Liquid chromatography tandem mass spectrometry (LC-MS/MS) has gradually become a promising alternative to ligand binding assay for the bioanalysis of biotherapeutic molecules,due to its rapid method development and high accuracy.In this study,we established a new LC-MS/MS method for the determination of the anti-sclerostin monoclonal antibody (SHR-1222) in cynomolgus monkey serum,and compared it to a previous electrochemiluminescence method.The antibody was quantified by detecting the surrogate peptide obtained by trypsin digestion.The surrogate peptide was carefully selected by investigating its uniqueness,stability and MS response.The quantitative range of the pro-posed method was 2.00-500 μg/mL,and this verified method was successfully applied to the tox-icokinetic assessment of SHR-1222 in cynomolgus monkey serum.It was found that the concentrations of SHR-1222 in cynomolgus monkeys displayed an excellent agreement between the LC-MS/MS and electrochemiluminescence methods (ratios of drug exposure,0.8-1.0).Notably,two monkeys in the 60 mg/kg dose group had abnormal profiles with a low detection value of SHR-1222 in their individual sample.Combining the high-level anti-drug antibodies (ADAs) in these samples and the consistent quantitative results of the two methods,we found that the decreased concentration of SHR-1222 was due to the accelerated clearance mediated by ADAs rather than the interference of ADAs to the detection platform.Taken together,we successfully developed an accurate,efficient and cost-effective LC-MS/MS method for the quantification of SHR-1222 in serum samples,which could serve as a powerful tool to improve the preclinical development of antibody drugs.

Objective:To evaluate the systemic absorption and safety of multiple doses of topical tazarotene/betamethasone dipropionate cream in healthy subjects and patients with psoriasis.Methods:From September 2008 to April 2009, 12 healthy subjects collected from Hospital for Skin Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College were randomly and equally divided into tazarotene 0.15%/betamethasone dipropionate 0.15% cream group and tazarotene 0.2%/betamethasone dipropionate 0.2% cream group; these subjects were instructed to apply 0.03 g of the test drug per day on each of the 4 body sites, including the flexor aspects of bilateral forearms, waist and back, for 7 consecutive days, and venous blood samples were obtained before, and 1, 3, 5 and 7 days after the start of drug application. From October 2010 to August 2011, 60 patients with non-cephalic psoriasis collected from the Hospital for Skin Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College were randomly divided into 3 groups at a ratio of 3∶1∶1, i.e., tazarotene 0.05%/betamethasone dipropionate 0.05% cream group ( n = 36) and tazarotene 0.05% gel group ( n = 12) topically treated with a cream vehicle in the morning and the test drug at night, and betamethasone dipropionate 0.05% cream group ( n = 12) topically treated with the test drug twice a day (once in the morning and again in the evening) ; the treatment lasted 6 consecutive weeks, and venous blood samples were collected before, and 2, 4 and 6 weeks after drug application. Liquid chromatography-tandem mass spectrometry was performed to determine the concentrations of tazarotenic acid and betamethasone in plasma. During the trial, adverse events in the subjects were recorded, routine blood and urine examinations were carried out, and liver and kidney function were evaluated before and after treatment. Results:The plasma concentrations of tazarotenic acid and betamethasone in the 12 healthy subjects were below the lower limit of quantitation (0.04 μg/L) after 1-, 3-, 5- and 7-day treatment. After the consecutive treatment, tazarotenic acid and betamethasone were detected in 2 (5.56%) and 4 (11.11%) patients respectively at week 2, 4 or 6 in the tazarotene 0.05%/betamethasone dipropionate 0.05% cream group, and the highest plasma concentrations of tazarotenic acid and betamethasone were 0.112 and 0.201 μg/L respectively; in the betamethasone dipropionate 0.05% cream group, betamethasone was detected in 2 of 12 patients, and the highest plasma concentration of betamethasone was 0.112 μg/L. No test drug-related systemic adverse reactions or laboratory abnormalities were observed in any of the healthy subjects or patients.Conclusion:Multiple doses of topical tazarotene/betamethasone dipropionate cream has advantages of little systemic absorption, no long-term accumulation and good systemic safety.

A chiral LC-MS/MS method for the simultaneous analysis of desvenlafaxine (DVS) enantiomers in human plasma was developed and applied to a pharmacokinetic study on 12 Chinese healthy volunteers. d6-Desvenlafaxine was used as internal standard (IS). Chromatographic separation was performed on the Astec Chirobiotic V chiral column (150 mm x 4.6 mm, 5 μm). The assay was linear over the concentration range of 0.500-150 ng x mL(-1) for both enantiomers (r2 > 0.99). The method was successfully applied to a stereoselective pharmacokinetic study of 100 mg desvenlafaxine sustained release tablets on 12 Chinese healthy volunteers under fasting conditions. The results showed that the pharmacokinetic parameters were similar to both enantiomers in Chinese healthy volunteers. The AUC(0-t), and C(max) of the two enantiomers were about 1.5 times higher than those of blacks and whites reported in the literature.

Ginsenoside compound K (GCK), the main metabolite of protopanaxadiol constituents of Panax ginseng, easily produces alkali metal adduct ions during mass spectrometry particularly with lithium. Accordingly, we have developed a rapid and sensitive liquid chromatography-tandem mass spectrometric method for analysis of GCK in human plasma based on formation of a lithium adduct. The analyte and paclitaxel (internal standard) were extracted from 50 µL human plasma using methyl tert-butyl ether. Chromatographic separation was performed on a Phenomenex Gemini C18 column (50 mm×2.0 mm; 5 μm) using stepwise gradient elution with acetonitrile-water and 0.2 mmol/L lithium carbonate at a flow rate of 0.5 mL/min. Detection was performed in the positive ion mode using multiple reaction monitoring of the transitions at m/z 629→449 for the GCK-lithium adduct and m/z 860→292 for the adduct of paclitaxel. The assay was linear in the concentration range 1.00-1000 ng/mL (r (2)>0.9988) with intra- and inter-day precision of ±8.4% and accuracy in the range of -4.8% to 6.5%. Recovery, stability and matrix effects were all satisfactory. The method was successfully applied to a pharmacokinetic study involving administration of a single GCK 50 mg tablet to healthy Chinese volunteers.

This study aims to develop a liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of ivabradine and N-demethylivabradine in human plasma, and investigate effects of stable isotope labeled (SIL) internal standard (IS) on ivabradine. The analytes and IS were extracted from plasma by protein precipitation with acetonitrile, and chromatographied on a Capcell PAK C18 (100 mm x 4.6 mm, 5 μm) column using a mobile phase of methanol and 5 mmol x L(-1) ammonium acetate. Multiple reaction monitoring with electrospray ionization (ESI) was used in the positive mode for mass spectrometric detection. The effect of ivabradine isotope peak [M+H+3] + on IS and the effect of SIL IS purity on ivabradine were evaluated. An appropriate concentration of SIL IS was chosen to permit method selectivity and linearity of the assay over the required range. The standard curves were demonstrated to be linear in the range of 0.100 to 60.0 ng x mL(-1) for ivabradine, and 0.050 0 to 20.0 ng x mL(-1) for N-demethylivabradine. The intra and inter day precision and accuracy were within the acceptable limits for all concentrations. Besides, the interaction between IS and ivabradine did not impact the determination of analytes. This method was successfully applied to a pharmacokinetic study of hydrogen sulfate ivabradine sustained release tablets on Chinese healthy volunteers.

A simple and rapid method was developed based on high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) to determine sivelestat and its metabolite XW-IMP-A in human plasma. After a simple protein precipitation, the samples and internal standards were analyzed on a C18 column by a gradient elution program. The mobile phase consisted of 30% acetonitrile in methanol and 5 mmol · L(-1) ammonium acetate at a flow rate of 0.7 mL · min(-1). The mass spectrometric data was collected in multiple reaction monitoring mode (MRM) in the negative electrospray ionization. The standard curves were linear in the range of 10.0-15,000 ng · mL(-1) for sivelestat, and 2.50-1000 ng · mL(-1) for XW-IMP-A. The low limits of quantitation were identified at 10.0 and 2.50 ng · mL for sivelestat and XW-IMP-A, respectively. The intra- and inter-day precision were within 11.3% and 13.1% for sivelestat and XW-IMP-A, and accuracy was 0.3% and 0.6% for sivelestat and XW-IMP-A, within the acceptable limits across all concentrations. The method was successfully validated in the pharmacokinetic study of sivelestat in healthy Chinese volunteers.

The study aims to evaluate the bioequivalence of valsartan hydrochlorothiazide tablets, and to investigate the potential cause of bioinequivalence. This was a single-center study with an open, randomized double-way crossover design. Test and reference preparations containing 160 mg of valsartan and 25 mg of hydrochlorothiazide were given to 36 healthy male volunteers. Plasma concentrations of valsartan and hydrochlorothiazide were determined simultaneously by LC-MS/MS. The pharmacokinetic parameters and relative bioavailability were calculated, while the bioequivalence between test and reference preparations were evaluated. The dissolution profiles of test and reference preparations in four different mediums were determined via dissolution test and HPLC. The similarity was investigated according to the similarity factors (f2). The F(o-t) and F(0-infinity) were (139.4 +/- 65.2)% and (137.5 +/- 61.2)% for valsartan of test preparations. It led to get the conclusion that test and reference preparations were not bioequivalent for valsartan. A significant difference was observed between test and reference tablets in the valsartan dissolution test of pH 1.2 hydrochloric acid solution. The key factor of the bioinequivalence might be that dissolution of valsartan in acid medium has marked difference between two preparations.

To study the metabolite excretion of theophylline, a rapid and specific method by liquid chromatography with heated electrospray ionization tandem mass spectrometry (LC-HESI/MS/MS) method for simultaneous determination of theophylline, 1, 3-dimethyluric acid (1,3-DMU), 3-methylxanthine (3-MX) and 1-methyluric acid (1-MU) in human urine was developed using theophylline-d6 and 5-fluorouracil as internal standards. Selected reaction monitoring (SRM) with heated electrospray ionization (HESI) was used in the negative mode for mass spectrometric detection. After diluted with methanol and centrifuged, the analytes and ISs were separated on a XDB-Phenyl (150 mm x 4.6 mm, 5 microm) column with a mixture of water-methanol-formic acid (30 : 70 : 0.15) as mobile phase at a flow rate of 0.6 mL x min(-1). The linear calibration curves for theophylline, 1, 3-DMU, 3-MX and 1-MU were obtained in the concentration range of 1.0-250 microg x mL(-1), separately. The method herein described is effective and convenient, and can be used for determination of theophylline and its three metabolites. The results showed that urinary excretion ratio of theophylline, 1,3-DMU, 3-MX and 1-MU is approximately 1 : 3 : 1 : 2 in Chinese subjects, which is similar to the reported excretion pattern in Caucasian.

The study aims to develop a rapid, sensitive and specified method of liquid chromatography with heated electrospray ionization tandem mass spectrometry (LC-HESI/MS/MS) for simultaneous determination of amlodipine, benazepril and benazeprilat in human plasma using amlodipine-d4 and ubenimex as internal standards (ISs). Selected reaction monitoring (SRM) with heated electrospray ionization (HESI) was used in the positive mode for mass spectrometric detection. Analytes and ISs were extracted from plasma by simple protein precipitation. The reconstituted samples were chromatographed on a C18 (100 mm x 4.6 mm, 5 microm) column with mixture of methanol-acetonitrile-5 mmol.L- ammonium acetate-formic acid (30 : 30 : 40 : 0.1) as mobile phase at a flow rate of 0.6 mL.min-1. The standard curves were demonstrated to be linear in the range of 0.02 to 6.00 ng.mL-1 for amlodipine, 0.2 to 1,500 ng.mL-1 for benazepril and benazeprilat with r2>0.99 for each analyte. The lower limit of quantitation was identifiable and reproducible at 0.02, 0.2 and 0.2 ng mL-1 for amlodipine, benazepril and benazeprilat, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limit across all concentrations. The plasma samples were stable after four freeze-thaw cycles and being stored for 93 days at -20 degrees C. The method was applied to a pharmacokinetic study of a fixed-dose combination of amlodipine and benazepril on Chinese healthy volunteers.

A rapid, sensitive and convenient LC-MS/MS method was developed for the determination of γ-aminobutyric acid (GABA) in human plasma. d2-γ-Aminobutyric acid (d2-GABA) was synthesized as internal standard (IS). After extraction from human plasma by protein precipitation with acetonitrile, all analytes were separated on a Luna HILIC column (100 mm x 3.0 mm, 3 μm) using an isocratic mobile phase of water: acetonitrile: formic acid (20 : 80 : 0.12) with a flow rate of 0.5 mL x min(-1). Acquisition of mass spectrometric data was performed in multiple reaction monitoring mode (MRM) in positive electrospray ionization using the transitions of m/z 104 --> 69 for GABA and m/z 106 --> 71 for d2-GABA. The method was linear in the concentration range of 5.00 to 1 000 ng x mL(-1). The intra- and inter-day precisions were within 9.9%, and accuracy ranged from 99.1% to 104%, within the acceptable limit across all concentrations. The method was successfully applied to a pharmacokinetic study of GABA tablets in healthy Chinese volunteers.