Flow Cytometry in Cell-Based Pharmacokinetics or Cellular Kinetics in Adoptive Cell Therapy

Pharmacokinetics (PK) defines the disposition of a drug in the body based primarily on measurements in fluids or tissues by various bioanalytical methods during the drug development.Most bioanalytical methods utilize ligandbinding or LC-MS technology, and the assays are validated and applied following the guidelines from various regulatory agencies in their countries (e.g., US FDA, EMEA or Health Canada) [1].These bioanalytical method guidelines focus on the PK of traditional drug compounds; small molecules and large biomolecules.The CAR-T (chimeric antigen receptor) cell therapies, recently approved by FDA, involve administration of 'living drugs' capable of proliferation after infusion.This behavior is very different from conventional drug compounds, and the term 'cellular kinetics' was coined for in vivo 'PK monitoring' of both the expansion and persistence of the genetically engineered CAR-T cells [2].The bioanalytical methods used to measure the levels of these infused cells also differ from conventional methodologies; molecular (polymerase chain reaction-qPCR and sequencing) and cellular assays (flow cytometry) [3].These two technologies play a significant role in the drug development in the recent years.This article is focused on the challenges in the development of flow cytometry bioanalytical methods to quantitatively measure CAR-T cell levels in adoptive cell therapy.