A Simplified Method for Determining Blood-to-Plasma Ratios in vitro and ex vivo by Matrix Matching with Blank Blood...

This work describes a simplified, 96-well plate method for determining the blood-to-plasma concentration ratio (BP ratio) for small molecules.

The need for calibration curves was eliminated using a matrix-matching approach in which blood samples were mixed with blank plasma and plasma samples were mixed with blank blood. As a result, both blood- and plasma-origin samples shared an equivalent matrix ahead of bioanalysis. In the in vitro assay, identical sample matrices were achieved by using the same source of blank plasma and blood.

In humans, a good correlation (R2 = 0.84) was observed between the data obtained in this matrix-matching method and literature values for 11 commercial compounds possessing a wide range of logD values across multiple chemical classes. In addition, this method showed good agreement with in vitro BP ratios for 10 proprietary compounds determined radiometrically (R2 = 0.72) in human and preclinical species. Finally, the in vitro matrix matching method compared favorably to BP ratios determined ex vivo for 13 proprietary and literature compounds (R2 = 0.87) in rat.

This method, suitable for in vitro and ex vivo BP ratio determinations, is operationally efficient, robust, and a useful improvement upon previously published methods.