Validation of a rapid and sensitive high-performance liquidchromatography–tandem mass spectrometry (HPLC–MS/MS) assay for the simultaneous determination of existing and new

antiretroviral compounds

Laura Elsea a,∗, Victoria Watsonab, John Tjia a, Andrew Hughesb, Marco Siccardia, Saye Khoo a, David Back a

a Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, UKb NIHR Biomedical Research Centre, Royal Liverpool Hospital Trust, Liverpool, UK

Journal of Chromatography B, 878 (2010) 1455–1465

Date:07/05/14Unit of Clinical Pharmacology,

Department of Biomedical and Clinical Sciences,"Luigi Sacco" University Hospital

Abstract Abstract |

Simple, fast and sensitive HPLC–MS/MS method for determination of the commonly used protease inhibitors (PI) amprenavir, atazanavir, darunavir, lopinavir, ritonavir, saquinavir and the non-nucleoside reverse transcriptase inhibitor (NNRTI) nevirapine, as well as the more recent antiretrovirals, the CCR5 antagonist maraviroc and the “second generation” NNRTI etravirine and rilpivirin

The method described is being successfully applied to measure plasma antiretroviral concentrations from samples obtained from clinical pharmacokinetic studies.

Introduction

Highly active antiretroviral therapy (HAART) has dramatically reduced HIV-1-associated mortality and morbidity and currently comprises 25 drugs from five different classes

Various guidelines recommend for treatment naive patients, a combination of three or more antiretroviral agents; an NNRTI or a ritonavir boosted PI in combination with a dual NRTI backbone.

An estimated 8% of treatment naive and 33% of experienced patients do not achieve viral suppression or experience viral rebound within 12 months of initiating HAART

Forty per cent of therapy-naive people with HIV experience virological failure during the first two years of antiretroviral therapy (ART)

low plasma concentrations of antiretroviral drugs is the predictive of more rapid immunological failure and failure to achieve virological success in the first year of therapy .

Furthermore, a substantial number of people receiving ART discontinue therapy in the first 45 weeks of treatment, the majority stop therapy because of drug related toxicity

Routine therapeutic drug monitoring (TDM) and pharmacokinetic drug interaction studies between existing and new antiretrovirals, and with concomitant medications are essential for the optimization and management of antiretroviral therapy

Drug Therapy Monitoring

Therapeutic drug monitoring (TDM) is the clinical practice of measuring specific drugs at designated intervals to maintain a constant concentration in a patient's bloodstream, thereby optimizing individual dosage regimens.

PurposeTDM is employed to measure blood drug levels so that the most effective dosage can be determined, with toxicity prevented. TDM is also utilized to identify noncompliant patients (those patients who, for whatever reason, either cannot or will not comply with drug dosages as prescribed by the physician).

Why TDM in ART

The PI and NNRTI undergo cytochrome P450 mediated metabolism via CYP3A4 and to a lesser extent by CYP2B6, CYP2D6 and CYP2C19 which renders them prone to variable pharmacokinetics and extensive drug–drug interactions when given incombination or with other concomitant medications .

All PI inhibit CYP3A4, ritonavir being the most potent and is used exclusively at subtherapeutic doses to “boost” other PI.

In addition, ritonavir, lopinavir and amprenavir have CYP enzyme inducing properties. The first generation NNRTI nevirapine and efavirenz are substrates and inducers of CYP3A4 and CYP2B6 .

The second generation NNRTI rilpivirine is metabolized primarily by CYP3A4, and etravirine by CYP3A4, CYP2C9, CYP2C19 .

Maraviroc is a substrate for both CYP3A4 and the efflux transporter P-gycloprotein, and has shown clinically significant interactions with both PI and NNRTI, rendering mandatory maraviroc dosage adjustments with some associations

Thus,

•Antiretroviral Shows Pharmacokinetics and pharmacodynamic relationship

•Antiretroviral Shows Pharmacokinetics and toxicity relationship

Characterisation of this relationship is a key to the selection of an optimal dose for a drug, understanding inter- and intra-subject variability, and to design strategies to optimize response and tolerability while avoiding unwanted toxicity.

Here, authors developed fast and sensitive HPLC–MS/MS method for the determination of the commonly used PI [amprenavir (APV), atazanavir (ATV), darunavir (DRV), lopinavir (LPV), ritonavir (RTV), saquinavir (SQV)] and NNRTI [nevirapine (NVP)], as well as recently licensed CCR5 antagonist maraviroc (MVC) and the second generation NNRTI etravirine (ETV) and rilpivirine (RPV).

Materials and methods1. ChemicalsAPV : Glaxo Wellcome Research and Development (Middlesex, UK)ATV (atazanavir sulphate) : Bristol-Myers Squibb (Hounslow, UK)SQV: by Roche Discovery (Welwyn, UK),LPV, RTV : Abbott Laboratories (Chicago, IL, USA) NVP: Boehringer Ingelheim Pharmaceuticals, Inc. (Berkshire, UK). DRV: (darunavir ethanolate), ETV, RPV (rilpivirine hydrochloride): Tibotec (Mechelen, Belgium) MVC: Pfizer (Sandwich, Kent, UK).

2. EquipmentThe HPLC system consisted of a variable loop Accela autosampler (200 vial capacity set at a temperature of 15 C) and an Accela LC pump (Thermo Electron Corporation, Hemel Hempstead, ◦UK).A reverse-phase AscentisTM C18 column (3m: 100mm×2.1mm) at an temperature of 26 C.◦

The HPLC system coupled with a triple-quadrupole TSQ Quantum Ultra mass spectrometer (Thermo Electron Corporation, with a heated-electrospray ionization (H-ESI) source.

TSQ Tune Software (Thermo Electron Corporation, Hemel Hepstead, UK) was used for the optimization of tuning parameters.

LC QuanTM software (Version 2.5.6, Thermo Electron Corporation, Hemel Hepstead, UK) was used for data acquisition and processing.

Chromatographic and mass spectrometric conditions

•Chromatographic separation was achieved using a rapid stepwise gradient [ACN:water (0.05% formic acid) 5:95 and 80:20,v/v] mobile phase at a flow rate of 400 μL /min over a total run time of 5 min.

•The triple-quadrupole mass spectrometer was operated in positive ionization mode and detection and quantification was performed using selective reaction monitoring (SRM).

Preparation of calibrators, quality controls and internal Standard

Calibration point range•10 to 10,000 ng/ml (APV, ATV, NVP, RPV and SQV)• 5 to 5000 ng/ml (ETV and RTV)• 5 to 1000 ng/ml (MVC)•15 to 15,000 ng/ml (DRV and LPV)

APV, ATV, NVP, RPV, SQV

ETV, RTV, MVC DRV LPV

LLQC 25 ng/ml 12.5 ng/ml 40 ng/ml

LQC 150 ng/ml 100 ng/ml; MVC 50 ng/ml

250 ng/ml),

MQC 1500 ng/ml 800 ng/ml; MVC 400 ng/ml

3500 ng/ml

HQC 8000 ng/ml 4000 ng/ml; MVC 700 ng/ml

12,000 ng/ml

Quality Controls

Sample pre-treatment

Calibrators and QC samples in duplicate (100µl) QX (20µl and 1 µg/ml ) protein precipitation with ACN (500µl) vortexed and left to stand at room temperature (15 min) re-vortexed and centrifuged supernatant decanted into correspondingly labelled 5ml glass tubes followed by the addition of 0.05% formic acid (200µl) re-vortexed and transferred to autosampler vials injection (10µl) onto the HPLC column.

Validation of calibrators and quality controls

•A minimum of 10 calibration curves on separate days to ascertain the concentration at each calibrator level for all 10 drugs.

•Calibrator curves were constructed using a 1/concentration weighted quadratic regression equation of analyte:internal standard peak area ratios versus target concentration, from which unknown drug concentrations were interpolated

• Minimum of 10 QC samples (at LLQC, LQC, MQC and HQC) were treated as unknown values and run in duplicate on separate days alongside a validated calibration curve in order determine the final QC concentration and inter assay precision and accuracy

• Intra-assay variation was ascertained by running six LLQC, LQC, MQC and HQC samples within a single analytical run.

Standard curve range10 standard curves run to ascertain mean target calibrator and QC concentrations

Drugs Mean calibration curve range (ng/ml)

Correlation Coefficient (r2)

APV 11-10,063> 0.998ATV 11-10,017

DRV 16-15,062ETV 5-5000LPV 16-15,083MVC 5-1,009NVP 11-10,056RPV 11-10,045RTV 5-5018SQU 10-10,087

Mean QC Concentration QC Levels % variation

LLQC <14LQC, MQC,HQC 2-11

Validation of calibrators and quality controls and Precision (Inter and Intra assay)

Assay lower and upper limits of quantification and limit of detections

LOD LLQ ULQ

APV 1.3 11 10,063

ATV 0.2 11 10,017

DRV 1.0 16 15,062

ETV 2.7 5 5000

LPV 2.0 16 15,083

MVC 0.7 5 1009

NPV 0.3 11 10,056

RPV 2.7 11 10,045

RTV 1.3 5 5018

SQV 0.3 10 10,087

Stability study

Detection and chromatography

•Triple-quadrupole mass spectrometer was operating in positive SRM mode set to a narrow scan width (0.01 m/z) and scan time (0.01 s) for all transitions. •The capillary temperature and vaporising temperature within the H-ESI source were maintained at 300 and 350 C throughout an assay◦

Recovery and matrix effects

Discussion

The developed bioanalytical method successfuly applied to measure antiretroviral plasma concentration for clinical pharmacokinetic studies.

This HPLC–MS/MS method was fully validated with accuracy (% bias) and precision (CV%), which did not exceed 13% and 10% for all compounds with Percentage recovery greater than 90% for all analytes.

Stability data suggest that all analytes remained sufficiently stable under our current storage conditions (−20 ◦C) for up to 1 month.

Assay describes very short run time of 5 min per sample with a quick and simple sample pre-treatment procedure and hence , suitable for high-throughput TDM purposes

This method requires small volume of plasma for analysis (100µl). This is advantageous when quantifying drug in patients such as children and neonates, or from alternative matrices

Conclusion

A simple and rapid assay for the quantification of all currently approved PI (APV, ATV, DRV, LPV, RTV and SQV) and NNRTI (NVP), as well as recently licensed antiretroviral classes (MRC) and the second generation NNRTI (ETV and RPV) in human plasma has been developed and validated.

This method is proven to be specific, accurate, precise and robust.

The assay is highly sensitivity for all analytes and the step-wise gradient potentially allows addition of new analytes into the same analytical run.

Due to the high signal-to-noise ratio at the LLQ level, this method could be adopt to measure low antiretroviral concentrations in sites such as the genital tract and in cerebrospinal fluid.

Atazanavir (ATV) is an azapeptide protease inhibitor.

Protease inhibitors ATV is not associated with abnormal lipid profiles .

ATV has a unique pharmacokinetic profile which makes it suitable for once-daily oraladministration.

Method

This is a observational study carried out at St. Vincent’s Hospital which evaluated TDM data from a cohort of 110 people (Treatment experienced ) with HIV who received ATV over a 5-month period.

The mean age and number of the participants in the study

•(ATV300/r), n=92, was 46± 9 years•(ATV400), n=26 46 ± 11 years

Plasma samples Collection : ATV300/r: 0–8 h (n = 5), 8–16 h (n=20) and 16–30 h (n=67) and ATV400: 8–16 h ( n = 2) and 16–30 h ( n = 24).

ATV Plasma concentration were quantified by HPLC on a phenyl hexyl column (250 x 4.6 mm; 5 mm) with ultraviolet detection at 205 nm.

The ATV calibration standards ranged from 50 to 10 000 µg/l and the lower limit of ATV quantification was 50 µg/l.

Results and Discussion :Out of 20 patient 11 with through plasma ATV concentration below the limit of detection (25 µg/l) participated in Steady-state pharmacokinetic analysis

•8 received 400 mg ATV daily and 3 received ATV300/r daily• Plasma samples were collected at 0, 3, 6, 9 and 24 h• 2nd Dose after 24h with Coca Cola and a single 3 h blood sample was collected to observe the effect on ATV concentrations.

ATV 400 ATV 300/r Median

C min Conc

30 µg/l (range < 25–390 µg/l )

476 µg/l (range < 25–2108 µg/l)

Half Life 1.9 to 4.1 h 2.3 to 11.2 h

(half life < 4h in 13% of patient)

ATV Trough 25 µg/l

(below detection limit)

13 (8 interviewed for adherence, 2 patient coadministered , efavirenz, colchicines.nandrolone and esomeprazole )

7 (3 interviewed for adherence. Coadministered esomeprazole, fluticasone , rtv,)

Elevated Bilirubin

35 % patient

(median 15.0; range 4–49 µmol l-1)

49 % patient

All ATV Cmin plasma concentrations >500

mg l-1 were associated with abnormal serum bilirubin results (median 55.5; range 24–119 µmol l-1

ATV Concentration-time Profile of 8 patient receiving 400 mg ATV daily

Pharmackinetic profile of the patient suffering from hypertension and asthama

•Fluticasone accuhaler 500 µg bid•Lopinavir/ritonavir for 11 month before switching on to ATV 300/r•First pharmacokinetic study•Diagnosed with Cushing syndrome after 7 month•Fluticasone replaced with montelukast•Second pharmacokinetic study after 2 week wash out period •The AUC for ATV increased from 21,447 mg h-1 l 38,384 mg h-1 l when fluticasone was ceased•No acidic beverage effect

Conclusion

Substantial Pharmacokinetic variability with the ATV dose of 300/r and ATV 400

This study confirmed a relationship between elevated serum bilirubin concentration and higher ATV concentrations

Study describes possible drug interaction between RTV, fluticasone and ATV.

Coadministration of RTV and fluticasone is not recommended due to the ability of RTV to inhibit CYP3A4 mediated fluticasone metabolism causing iatrogenic Cushing Syndrome

Reduced plasma concentrations of ATV are expected when the drug is used in combination with antacids, buffered medications, H2-receptor antagonists and proton-pump inhibitors

Thank you