Analysis of small molecule antibody-drug conjugate catabolites in rat liver and tumor tissue by liquid extraction surface analysis micro-capillary liquid chromatography/tandem mass spectrometry.

RATIONALE: Antibody-drug conjugates (ADCs) are some of the most promising antibody-related therapeutics. The fate of the cytotoxic moiety of ADCs in vivo after proteolytic degradation of the antibody needs to be well understood in order to mitigate toxicity risks and design proper first in patient studies. METHODS: The feasibility of liquid extraction surface analysis micro-capillary liquid chromatography/tandem mass spectrometry (LESA-µLC/MS/MS) was tested for direct surface sampling of two possible ADC catabolites composed of synthetically modified maytansinoid (DM1) and 4-[N-maleimidomethyl]cyclohexane-1-carbonyl (MCC) from rat liver and tumor tissue. Moreover, the iMatrixSpray was incorporated to prepare calibration standards (Cs) and quality control (QC) samples by spraying analyte solution at different concentrations directly on blank tissue. RESULTS: Lys-MCC-DM1 sprayed on blank liver tissue was homogeneously distributed (12.3% variability). The assay was selective (inference ≤20%) and linear from 50.0 to 1000 ng/mL without any carry-over. Inter-run accuracy and precision were ≤2.3% and ≤25.9% meeting acceptance. Lys-MCC-DM1 was the only catabolite detected in liver and tumor tissue and was most likely responsible for the total radioactivity signal in liver tissue 72 h post-dose measured by quantitative whole body autoradiography (QWBA). CONCLUSIONS: Both analytical assays (LESA-µLC/MS/MS and QWBA) are complementary to each other and provide useful quantitative and qualitative information in spatial tissue distribution of ADCs and their related catabolites. Copyright © 2016 John Wiley & Sons, Ltd.

Quantitative analysis of maytansinoid (DM1) in human serum by on-line solid phase extraction coupled with liquid chromatography tandem mass spectrometry - Method validation and its application to clinical samples.

A sensitive and specific method was developed and validated for the quantitation of maytansinoid (DM1) in human serum using on-line solid phase extraction (SPE)-liquid chromatography-tandem mass spectrometry (LC-MS/MS). Because DM1 contains a free thiol moiety, likely to readily dimerize or react with other thiol-containing molecules in serum, samples were pre-treated with a reducing agent [tris (2-carboxyethyl) phosphine] (TCEP) and further blocked with N-ethylmaleimide (NEM). The resulting samples were diluted with acetonitrile prior to the on-line solid phase extraction (SPE) on a C18 cartridge. A C18 (150×4.6mm ID 3µm particle size) column was used for chromatographic separation with a 10.0min HPLC gradient and DM1-NEM was detected in the selected reaction monitoring mode of a triple quadrupole mass spectrometer. DM1 concentrations were back-calculated from DM1-NEM amount found in the human serum samples. The quantitation range of the method was 0.200-200ng/mL when using 0.25mL serum. Within-run day precisions (n=6) were 0.9-4.4% and between-run day (3 days runs; n=18) precisions 2.5-5.6%. Method biases were between 3.5-14.5% across the whole calibration range. DM1-NEM exhibited sufficiently stability under all relevant analytical conditions and no DM1 losses from the ADC were observed. Finally, the assay was used for DM1 determination in human serum concentration after the intravenous administration of an investigational antibody drug conjugate (ADC) containing DM1 as payload.

The use of generic surrogate peptides for the quantitative analysis of human immunoglobulin G1 in pre-clinical species with high-resolution mass spectrometry.

In the present study, the application of a liquid chromatography high-resolution mass spectrometry (LC-HRMS) analytical assay for the quantitative analysis of a recombinant human immunoglobulin G1 (hIgG1) in rat serum is reported using three generic peptides GPSVFPLAPSSK (GPS), TTPPVLDSDGSFFLYSK (TTP), and VVSVLTVLHQDWLNGK (VVS). Moreover, the deamidation site of a fourth peptide FNWYVDGVEVHNAK (FNW) was identified and further excluded from the assay evaluation due to the inaccuracy of the quantitative results. The rat serum samples were spiked with a fully labeled hIgG1 as internal standard (ISTD). The digestion with trypsin was performed onto the pellet prior to peptide analysis by LC-HRMS using a quadrupole time of flight (QTOF) mass analyzer operating in selected reaction monitoring (SRM) mode with enhanced duty cycles (EDC). The assay linearity for the three investigated peptides was established for a hIgG1 (hIgG1A) from 1.00 to 1000 µg mL(-1) with a mean coefficient of determination (R (2)) higher than 0.9868. The inter-day accuracy and precision obtained in rat serum over 3 days were ≤11.4 and ≤10.5%, respectively. Short-term stability on the auto-sampler at 6 °C for 30 h, at RT for 48 h, and a 100-fold dilution factor were demonstrated. In addition, QC samples prepared in cynomolgus monkey serum and measured with the present method met the acceptance criteria of ±20.0 and ≤20.0% for all three peptides regarding accuracy and precision, respectively. The LC-HRMS method was applied to the analysis of samples from five individual cynomolgus monkeys dosed with a second hIgG1 (hIgG1B) and consistent data were obtained compared to the LC-MS/MS method (conventional triple quadrupole (QqQ) mass analyzer operating in SRM). The present data demonstrate that LC-HRMS can be used for the quantitative analysis of hIgG1 in both species and that quantification is not only limited to classical QqQ instruments.

Phase II metabolism in human skin: skin explants show full coverage for glucuronidation, sulfation, N-acetylation, catechol methylation, and glutathione conjugation.

Although skin is the largest organ of the human body, cutaneous drug metabolism is often overlooked, and existing experimental models are insufficiently validated. This proof-of-concept study investigated phase II biotransformation of 11 test substrates in fresh full-thickness human skin explants, a model containing all skin cell types. Results show that skin explants have significant capacity for glucuronidation, sulfation, N-acetylation, catechol methylation, and glutathione conjugation. Novel skin metabolites were identified, including acyl glucuronides of indomethacin and diclofenac, glucuronides of 17ß-estradiol, N-acetylprocainamide, and methoxy derivatives of 4-nitrocatechol and 2,3-dihydroxynaphthalene. Measured activities for 10 µM substrate incubations spanned a 1000-fold: from the highest 4.758 pmol·mg skin(-1)·h(-1) for p-toluidine N-acetylation to the lowest 0.006 pmol·mg skin(-1)·h(-1) for 17ß-estradiol 17-glucuronidation. Interindividual variability was 1.4- to 13.0-fold, the highest being 4-methylumbelliferone and diclofenac glucuronidation. Reaction rates were generally linear up to 4 hours, although 24-hour incubations enabled detection of metabolites in trace amounts. All reactions were unaffected by the inclusion of cosubstrates, and freezing of the fresh skin led to loss of glucuronidation activity. The predicted whole-skin intrinsic metabolic clearances were significantly lower compared with corresponding whole-liver intrinsic clearances, suggesting a relatively limited contribution of the skin to the body's total systemic phase II enzyme-mediated metabolic clearance. Nevertheless, the fresh full-thickness skin explants represent a suitable model to study cutaneous phase II metabolism not only in drug elimination but also in toxicity, as formation of acyl glucuronides and sulfate conjugates could play a role in skin adverse reactions.

Liquid chromatography tandem mass spectrometry method for the quantitative analysis of ceritinib in human plasma and its application to pharmacokinetic studies.

Ceritinib is a highly selective inhibitor of an important cancer target, anaplastic lymphoma kinase (ALK). Because it is an investigational compound, there is a need to develop a robust and reliable analytical method for its quantitative determination in human plasma. Here, we report the validation of a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the rapid quantification of ceritinib in human plasma. The method consists of protein precipitation with acetonitrile, and salting-out assisted liquid-liquid extraction (SALLE) using a saturated solution of sodium chloride prior to analysis by LC-MS/MS with electrospray ionization (ESI) technique in positive mode. Samples were eluted at 0.800 mL min(-1) on Ascentis Express® C18 column (50 mm × 2.1 mm, 2.7 µm) with a mobile phase made of 0.1 % formic acid in water (A) and 0.1 % formic acid in acetonitrile (B). The method run time was 3.6 min and the low limit of quantification (LLOQ) was estimated at 1.00 ng mL(-1) when using 0.100 mL of human plasma. The assay was fully validated and the method exhibited sufficient specificity, accuracy, precision, and sensitivity. In addition, recovery data and matrix factor (MF) in normal and in hemolyzed plasmas were assessed, while incurred samples stability (ISS) for ceritinib was demonstrated for at least 21 months at a storage temperature of -65 °C or below. The method was successfully applied to the measurement of ceritinib in clinical samples and the data obtained on incurred samples reanalysis (ISR) showed that our method was reliable and suitable to support the analysis of samples from the clinical studies.

Laser diode thermal desorption atmospheric pressure chemical ionization tandem mass spectrometry applied for the ultra-fast quantitative analysis of BKM120 in human plasma.

A sensitive and ultra-fast method utilizing the laser diode thermal desorption ion source using atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS) was developed for the quantitative analysis of BKM120, an investigational anticancer drug in human plasma. Samples originating from protein precipitation (PP) followed by salting-out assisted liquid-liquid extraction (SALLE) were spotted onto the LazWell™ plate prior to their thermal desorption and detection by tandem mass spectrometry in positive mode. The validated method described in this paper presents a high absolute extraction recovery (>90 %) for BKM120 and its internal standard (ISTD) [D8]BKM120, with precision and accuracy meeting the acceptance criteria. Standard curves were linear over the range of 5.00 to 2000 ng mL(-1) with a coefficient of determination (R (2)) >0.995. The method specificity was demonstrated in six different batches of human plasma. Intra- and inter-run precision as well as accuracy within ±20 % at the lower limit of quantification (LLOQ) and ±15 % (other levels) were achieved during a three-run validation for quality control (QC) samples. The post-preparative stability on the LazWell™ plate at room temperature was 72 h and a 200-fold dilution of spiked samples was demonstrated. The method was applied successfully to three clinical studies (n = 847) and cross-checked with the validated LC-ESI-MS/MS reference method. The sample analysis run time was 10 s as compared to 4.5 min for the current validated LC-ESI-MS/MS method. The resultant data were in agreement with the results obtained using the validated reference LC-ESI-MS/MS assay and the same pharmacokinetic (PK) parameters were calculated for both analytical assays. This work demonstrates that LDTD-APCI-MS/MS is a reliable method for the ultra-fast quantitative analysis of BKM120 which can be used to speed-up and support its bioanalysis in the frame of the clinical trials.

Towards absolute quantification of therapeutic monoclonal antibody in serum by LC-MS/MS using isotope-labeled antibody standard and protein cleavage isotope dilution mass spectrometry.

Although LC-MS methods are increasingly used for the absolute quantification of proteins, the lack of appropriate internal standard (IS) hinders the development of rapid and standardized analytical methods for both in vitro and in vivo studies. Here, we have developed a novel method for the absolute quantification of a therapeutic protein, which is monoclonal antibody (mAb). The method combines liquid chromatography tandem mass spectrometry (LC-MS/MS) and protein cleavage isotope dilution mass spectrometry with the isotope-labeled mAb as IS. The latter was identical to the analyzed mAb with the exception that each threonine contains four (13)C atoms and one (15)N atom. Serum samples were spiked with IS prior to the overnight trypsin digestion and subsequent sample cleanup. Sample extracts were analyzed on a C18 ACE column (150 mm x 4.6 mm) using an LC gradient time of 11 min. Endogenous mAb concentrations were determined by calculating the peak height ratio of its signature peptide to the corresponding isotope-labeled peptide. The linear dynamic range was established between 5.00 and 1000 microg/mL mAb with accuracy and precision within +/-15% at all concentrations and below +/-20% at the LLOQ (lower limit of quantification). The overall method recovery in terms of mAb was 14%. The losses due to sample preparation (digestion and purification) were 72% from which about 32% was due to the first step of the method, the sample digestion. This huge loss during sample preparation strongly emphasizes the necessity to employ an IS right from the beginning. Our method was successfully applied to the mAb quantification in marmoset serum study samples, and the precision obtained on duplicate samples was, in most cases, below 20%. The comparison with enzyme-linked immunosorbent assay (ELISA) showed higher exposure in terms of AUC and Cmax with the LC-MS/MS method. Possible reasons for this discrepancy are discussed in this study. The results of this study indicate that our LC-MS/MS method is a simple, rapid, and precise approach for the therapeutic mAb quantification to support preclinical and clinical studies.

In vitro blood distribution and plasma protein binding of the iron chelator deferasirox (ICL670) and its iron complex Fe-[ICL670]2 for rat, marmoset, rabbit, mouse, dog, and human.

Deferasirox (Exjade, ICL670) is an orally active iron chelator. Two molecules of deferasirox can form a complex with ferric iron (Fe-[ICL670]2) that can be excreted, reducing body iron overload. The blood binding parameters across species and the interaction with human serum albumin were analyzed for deferasirox and its iron complex. Both molecules were very highly bound to plasma proteins in all the tested species with unbound fractions in plasma in the range of 0.4 to 1.8% and 0.2 to 1.2% for deferasirox and Fe-[ICL670]2, respectively; binding of the iron complex was either similar or higher in all the species. The high plasma protein binding was in line with a distribution mainly into the plasma fraction of blood; the fraction in plasma was around 100% for Fe-[ICL670]2 in all the species and 65 to 95% for deferasirox depending on the species. Investigations with isolated proteins pointed to serum albumin as the principal binding protein for deferasirox and its iron complex in human plasma. Competition binding experiments indicated that deferasirox at high concentrations displaced markers from the two main drug binding sites of human albumin, whereas Fe-[ICL670]2 displaced only warfarin. In the context of the pharmacokinetic properties of deferasirox and Fe-[ICL670]2, the data indicate the importance of plasma protein binding for their disposition and support a comparison of the pharmacokinetics of deferasirox and its iron complex across species. The low likelihood of clinically relevant drug displacement by deferasirox in plasma is discussed.

Hepatic transport of PKI166, an epidermal growth factor receptor kinase inhibitor of the pyrrolo-pyrimidine class, and its main metabolite, ACU154.

PKI166, a specific inhibitor of the tyrosine kinase activity of two epidermal growth factor receptors, was under development for the treatment of cancer. In preclinical studies PKI166 was mainly cleared by metabolism, and its metabolites were eliminated by biliary excretion, emphasizing the role of liver transport processes for its disposition. Here the transport properties of [14C]PKI166 and its main metabolite [14C]ACU154, an O-glucuronide, were analyzed using 1) Madin-Darby canine kidney II (MDCKII) cells stably transfected with human multidrug resistance-associated protein 2 (MRP2) and/or human organic anion-transporting peptide 2 (OATP2) and 2) liver canalicular membrane vesicles (CMVs) prepared from Wistar and mrp2-deficient TR- rats. Analysis of transport through MDCKII cells revealed that [14C]ACU154 was a substrate of MRP2 and OATP2. Rat mrp2 was shown to transport [14C]ACU154 with a Km of approximately 1 microM. [14C]PKI166 efficiently crossed MDCKII cells, particularly toward the apical side, but expression of MRP2 and/or OATP2 did not increase the flux. The effect of PKI166 and ACU154 on transport of [3H]estradiol-17beta-d-glucuronide (EG; via mrp2/MRP2 and OATP2) or [3H]taurocholic acid (TCA; via bile salt export pump (bsep) was analyzed. PKI166 inhibited the transport of [3H]EG by OATP2. ACU154 did strongly inhibit [3H]TCA uptake into CMVs from Wistar but not from TR- rats, demonstrating a dependence of bsep inhibition on mrp2 activity. ATP-dependent uptake of [3H]EG into CMVs from Wistar rats was inhibited by ACU154 but up to 4-fold increased by PKI166. In conclusion, OATP2 and MRP2/mrp2 were identified as transporters involved in ACU154 transport into bile. Both PKI166 and its O-glucuronide ACU154 affected mrp2/MRP2-, OATP2-, and/or bsep-mediated transport processes.

In vitro blood distribution and plasma protein binding of the tyrosine kinase inhibitor imatinib and its active metabolite, CGP74588, in rat, mouse, dog, monkey, healthy humans and patients with acute lymphatic leukaemia.

AIMS: To determine blood binding parameters of imatinib and its metabolite CGP74588 in humans and non-human species. METHODS: The blood distribution and protein binding of imatinib and CGP74588 were determined in vitro using (14)C labelled compounds. RESULTS: The mean fraction of imatinib in plasma (f(p)) was 45% in dog, 50% in mouse, 65% in rat, 70% in healthy humans and up to 92% in acute lymphatic leukaemia (AML) patients. Similarly, f(p) for CGP74588 was low in dog and monkey (30%), higher in rat, mouse and humans (70%) and highest in some AML patients (90%). The unbound fraction of imatinib and CGP74588 in plasma was lower in rat, mouse, healthy humans and AML patients (2.3-6.5% at concentrations < or = 5000 ng ml(-1)) compared to monkey and dog (7.6-19%). Both compounds displayed high binding to human alpha(1)-acid glycoprotein. AML patients had a reduced haematocrit and showed greatest variability in their blood binding parameters. CONCLUSION: Imatinib and CGP74588 displayed very similar blood binding parameters within all species/groups investigated. The five species clustered into two distinct groups with rat, mouse and humans being clearly different from dog and monkey. For both compounds, higher protein binding was associated with a decreased partitioning into blood cells.