Michael T. Furlong

Pellet digestion: a simple and efficient sample preparation technique for LC–MS/MS quantification of large therapeutic proteins in plasma

BACKGROUND There is a need for a simple and efficient sample preparation technique for LC-MS/MS quantification of large therapeutic proteins in plasma. RESULTS The sample preparation technique presented here is based upon trypsin digestion of the pellet obtained following precipitation of the protein analyte from plasma. The pellet digestion technique was shown to facilitate efficient digestion of large therapeutic proteins, with concomitant removal of a substantial amount of potentially problematic plasma phospholipids. The technique was successfully applied to a pharmacokinetic study of a large therapeutic protein. CONCLUSION This simple sample preparation approach will be beneficial to bioanalytical laboratories engaged in the LC-MS/MS quantification of large therapeutic proteins in biological matrices.

Innovative Use of LC-MS/MS for Simultaneous Quantitation of Neutralizing Antibody, Residual Drug, and Human Immunoglobulin G in Immunogenicity Assay Development

Immunogenicity testing for antidrug antibodies (ADA) faces challenges when high levels of the drug are present in clinical patient samples. In addition, most functional cell-based assays designed to characterize the neutralizing ability of ADA are vulnerable to interference from endogenous serum components. Bead extraction and acid dissociation (BEAD) has been successfully applied to extract ADA from serum samples prior to conduction of cell-based assays. However, in the BEAD, certain amounts of the drug and endogenous serum components (so-called residual drug and serum components) from serum samples are carried over to final BEAD eluates due to formation of protein complexes with ADA or nonspecific binding with the beads. Using current enzyme-linked immunosorbent assay (ELISA)-based ligand-binding assays, it is difficult to evaluate the residual drug, which is complexed with excessive amounts of ADA and endogenous serum components in the BEAD eluates. Here, we describe an innovative application of LC-MS/MS for simultaneous detection of the residual human monoclonal antibody drug and endogenous human IgG and the neutralizing antibody positive-control (NAb-PC) in the BEAD eluates. In this study, the low levels of the residual drug and human IgG in the BEAD eluates indicate that the BEAD efficiently removed the high-concentration drug and serum components from the serum samples. Meanwhile, the NAb-PC recovery (∼42%) in the BEAD provided an acceptable detection limit for the cell-based assay. This novel application of LC-MS/MS to immunogenicity assay development demonstrates the advantages of LC-MS/MS in selectivity and multiplexing, which provides direct and fast measurements of multiple components for immunogenicity assay development.

Dual universal peptide approach to bioanalysis of human monoclonal antibody protein drug candidates in animal studies

BACKGROUND There is a need for general and reliable LC-MS assays capable of supporting the bioanalysis of a variety of human monoclonal antibody-based therapeutic drug candidates in animal PK/TK studies. RESULTS We present herein improvements in our previously reported universal peptide approach to the bioanalysis of human monoclonal antibody protein drug candidates in animal studies. These improvements include incorporation of a second, light chain-based universal peptide into the assay, thus introducing the concept of a dual universal peptide assay; and incorporation of a universal stable isotope-labeled monoclonal antibody into the assay. CONCLUSION Improvements reported herein to the universal peptide assay will enable more reliable quantification of human monoclonal antibody protein drug candidates in animal studies.

A validated LC–MS/MS assay for the simultaneous determination of the anti-leukemic agent dasatinib and two pharmacologically active metabolites in human plasma: Application to a clinical pharmacokinetic study

Dasatinib (Sprycel) is a potent antitumor agent prescribed for patients with chronic myeloid leukemia (CML). To enable reliable quantification of dasatinib and its pharmacologically active metabolites in human plasma during clinical testing, a sensitive and reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated. Samples were prepared using solid phase extraction on Oasis HLB 96-well plates. Chromatographic separation was achieved isocratically on a Luna phenyl-hexyl analytical column. Analytes and the stable labeled internal standards were detected by positive ion electrospray tandem mass spectrometry. The assay was validated over a concentration range of 1.00-1000 ng/mL for dasatinib and its two active metabolites. Intra- and inter-assay precision values for replicate QC control samples were within 5.3% for all analytes during the assay validation. Mean QC control accuracy values were within ± 9.0% of nominal values for all analytes. Assay recoveries were high (>79%) and internal standard normalized matrix effects were minimal. The three analytes were stable in human plasma for at least 22 h at room temperature, for at least 123 days at -20°C, and following at least six freeze-thaw cycles. The validated method was successfully applied to the quantification of dasatinib and two active metabolites in a human pharmacokinetic study.

Use of high-resolution mass spectrometry to investigate a metabolite interference during liquid chromatography/tandem mass spectrometric quantification of a small molecule in toxicokinetic study samples

During routine liquid chromatography/tandem mass spectrometric (LC/MS/MS) bioanalysis of a small molecule analyte in rat serum samples from a toxicokinetic study, an unexpected interfering peak was observed in the extracted ion chromatogram of the internal standard. No interfering peaks were observed in the extracted ion chromatogram of the analyte. The dose-dependent peak area response and peak area response versus time profiles of the interfering peak suggested that it might have been related to a metabolite of the dosed compound. Further investigation using high-resolution mass spectrometry led to unequivocal identification of the interfering peak as an N-desmethyl metabolite of the parent analyte. High-resolution mass spectrometry (HRMS) was also used to demonstrate that the interfering response of the metabolite in the multiple reaction monitoring (MRM) channel of the internal standard was due to an isobaric relationship between the (13)C-isotope of the metabolite and the internal standard (i.e., common precursor ion mass), coupled with a metabolite product ion with identical mass to the product ion used in the MRM transition of the internal standard. These results emphasize (1) the need to carefully evaluate internal standard candidates with regard to potential interferences from metabolites during LC/MS/MS method development, validation and bioanalysis of small molecule analytes in biological matrices; (2) the value of HRMS as a tool to investigate unexpected interferences encountered during LC/MS/MS analysis of small molecules in biological matrices; and (3) the potential for interference regardless of choice of IS and therefore the importance of conducting assay robustness on incurred in vitro or in vivo study samples.

The γ-Secretase Modulator, BMS-932481, Modulates Aβ Peptides in the Plasma and Cerebrospinal Fluid of Healthy Volunteers.

The pharmacokinetics, pharmacodynamics, safety, and tolerability of BMS-932481, a γ-secretase modulator (GSM), were tested in healthy young and elderly volunteers after single and multiple doses. BMS-932481 was orally absorbed, showed dose proportionality after a single dose administration, and had approximately 3-fold accumulation after multiple dosing. High-fat/caloric meals doubled the Cmax and area under the curve and prolonged Tmax by 1.5 hours. Consistent with the preclinical pharmacology of GSMs, BMS-932481 decreased cerebrospinal fluid (CSF) Aβ39, Aβ40, and Aβ42 while increasing Aβ37 and Aβ38, thereby providing evidence of γ-secretase enzyme modulation rather than inhibition. In plasma, reductions in Aβ40 and Aβ42 were observed with no change in total Aβ; in CSF, modest decreases in total Aβ were observed at higher dose levels. Increases in liver enzymes were observed at exposures associated with greater than 70% CSF Aβ42 lowering after multiple dosing. Although further development was halted due to an insufficient safety margin to test the hypothesis for efficacy of Aβ lowering in Alzheimer’s disease, this study demonstrates that γ-secretase modulation is achievable in healthy human volunteers and supports further efforts to discover well tolerated GSMs for testing in Alzheimer’s disease and other indications.

Robust Translation of γ-Secretase Modulator Pharmacology across Preclinical Species and Human Subjects

The amyloid-β peptide (Aβ)—in particular, the 42–amino acid form, Aβ1-42—is thought to play a key role in the pathogenesis of Alzheimer’s disease (AD). Thus, several therapeutic modalities aiming to inhibit Aβ synthesis or increase the clearance of Aβ have entered clinical trials, including γ-secretase inhibitors, anti-Aβ antibodies, and amyloid-β precursor protein cleaving enzyme inhibitors. A unique class of small molecules, γ-secretase modulators (GSMs), selectively reduce Aβ1-42 production, and may also decrease Aβ1-40 while simultaneously increasing one or more shorter Aβ peptides, such as Aβ1-38 and Aβ1-37. GSMs are particularly attractive because they do not alter the total amount of Aβ peptides produced by γ-secretase activity; they spare the processing of other γ-secretase substrates, such as Notch; and they do not cause accumulation of the potentially toxic processing intermediate, β-C-terminal fragment. This report describes the translation of pharmacological activity across species for two novel GSMs, (S)-7-(4-fluorophenyl)-N2-(3-methoxy-4-(3-methyl-1H-1,2,4-triazol-1-yl)phenyl)-N4-methyl-6,7-dihydro-5H-cyclopenta[d]pyrimidine-2,4-diamine (BMS-932481) and (S,Z)-17-(4-chloro-2-fluorophenyl)-34-(3-methyl-1H-1,2,4-triazol-1-yl)-16,17-dihydro-15H-4-oxa-2,9-diaza-1(2,4)-cyclopenta[d]pyrimidina-3(1,3)-benzenacyclononaphan-6-ene (BMS-986133). These GSMs are highly potent in vitro, exhibit dose- and time-dependent activity in vivo, and have consistent levels of pharmacological effect across rats, dogs, monkeys, and human subjects. In rats, the two GSMs exhibit similar pharmacokinetics/pharmacodynamics between the brain and cerebrospinal fluid. In all species, GSM treatment decreased Aβ1-42 and Aβ1-40 levels while increasing Aβ1-38 and Aβ1-37 by a corresponding amount. Thus, the GSM mechanism and central activity translate across preclinical species and humans, thereby validating this therapeutic modality for potential utility in AD.

Pharmacokinetic Interactions between BMS-626529, the Active Moiety of the HIV-1 Attachment Inhibitor Prodrug BMS-663068, and Ritonavir or Ritonavir-Boosted Atazanavir in Healthy Subjects

ABSTRACT BMS-663068 is a prodrug of BMS-626529, a first-in-class attachment inhibitor that binds directly to HIV-1 gp120, preventing initial viral attachment and entry into host CD4+ T cells. This open-label, multiple-dose, four-sequence, crossover study addressed potential two-way drug-drug interactions following coadministration of BMS-663068 (BMS-626529 is a CYP3A4 substrate), atazanavir (ATV), and ritonavir (RTV) (ATV and RTV are CYP3A4 inhibitors). Thirty-six healthy subjects were randomized 1:1:1:1 to receive one of four treatment sequences with three consecutive treatments: BMS-663068 at 600 mg twice daily (BID), BMS-663068 at 600 mg BID plus RTV at 100 mg once daily (QD), ATV at 300 mg QD plus RTV at 100 mg QD (RTV-boosted ATV [ATV/r]), or BMS-663068 at 600 mg BID plus ATV at 300 mg QD plus RTV at 100 mg QD. Compared with the results obtained by administration of BMS-663068 alone, coadministration of BMS-663068 with ATV/r increased the BMS-626529 maximum concentration in plasma (Cmax) and the area under the concentration-time curve in one dosing interval (AUCtau) by 68% and 54%, respectively. Similarly, coadministration of BMS-663068 with RTV increased the BMS-626529 Cmax and AUCtau by 53% and 45%, respectively. Compared with the results obtained by administration of ATV/r alone, ATV and RTV systemic exposures remained similar following coadministration of BMS-663068 with ATV/r. BMS-663068 was generally well tolerated, and there were no adverse events (AEs) leading to discontinuation, serious AEs, or deaths. Moderate increases in BMS-626529 systemic exposure were observed following coadministration of BMS-663068 with ATV/r or RTV. However, the addition of ATV to BMS-663068 plus RTV did not further increase BMS-626529 systemic exposure. ATV and RTV exposures remained similar following coadministration of BMS-663068 with either ATV/r or RTV. BMS-663068 was generally well tolerated alone or in combination with either RTV or ATV/r.

A validated enantioselective LC–MS/MS assay for quantification of a major chiral metabolite of an achiral 11-β-hydroxysteroid-dehydrogenase 1 inhibitor in human plasma: Application to a clinical pharmacokinetic study

BMS-823778 is a potent 11-β-hydroxysteroid-dehydrogenase 1 (11βHSD-1) inhibitor and a potential therapeutic agent for type 2 diabetes mellitus (T2DM). A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated to enable reliable separation and quantification of both enantiomers of a chiral hydroxy metabolite (BMT-094817) in human plasma. Following liquid-liquid extraction in a 96-well plate format, chromatographic separation of the metabolite enantiomers was achieved by isocratic elution on a Chiralpak IA-3 column. Chromatographic conditions were optimized to ensure separation of both metabolite enantiomers. Metabolite enantiomers and stable isotope-labeled (SIL) internal standards were detected by positive ion electrospray tandem mass spectrometry. The LC-MS/MS assay was validated over a concentration range of 0.200-200ng/mL. Intra- and inter-assay precision values for replicate quality control samples were less than 9.9% for both enantiomers during the assay validation. Mean quality control accuracy values were within ±7.3%. Assay recoveries were high (>75%) and consistent across the assay range. The metabolite enantiomers were stable in human blood for 2h on ice. The analytes were also stable in human plasma for 25h at room temperature, 34days at -20°C and -70°C, and following five freeze-thaw cycles. No interconversion of the metabolite enantiomers was detected under any bioanalytical stress conditions, from blood collection/processing through extracted sample storage. The validated assay was successfully applied to the quantification of both metabolite enantiomers in human plasma in support of a human pharmacokinetic study.

Identifying and overcoming bioanalytical challenges associated with chlorine-containing dehydrogenation metabolites

Liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) is a widely utilized analytical tool for quantifying small molecules in complex biological matrices. In certain situations the mass-selection capabilities of the tandem mass spectrometer may be insufficient to discriminate between the analyte of interest and its metabolites, particularly those metabolites that are isobaric with the analyte. One scenario by which isobaric interference may occur is the metabolism of a chlorine- or bromine-containing small molecule to a metabolite with the concomitant loss of 2 Da. This report describes the detection and characterization of two distinct dehydrogenation [M-2] metabolites during LC/MS/MS quantification of a chlorinated small molecule in rat plasma samples derived from a toxicokinetic study. The potential isotope-related impact of these metabolites on quantification of the parent compound was assessed. Several alternate precursor ion and product ion combinations were evaluated and shown to minimize the quantitative impact of the interfering metabolites without having to rely on their stringent chromatographic resolution from the parent compound. These results indicate that when quantifying chlorine- or bromine-containing small molecules from in vivo samples or in vitro metabolic incubations: (1) efforts to detect potential dehydrogenation metabolites should be undertaken and (2) if such metabolites are detected, the judicious choice of alternate multiple-reaction monitoring (MRM) transitions can limit their impact on quantification of the parent molecule without the need for robust chromatographic resolution.