Simultaneous quantification of seven active metabolites of roxifiban in human plasma by LC/MS/MS in the presence of an interfering displacer at millimolar concentrations

Making methods rugged for regulated bioanalysis

Methods started in discovery are optimized as they progress through preclinical and clinical development. Making a robust assay includes testing individual steps for consistency and points of failure. Assays may be transferred, optimized and revalidated several times. A rugged assay will not only meet regulatory requirements, but will execute with a low failure rate and confirm results under repeat analysis. Challenging aspects such as differential recovery, sample stabilization, resolution of isomers or conjugate analysis must be tackled and made routine. The proper selection of the IS can overcome limitations. It is best to know the potential points of failure before a study has started, but lessons learned from each study also provide invaluable insights to improve assay ruggedness.

The science of laboratory and project management in regulated bioanalysis

Pharmaceutical drug development is a complex and lengthy process, requiring excellent project and laboratory management skills. Bioanalysis anchors drug safety and efficacy with systemic and site of action exposures. Development of scientific talent and a willingness to innovate or adopt new technology is essential. Taking unnecessary risks, however, should be avoided. Scientists must strategically assess all risks and find means to minimize or negate them. Laboratory Managers must keep abreast of ever-changing technology. Investments in instrumentation and laboratory design are critical catalysts to efficiency and safety. Matrix management requires regular communication between Project Managers and Laboratory Managers. When properly executed, it aligns the best resources at the right times for a successful outcome. Attention to detail is a critical aspect that separates excellent laboratories. Each assay is unique and requires attention in its development, validation and execution. Methods, training and facilities are the foundation of a bioanalytical laboratory.

Critical topics in ensuring data quality in bioanalytical LC–MS method development

The use of LC–MS for bioanalysis of pharmaceuticals is entering its third decade and may be considered to be a mature technology. In many respects this is true, considering the advances made in such areas as instrument performance, electronics, software and automation of use. However, there remain instrumental and noninstrumental areas that require significant attention to ensure data quality. Increasing regulatory focus on analytical method performance and unaddressed method issues require the bioanalyst to understand those areas that most greatly impact data quality. This review will focus on instrumental and noninstrumental areas that can influence data quality, including reference standard and internal standard quality and physicochemical properties, matrix effects, stability in matrix, sample preparation, LC and MS.

Tracking problems and possible solutions in the quantitative determination of small molecule drugs and metabolites in biological fluids using liquid chromatography–mass spectrometry

During the last decade, quantification of low molecular weight molecules using liquid chromatography-tandem mass spectrometry in biological fluids has become a common procedure in many preclinical and clinical laboratories. This overview highlights a number of issues involving "small molecule drugs", bioanalytical liquid chromatography-tandem mass spectrometry, which are frequently encountered during assay development. In addition, possible solutions to these issues are proposed with examples in some of the case studies. Topics such as chromatographic peak shape, carry-over, cross-talk, standard curve non-linearity, internal standard selection, matrix effect, and metabolite interference are presented. Since plasma is one of the most widely adopted biological fluid in drug discovery and development, the focus of this discussion will be limited to plasma analysis. This article is not intended to be a comprehensive overview and readers are encouraged to refer to the citations herein.

Recent developments in extraction procedures relevant to analytical toxicology

Sample preparation is an important step in the development of an analytical method but is often regarded as time-consuming, laborious work. Optimum sample preparation leads to enhanced selectivity and sensitivity, however, and reduces amounts of interfering matrix compounds, resulting in less signal suppression or enhancement. Recent developments in extraction techniques that could be of interest in clinical and forensic toxicology, for example liquid-liquid, solid-phase, and headspace extraction, are summarized in this review. The advantages and disadvantages of several extraction techniques are discussed, to enable the reader to choose an appropriate method of extraction for his or her application. Attention is paid to current trends in analytical toxicology, for example miniaturization, high throughput, and automation.

AlphaIIbbeta3 priming and clustering by orally active and intravenous integrin antagonists

BACKGROUND

Drugs that block platelet-platelet and platelet-fibrin interactions via the alpha(IIb)beta(3) (glycoprotein IIb/IIIa) receptor are used daily in patients undergoing percutaneous coronary interventions. Along with expected increases in spontaneous bleeding, clinical trials have revealed a surprising increase in thrombosis when these drugs are used without other anticoagulants. A better understanding of their mechanisms can minimize these risks.

OBJECTIVES

This study tested the hypothesis that interventions designed to block fibrinogen binding inevitably leave the alpha(IIb)beta(3) receptor in an activated state. It compared the effects on platelet function and alpha(IIb)beta(3) conformation of the orally active compounds orbofiban and roxifiban, the i.v. agents eptifibatide and tirofiban, and echistatin, an arginine-glycine-aspartate (RGD) disintegrin.

METHODS

The integrin antagonist concentrations required to saturate platelets and to block platelet-platelet and platelet-fibrin interactions were determined by flow cytometry, aggregometry, and clot-based adhesion assays, respectively. Analytical ultracentrifugation measured each antagonist's effects on the solution structure of alpha(IIb)beta(3). Fluorescence anisotropy provided equilibrium and kinetic data for integrin:antagonist interactions.

RESULTS

Both orally active drugs bound more tightly and inhibited platelet aggregation and adhesion to fibrin more effectively than echistatin. Analytical ultracentrifugation yielded this order for perturbing alpha(IIb)beta(3) conformation (priming) and promoting oligomerization (clustering): echistatin > eptifibatide > orbofiban > tirofiban > roxifiban. Roxifiban was also most effective at disrupting the rapidly forming/slowly dissociating alpha(IIb)beta(3):echistatin complex.

CONCLUSIONS

Our results suggest that the same molecular mechanisms that enable glycoprotein IIb/IIIa inhibitors to bind tightly to the alpha(IIb)beta(3) receptor and block fibrinogen binding contribute to their ability to perturb the resting integrin's conformation, thus limiting the safety and efficacy of both oral and i.v. integrin antagonists.