Category: Assay Development and Screening
Functional agonism of a compound is a property of both the compound and the cell system the compound is tested in. Receptor expression in a cell line, signaling pathway evaluated and assay technology used can all influence the functional potency and efficacy of an agonist. Ehlert, Kenakin, Christopoulos and others have published methods to evaluate the potency and efficacy of test compounds relative to endogenous or standard agonists, and use that data to compare between signaling pathways. This has been discussed for both agonist bias at a specific receptor and selectivity between receptors. In an effort to better understand the use of bias calculations for receptor selectivity, we tested a small cohort of muscarinic agonists in 3 different M1 cell lines as well as additional receptor subtypes. M1, M3, and M5 activity was evaluated using FLIPR and calcium dyes, while M2 and M4 activity was evaluated using Promega Glosensor cAMP technology. Acetylcholine was used as the common agonist across all cell lines. We saw a range of potencies and efficacies for the agonists in cell lines expressing different muscarinic subtypes, even between M1 cell lines. The poster will highlight the use of bias calculations in comparison to traditional methods of determining receptor selectivity.
John Lazzaro– Principal Scientist, Pfizer, Groton, Connecticut