034994 NIAID NIH HHS
• K23 AI067065-03 NIAID NIH HHS
• UO1-AI-42590 NIAID NIH HHS
• U01 AI034993 NIAID NIH HHS
• K23 A1067065 PHS HHS
• MO1-RR-00083 NCRR NIH HHS
• U01 AI031834 NIAID NIH HHS
• UO1-AI-35004 NIAID NIH HHS
• K23 AI067065-02 NIAID NIH HHS
• U01 AI042590-12 NIAID NIH HHS
• MO1-RR-00079 NCRR NIH HHS
• UO1-AI-31834 NIAID NIH HHS
• M01 RR000083 NCRR NIH HHS
• MO1-RR-00071 NCRR NIH HHS
• U01 AI042590 NIAID NIH HHS

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Affiliation(s)

Monica Gandhi Department of Medicine, University of California, San Francisco, San Francisco, California, USA.
Niloufar Ameli
Peter Bacchetti
Stephen J Gange
Kathryn Anastos
Alexandra Levine
Charles L Hyman
Mardge Cohen
Mary Young
Yong Huang
Ruth M Greenblatt

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A randomized trial of therapeutic drug monitoring of protease inhibitors in antiretroviral-experienced, HIV-1-infected patients

OBJECTIVE

Whether therapeutic drug monitoring of protease inhibitors improves outcomes in HIV-infected patients is controversial. We evaluated this strategy in a randomized, open-label clinical trial, using a normalized inhibitory quotient (NIQ), which incorporates drug exposure and viral drug resistance. NIQs < or = 1 may predict poor outcome and identify patients who could benefit from dose escalation.

DESIGN/METHODS

Eligible patients had a viral load > or =1000 copies/ml on a failing regimen, and began a new protease inhibitor containing regimen at entry. All FDA-approved protease inhibitors available during the study recruitment (June 2002-May 2006) were allowed. One hundred and eighty-three participants with NIQ < or = 1, on the basis of their week 2 protease inhibitor trough concentration and pre-entry drug resistance test, were randomized at week 4 to standard of care (SOC) or protease inhibitor dose escalation (TDM). The primary endpoint was change in log10 plasma HIV-1 RNA concentration from randomization to 20 weeks later.

RESULTS

Ninety-one patients were randomized to SOC and 92 to TDM. NIQs increased more in the TDM arm compared to SOC (+69 versus +25%, P = 0.01). Despite this, TDM and SOC arms showed no difference in outcome (+0.09 versus +0.02 log10, P = 0.17). In retrospective subgroup analyses, patients with less HIV resistance to their protease inhibitors benefited from TDM (P = 0.002), as did black and Hispanic patients (P = 0.035 and 0.05, respectively). Differences between black and white patients persisted when accounting for protease inhibitor susceptibility.

CONCLUSIONS

There was no overall benefit of TDM. In post hoc subgroup analyses, TDM appeared beneficial in black and Hispanic patients, and in patients whose virus retained some susceptibility to the protease inhibitors in their regimen.

Antiretroviral therapy in HIV-infected patients with multidrug-resistant virus: applying the guidelines to practice

Abstract Current treatment guidelines recommend maintenance of HIV-1 viral load below detectable levels (<50 copies per milliliter), even in extensively treated patients with multidrug-resistant HIV-1. Given recent advances in drug development and the availability of new agents with activity against antiretroviral-resistant HIV-1 viral strains, this goal is increasingly attainable for treatment-experienced patients. A stepwise approach to management of patients harboring antiretroviral-resistant HIV is presented, including assessment of adherence, a description of the use of resistance testing and utilization of new antiretroviral agents.

Sensitive analysis of anti-HIV drugs, efavirenz, lopinavir and ritonavir, in human hair by liquid chromatography coupled with tandem mass spectrometry

A highly sensitive and selective method using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) was developed and validated for the measurement of three antiretroviral agents, efavirenz, lopinavir and ritonavir, in human hair. Hair samples from adherent HIV-infected patients on antiretroviral therapies were cut into about 1 mm length segments and drugs were extracted by first shaking the samples with methanol in a 37 degrees C water bath overnight (>14 h), followed by methyl tert-butyl ether/ethyl acetate (1:1) extraction under weak alkaline conditions. The extracted lopinavir and ritonavir were separated by reversed-phase chromatography and detected by tandem mass spectrometry in electrospray positive ionization mode with multiple reaction monitoring (MRM), while efavirenz was monitored in negative ionization MRM mode. This method was validated from 0.01 to 4.0 ng/mg hair for ritonavir and 0.05-20 ng/mg hair for lopinavir and efavirenz by using 2 mg of a human hair sample. The interday and intraday assay precision (coefficients of variation, CV) for spiked quality control (QC) samples at low, medium and high concentrations were within 15% and accuracy ranged from 89% to 110%. Assay reproducibility was also demonstrated by analysis of incurred hair QC samples (CV <14%). No significant matrix ionization suppression was observed. This developed method allowed for the monitoring of these target medications in the hair samples of HIV-infected women on antiretroviral therapy in an observational study using small amounts of hair.

Practical therapeutic drug management in HIV-infected patients: use of population pharmacokinetic models supplemented by individualized Bayesian dose optimization

Individualized, model-based, target-oriented optimal concentration-controlled dosing of HIV medications can be beneficial to patients for whom there are limited dosing guidelines, such as children, adolescents, or patients with altered physiologic function. Barriers to this approach include lack of training, expertise, and access to appropriate software to assist the clinician. The authors present 4 illustrative clinical cases of HIV-infected patients whose therapy was optimized using population pharmacokinetic models (here generated from published studies) and supplemented by individualized Bayesian adaptive control of dosage regimens as implemented in the MM-USCPACK software. These 4 cases illustrate how clinicians can maximize therapeutic success in (1) patients with reduced drug clearance, (2) young adolescents transitioning to adult physiology, (3) patients with dose-dependent toxicity, and (4) adolescents with limited therapeutic options.

The genotypic inhibitory quotient: a predictive factor of atazanavir response in HIV-1-infected treatment-experienced patients

OBJECTIVE

To evaluate the predictive value of the genotypic inhibitory quotient (GIQ) on the atazanavir response in treatment-experienced HIV-1-infected patients.

PATIENTS AND METHODS

Thirty-six patients receiving an atazanavir-containing regimen were enrolled in the study. Atazanavir plasma concentrations were measured at month (M) 1, and genotype was performed at baseline. Virologic response was defined as a viral load <400 copies/mL or a decrease > or =1 log10.

RESULTS

The median numbers (range) of previous regimens, baseline protease inhibitors, and atazanavir resistance mutations were 8 (0 to 20), 3 (0 to 15), and 1 (0 to 10), respectively. The atazanavir-GIQ was associated with virologic response at M6, with a median value (range) of 365 (50 to 1172) in responder patients compared with 126 (23 to 1126) in nonresponders (P = 0.05). The cutoff value estimated for the atazanavir-GIQ was 183 (receiver operating characteristic curve test: 60% specificity, 74% sensitivity). Virologic response was achieved in 74% of patients with an atazanavir-GIQ >183 compared with only 26% of patients with an atazanavir-GIQ <183 (P = 0.02). Neither the number of mutations nor the atazanavir trough concentration was predictive of the virologic response.

CONCLUSION

In pretreated patients, the atazanavir-GIQ might be useful to predict early virologic response and allow the determination of the target atazanavir trough concentration required to achieve virologic response and overcome drug resistance emergence in a given patient.

The design and implementation of A5146, a prospective trial assessing the utility of therapeutic drug monitoring using an inhibitory quotient in antiretroviral-experienced HIV-infected patients

The AIDS Clinical Trials Group designed and implemented a prospective, randomized, strategy trial in antiretroviral-experienced, HIV-infected patients to evaluate the virologic impact of protease inhibitor dose escalation in response to therapeutic drug monitoring (TDM) with an inhibitory quotient, which integrates both drug exposure and viral drug resistance. In the process of developing this clinical trial, several unique challenges were identified that required innovative solutions. The major challenge was the need to integrate resistance testing, pharmacokinetic data, medication adherence, toxicity data, clinical assessments, randomization assignment, and protocol-specified clinical management in a way that could be utilized in real time by the protocol team, communicated promptly to the clinical sites, and transmitted accurately to the study database. In addition, the protocol team had to address the relative lack of commercially available TDM laboratories in the United States that were experienced in antiretroviral drug assays and a lack of familiarity with the principles of pharmacokinetic monitoring at participating clinical sites. This article outlines the rationale for the design of this strategy trial, specific barriers to implementation that were identified, and solutions that were developed with the hope that these experiences will facilitate the design and conduct of future trials of TDM.

A Randomized Controlled Trial of Therapeutic Drug Monitoring in Treatment-Naive and -Experienced HIV-1-Infected Patients

OBJECTIVE

To improve the utility of therapeutic drug monitoring (TDM) by defining the proportion of patients with and predictors of above or below target protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor (NNRTI) concentrations.

METHODS

This 48-week, multicenter, open-label clinical trial randomized patients to TDM versus standard of care (SOC). Serial pharmacokinetics, including a week-2 3-sample sparse collection, and expert committee TDM recommendations were given to TDM-arm patients' providers.

RESULTS

Seventy-four (39%) of 190 patients had week-2 concentrations outside of targets and 122 (64%) of 190 had nontarget exposure at least once over 48 weeks. Providers accepted 75% of TDM recommendations. Among patients with below-target concentrations, more TDM-arm than SOC-arm patients achieved targets (65% vs. 45%; P = 0.09). Increased body weight and efavirenz or lopinavir/ritonavir use were significant predictors of nontarget concentrations. Patients at target and patients who achieved targets after TDM-directed dose modifications trended toward greater viral load reductions at week 48 than patients with below-target exposures (HIV RNA reductions: 2.4, 2.3, and 1.9 log10 copies/mL, respectively; P = 0.09).

CONCLUSIONS

Most patients had nontarget PI and/or NNRTI concentrations over 48 weeks. TDM recommendations were well accepted and improved exposure. Patients below TDM targets trended toward worse virologic response.

Pharmacokinetics of two randomized trials evaluating the safety and efficacy of indinavir, saquinavir and lopinavir in combination with low-dose ritonavir: the MaxCmin1 and 2 trials

Our objective was to identify possible differences in protease inhibitor plasma concentrations between and within three protease inhibitor regimens (indinavir, saquinavir and lopinavir all in combination with low-dose ritonavir) and to relate these differences to safety and efficacy. Data originated from pre-defined pharmacokinetic substudies within two randomized 48-week trials evaluating the safety and efficacy of three protease inhibitor regimens. At weeks 4 and 48, plasma was collected and minimum drug plasma concentrations, C(min), were obtained. Out of 656 randomized patients, 283 patients had available C(min) at week 4. Indinavir, saquinavir and lopinavir C(min) were high when combined with low-dose ritonavir. No significant difference in the proportion of patients experiencing treatment failure could be found according to the C(min) within any treatment arm. A saquinavir C(min) > 2000 ng/ml was associated with an increased risk of gastrointestinal grade 3 or 4 adverse events and higher total cholesterol. Overall, there were no changes in C(min) from week 4 to week 48 in patients who remained on therapy. No association between treatment failure and the C(min) could be demonstrated. Associations between high C(min) and toxicity were identified in the saquinavir arm; therefore, dose reductions may be appropriate in certain patients with C(min) several times above the minimum effective concentration.

A Computer-Based System to aid in the Interpretation of Plasma Concentrations of Antiretrovirals for Therapeutic Drug Monitoring

Objectives

To develop a computer-based system for modelling and interpreting plasma antiretroviral concentrations for therapeutic drug monitoring (TDM).

Methods

Data were extracted from a prospective TDM study of 199 HIV-infected patients (CCTG 578). Lopinavir (LPV) and efavirenz (EFV) pharmacokinetic (PK) parameters were modelled using a Bayesian method and interpreted by an expert committee of HIV specialists and pharmacologists who made TDM recommendations. These PK models and recommendations formed the knowledge base to develop an artificial intelligence (AI) system that could estimate drug exposure, interpret PK data and generate TDM recommendations. The modelled PK exposures and expert committee TDM recommendations were considered optimum and used to validate results obtained by the AI system.

Results

A group of patients, 67 on LPV, 46 on EFV and three on both drugs, were included in this analysis. Correlations were high for LPV and EFV estimated trough and 4 h post-dose concentrations between the AI estimates and modelled values (r>0.79 for all comparisons; P<0.0001). Although trough concentrations were similar, significant differences were seen for mean predicted 4 h concentrations for EFV (4.16 μg/ml versus 3.89 μg/ml; P=0.02) and LPV (7.99 μg/ml versus 8.79 μg/ml; P<0.001). The AI and expert committee TDM recommendations agreed in 53 out of 69 LPV cases [kappa (κ)=0.53; P<0.001] and 47 out of 49 EFV cases (κ=0.91; P<0.001).

Conclusions

The AI system successfully estimated LPV and EFV trough concentrations and achieved good agreement with expert committee TDM recommendations for EFV- and LPV-treated patients.

Approach to salvage antiretroviral therapy in heavily antiretroviral-experienced HIV-positive adults

Despite dramatic declines in HIV-associated morbidity and mortality as a result of highly active antiretroviral therapy, management of heavily treatment-experienced patients remains complex and challenging. Treatment response rates with subsequent antiretroviral regimens are lower than with initial antiretroviral therapy. Additionally, increased mortality has been associated with multidrug-resistant HIV. We review data relevant to management of such patients and offer a systematic approach to constructing a salvage antiretroviral regimen.

Serum concentrations of protease inhibitors as predictors of HIV-related clinical events in patients on antiretroviral therapy

Serum concentrations of protease inhibitors (PIs) show large interindividual variations. It is not clear what clinical impact these differences in drug concentrations might have. In this study we explored the association between serum concentration of protease inhibitors and HIV-related disease. 130 patients on PI-containing regimen underwent PI concentration measurement in serum. The results were divided into 3 categories: high level, therapeutic level, and low level. HIV-related events (CDC category B and C) and death were prospectively recorded after the drug monitoring. The results were statistically analysed employing Cox regression. Median follow-up was 709 d, and 22 patients reached an endpoint. For the trough concentrations the hazard ratio (HR) for patients with therapeutic level vs low level was 0.63 (95% CI 0.20-1.95) and high level vs low level was 0.56 (95% CI 0.14-2.26). For the maximum concentrations the HR for therapeutic level vs low level was 1.32 (95% CI 0.48-3.62) and high level vs low level was 0.47 (95% CI 0.06-3.90). In conclusion, in this small pilot study we could not show any association between the serum concentrations of PIs and subsequent clinical HIV-related events. Larger studies are needed to explore this subject further.

Pharmacologic optimization of protease inhibitors and nonnucleoside reverse transcriptase inhibitors (POPIN)--a randomized controlled trial of therapeutic drug monitoring and adherence support

We evaluated the feasibility and effectiveness of therapeutic drug monitoring (TDM) and adherence support (collectively, AT) vs standard of care (SOC) in patients receiving HIV protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) within a nurse-led clinic. Primary end points were failure to achieve viral load of <50 copies/mL at 24 weeks, viral rebound, or development of treatment limiting toxicity. One hundred twenty-two patients (AT 63 and SOC 59) were followed-up every 12 weeks, for a median of 72 weeks. No difference was observed between arms in risk of reaching a study end point or between groups of patients with abnormal vs "therapeutic" drug concentrations. Interindividual variabilities (coefficient of variation) were the following: efavirenz, 77.5%; nevirapine, 74.5%; lopinavir, 73.4%; nelfinavir, 83.7%; indinavir, 80.8%; saquinavir, 112.4%. Intraindividual variabilities (median coefficient of variation) were the following: NNRTIs, approximately 25%; PIs, 48.4%. Despite persistently abnormal results in 26 of patients in the AT arm (38%), dosage adjustment was only undertaken in 9 patients (35%).A significant proportion of patients had drug concentrations outside the therapeutic range. The Pharmacologic Optimization of PIs and NNRTIs (POPIN) study confirms that TDM trials are complex to interpret and statistically underpowered, with effectiveness better assessed through the clinical utility of a TDM result, whether normal or abnormal. Although TDM of PIs and NNRTIs may be useful in selected patients, routine and unselected use is not supported by current evidence.

An Update on Therapeutic Drug Monitoring for Antiretroviral Drugs

There is an increasing uptake of TDM of antiretroviral drugs, particularly in Europe. There is consensus that current antiretroviral drugs meet most of the criteria of drugs that can be considered as candidates for a TDM strategy. This review examines the pharmacokinetic-pharmacodynamic relationship for protease inibitors and non nucleoside reverse transcriptase inhibitor, give an overview of the published randomised clinical trials and then summarises the scenarios for use of TDM. Finally the development of the inhibitory quotient (IQ) concept is discussed.

Marked Intraindividual Variability in Antiretroviral Concentrations May Limit the Utility of Therapeutic Drug Monitoring

BACKGROUND

Effective therapeutic drug monitoring for antiretrovirals requires a better understanding of intraindividual variability in pharmacokinetics.

METHODS

We determined concentrations of human immunodeficiency virus (HIV) protease and nonnucleoside reverse-transcriptase inhibitors for 10 patients with undetectable plasma HIV RNA levels who had been receiving stable regimens for > or = 11 months. Plasma samples were collected at the same time of day 3 times per week for up to 4 months. Patients were instructed to take their antiretrovirals at the same time every day. Plasma protease and nonnucleoside reverse-transcriptase inhibitor concentrations were determined using high-performance liquid chromatographic methods. Pharmacokinetic variability was expressed as intraindividual percentage coefficient of variation (ICV), which was calculated as the patient's standard deviation divided by the mean drug concentration for that patient.

RESULTS

ICV was determined for 6 drugs for 10 patients, for a total of 17 different patient-drug combinations, using 600 total samples. ICV was unexpectedly high for most patients who were receiving protease inhibitors (ICVs for individual patients taking lopinavir/ritonavir were 24%, 33%, 51%, and 92%; for patients taking nelfinavir/M8 metabolite, they were 30%/44% and 39%/54%; for patients taking ritonavir, they were 34% and 43%; for patients taking saquinavir, they were 52% and 55%). ICVs for patients receiving nonnucleoside reverse-transcriptase inhibitors were lower (for patients receiving efavirenz, they were 7%, 13%, 29%, and 51%; for a patient receiving nevirapine, it was 25%). The median ICV for all patients receiving protease inhibitors (n = 12) was 43.5%, and for all patients receiving nonnucleoside reverse-transcriptase inhibitors (n = 5), the median ICV was 25%.

CONCLUSIONS

Intraindividual variability in concentrations of antiretrovirals was surprisingly high in virologically suppressed patients. Possible contributors include food effects, concomitant use of prescription and herbal medications, assay variability, or medication timing, which was assessed by self-report. High intraindividual pharmacokinetic variability may limit the utility of single measurements in therapeutic drug monitoring for some antiretroviral agents.

Clinical pharmacodynamics of HIV-1 protease inhibitors: use of inhibitory quotients to optimise pharmacotherapy

The introduction of HIV-1 protease inhibitors and non-nucleoside reverse transcriptase inhibitors in 1996 began an era described as that of highly active antiretroviral therapy. In addition, the more recent development and availability of HIV-1 genotypic and phenotypic resistance tests and advances in pharmacological assays that support therapeutic drug monitoring (TDM) have created tools that may help clinicians to provide more individualised treatment with HIV-1 protease inhibitors. All current treatment guidelines provide fixed doses of protease inhibitors with vague recommendations for the use of TDM in selected clinical situations. In patients with resistance to protease inhibitors, the combined use of resistance tests with TDM provide a mechanism for individualising the clinical pharmacodynamics of protease inhibitors. Current therapeutic approaches seek to include the monitoring of protease-inhibitor concentrations as part of a TDM programme with phenotypic assays to calculate an inhibitory quotient, virtual inhibitory quotient, or normalised inhibitory quotient, whereas genotypic tests are used with TDM to calculate a genotypic inhibitory quotient. Current investigation is focused on examining the predictive value of this approach for clinical monitoring.

Pharmacokinetic parameters of nevirapine and efavirenz in relation to antiretroviral efficacy

Optimal adherence is essential for successful antiretroviral therapy. We analyzed the relation between minimum plasma drug concentration (Cmin) and total drug exposure over 24 hr (AUC24) with virologic failure for therapy-adherent patients in the nevirapine (NVP) and efavirenz (EFV) groups of the double nonnucleoside study (2NN), which compared the efficacy of NVP and/or EFV together with stavudine and lamivudine. The objective was to find cutoff values of the Cmin and AUC24 below which the risk of virologic failure increased. The relation between Cmin and AUC24 with virologic failure (never a plasma viral load [pVL] < 50 copies/ml or a rebound to two consecutive pVL > 50 copies/ml) was analyzed with proportional hazard analyses. Data were censored at end of study or change of allocated treatment. The risk of virologic failure with NVP (n = 511) started to increase at a Cmin < 3.1 mg/L (hazard ratio [HR], 1.33; 95% confidence interval [CI], 0.89-1.97), but there was no cutoff value below which a statistically significant increased risk occurred. Neither was such a cutoff point identified for the AUC24. The risk of virologic failure with EFV (n = 312) was significantly increased at a Cmin < 1.1 mg/L (HR, 1.95; 95% CI, 1.08-3.54) and an AUC24 < 40 mg x hr x L1 (HR, 1.95; 95% CI, 1.07-3.54). Both cutoff values represent the median values for adherent patients. These associations were driven by patients from Thailand. Adjusting for geographical region made the association between Cmin and AUC24 with virologic failure statistically nonsignificant. The sensitivity of the Cmin values was too low (29% for NVP, 64% for EFV) to be an adequate predictor for virologic failure. We conclude that identifying the Cmin value for the sole purpose of predicting virologic failure in patients who report to be adherent to NVP or EFV is questionable because of the absence of a concentration-response relation (NVP) or the low sensitivity for such a cutoff value (NVP and EFV).

Therapeutic Drug Monitoring and Human Immunodeficiency Virus (HIV) Antiretroviral Therapy

Treatment with antiretroviral drugs such as the HIV protease inhibitors and non-nucleoside reverse transcriptase inhibitors have contributed to the improvement of life of many HIV-infected patients in recent years, but antiretroviral therapy is not without problems. In some patients, treatment is not effective and suppression of viral replication is not achieved. Other patients experience toxicity and have to stop treatment or change to a less effective treatment. Several studies have demonstrated a relationship between plasma concentrations of the protease inhibitors and non-nucleoside reverse transcriptase inhibitors and viral suppression and toxicity. Therapeutic drug monitoring uses drug concentrations to individualize and optimise therapy by dosage adjustments and many clinicians have advocated for the use of therapeutic drug monitoring in HIV antiretroviral therapy. Evidence from a number of randomized clinical trials supports the use of therapeutic drug monitoring, but the studies have limitations and might not apply to all the antiretroviral drugs. However, the consensus is that certain patients are very likely to benefit from therapeutic drug monitoring. Additionally, the combination of therapeutic drug monitoring and genotypic or phenotypic resistance testing might further improve antiretroviral therapy.

Simultaneous determination of HIV protease inhibitors amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in human plasma by high-performance liquid chromatography-tandem mass spectrometry

We report a precise and accurate method for simultaneous quantification of protease inhibitors (PIs) amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in plasma. An internal standard was added to samples prior to protein precipitation with acetonitrile followed by addition of ammonium formate buffer. Analysis was by HPLC-MS/MS. Calibration curves were validated over concentration ranges encompassing both subtherapeutic and potentially 'toxic' drug concentrations. Inter- and intra-assay variation were below 11% and PI recovery was above 87%. The bioanalytical method described is successfully applied to measure PI concentrations obtained from clinical pharmacokinetic studies and routine therapeutic drug monitoring (TDM).