Application of rapid equilibrium dialysis (RED) in the determination of plasma protein binding (PPB) using LC-MS/MS

CBF 2.0 2025 -- When a drug enters the bloodstream, it can bind to various plasma proteins. Only the unbound drug fraction is pharmacologically active. Plasma protein binding (PPB) is one of the most important determinants in understanding the distribution, clearance, pharmacokinetics and pharmacodynamics of a drug. Equilibrium dialysis, which is widely accepted as the “gold standard”, is commonly used in drug-PPB studies to quantitate the free fraction of drugs in plasma. Rapid equilibrium dialysis (RED) device is a superior method for conducting this analysis because it delivers accurate and consistent data with shorter preparation and dialysis times. Compound A is an EZH1/2 dual inhibitor and potential therapy for peripheral T-cell lymphoma. In this study, we developed a reproducible and reliable RED process, following a protein precipitation extraction, to assess the protein binding of this analyte in human plasma.