A novel LC-MS/MS method for simultaneous quantification of tenofovir and lamivudine in human plasma and its application to a pharmacokinetic study

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

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

Detection and quantification of Covid-19 antiviral drugs in biological fluids and tissues

Since coronavirus disease 2019 (COVID-19) started as a fast-spreading pandemic, causing a huge number of deaths worldwide, several therapeutic options have been tested to counteract or reduce the clinical symptoms of patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific drugs for COVID-19 are available, but many antiviral agents have been authorised by several national agencies. Most of them are under investigation in both preclinical and clinical trials; however, pharmacokinetic and metabolism studies are needed to identify the most suitable dose to achieve the desired effect on SARS-CoV-2. Therefore, the efforts of the scientific community have focused on the screening of therapies able to counteract the most severe effects of the infection, as well as on the search of sensitive and selective analytical methods for drug detection in biological matrices, both fluids and tissues. In the last decade, many analytical methods have been proposed for the detection and quantification of antiviral compounds currently being tested for COVID-19 treatment. In this review, a critical discussion on the overall analytical procedure is provided, i.e (a) sample pre-treatment and extraction methods such as protein precipitation (PP), solid-phase extraction (SPE), liquid-liquid extraction (LLE), ultrasound-assisted extraction (UAE) and QuEChERS (quick, easy, cheap, effective, rugged and safe), (b) detection and quantification methods such as potentiometry, spectrofluorimetry and mass spectrometry (MS) as well as (c) methods including a preliminary separation step, such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) coupled to UV-Vis or MS detection. Further current trends, advantages and disadvantages and prospects of these methods have been discussed, to help the analytical advances in reducing the harm caused by the SARS-CoV-2 virus.

Novel High-Throughput Quantitation of Potent hERG Blocker Dofetilide in Human Plasma by Liquid Chromatography Tandem Mass Spectrometry: Application in a Phase 1 ECG Biomarker Validation Study

The authors developed a novel, sensitive high-throughput ultra-performance liquid chromatography-tandem mass spectrometric method for the determination of dofetilide in human plasma. To compensate for the matrix effect, a deuterated internal standard was used. The method employed a very low sample volume (50 μL) of plasma for sample processing by using simple protein precipitation extraction in a 96-well plate. The extracted samples were chromatographed on an Acquity BEH C18 column (2.1 × 100 mm, 1.7 μm) and eluted in a gradient manner at a flow rate of 0.5 mL/min for 2 min using 5 mM ammonium formate (0.1% formic acid) and methanol. The calibration curve was linear from 25 to 2,500 pg/mL with a correlation coefficient (r2) ≥ 0.99 (0.9969-0.9980; n = 3). The developed method was validated as per the current United States Food and Drug Administration's guidance for industry on 'Bioanalytical Method Validation'. The multiple reaction-monitoring mode was employed for quantitation of dofetilide with m/z 442.2/198.2 and dofetilide d4 with m/z 446.2/198.2. The validated method was used for evaluation of dofetilide concentration in the Comprehensive in vitro Proarrhythmia Assay phase 1 electrocardiogramic biomarker validation study.

A high-throughput bioanalytical assay to support pharmacokinetic interaction study of oxycodone and diazepam in Sprague Dawley rats

Benzodiazepines potentiate respiratory depression when combined with an opioid leading the U.S Food and Drug Administration (FDA) to recommend updating the labels of these products with a boxed warning for respiratory depression with co-use. Potential respiratory depression upon co-administration of opioids with some psychotropic drugs is not well understood. The FDA is currently investigating various psychotropic drug interactions with the commonly used opioid, oxycodone, in a rat model assessing respiratory depression. Pharmacokinetic and/or pharmacodynamic (PK/PD) interaction between oxycodone and diazepam was evaluated in a positive control arm of these experiments. Understanding the systemic exposure of these drugs alone and in combination exposures was used to identify PK/PD interactions. The authors developed a simple, high throughput liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay for the simultaneous determination of oxycodone and diazepam in rat plasma. Sample preparation was performed in 96-well protein precipitation plates using acetonitrile. Processed samples were analyzed using a C₁₈ column with a gradient mobile phase composed of 2 mM aqueous ammonium formate with 0.1% formic acid and acetonitrile. A Thermo TSQ Quantum Ultra AM triple quadrupole mass spectrometer with multiple reaction monitoring (MRM) mode was used to acquire data. The method was validated for selectivity, specificity, linearity, precision and accuracy, dilution integrity and stability. The validated LC-MS/MS assay was utilized for quantifying oxycodone and diazepam in concomitantly treated Sprague Dawley (SD) rats.

A high-throughput bioanalytical method for the simulataneous determination of oxycodone and diazepam to support the evaluation of respiratory depression in rats upon co-administration of oxycodone and diazepam.

Application of the HIV prevention cascade to identify, develop and evaluate interventions to improve use of prevention methods: examples from a study in east Zimbabwe

INTRODUCTION

The HIV prevention cascade could be used in developing interventions to strengthen implementation of efficacious HIV prevention methods, but its practical utility needs to be demonstrated. We propose a standardized approach to using the cascade to guide identification and evaluation of interventions and demonstrate its feasibility for this purpose through a project to develop interventions to improve HIV prevention methods use by adolescent girls and young women (AGYW) and potential male partners in east Zimbabwe.

DISCUSSION

We propose a six-step approach to using a published generic HIV prevention cascade formulation to develop interventions to increase motivation to use, access to and effective use of an HIV prevention method. These steps are as follows: (1) measure the HIV prevention cascade for the chosen population and method; (2) identify gaps in the cascade; (3) identify explanatory factors (barriers) contributing to observed gaps; (4) review literature to identify relevant theoretical frameworks and interventions; (5) tailor interventions to the local context; and (6) implement and evaluate the interventions using the cascade steps and explanatory factors as outcome indicators in the evaluation design. In the Zimbabwe example, steps 1-5 aided development of four interventions to overcome barriers to effective use of pre-exposure prophylaxis (PrEP) in AGYW (15-24 years) and voluntary medical male circumcision in male partners (15-29). For young men, prevention cascade analyses identified gaps in motivation and access as barriers to voluntary medical male circumcision uptake, so an intervention was designed including financial incentives and an education session. For AGYW, gaps in motivation (particularly lack of risk perception) and access were identified as barriers to PrEP uptake: an interactive counselling game was developed addressing these barriers. A text messaging intervention was developed to improve PrEP adherence among AGYW, addressing reasons underlying lack of effective PrEP use through improving the capacity ("skills") to take PrEP effectively. A community-led intervention (community conversations) was developed addressing community-level factors underlying gaps in motivation, access and effective use. These interventions are being evaluated currently using outcomes from the HIV prevention cascade (step 6).

CONCLUSIONS

The prevention cascade can guide development and evaluation of interventions to strengthen implementation of HIV prevention methods by following the proposed process.

Overview of the Chromatographic and Mass Spectrometry Analytical Methods for Determination of Lamivudine in Biological Fluids

Background:

Lamivudine was approved by Food and Drug Administration of the United States for the treatment of both HIV and HBV infection, which has been widely used as monotherapy or a component of combination therapy in clinics in many countries and nationalities.

Methods:

In this paper, the recent chromatographic and mass spectrometry analytical methods for the determination of lamivudine individually or combination with other drugs simultaneously were presented. These methods were widely applied in pharmacokinetics studies, bioequivalence studies, therapeutic drug monitoring studies, cell and animal experiments.

Conclusion:

The review paper might provide references for determining lamivudine in biological fluids, the intracorporal process of lamivudine, and the clinical practice by monitoring plasma concentration of lamivudine in the future.

A LC/MS/MS method for determination of tenofovir in human plasma and its application to toxicity monitoring

Tenofovir disoproxil fumarate is a pro-drug of the active metabolite tenofovir widely used against the HIV1, HIV2, and Hepatitis B virus. Several studies have been conducted and found kidney injury associated with tenofovir exposure. High tenofovir plasma concentration correlated with kidney injury in tenofovir-exposed patients. The present study developed and validated a simple and cost-effective LC/MS/MS method to determine tenofovir level in human plasma. A small plasma volume of 80 μl is utilized for the sample preparation. The samples were separated by Luna C18 (100 mm × 2.0 mm, 3 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile (90:10, v/v). The detection was achieved through multiple reaction monitoring using positive ionization mode on the triple quadrupole mass spectrometer with a run time of 10 min. The monitoring transitions were set at m/z 288.0 → 176.1 and 136.1 for tenofovir and m/z 226.1 → 152.0 for acyclovir (as the internal standard). This standard curve was linear from 10 to 640 ng/ml, with the lower limit of quantification of 10 ng/ml. The inter- and intra-day precision results were less than 12.3% and their accuracies were within the acceptable range of 84.9-113.1%. The validated method was successfully applied to the study of tenofovir induced kidney injury in HIV-1 infected patients taking 300 mg once daily for more than 4 weeks.

Chromatographic methods in HIV medicine: Application to therapeutic drug monitoring

HIV antiretroviral therapy spans several different drug classes, meant to combat various aspects of viral infection and replication. Many authors have argued the benefits of therapeutic drug monitoring (TDM) for the HIV patient including compliance assurance and assessment of appropriate drug concentrations; however, the array of drug chemistries and combinations makes TDM an arduous task. HPLC-UV and LC-MS/MS are both frequent instruments for the quantification of HIV drugs in biological matrices with investigators striving to balance sensitivity and affordability. Plasma, the dominant matrix for these analyses, is prepared using protein precipitation, liquid-liquid extraction or solid-phase extraction depending on the specific complement of analytes. Despite the range of polarities found in drug classes relevant to HIV therapeutics, most chromatographic separations utilize a hydrophobic column (C₁₈ ). Additionally, as the clinically relevant samples for these assays are infected with HIV, along with possible co-infections, another important aspect of sample preparation concerns viral inactivation. Although not routine in clinical practice, many published analytical methods from the previous two decades have demonstrated the ability to conduct TDM in HIV patients receiving various medicinal combinations. This review summarizes the analytical methods relevant to TDM of HIV drugs, while highlighting respective challenges.

Bioanalysis of monomethyl fumarate in human plasma by a sensitive and rapid LC-MS/MS method and its pharmacokinetic application

Dimethyl fumarate (DMF) is the methyl ester of fumaric acid, after oral administration completely converts to its active metabolite monomethyl fumarate (MMF). A simple, rapid and sensitive LC-MS/MS method was developed and validated for the quantification of MMF in human plasma. Monomethyl fumarate d3 was used as an internal standard (IS). The analyte and the IS were extracted from plasma using a selective solid phase extraction technique. The clean samples were chromatographed on a C₁₈ column using formic acid and acetonitrile (25:75, v/v) as mobile phase. An API-4000 LC-MS/MS system equipped with turbo ion spray (TIS) source and operated in multiple reactions monitoring (MRM) mode was used for the study. The method was validated for linearity in the range of 5.03-2006.92ng/mL. Also, a number of stability tests were conducted to evaluate the stability of analyte, IS in plasma samples and in neat samples, the results comply with recent bioanalytical guidelines. A shortest run time helped us to analyze more than 300 samples in a day. The method was applied to a pharmacokinetic study in ten healthy male Indian subjects and the study data was authenticated by conducting incurred sample reanalysis (ISR).

Simultaneous determination of entecavir and lamivudine in rat plasma by UPLC-MS/MS and its application to a pharmacokinetic study

The study's aim is to develop and validate a rapid, selective and sensitive ultra-performance liquid chromatography-tandem mass spectrometry with multiple reaction monitoring (MRM) mode method for the simultaneous determination of entecavir and lamivudine in rat plasma.

UPLC-MS/MS method for the simultaneous quantification of anti-HBV nucleos(t)ides analogs: Entecavir, lamivudine, telbivudine and tenofovir in plasma of HBV infected patients

Hepatitis B infection affects two billion people worldwide and 350 million of these are chronically infected. Chronic hepatitis B virus is one of the most important cause of mortality and morbidity worldwide. If it is left untreated, about one-third of affected people will develop progressive and possibly fatal liver disease, like hepatic cirrhosis and primary hepatocellular carcinoma. Currently, five nucleos(t)ide analogs are approved for the treatment of chronic HBV infection. They are: lamivudine, adefovir dipivoxil, telbivudine, entecavir and tenofovir disoproxil fumarate. In this work, we developed and validated an UPLC-Tandem mass spectrometry assay method capable of monitoring lamivudine, telbivudine, tenofovir and entecavir plasma concentrations. Both standards and quality controls (high, medium and low) were prepared in human plasma. Each sample was added with internal standard (5'amino-5'deoxy-thymidine) and then drugs were extracted through a protein precipitation protocol with acetonitrile+0.1% formic acid and then dried. The extracts were resuspended in water and then injected into the chromatographic system. The chromatographic separation was performed on an Acquity UPLC HSS T3 1.8 μm 2.1 × 150 mm column, with a gradient of water and acetonitrile, both added with formic acid (0.05%). Accuracy, intra-day and inter-day precision at quality controls levels fitted all FDA guidelines for all analytes, while matrix effects and recoveries resulted stable between samples for each analyte. Finally, we tested this method by monitoring plasma concentrations in 30 HBV+ patients with good results. This simple analytical method could represent a useful tool for the management of anti-HBV therapy.

Evaluation of degradation kinetics and physicochemical stability of tenofovir

Tenofovir (TFV) has been proven to prevent the transmission of the Human Immunodeficiency Virus (HIV) through the vagina. But, there is little information available about its stability under various storage and stress conditions. Hence, this study aimed to investigate the degradation behavior and physicochemical stability of TFV using liquid chromatography coupled mass spectrometry (LC-MS) and solid state X-ray diffraction (XRD) analyses. The LC-MS analysis was performed on a QTrap mass spectrometer with an enhanced mass spectrum (EMS) scan in positive mode. A reversed phase C18 column was used as the stationary phase. TFV exhibited degradation under acidic and alkaline hydrolytic conditions. The degradation products with m/z 289.2 and 170 amu have been proposed as 6-Hydroxy adenine derivative of TFV, and (2-hydroxypropan-2-yloxy) methylphosphonic acid, respectively. A pseudo-first-order degradation kinetic allowed for estimating the shelf-life, half-life, and time required for 90% degradation of 3.84, 25.34, and 84.22 h in acidic conditions, and 58.26, 384.49, and 1277.75 h in alkaline conditions, respectively. No significant degradation was observed at pH 4.5 (normal cervicovaginal pH) and oxidative stress conditions of 3% and 30% v/v hydrogen peroxide solutions. The shelf life of TFV powder at room temperature was 23 months as calculated by using an Arrhenius plot. The XRD pattern showed that the drug was stable and maintained its original crystallinity under the accelerated and thermal stress conditions applied. Stability analyses revealed that the TFV was stable in various stress conditions; however, formulation strategies should be implemented to protect it in strong acidic and alkaline environments.

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

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

Development and validation of an assay for the simultaneous determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography-tandem mass spectrometry

This paper describes the development and validation of an assay for the simultaneous quantification of the antiviral and antiretroviral drugs zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma using liquid chromatography coupled to tandem mass spectrometry. Sample pretreatment consisted of protein precipitation with 0.1% (v/v) formic acid in methanol, evaporation and reconstitution. Chromatographic separation was performed on a Synergy Polar reversed phase C18 column (150 mm × 2.0 mm ID, particle size 4 μm) using a stepwise gradient with 0.1% (v/v) formic acid in water and 0.1% (v/v) formic acid in methanol at a flow rate of 300 μL/min. A triple quadrupole mass spectrometer operating in the positive ionization mode was used for drug detection and quantification. Isotopically labeled zidovudine, lamivudine, tenofovir and ribavirin were used as internal standards. The method was validated over a clinical range of 20-2500 ng/mL for zidovudine, lamivudine and tenofovir, 4-500 ng/mL for abacavir and emtricitabine and 160-20,000 ng/mL for ribavirin. The inter and intra-assay accuracies and precisions were between -8.47% and 14.2% for zidovudine, emtricitabine and ribavirin. For abacavir, lamivudine and tenofovir, the inter and intra-assay accuracies and precisions at the lower limit of quantification were between -11.0% and 18.3%, whereas at all other levels these accuracies and precisions were between -11.7% and 12.0%. The described method is suitable for the determination of zidovudine, abacavir, emtricitabine, lamivudine, tenofovir and ribavirin in human plasma in clinical practice to monitor plasma concentrations in selected cases to optimize therapy.