Pharmacokinetics/Pharmacodynamics

Plasma asparaginase activity was determined by a validated enzymatic-coupled assay with a lower limit of detection of 0.013 IU/mL.[16] Asparagine was determined using validated reverse-phase high-performance-liquid chromatography and double mass spectrometry that has a lower limit of quantification of 0.05 µg/mL.[16] Both were performed at a central laboratory [Frontage Laboratories (Malvern, PA)] as previously reported.[16] This trial was conducted with strict on-site instruction and monitoring of the processing of blood samples to minimize ex vivo hydrolysis of asparagine including: placing specimens on ice within 1 minute of collection, centrifugation at 4°C (within 5 minutes of blood collection), subsequent separation of plasma, addition of SERAPREP® to the aliquot to be used for asparagine analysis, and flash freezing with dry ice and storage at −70°C until analysis. The maximum total processing time was required to be less than 15 minutes.[16]