A fully validated flow cytometry method to quantitatively analyze active rATG in human serum and its application in pharmacokinetic study for therapeutic drug monitoring.

Rabbit anti-thymocyte globulin (rATG) has been widely used to prevent graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The therapeutic window of rATG is narrow, and it may increase the risk of relapse, viral reactivation, delayed immune reconstitution and GvHD when overexposed or underexposed. Therefore, a reliable method for detecting the rATG concentration in human serum by flow cytometry was established and fully validated for therapeutic drug monitoring. In this method, Jurkat T cells were used to capture active rATG in human serum, and PE-labeled donkey anti-rabbit IgG was used as a secondary antibody. The method showed good specificity, selectivity and excellent linearity at concentration of 0.00300-20.0 AU/mL. The intra- and interday precision values were all within 20% at four concentration levels for the analyte. The stock solutions of rATG showed no significant degradation after storage at ambient temperature for 8 h and at - 80 °C for 481 days. No significant degradation of rATG in serum was observed at ambient temperature for 6 h, during six freezethaw cycles and at - 80 °C for at least 373 days. This method was fully validated and successfully applied to monitor active rATG concentration in serum of patients with haploid-identical hematopoietic stem cell transplantation.

Method development and validation for simultaneous determination of six tyrosine kinase inhibitors and two active metabolites in human plasma/serum using UPLC-MS/MS for therapeutic drug monitoring.

Over the past decades, therapeutic drug monitoring (TDM) of tyrosine kinase inhibitors (TKIs) and their main active metabolites has shown benefits in improving treatment efficacy and safety. Therefore, a sensitive, simple and economical ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the determination of six oral tyrosine kinase inhibitors (TKIs) and two active metabolites, including imatinib (IMA), N-desmethyl imatinib (NDIMA), sunitinib (SUNI), N-desethyl sunitinib (NDSUNI), regorafenib (REGO), nilotinib (NILO), dasatinib (DASA) and osimertinib (OSI) in human plasma/serum for therapeutic drug monitoring. The plasma/serum samples were deproteinated with acetonitrile after spiking with two deuterated internal standards (ISs, [2H8]-imatinib and [2H10]-sunitinib) and separated on a 40 °C ACQUITY UPLC® BEH C18 column (1.7 µm, 2.1 mm × 50 mm). The mobile phase was composed of acetonitrile (solution A) and water-formic acid-ammonium acetate (1 M) (994:1:5, v/v/v, solution B). Gradient elution was applied at a flow rate of 0.4 mL/min. Detection was carried out using a Triple Quad 5500 tandem mass spectrometer coupled with an electrospray ionization (ESI) source in positive mode. The method was validated over the calibration curve (CV) range of 2-400 ng/mL for NDSUNI and DASA, 2.5-500 ng/mL for SUNI, 10-2000 ng/mL NDIMA and OSI, 20-4000 ng/mL for NILO, 30-6000 ng/mL for REGO and 50-10000 ng/mL for IMA using linear regression and 1/x2 weighting. No difference was observed in the matrix effect (ME) among blank human plasma, hemolytic plasma, lipemic plasma, plasma spiked with ten commonly used drugs by cancer patients, or serum samples in general. The standard curve fitted by two standard curves of serum and plasma showed good linearity, and the precision and accuracy results of QC samples in both plasma and serum were acceptable and the concentration was comparable. To provide a clinical reference for the operation, the stability of the whole process from sample collection to drug detection was verified. SUNI and NDSUNI showed obvious photoisomerization under light exposure. Therefore, strict light protection was applied for all sample collection and handling steps of SUNI and NDSUNI. Compared with heparin anticoagulant tubes, the stability of the eight compounds in both whole blood and plasma was better in K3-EDTA and sodium citrate anticoagulant tubes. Given that all the analytes were stable in plasma at 4 °C for 48 h and in whole blood at room temperature for 48 h but OSI and REGO were unstable in whole blood and plasma at room temperature, samples should be centrifuged as soon as possible to be preserved as plasma at 4 °C when OSI or REGO is detected. In conclusion, this validated method can provide support for clinical practice, such as therapeutic drug monitoring (TDM) and pharmacokinetic studies of these six TKIs and two active metabolites.