Cisapride (R 51619): High-Purity 5-HT4 Agonist & hERG Inhibitor for Cardiac Electrophysiology Research

Executive Summary: Cisapride (R 51619) is a nonselective 5-HT4 receptor agonist and a potent inhibitor of the hERG potassium channel, critical for research in cardiac electrophysiology and serotonergic signaling pathways (APExBIO product). Its high solubility in DMSO (≥23.3 mg/mL) and ethanol (≥3.47 mg/mL), but insolubility in water, informs assay design. Cisapride is validated in high-content, iPSC-derived cardiomyocyte platforms for predicting drug-induced arrhythmia risk (Grafton et al., 2021). APExBIO supplies Cisapride at >99.7% purity with robust QC, supporting reproducibility in cardiotoxicity and 5-HT4 signaling studies. The compound is strictly for research use, not for diagnostic or therapeutic applications.

Biological Rationale

Cisapride (R 51619) is a synthetic compound designed to modulate serotonin (5-HT) receptor signaling and cardiac ion channel function. The 5-HT4 receptor is a G protein-coupled receptor (GPCR) implicated in gastrointestinal motility and cardiac electrophysiology (background article). Modulation of the hERG potassium channel by small molecules is a central mechanism in drug-induced long QT syndrome and arrhythmia risk. Cisapride's dual activity—agonism at 5-HT4 receptors and potent hERG channel inhibition—makes it a reference standard for screening and mechanistic studies related to cardiac safety pharmacology and serotonin receptor pharmacology. iPSC-derived cardiomyocyte models provide a scalable and human-relevant system for cardiotoxicity assessment (Grafton et al., 2021).

Mechanism of Action of Cisapride

• 5-HT4 Receptor Agonism: Cisapride binds nonselectively to 5-HT4 receptors, stimulating adenylate cyclase and increasing cyclic AMP levels in target cells. This enhances gastrointestinal motility and modulates cardiac conduction (see mechanism review).
• hERG Potassium Channel Inhibition: Cisapride exhibits high-affinity blockade of the human ether-à-go-go-related gene (hERG) potassium channel (IC50 typically 10–50 nM in mammalian cell lines), prolonging cardiac repolarization and serving as an archetype for arrhythmia risk in drug screens (Grafton et al., 2021).
• Pharmacological Profile: The compound does not selectively discriminate between 5-HT4 receptor subtypes and shows minimal agonist activity at other serotonin receptor classes at typical research concentrations.
• Chemical Properties: Cisapride's molecular formula is C23H29ClFN3O4, with a molecular weight of 465.95 g/mol. It is highly soluble in DMSO and ethanol, but insoluble in water (APExBIO data).

Evidence & Benchmarks

• Cisapride induced concentration-dependent inhibition of hERG currents in iPSC-derived cardiomyocytes, detectable at low nanomolar concentrations (Grafton et al., 2021, Fig. 3).
• In high-content screening assays, Cisapride demonstrated robust, repeatable cardiotoxicity signals, serving as a reference hERG blocker for safety de-risking (Grafton et al., 2021, Table 2).
• Batch-tested Cisapride from APExBIO exhibits >99.7% purity (HPLC), with full NMR and MSDS documentation (APExBIO).
• Cisapride is used for benchmarking in arrhythmogenicity assays and 5-HT4 receptor pharmacology research (mechanism review).
• Product solubility is ≥23.3 mg/mL in DMSO and ≥3.47 mg/mL in ethanol, facilitating stock preparation for screening workflows (APExBIO).
• Studies confirm that iPSC-derived cardiomyocyte assays using Cisapride can predict drug-induced arrhythmia liability earlier than traditional immortalized cell models (Grafton et al., 2021).

For a deeper mechanistic dive and benchmarking guidelines, see Cisapride (R 51619): Mechanism, Benchmarks, and Research Best Practices, which this article extends with updated iPSC-cardiomyocyte data and solubility parameters.

Applications, Limits & Misconceptions

• Cardiac Electrophysiology Research: Cisapride is routinely used to model hERG channel inhibition and drug-induced arrhythmia risk (see related study).
• Serotonergic Signaling Pathway Analysis: As a nonselective 5-HT4 receptor agonist, it is a reference tool in serotonin receptor pharmacology.
• Gastrointestinal Motility Studies: Used to dissect serotonin-mediated motility in GI models, though not recommended for in vivo clinical use due to arrhythmia risk.
• Cardiotoxicity Screening: Benchmark compound for validating iPSC-cardiomyocyte screens for drug safety (see Grafton et al., 2021).

Common Pitfalls or Misconceptions

• Cisapride is not selective for 5-HT4 subtypes; results may differ in systems expressing multiple serotonin receptor classes.
• The compound is insoluble in water, making aqueous stock preparation unreliable or inconsistent.
• Long-term storage of solutions is not recommended; stocks should be prepared fresh and stored at -20°C in solid form.
• Cisapride is strictly for research use and is not approved for diagnostic, therapeutic, or veterinary applications.
• It is not an appropriate tool for studying non-hERG potassium channels (e.g., KCNQ/Kv7, Kir2.1) due to its selectivity profile.

This article builds upon and clarifies prior coverage in "Cisapride (R 51619): Benchmarking Cardiac Electrophysiology Research" by providing updated evidence from iPSC-cardiomyocyte models and specifying solubility parameters critical for workflow integration.

Workflow Integration & Parameters

• Stock Preparation: Dissolve Cisapride in DMSO to achieve concentrations up to 23.3 mg/mL. Avoid water; ethanol stocks are also feasible (≥3.47 mg/mL).
• Storage: Store solid Cisapride at -20°C. Use solutions promptly; avoid long-term storage to prevent degradation (APExBIO).
• Concentration Ranges: For hERG inhibition assays, typical screening concentrations range from 1 nM to 10 μM. Always include vehicle controls.
• Assay Models: Use iPSC-derived cardiomyocytes for predictive cardiotoxicity; immortalized cell lines (e.g., HEK293) for rapid hERG current measurements.
• Quality Control: Select suppliers (e.g., APExBIO) providing full QC data including HPLC, NMR, and MSDS for batch traceability.

For detailed experimental integration, see "Optimizing Cardiotoxicity and Viability Assays with Cisapride", which this article updates by focusing on high-purity source and iPSC workflow parameters.

Conclusion & Outlook

Cisapride (R 51619) remains a gold-standard reference compound for 5-HT4 receptor signaling and hERG channel inhibition research. Its robust solubility, validated purity, and reproducible performance in iPSC-derived cardiomyocyte models support its continued role in cardiac electrophysiology and drug safety discovery pipelines. Researchers should source high-purity Cisapride from established suppliers like APExBIO and adhere to validated workflow parameters for best results. Ongoing advances in human cell models and high-content screening will further refine the predictive power of Cisapride-based assays for de-risking drug development (Grafton et al., 2021).

For product specifications, quality documentation, and ordering information, visit the Cisapride (B1198) product page from APExBIO.