Evacetrapib
Stable-isotope tracer study measures evacetrapib absolute oral bioavailability at 44.8% (J Labelled Comp Radiopharm 2016)
Original title: Absolute bioavailability of evacetrapib in healthy subjects determined by simultaneous administration of oral evacetrapib and intravenous [(13) C8 ]-evacetrapib as a tracer
Healthy subjects received a 130-mg oral dose of evacetrapib simultaneously with a 4-hour intravenous infusion of 175 ug of isotopically labeled [13C8]-evacetrapib as a tracer, with plasma sampled through 168 hours and analyzed by LC-MS/MS. Comparing dose-normalized area-under-the-curve values for the oral and intravenous doses, the researchers calculated an absolute bioavailability of 44.8% (90% CI, 42.2-47.6%) using AUC to infinity and 44.3% (90% CI, 41.8-46.9%) using AUC to the last measurable concentration. Evacetrapib was well tolerated with no clinically significant safety findings, and the study demonstrates a microdose tracer approach that avoids additional toxicology studies for poorly soluble drugs like evacetrapib.
Original abstract
This open-label, single-period study in healthy subjects estimated evacetrapib absolute bioavailability following simultaneous administration of a 130-mg evacetrapib oral dose and 4-h intravenous (IV) infusion of 175 µg [(13) C8 ]-evacetrapib as a tracer. Plasma samples collected through 168 h were analyzed for evacetrapib and [(13) C8 ]-evacetrapib using high-performance liquid chromatography/tandem mass spectrometry. Pharmacokinetic parameter estimates following oral and IV doses, including area under the concentration-time curve (AUC) from zero to infinity (AUC[0-∞]) and to the last measureable concentration (AUC[0-tlast ]), were calculated. Bioavailability was calculated as the ratio of least-squares geometric mean of dose-normalized AUC (oral : IV) and corresponding 90% confidence interval (CI). Bioavailability of evacetrapib was 44.8% (90% CI: 42.2-47.6%) for AUC(0-∞) and 44.3% (90% CI: 41.8-46.9%) for AUC(0-tlast ). Evacetrapib was well tolerated with no reports of clinically significant safety assessment findings. This is among the first studies to estimate absolute bioavailability using simultaneous administration of an unlabeled oral dose with a (13) C-labeled IV microdose tracer at about 1/1000(th) the oral dose, with measurement in the pg/mL range. This approach is beneficial for poorly soluble drugs, does not require additional toxicology studies, does not change oral dose pharmacokinetics, and ultimately gives researchers another tool to evaluate absolute bioavailability.
Summary written by cetpinhibition.org from the published abstract; figures as published. Page updated 18 August 2026. Methods.