Related Experiment Video
Updated: Feb 20, 2026

Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase
Published on: November 23, 2016
Overcoming challenges associated with the bioanalysis of an ester prodrug and its active acid metabolite
Hermes Licea Perez1, Dana Knecht1, Maria Busz1
1Bioanalysis, Immunogenicity, & Biomarkers, IVIVT, GlaxoSmithkline (GSK) Pharmaceuticals, 709 Swedeland Road, King of Prussia, PA 19406, USA.
Aim:
Bioanalysis of ester prodrugs represents a great analytical challenge due to poor matrix stability in the presence of esterases. Materials & methods: An approach that includes pH control, temperature and the use of an inhibitor (sodium fluoride, NaF) was employed for complete stabilization of an ester prodrug and its corresponding acid metabolite. Stability information was used to design a methodology with negligible ex vivo hydrolysis of the ester to the corresponding acid analyte during all critical parts of bioanalysis. Results & conclusion: The assay was fully validated to regulatory expectations and employed to support a preclinical Good Laboratory Practice study in rats. Incurred sample reanalysis was also conducted and the percent difference between repeat and original results were within ±20%, thus confirming the repeatability of the assay.
Related Concept Videos
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Prodrugs
Prodrugs help overcome...
Drug Biotransformation: Overview
Drug Biotransformation: Overview
Drug Metabolism: Phase II Reactions
Bioavailability Enhancement: Determination and Conceptual Approaches in Overcoming Bioavailability Problems

