Review of the validated HPLC and LC-MS/MS methods for determination of drugs used in clinical practice for Alzheimer's disease

Mass spectrometry-based metabolomics in health and medical science: a systematic review

Metabolomics is the study of the investigation of small molecules derived from cellular and organism metabolism, which reflects the outcomes of the complex network of biochemical reactions in living systems.

Influence of CYP2D6, CYP3A5, ABCB1, APOE polymorphisms and nongenetic factors on donepezil treatment in patients with Alzheimer's disease and vascular dementia

PURPOSE

This study aims to evaluate the influence of genetic polymorphisms of CYP2D6, CYP3A5, ABCB1, and APOE genes and nongenetic factors on steady-state plasma concentrations (Cpss) of donepezil and therapeutic outcomes in Thai patients with Alzheimer's disease (AD) and vascular dementia (VAD).

PATIENTS AND METHODS

Eighty-five dementia patients who received donepezil for at least six months were recruited. CYP2D6, CYP3A5, ABCB1, and APOE polymorphisms were genotyped. Cpss of donepezil was measured. Association of genetic and non-genetic factors with Cpss and clinical outcomes of donepezil (cognitive function as measured by the Thai Mental State Examination score; TMSE) were determined by using univariate and multivariate analysis.

RESULTS

Both univariate and multiple linear regression analysis indicated that only CYP2D6*10 allele was associated with higher Cpss (p-value =0.029 and B =0.478, p-value =0.032, respectively) that might influence the clinical outcomes of donepezil. ie, TMSE (p-value =0.010 and B =4.527, p-value =0.001) and ΔTMSE (p-value =0.023 and B =4.107, p-value =0.002), especially in patients with AD. Interestingly, concomitant use of memantine was found to be associated with increased Cpss of donepezil (p-value =0.007 and B =0.511, p-value =0.014). Whereas, co-medication with antidepressant drugs attenuated clinical responses in patients with AD (TMSE: B =-2.719, p-value =0.013 and ΔTMSE: B =-2.348, p-value =0.028). Age was a significant predictor of donepezil response in VAD patients. No significant association of CYP3A5*3, ABCB1 3435C>T or ABCB1 1236C>T, and APOE ε4 genotypes with Cpss or clinical outcomes of donepezil was found in this study.

CONCLUSION

Our results suggests that CYP2D6*10 strongly influences Cpss and there is a trend toward better outcomes of donepezil in patients with AD. Nongenetic factors including concomitant drugs treatment might alter Cpss of donepezil or clinical outcomes.

Determination of donepezil in human plasma using ultra performance liquid chromatography-tandem mass spectrometry

An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantification of donepezil in human plasma. Donepezil and donepezil-D4 were extracted from human plasma by liquid-liquid extraction using a mixture of hexane and ethyl acetate (70:30 v/v). The extracted samples were analyzed using a Thermo Hypersil Gold C18 column with 5% acetic acid in 20 mM ammonium acetate buffer (pH 3.3) and 100% acetonitrile as a mobile phase with the 60:40 (v:v) isocratic method, at a flow rate of 0.3 mL/min. The injection volume was 3 µL, and the total run time was 3 min. Inter- and intra-batch accuracies ranged from 98.0% to 110.0%, and the precision was below 8%. The developed method was successfully applied to the quantification of donepezil in human plasma. The mean (standard deviation) maximum concentration and the median (range) time to maximum concentration were 8.6 (2.0) ng/mL and 2.0 h (1.0~5.0 h), respectively, in healthy Koreans after oral administration of 5 mg donepezil.

A Stability Indicating HPLC Assay Method for Analysis of Rivastigmine Hydrogen Tartrate in Dual-Ligand Nanoparticle Formulation Matrices and Cell Transport Medium

The objective of this study was to develop and validate a method for quantitative analysis of rivastigmine hydrogen tartrate (RHT) in dual-ligand polymeric nanoparticle formulation matrices, drug release medium, and cellular transport medium. An isocratic HPLC analysis method using a reverse phase C₁₈ column and a simple mobile phase without buffer was developed, optimised, and fully validated. Analyses were carried out at a flow rate of 1.5 mL/min at 50°C and monitored at 214 nm. This HPLC method exhibited good linearity, accuracy, and selectivity. The recovery (accuracy) of RHT from all matrices was greater than 99.2%. The RHT peak detected in the samples of a forced degradation study, drug loading study, release study, and cellular transport study was pure and free of matrix interference. The limit of detection (LOD) and limit of quantification (LOQ) of the assay were 60 ng/mL and 201 ng/mL, respectively. The method was rugged with good intra- and interday precision. This stability indicating HPLC method was selective, accurate, and precise for analysing RHT loading and its stability in nanoparticle formulation, RHT release, and cell transport medium.

Simultaneous quantitation of the BACE1 inhibitor AZD3293 and its metabolite AZ13569724 in human matrices by LC-MS/MS

AIM

AZD3293 is a novel BACE1 inhibitor in Phase III development for Alzheimer's disease. Sensitive and robust bioanalytical methods were required to quantitate AZD3293 and its metabolite AZ13569724 in human biological matrices.

METHODOLOGY/RESULTS

Human plasma was prepared by protein precipitation. Linearity for both analytes was in the range of 0.5-500 ng/ml with up to 100-fold dilution. Plasma ultrafiltrate samples were prepared using Centrifree^® ultrafiltration device. Urine and CSF samples were analyzed directly after dilution. A 27% decrease in AZD3293 concentrations in the CSF collection apparati was found due to nonspecific binding. Incurred sample reanalysis was acceptable.

CONCLUSION

Methods for simultaneous quantitation of AZD3293 and its metabolite AZ13569724 in human biological matrices have been validated and successfully applied to clinical studies.

Elevated DRD4 promoter methylation increases the risk of Alzheimer's disease in males

Aberrant promoter methylation of multiple genes is associated with various diseases, including Alzheimer's disease (AD). The goal of the present study was to determine whether dopamine receptor D4 (DRD4) promoter methylation is associated with AD. In the current study, the methylation levels of the DRD4 promoter were measured in 46 AD patients and 61 controls using bisulfite pyrosequencing technology. The results of the present study demonstrated that DRD4 promoter methylation was significantly higher in AD patients than in controls. A further breakdown analysis by gender revealed that there was a significant association of DRD4 promoter methylation with AD in males (23 patients and 45 controls). In conclusion, the results of the present study demonstrated that elevated DRD4 promoter methylation was associated with AD risk in males.

Reduction of dilution error in ELISAs using an internal standard

Background: Dilution bias is a major cause of immunoassay variability due to the lack of an internal standard to determine the true versus the expected dilution value. Methodology: We used an internal control to measure dilution bias in an ELISA. Acridine-orange was added at the first dilution step and monitored throughout dilutions. Assay results were corrected using the fluorescent signal ratio between samples and reference. Acridine dilution correlated with analyte-specific assay measurements (R2 = 0.987). Correction of assay results with the measured dilution factor improved both accuracy and precision resulting in a reduction of >50% %CV reduction. Conclusion: Dilution correction can significantly improve accuracy and precision of immunoassays. Additional control strategies may further mitigate other sources of variability.

Emerging applications of metabolomics in drug discovery and precision medicine

Metabolomics is an emerging 'omics' science involving the comprehensive characterization of metabolites and metabolism in biological systems. Recent advances in metabolomics technologies are leading to a growing number of mainstream biomedical applications. In particular, metabolomics is increasingly being used to diagnose disease, understand disease mechanisms, identify novel drug targets, customize drug treatments and monitor therapeutic outcomes. This Review discusses some of the latest technological advances in metabolomics, focusing on the application of metabolomics towards uncovering the underlying causes of complex diseases (such as atherosclerosis, cancer and diabetes), the growing role of metabolomics in drug discovery and its potential effect on precision medicine.

Quantitative analysis of drugs in biological matrices by HPLC hyphenated to fluorescence detection

An overview of the state-of-the art in HPLC coupled with fluorescence detection is presented. Over the last 20 years, the increasing number of methodological papers on this topic (4082 between 1994 and 2004 and 7725 between 2004 and 2014) is testament to its utility in bioanalytical applications. Compared with conventional UV absorbance detection used in HPLC, fluorescence detection can greatly enhance the sensitivity leading to limits of detection similar to those obtained with mass spectrometry, offering researchers a sensitive, robust and relatively inexpensive instrumental method. This work will focus on the analysis of pharmaceutical compounds in different biological matrices, either naturally fluorescent or derivatized with a fluorescent agent, and some of them chiral. Therapeutic applications, sample preparation and derivatization, sensitivity for each example are described.

Osteoporosis and alzheimer pathology: Role of cellular stress response and hormetic redox signaling in aging and bone remodeling

Alzheimer’s disease (AD) and osteoporosis are multifactorial progressive degenerative disorders. Increasing evidence shows that osteoporosis and hip fracture are common complication observed in AD patients, although the mechanisms underlying this association remain poorly understood. Reactive oxygen species (ROS) are emerging as intracellular redox signaling molecules involved in the regulation of bone metabolism, including receptor activator of nuclear factor-κB ligand-dependent osteoclast differentiation, but they also have cytotoxic effects that include lipoperoxidation and oxidative damage to proteins and DNA. ROS generation, which is implicated in the regulation of cellular stress response mechanisms, is an integrated, highly regulated, process under control of redox sensitive genes coding for redox proteins called vitagenes. Vitagenes, encoding for proteins such as heat shock proteins (Hsps) Hsp32, Hsp70, the thioredoxin, and the sirtuin protein, represent a systems controlling a complex network of intracellular signaling pathways relevant to life span and involved in the preservation of cellular homeostasis under stress conditions. Consistently, nutritional anti-oxidants have demonstrated their neuroprotective potential through a hormetic-dependent activation of vitagenes. The biological relevance of dose–response affects those strategies pointing to the optimal dosing to patients in the treatment of numerous diseases. Thus, the heat shock response has become an important hormetic target for novel cytoprotective strategies focusing on the pharmacological development of compounds capable of modulating stress response mechanisms. Here we discuss possible signaling mechanisms involved in the activation of vitagenes which, relevant to bone remodeling and through enhancement of cellular stress resistance provide a rationale to limit the deleterious consequences associated to homeostasis disruption with consequent impact on the aging process.