Comparison of manual protein precipitation (PPT) versus a new small volume PPT 96-well filter plate to decrease sample preparation time

Isolation and characterization of glycosylated neuropeptides

Glycosylation is one of the most ubiquitous and complex post-translational modifications (PTMs). It plays pivotal roles in various biological processes. Studies at the glycopeptide level are typically considered as a downstream work resulting from enzymatic digested glycoproteins. Less attention has been focused on glycosylated endogenous signaling peptides due to their low abundance, structural heterogeneity and the lack of enabling analytical tools. Here, protocols are presented to isolate and characterize glycosylated neuropeptides utilizing nanoflow liquid chromatography coupled with mass spectrometry (LC-MS). We first demonstrate how to extract neuropeptides from raw tissues and perform further separation/cleanup before MS analysis. Then we describe hybrid MS methods for glycosylated neuropeptide profiling and site-specific analysis. We also include recommendations for data analysis to identify glycosylated neuropeptides in crustaceans where a complete neuropeptide database is still lacking. Other strategies and future directions are discussed to provide readers with alternative approaches and further unravel biological complexity rendered by glycosylation.

High throughput screening of particle conditioning operations: I. System design and method development

The biotech industry is under increasing pressure to decrease both time to market and development costs. Simultaneously, regulators are expecting increased process understanding. High throughput process development (HTPD) employs small volumes, parallel processing, and high throughput analytics to reduce development costs and speed the development of novel therapeutics. As such, HTPD is increasingly viewed as integral to improving developmental productivity and deepening process understanding. Particle conditioning steps such as precipitation and flocculation may be used to aid the recovery and purification of biological products. In this first part of two articles, we describe an ultra scale-down system (USD) for high throughput particle conditioning (HTPC) composed of off-the-shelf components. The apparatus is comprised of a temperature-controlled microplate with magnetically driven stirrers and integrated with a Tecan liquid handling robot. With this system, 96 individual reaction conditions can be evaluated in parallel, including downstream centrifugal clarification. A comprehensive suite of high throughput analytics enables measurement of product titer, product quality, impurity clearance, clarification efficiency, and particle characterization. HTPC at the 1 mL scale was evaluated with fermentation broth containing a vaccine polysaccharide. The response profile was compared with the Pilot-scale performance of a non-geometrically similar, 3 L reactor. An engineering characterization of the reactors and scale-up context examines theoretical considerations for comparing this USD system with larger scale stirred reactors. In the second paper, we will explore application of this system to industrially relevant vaccines and test different scale-up heuristics.

Critical review of p38 MAP kinase inhibitors: a bioanalytical perspective

p38 MAP kinase is a key enzyme in the proinflammatory response and a large number of compounds have been studied as potential therapeutic drugs. This review summarizes the bioanalytical methods used for the analysis of p38 MAP kinase inhibitors, with a special focus on sample preparation and chromatographic analysis. Biological sample extraction techniques utilized included protein precipitation, liquid–liquid extraction and SPE. Applications include determinations of compounds in a variety of biological fluids and tissues. Extracted samples are typically separated by reverse-phase LC and quantitated either by UV or MS/MS detection. The benefits and limitations of each sample preparation strategy are discussed. The importance of chromatographic separation to avoid matrix effect and interference from endogenous compounds or drug-related biotransformation products are also discussed herein.

Quantification of oltipraz using liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study in rat plasma

An assay method for the determination of oltipraz, a candidate drug for the treatment of liver fibrosis and liver cirrhosis, was developed in rat plasma using a fast-flow protein precipitation (FF-PPT) method coupled with LC-MS/MS for quantification to reduce the labor and to improve the speed of analysis. The applicability of the assay to pharmacokinetic studies was also evaluated. Oltipraz and ethyl-oltipraz, an internal standard (IS), were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 227→193 and 241→174, respectively. A lower limit of quantification (LLOQ) of 20 ng/mL was observed, with a linear dynamic range from 20 to 4000 ng/mL (R>0.997). The accuracy, precision, dilution, recovery, and stability of the assay were deemed acceptable according to FDA guidelines. Oltipraz concentrations were measured successfully in plasma samples up to 12h post-dose in rats that had received an oral dose of 60 mg/kg. The findings indicate that the assay method is rapid and sensitive to oltipraz, showing applicability for pharmacokinetics (PK) studies of oltipraz in other small animals, including rats.

Automated micropipette tip-based SPE in quantitative bioanalysis

Background: Automated methodologies using silica-based, monolithic, micropipette tip-based SPE have been developed for the analysis of small molecules in support of both preclinical and first-in-human development studies using LC–MS/MS. The use of micropipette tip-based SPE with the Tomtec Quadra 96® and the evaluation of prototype micropipette tips for use with the Hamilton Microlab® Star robot is outlined. Results: Mixed-mode cation exchange and C18 SPE methods have been developed using human and rat plasma for the extraction of lipophilic and polar analytes. These methods are advantageous as they use low plasma sample, washing and elution volumes and result in a method extraction cycle time of approximately 6.2 min for 96 samples. Conclusion: This significantly reduced extraction time, compared with 96-well plate format SPE, indicates that the sample preparation stage is no longer the rate-limiting stage in performing a selective extraction procedure. Robust and sensitive methods have been developed that have proven to be more cost effective than traditional 96-well plate format SPE methods.

Quantification of CKD-501, lobeglitazone, in rat plasma using a liquid-chromatography/tandem mass spectrometry method and its applications to pharmacokinetic studies

CKD-501 (i.e., lobeglitazone), a potent agonist for both PPARalpha/gamma, is a new drug that has potential clinical applications in the management of type-2 diabetes. The objective of this study was to develop a rapid and sensitive method for the determination of CKD-501 in rat plasma and to assess the applicability of the assay to pharmacokinetic studies. Rat plasma samples were processed using a fast flow protein precipitation (FF-PPT) method and then introduced onto an LC-MS/MS system for quantification. The analyte and rosiglitazone, an internal standard, were analyzed by multiple reactions monitoring (MRM) at m/z transitions of 482.0-->258.0 for CKD-501 and 358.0-->135.0 for the internal standard. The lower limit of quantification (LLOQ) was determined at 50 ng/mL, with an acceptable linearity in the range from 50 to 10,000 ng/mL (R>0.999). Validation parameters such as accuracy, precision, dilution, recovery, matrix effect and stability were found to be within the acceptance criteria of the assay validation guidelines, indicating that the assay is applicable to estimating the concentration in the range studied. The concentration of CKD-501 was readily quantifiable in plasma samples up to 24 h post-dose in rats that had received an oral dose of 1 mg/kg. These observations suggest, therefore, that the validated assay can be used in pharmacokinetic studies of CKD-501 in small animals such as the rat.

A 96-well single-pot protein precipitation, liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of muraglitazar, a novel diabetes drug, in human plasma

A 96-well single-pot protein precipitation, liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the determination of muraglitazar, a PPAR alpha/gamma dual agonist, in human plasma. The internal standard, a chemical analogue, was dissolved in acetonitrile containing 0.1% formic acid. The solvent system was also served as a protein precipitation reagent. Human plasma samples (0.1 mL) and the internal standard solution (0.3 mL) were added to a 96-well plate. The plate was vortexed for 1 min and centrifuged for 5 min. Then the supernatant layers were directly injected into the LC/MS/MS system. The chromatographic separation was achieved isocratically on a Phenomenox C18(2) Luna column (2 mm x 50 mm, 5 microm). The mobile phase contained 20/80 (v/v) of water and acetonitrile containing 0.1% formic acid. Detection was by positive ion electrospray tandem mass spectrometry on a Sciex API 3000. The standard curve, which ranged from 1 to 1000 ng/mL, was fitted to a 1/x weighted quadratic regression model. This single-pot approach effectively eliminated three time consuming sample preparation steps: sample transfer, dry-down, and reconstitution before the injection, while it preserved all the benefits of the traditional protein precipitation. By properly adjusting the autosampler needle offset level, only the supernatant was injected, without disturbing the precipitated proteins in the bottom. As a result, the quality of chromatography and column life were not compromised. After more than 600 injections, there was only slightly increase of column back-pressure. The validation results demonstrated that this method was rugged and provide satisfactory precision and accuracy. The method has been successfully applied to analyze human plasma samples in support of a first-in-man study. This method has also been validated in monkey and mouse plasma for the determination of muraglitazar.

Liquid chromatography–negative ion electrospray tandem mass spectrometry method for the quantification of tacrolimus in human plasma and its bioanalytical applications

A simple, rapid, novel and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of tacrolimus (I) in human plasma, a narrow therapeutic index, potent macrolide immunosuppressive drug. The analyte and internal standard (tamsulosin (II)) were extracted by liquid-liquid extraction with t-butylmethylether using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of 99% methanol and 1% 10mM ammonium acetate buffer. The deprotonate of analyte was quantitated in negative ionization by multiple reaction monitoring (MRM) with a mass spectrometer. The mass transitions m/z 802.5-->560.3 and m/z 407.2-->151.9 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.05-25ng/ml for tacrolimus in human plasma. The lower limit of quantitation was 50pg/ml with a relative standard deviation of less than 20%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. Run time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in comparative bioavailability studies. The tacrolimus plasma concentration profile could be obtained for pharmacokinetic study. The observed maximum plasma concentration (C(max)) of tacrolimus (5mg oral dose) is 440pg/ml, time to observed maximum plasma concentration (T(max)) is 2.5h and elimination half-life (T(1/2)) is 21h.

Protein precipitation for the analysis of a drug cocktail in plasma by LC–ESI–MS

Three protein precipitation (PP) procedures with acetonitrile (ACN), perchloric acid (PA) and trichloroacetic acid (TCA) were investigated for the analysis of a drug cocktail from human plasma samples containing three pharmaceutical compounds and their primary metabolites. For this purpose, a capillary liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method was developed for the simultaneous analysis of the six tested compounds in less than 6 min. Matrix effect was tested for each PP procedure by means of a post-column infusion system. The three PP techniques were found effective in removing proteins from human plasma and were fully compatible with capillary LC-ESI-MS analysis. However, with acid precipitations, low analyte recovery and a high variability, probably due to analyte coprecipitation, were obtained. Finally, ACN was found to be the most effective PP technique with a recovery higher than 80% and CV inferior to 6%.

Quantification of the anti-leukemia drug STI571 (Gleevec) and its metabolite (CGP 74588) in monkey plasma using a semi-automated solid phase extraction procedure and liquid chromatography-tandem mass spectrometry

Signal Transduction Inhibitor 571 (STI571, formerly known as CGP 57148B) or Gleevec received fast track approval by the US Food and Drug Administration (FDA) for treatment of chronic myeloid leukemia (CML). STI571 (Gleevec) is a revolutionary and promising new oral therapy for CML, which functions at the molecular level with high specificity. The dramatic improvement in efficacy compared with existing treatments prompted an equally profound increase in the pace of development of Gleevec. The duration from first dose in man to completion of the New Drug Application (NDA) filing was less than 3 years. In addition, recently, FDA approved Gleevec for the treatment of gastrointestinal stromal tumor (GIST). In order to support all toxicokinetic (TK) studies with sufficient speed to meet various target dates, a semi-automated procedure using solid phase extraction (SPE) was developed and validated. A Packard Multi-Probe I and a SPE step in a 96-well plate format were utilized. A 3M Empore octyl (C(8))-standard density 96-well plate was used for plasma sample extraction. A Sciex API 3000 triple quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) interface operated in positive ion mode was used for detection. Lower limits of quantification of 1.00 and 2.00 ng/ml were attained for STI571 and its metabolite, CGP 74588, respectively. The method proved to be rugged and allowed the simultaneous quantification of STI571 and CGP 74588 in monkey plasma. Herein, assay development, validation, and representative concentration-time profiles obtained from TK studies are presented.

High-throughput quantification of the anti-leukemia drug STI571 (Gleevec) and its main metabolite (CGP 74588) in human plasma using liquid chromatography-tandem mass spectrometry

The signal transduction inhibitor STI571 (formerly known as CGP 57148B) or Gleevec received fast track approval by the US Food and Drug Administration (FDA) for treatment of chronic myeloid leukemia (CML). STI571 is a revolutionary and promising new oral therapy for CML, which functions at the molecular level with high specificity. The dramatic improvement in efficacy compared to existing treatments prompted an equally profound increase in the pace of development of Gleevec. The duration from first dose in man to completion of the New Drug Application (NDA) filing was approximately 2.6 years. In order to support all pharmacokinetics studies with sufficient speed to meet various target dates, a semi-automated procedure using protein precipitation was developed and validated. A Tomtec Quadra 96 (Model 320) and a protein precipitation step in a 96-well plate format were utilized. A Sciex API 3000 triple quadrupole mass spectrometer with an atmospheric pressure chemical ionization interface operated in positive ion mode was used for detection. The method proved to be rugged and allowed the simultaneous quantification of STI571 and its main metabolite (CGP 74588) in human plasma. Herein, assay development, validation, and representative concentration-time profiles obtained from clinical studies are presented.