Selected reaction monitoring to differentiate and relatively quantitate isomers of sulfated and unsulfated core 1 O-glycans from salivary MUC7 protein in rheumatoid arthritis.

Rheumatoid arthritis is a common and debilitating systemic inflammatory condition affecting up to 1% of the world's population. This study aimed to investigate the immunological significance of O-glycans in chronic arthritis at a local and systemic level. O-Glycans released from synovial glycoproteins during acute and chronic arthritic conditions were compared and immune-reactive glycans identified. The sulfated core 1 O-glycan (Galß1-3GalNAcol) was immune reactive, showing a different isomeric profile in the two conditions. From acute reactive arthritis, three isomers could be sequenced, but in patients with chronic rheumatoid arthritis, only a single 3-Gal sulfate-linked isomer could be identified. The systemic significance of this glycan epitope was investigated using the salivary mucin MUC7 in patients with rheumatoid arthritis and normal controls. To analyze this low abundance glycan, a selected reaction monitoring (SRM) method was developed to differentiate and relatively quantitate the core 1 O-glycan and the sulfated core 1 O-glycan Gal- and GalNAc-linked isomers. The acquisition of highly sensitive full scan linear ion trap MS/MS spectra in addition to quantitative SRM data allowed the 3- and 6-linked Gal isomers to be differentiated. The method was used to relatively quantitate the core 1 glycans from MUC7 to identify any systemic changes in this carbohydrate epitope. A statistically significant increase in sulfation was identified in salivary MUC7 from rheumatoid arthritis patients. This suggests a potential role for this epitope in chronic inflammation. This study was able to develop an SRM approach to specifically identify and relatively quantitate sulfated core 1 isomers and the unsulfated structure. The expansion of this method may afford an avenue for the high throughput investigation of O-glycans.

Determination of the immunomodulator laquinimod in human plasma by liquid chromatography/tandem mass spectrometry; development, validation and application of two methods in clinical pharmacokinetic profiling.

Laquinimod (ABR-215062) is a synthetic compound currently undergoing clinical development for oral treatment of multiple sclerosis. The present paper describes the development, validation and clinical application of two rapid and sensitive methods for the determination of ABR-215062 in human plasma. Both methods use liquid chromatography/tandem mass spectrometry (LC/MS/MS) with electrospray ionization in positive mode and a stable isotope (13C6)-labeled ABR-215062 as internal standard for calibration. The selected reaction monitoring was based on the transitions m/z 357.1 --> 236.1 for ABR-215062, and either m/z 363.2 --> 236.1 or 365.2 --> 238.1 for 13C6-ABR-215062. Method 1, aimed and validated for low level determinations (0.4-100 nmol/L) of ABR-215062, utilizes solid-phase extraction followed by isocratic elution. Method 2, aimed and validated for wide range determinations (0.75-15000 nmol/L) of ABR-215062, utilizes protein precipitation followed by fast gradient elution. The methods were validated with respect to selectivity, lower limit of quantification (LLOQ), dynamic range, precision, accuracy, extraction recovery and ruggedness. Furthermore, the stability of low level ABR-215062 in plasma was investigated. The methods were also applied in clinical trials. The LLOQs were 0.4 and 0.75 nmol/L for methods 1 and 2, respectively. The intra- and inter-day precision for the methods were 1.6-3.5% and 2.1-5.7%. The extraction recoveries were 90-97% for both methods. ABR-215062 was stable in plasma for at least 3 months when stored at -20 degrees C. In conclusion, our developed methods were found to be selective, sensitive, robust and suitable for applications in clinical pharmacokinetic profiling.

Pharmacokinetics and splenic accumulation of N-acetylamino-3-chloro-N-(2-diethylamino-ethyl) benzamide after a single administration to rats.

The purpose of this study was to measure the pharmacokinetics and tissue accumulation of N-acetylamino-3-chloro-N-(2-diethylamino-ethyl) benzamide (NACPA) after oral or intravenous administration at a single dose of 25 mg/kg to female W/Fu rats. The serum pharmacokinetics of NACPA were characterized by rapid absorption, distribution and elimination. However, in comparison with its parent compound, 4-amino-3-chloro-N-(2-diethylamino-ethyl) benzamide (3-CPA), NACPA displayed a higher Cmax (mean+/-SD, 201+/-21 vs 33.6+/-0.5 nmol/ml, p < 0.05), and a longer elimination half-life (50+/-0.8 vs 36.6+/-1.1 min, p < 0.05) following intravenous administration. Bioavailability of NACPA was significantly greater than that of 3-CPA (50% compared with 14%, p < 0.05). The tissue accumulation of NACPA was generally higher than that of 3-CPA. NACPA was deposited at higher concentrations in the spleen than in the kidney and liver. Cellular pharmacokinetics indicated that NACPA accumulated more readily in lymphocyte related cells than in liver related cells. Furthermore, incubation of human peripheral lymphocytes with NACPA resulted in inhibition of lymphocyte proliferation, INF-gamma production and chemotaxis. All these results suggest that NACPA may be a good candidate drug for oral administration for immune modulation.