title: Predicting changes in cardiac myocyte contractility during early drug discovery with in vitro assays.
abstract: Cardiovascular-related adverse drug effects are a major concern for the pharmaceutical industry. Activity of an investigational drug at the L-type calcium channel could manifest in a number of ways, including changes in cardiac contractility. The aim of this study was to define which of the two assay technologies - radioligand-binding or automated electrophysiology - was most predictive of contractility effects in an in vitro myocyte contractility assay. The activity of reference and proprietary compounds at the L-type calcium channel was measured by radioligand-binding assays, conventional patch-clamp, automated electrophysiology, and by measurement of contractility in canine isolated cardiac myocytes. Activity in the radioligand-binding assay at the L-type Ca channel phenylalkylamine binding site was most predictive of an inotropic effect in the canine cardiac myocyte assay. The sensitivity was 73%, specificity 83% and predictivity 78%. The radioligand-binding assay may be run at a single test concentration and potency estimated. The least predictive assay was automated electrophysiology which showed a significant bias when compared with other assay formats. Given the importance of the L-type calcium channel, not just in cardiac function, but also in other organ systems, a screening strategy emerges whereby single concentration ligand-binding can be performed early in the discovery process with sufficient predictivity, throughput and turnaround time to influence chemical design and address a significant safety-related liability, at relatively low cost.
authors: Discovery Sciences, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK. Electronic address: michael.morton@astrazeneca.com.
authors: M J
authors: MJ
authors: Morton
authors: Drug Safety & Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: D
authors: D
authors: Armstrong
authors: Drug Safety & Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: N
authors: N
authors: Abi Gerges
authors: Discovery Sciences, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: M
authors: M
authors: Bridgland-Taylor
authors: Drug Safety & Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: C E
authors: CE
authors: Pollard
authors: Drug Safety & Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: J
authors: J
authors: Bowes
authors: Drug Safety & Metabolism, AstraZeneca, Macclesfield, Cheshire SK10 4TG, UK.
authors: J-P
authors: JP
authors: Valentin
mesh_terms: D000818:Animals; D001331:Automation; D001665:Binding Sites; D016466:CHO Cells; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004285:Dogs; D055808:Drug Discovery / Q000379:methods*; D005260:Female; D057166:High-Throughput Screening Assays; D006801:Humans; D008024:Ligands; D008564:Membrane Potentials; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011237:Predictive Value of Tests; D011485:Protein Binding; D011869:Radioligand Assay; D018570:Risk Assessment; D018675:Toxicity Tests / Q000379:methods*; D014162:Transfection
chemical_list: D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D008024:Ligands
keywords: Automated electrophysiology; Cardiac drug safety; Contractility; L-type calcium channel; Myocyte; Radioligand-binding