Nucleoside reverse transcriptase inhibitors and their phosphorylated metabolites in human immunodeficiency virus-infected human matrices

Gender Affirming Hormones Do Not Affect the Exposure and Efficacy of F/TDF or F/TAF for HIV Preexposure Prophylaxis: A Subgroup Analysis from the DISCOVER Trial

Purpose

Transgender women are disproportionately affected by HIV and are underutilizing preexposure prophylaxis (PrEP). The lower uptake of PrEP by transgender women may be, in part, owing to the perception that taking PrEP may lower the efficacy of gender-affirming hormone therapy (GAHT) or to provider concerns that GAHT may lower the efficacy of PrEP.

Methods

DISCOVER was a randomized, double-blind, noninferiority trial comparing emtricitabine (FTC, F) and tenofovir alafenamide (F/TAF) versus emtricitabine and tenofovir disoproxil fumarate (F/TDF) as PrEP among transgender women and cisgender men who have sex with men (MSM). This nested substudy of the DISCOVER trial compared the exposure of the active intracellular metabolites of FTC and tenofovir (TFV), FTC triphosphate (FTC-TP) and TFV diphosphate (TFV-DP), in peripheral blood mononuclear cells (PBMC) among transgender women receiving GAHT versus MSM within the F/TAF and F/TDF groups.

Results

Our results demonstrate that TFV-DP and FTC-TP levels in PBMC were comparable between transgender women on GAHT and MSM receiving F/TAF, and between transgender women on GAHT and MSM receiving F/TDF. TFV-DP concentrations remained above the EC90 of 40 fmol/106 cells across all groups. No clinically significant drug-drug interactions of GAHT were observed with either F/TAF or F/TDF in this subanalysis.

Conclusions

These findings are consistent with the clinical pharmacology of GAHT, FTC, TDF, and TAF reported in previous studies, and support the continued use of F/TAF and F/TDF for PrEP in transgender women.

Clinicaltrials.gov registration number: NCT02842086.

Tandem mass spectrometry of small-molecule antiviral drugs: 1. HIV-related antivirals

Antiviral drugs are a class of compounds developed specifically for the treatment of viral infections. In the development and subsequent application of antiviral drugs, like for any other class of drugs, quantitative analysis in biological matrix is important, e.g., to establish bioavailability, to study pharmacokinetics, and later on possibly for therapeutic drug monitoring. Liquid chromatography-mass spectrometry (LC-MS) with tandem mass spectrometry (MS-MS) operated in selected-reaction monitoring (SRM) mode is the method of choice in quantitative bioanalysis. As information of the fragmentation of antiviral drugs in MS-MS is very much scattered in the scientific literature, it was decided to collect this information and to review it, not only to understand which product ions are actually used in SRM, but also to assist in other studies, e.g., in the identification of drug metabolites or (forced) degradation products. In this first study, attention is paid to antiviral agents used against HIV infection. The review provides fragmentation schemes of ca. 40 antiviral agents as well as several phosphorylated anabolites. The identity of the product ions used in SRM, i.e., elemental composition and exact-m/z, is tabulated, and more detailed fragmentation schemes are provided.

Hollow mesoporous structured molecularly imprinted polymer as adsorbent in pipette-tip solid-phase extraction for the determination of antiretrovirals from plasma of HIV-infected patients

In this work a hollow mesoporous structured molecularly imprinted polymer was synthetized and used as adsorbent in pipette-tip solid-phase extraction for the determination of lamivudine (3TC), zidovudine (AZT) and efavirenz (EFZ) from plasma of human immunodeficiency virus (HIV) infected patients by high-performance liquid chromatography (HPLC). All parameters that influence the recovery of the pipette tip based on hollow mesoporous molecularly imprinted polymer solid-phase extraction (PT-HM-MIP-SPE) method were systematically studied and discussed in detail. The adsorbent material was prepared using methacrylic acid and 4-vinylpyridine as functional monomers, ethylene glycol dimethacrylate as crosslinker, acetonitrile as solvent, 4,4'-azobis(4-cyanovaleric acid) as radical initiator, benzalkonium chloride as surfactant, 3TC, and AZT as templates. The simultaneous separation of 3TC, AZT and EFZ by HPLC-UV was performed using a Gemini C18 Phenomenex® column (250 mm × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile: water pH 3.2 (68:32, v/v), flow rate of 1.0 mL/min and λ = 260 nm. The method was linear over the concentration range from 0.25 to 10 μg/mL for 3TC and EFZ, and 0.05 to 2.0 μg mL^-1 for AZT, with correlation coefficients larger than 0.99 for all analytes. Recovery ± relative standard deviations (RSDs %) were 41.99 ± 2.38%, 82.29 ± 1.63%, and 83.72 ± 7.52% for 3TC, AZT, and EFZ, respectively. The RSDs and relative errors (REs) were lower than 15% for intra and interday assays. The method has been successfully applied for monitoring HIV-infected patients outside the therapeutic dosage.

Determination of nucleosidic/tidic reverse transcriptase inhibitors in plasma and cerebrospinal fluid by ultra-high-pressure liquid chromatography coupled with tandem mass spectrometry

Nucleoside reverse transcriptase inhibitors (NRTIs) have been the first class of antiretroviral drugs used against HIV infection. Despite NRTI-free regimens have been eagerly sought over the years in an effort for treatment simplification, NRTIs remain in most antiretroviral combination treatment. There has been generally a limited interest for their therapeutic drug monitoring, arguably because NRTIs levels measured in plasma poorly predict the concentration of pharmacologically active metabolites in cells. Plasma concentrations do impact cellular levels, while large differences between NRTIs have been found with regard to their ability to distribute into the cerebrospinal fluid (CSF) compartment. The renewed interest for the measurements of NRTIs concentrations in plasma and CSF was raised by ongoing efforts to understand some instances of toxicity or for determining their actual implication in the development of HIV-associated neurological disorders. In this context, a 5-min multiplex ultra-high-pressure chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis in human plasma and CSF was developed for NRTIs used in clinical practice: abacavir, emtricitabine, lamivudine, tenofovir and zidovudine along with zidovudine glucuronide (Gln-ZDV). The 200-fold dilution of blank human plasma was shown to be a reliable surrogate matrix for quantification of NRTIs and Gln-ZDV in CSF. Both methodologies were fully validated over the clinically relevant concentrations, and satisfactorily fulfilled all parameters for bioanalytical methods validation. This sensitive, rapid, and robust UHPLC-MS/MS assay offers a methodology for increasing our understanding of the ability of NRTIs to cross the blood-brain barrier and their potential implication in neuropsychological disorders observed in HIV-infected patients.

Determination of Strong Acidic Drugs in Biological Matrices: A Review of Separation Methods

Strong acidic drugs are a class of chemical compounds that normally have high hydrophilicity and large negative charges, such as organophosphatic compounds and organosulphonic compounds. This review focuses on sample preparation and separation methods for this group of compounds in biological matrices in recent years. A wide range of separation techniques, especially chromatographic method, are presented and critically discussed, which include liquid chromatography (e.g., ion-pair and ion-exchange chromatography), capillary electrophoresis (CE), and other types. Due to the extremely low concentration level of target analytes as well as the complexity of biological matrices, sample pretreatment methods, such as dilute and shoot methods, protein precipitation (PP), liquid-liquid extraction (LLE), solid-phase extraction (SPE), degradation, and derivatization strategy, also play important roles for the development of successful analytical methods and thus are also discussed.

Improved ruggedness of an ion-pairing liquid chromatography/tandem mass spectrometry assay for the quantitative analysis of the triphosphate metabolite of a nucleoside reverse transcriptase inhibitor in peripheral blood mononuclear cells

RATIONALE

Nucleotide analogs are highly polar and ionic, which impose great challenges on bioanalysis. Ion-pairing liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the predominant reported approach for such compounds. Assay ruggedness of ion-pairing LC/MS/MS methods was often a challenge due to the potential contamination of the ion source of the mass spectrometer and LC column performance deterioration caused by ion-pairing reagents.

METHODS

An ion-pairing reagent was only added to the reconstitution solution to minimize its exposure to the MS ion source. To achieve optimum sensitivity, high pH mobile phases and negative ion ESI were needed for the LC/MS/MS method. However, high pH mobile phases led to the accumulation of ion-pairing reagent on the analytical column, which was washed off with an acidic solution to restore the column performance. In addition, isopropanol was used as a mobile phase modifier to improve peak shape and sensitivity.

RESULTS

The limit of detection was established at 1.0 ng/mL in the cell lysate. The calibration curve showed good linearity over the range of 1.0 to 100 ng/mL. The overall accuracy was no less than 87.7% based on four levels of quality control samples. Inter-run precision and intra-run precision across four analytical runs for low, geometric, medium and high QCs were less than 12.9.

CONCLUSIONS

By identifying and addressing the root cause of the assay ruggedness problem, we have developed a rugged ion-pairing LC/MS/MS method for a triphosphate (TP) metabolite of BMS-986001 in peripheral blood mononuclear cells. The new method overcame challenges such as a rapid deterioration of the peak shape, increased carryover and extremely poor column life. The peak shape was well maintained throughout multiple analytical runs. This method has been successfully applied to a toxicology study in cynomolgus monkey.

Comprehensive analysis of the intracellular metabolism of antiretroviral nucleosides and nucleotides using liquid chromatography-tandem mass spectrometry and method improvement by using ultra performance liquid chromatography

Nucleoside reverse transcriptase inhibitors (NRTIs) are a key class of drugs for the treatment of HIV infection. NRTIs are intracellularly phosphorylated to their active triphosphate metabolites and compete with endogenous deoxynucleotides (dNTP) for substrate binding. It is therefore important to analyze the intracellular concentrations of these compounds to understand drug efficacy and toxicity. To that purpose an analytical platform was developed that is capable of analyzing 8 NRTIs, 12 phosphorylated NRTIs and 4 dNTPs in small numbers of peripheral blood mononuclear cells, i.e. 1 × 10(6) cells. The platform consists of two liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods: a reversed-phase method for NRTIs using positive electrospray ionization (ESI) and an ion-pair LC-MS/MS method for the phosphorylated compounds using negative ESI. The methods use the same LC-MS system and column and changing from one method to the other only includes changing the mobile phase. The methods were partially validated, focussing on sensitivity, accuracy and precision. Successful transfer of the methods to ultra performance liquid chromatography (UPLC) led to a significant improvement of speed for the analysis of NRTIs and sensitivity for both NRTIs and phosphorylated NRTIs. The latter was demonstrated by the improved separation by UHPLC of dGTP vs. AZT-TP and ATP which made direct analysis of dGTP possible using the optimal MS/MS transition thereby significantly improving the detection limit of dGTP. Typically LLOQs observed for both the NRTIs and phosphorylated NRTIs were 1 nM, while the mean accuracy varied between 82 and 120% and inter- and intra-assay precision was generally <20%.

Mass spectrometry in the quantitative analysis of therapeutic intracellular nucleotide analogs

Nucleoside analogs are widely used in anti-cancer, anti-(retro)viral, and immunosuppressive therapy. Nucleosides are prodrugs that require intracellular activation to mono-, di-, and finally triphosphates. Monitoring of these intracellular nucleotides is important to understand their pharmacology. The relatively involatile salts and ion-pairing agents traditionally used for the separation of these ionic analytes limit the applicability of mass spectrometry (MS) for detection. Both indirect and direct methods have been developed to circumvent this apparent incompatibility. Indirect methods consist of de-phosphorylation of the nucleotides into nucleosides before the actual analysis. Various direct approaches have been developed, ranging from the use of relatively volatile or very low levels of regular ion-pairing agents, hydrophilic interaction chromatography (HILIC), weak anion-exchange, or porous graphitic carbon columns to capillary electrophoresis and matrix-assisted light desorption--time of flight (MALDI-TOF) MS. In this review we present an overview of the publications describing the quantitative analysis of therapeutic intracellular nucleotide analogs using MS. The focus is on the different approaches for their direct analysis. We conclude that despite the technical hurdles, several useful MS-compatible chromatographic approaches have been developed, enabling the use of the excellent selectivity and sensitivity of MS for the quantitative analysis of intracellular nucleotides.

Chromatographic separation of antiviral/anticancer nucleoside reverse transcriptase inhibitor drugs

This paper discusses the current methods used for quantitative determination of analogues of nucleotide reverse transcriptase inhibitors (NtRTIs) in body fluids, cells, and tissues. Nucleoside reverse transcriptase inhibitors (NRTIs) prodrugs given to AIDS/herpes/cancer patients conjugate with phosphates at the site of their action. Separation of phosphorylated NRTIs is generally performed by reversed-phase chromatography. After separation, plasma NRTIs can be detected using a variety of methods, including immunoassay through monitoring of UV absorbance, fluorescence, and mass spectrometry. The most recent development in the field of detection of plasma NtRTIs shows a tendency toward the use double- or triple-focusing mass spectrometry, the most specific and sensitive monitoring technique.

Simultaneous quantification of 2',2'-difluorodeoxycytidine and 2',2'-difluorodeoxyuridine nucleosides and nucleotides in white blood cells using porous graphitic carbon chromatography coupled with tandem mass spectrometry

A novel assay for the simultaneous quantification of the widely used anticancer agent 2',2'-difluorodeoxycytidine (gemcitabine; dFdC), its deaminated metabolite 2',2'-difluorodeoxyuridine (dFdU) and their mono-, di- and triphosphates (dFdCMP, dFdCDP, dFdCTP, dFdUMP, dFdUDP and dFdUTP) in peripheral blood mononuclear cells (PBMCs) is described. Separation of all eight compounds was achieved within 15 min using a porous graphitic carbon column (Hypercarb) with a gradient from 0 to 25 mM ammonium bicarbonate in acetonitrile/water (15:85, v/v). Calibration ranges in PBMC lysate from 4.29 to 429, 29.0 to 2900, 31.4 to 3140 and 36.9 to 3690 nM for dFdC, dFdCMP, dFdCDP and dFdCTP and from 42.1 to 4210, 25.4 to 2540, 43.2 to 4320 and 52.7 to 5270 nM for dFdU, dFdUMP, dFdUDP and dFdUTP, respectively, were validated. Accuracies were within 82.3-119% at the lower limit of quantification (LLOQ) and the precisions were less than 20.0%. At the other tested levels accuracies were within 91.4-114% and precisions less than 14.9%. Mixtures of (13)C,(15)N(2)-labeled dFdC and dFdU nucleotides were synthesized and used as internal standards. Whole blood samples showed extensive ongoing dFdC metabolism when stored at room temperature, but not on ice-water, which made the addition of enzyme inhibitors unnecessary. Stock solutions and samples were stable under all analytically relevant conditions. The method was successfully applied to clinical samples.

Quantification of polar drugs in human plasma with liquid chromatography–tandem mass spectrometry

Liquid chromatography–tandem mass spectrometry (LC–MS/MS) has played an important role in quantitative bioanalytical assays. This review summarizes the recent progress on quantification of polar drugs in plasma with LC–MS/MS. Various types of polar analytes were extracted using protein precipitation or solid-phase extraction and precolumn derivatization was utilized in some cases. The analytes were then separated using different types of chromatographic method, which included reversed-phase chromatography, aqueous normal-phase chromatography, hydrophilic interaction liquid chromatography and ion-pairing chromatography. Stationary phases of mixed mode and porous graphitic carbon materials are gaining acceptance in bioanalytical applications. These technologies can be valuable supplements in the quantification of polar drugs in human plasma with LC–MS/MS. Matrix effects have also been discussed in this review.

Retention studies of 2'-2'-difluorodeoxycytidine and 2'-2'-difluorodeoxyuridine nucleosides and nucleotides on porous graphitic carbon: development of a liquid chromatography-tandem mass spectrometry method

The development of a method for the separation of 2'-2'-difluorodeoxycytidine (gemcitabine, dFdC), 2'-2'-difluorodeoxyuridine (dFdU) and their mono-, di- and triphosphates using a porous graphitic carbon column (Hypercarb), without ion-pairing agent, is described. The retention of dFdC and dFdU could be controlled with an organic modifier (acetonitrile, CH(3)CN) and the retention of the anionic nucleotides with an eluting ion (bicarbonate). Separation of all analytes was achieved using a 0-25 mM ammonium bicarbonate gradient in CH(3)CN-H(2)O (15:85, v/v). Under these conditions, however, very long re-equilibration times were required. Injection of an acidic solution (100 microL 10% formic acid in H(2)O, v/v; 2.65 M) after running a gradient directly restored the separation capabilities of the column. Still, separation between the analytes slowly deteriorated over a period of months. These problems were solved by preconditioning the column with a pH buffered hydrogen peroxide (H(2)O(2)) solution (0.05% H(2)O(2) in CH(3)CN-H(2)O (15:85, v/v), pH 4) before starting an analytical run. The oxidation of the stationary phase with H(2)O(2) prevented its slow reduction, which most likely caused the decreasing retention times. The analytes were detected using tandem mass spectrometry.