Measurement of bempedoic acid and its keto metabolite in human plasma and urine using solid phase extraction and electrospray LC-MS/MS.

Bempedoic acid, a new therapeutic for treatment of hypercholesterolemia, inhibits hepatic ATP-citrate lyase in the cholesterol synthesis pathway after its conjugation with coenzyme A. Sensitive and selective methods were required to study the pharmacokinetic behavior of bempedoic acid and its active 8-keto metabolite in clinical studies. A mixed mode anion exchange extraction on 96-well plates was developed to favor high, selective recoveries of these dicarboxylic acids from urine or plasma. Adsorptive losses in urine led to inaccurate measurements unless samples were acidified and diluted with isopropanol prior to any specimen transfers. Tandem mass spectrometry with negative ion electrospray ionization permitted lower limits of measurement of 20 and 10 ng/mL for the drug and metabolite in either matrix. The methods were validated to current regulatory standards and have been the basis for pharmacokinetic measurements in 26 clinical studies involving over 15,000 samples.