Quantification of T Cell Binding Polyclonal Rabbit Anti-thymocyte Globulin in Human Plasma with Liquid Chromatography Tandem-Mass Spectrometry

Abstract

The addition of rabbit anti-human thymocyte globulin (ATG) to the conditioning regimen prior to allogeneic hematopoietic cell transplantation has significantly reduced the risk of graft-versus-host disease (GvHD) and graft failure. However, ATG has a small therapeutic window. Overexposure of ATG post-HCT hampers T cell immune reconstitution and has been associated with increased relapse rates and viral reactivations, whereas underexposure has been associated with an increased incidence of GvHD, both of which lead to increased mortality. Therapeutic drug monitoring of T cell binding ATG plasma levels provides a means to optimize dosing for patients at high risk for graft failure to ensure timely T cell immune reconstitution and subsequently increase survival chances. This manuscript describes the first liquid chromatography tandem-mass spectrometry (LC-MS/ MS) method to quantify the pharmacologically active fraction of polyclonal ATG in plasma. This was achieved through immunoaffinity purification of active ATG from plasma with Jurkat T cells. After the binding and washing, samples were eluted, denatured, and trypsindigested. Signature peptides originating from the IgG constant chain were measured with LC-MS/MS. Critical method parameters were optimized, and the method was successfully validated following European Medicines Agency (EMA) guidelines. The method covered the therapeutic range of ATG and was validated at a lower limit of quantification (LLOQ) of 1 AU/mL with an overall CV and bias of 11.8% and − 2.5%, respectively. In conclusion, we developed a LC-MS/MS-based method to quantify active polyclonal rabbit ATG in human plasma. We suggest that this novel assay can be used to monitor and optimize dosing of ATG in clinical practice.

Fludarabine–Cyclophosphamide-Based Conditioning with Antithymocyte Globulin Serotherapy Is Associated with Durable Engraftment and Manageable Infections in Children with Severe Aplastic Anemia

“…The question of the best GVHD prophylaxis is yet unanswered, but ATG is widely used in SAA. ATG has a narrow therapeutic window and therapeutic drug monitoring of ATG levels helps to optimize dosing to ensure timely T-cell immune reconstitution [ 30 , 31 ]. Exposure to ATG affects survival after HCT in adults, highlighting the importance of optimum ATG dosing.…”

Modified ELISA for Ultrasensitive Diagnosis

“…The potential applications of this method depend on the specificity and strength of the antigen–antibody reaction being evaluated. Due to the limitation of ELISAs requiring the use of a purified antigen and an extraordinarily functional antibody, some researchers strongly propose that other methods be used, such as liquid chromatography–mass spectrometry (LC-MS) [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ] and various lab-on-a-chip methods [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. A recent trend in LC-MS development for diagnosis is to focus on the detection of drugs and biomarkers, including peptides and steroids, owing to difficulties in preparing suitable antibodies against these small molecules, whereas lab-on-a-chip–based platforms are thought to offer easier sample preparation, chemical manipulation and reaction, and high throughput using various novel detection techniques with, sometimes, label-free detection.…”