Predicting changes in cardiac myocyte contractility during early drug discovery with in vitro assays

• Published in: Toxicology and applied pharmacology Vol. 279; no. 2; pp. 87 - 94
• Main Authors: Morton, M.J., Armstrong, D., Abi Gerges, N., Bridgland-Taylor, M., Pollard, C.E., Bowes, J., Valentin, J.-P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-09-2014; Elsevier
• Subjects: 60 APPLIED LIFE SCIENCES; ABUNDANCE; Animals; Automated electrophysiology; Automation; Binding Sites; Biological and medical sciences; CALCIUM; Calcium Channels, L-Type - drug effects; Calcium Channels, L-Type - genetics; Calcium Channels, L-Type - metabolism; Cardiac drug safety; CHO Cells; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; Contractility; COST; Cricetinae; Cricetulus; DESIGN; DOGS; Drug Discovery - methods; DRUGS; ECOLOGICAL CONCENTRATION; ELECTROPHYSIOLOGY; Female; FORMATES; High-Throughput Screening Assays; Humans; IN VITRO; INDUSTRY; L-type calcium channel; LIABILITIES; LIGANDS; Medical sciences; Membrane Potentials; Myocardial Contraction - drug effects; Myocyte; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - metabolism; Patch-Clamp Techniques; Predictive Value of Tests; Protein Binding; Radioligand Assay; Radioligand-binding; Risk Assessment; SAFETY; SCREENING; SENSITIVITY; SPECIFICITY; Toxicity Tests - methods; Toxicology; Transfection; Automated electrophysiology; L-type calcium channel; Cardiac drug safety; Radioligand-binding; Contractility; Myocyte; Heart; Drug; Toxicity; Prediction; Electrophysiology; In vitro; Research and development; Cardiomyocyte; Early; Circulatory system; Safety
• ISSN: 0041-008X; 1096-0333
• DOI: 10.1016/j.taap.2014.06.005

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.
•The L-type calcium channel is a significant safety liability during drug discovery.•Radioligand-binding to the L-type calcium channel can be measured in vitro.•The assay can be run at a single test concentration as part of a screening cascade.•This measurement is highly predictive of changes in cardiac myocyte contractility.