Tuesday, July 27, 2010

Automated Drug Absorption Assays

Drug absorption assays, making up the “A” in ADME/Tox testing, examine how a compound is able to cross various membranes in the body. One of the most important barriers is the intestinal membrane. In order for an orally administered drug to be able to affect its target area within the body, it must be able to pass from the intestine into the blood stream. Therefore, it is crucial to be able to assess compound movement in an accurate, easy to use in vitro format before testing in man during clinical trials.

Cell-based drug absorption assays, such as Caco-2 and MDCK are considered suitable surrogates for intestinal lining absorbtion of small molecule drugs. BioTek Instruments has partnered with Corning Life Sciences to develop automated drug absorption assays in a 96-well format. The assay uses HTS Transwell®-96 Permeable Supports from Corning, in conjunction with BioTek’s EL406 and Precision liquid handling instrumentation. All steps within the assay process were automated, including cell dispense, media exchange, plate washing, and compound dispense. The small footprint of the EL406 enabled the instrument to be easily placed within a laminar flow hood to ensure aseptic manipulations of the cells and media.

MDCK cells, expressing P-glycoprotein, were used as the model cell line for this application. Monolayer integrity was measured using Lucifer Yellow. Data from these tests show that little or no Lucifer Yellow was able to cross the cell monolayer from the apical chamber to the basolateral chamber, indicative of a consistently tight monolayer of cells being able to form within each well (Figure 1).

Drug efflux was also monitored using Rhodamine 123, which was placed into the basolateral chamber. This compound, being a substrate of P-glycoprotein, should be pumped through the cell layer into the apical chamber. Results from automated versus manual assay comparisons demonstrated that the automated assay showed higher efflux values due to lower variability across multiple replicates when compared to manual data (Figure 2).

Do you currently run your drug absorption assays in 96-well format? How do you feel automated high-throughput drug absorption assays can aid in your drug discovery process?

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