Method Profile
Measure human cardiac channel inhibition under near-physiological conditions and combine parent–metabolite hERG effects with clinical exposure estimates.
Investigate nonclinical–clinical discrepancies in drug-related electrical effects and proarrhythmia assessment.
Human hERG1a in HEK293 cells; human CaV1.2 with auxiliary subunits in CHO cells; human NaV1.5 with β1 in HEK293 cells.
Manual whole-cell patch clamp at 37 ± 2°C; defined voltage/state protocols; selected LC–MS/MS or UV exposure checks and precipitation measurements.
Multichannel comparisons
Chloroquine, lopinavir, ritonavir, vanoxerine, verapamil and ranolazine; hERG, calcium and/or sodium current profiles.
Parent–metabolite pairs
Astemizole/desmethylastemizole, risperidone/paliperidone and clarithromycin/14-hydroxyclarithromycin; published unbound peak clinical exposures.
Fit cell-level concentration-response data with a Hill equation. Compare channel states explicitly. Estimate combined parent–metabolite inhibition assuming competitive binding at overlapping sites; keep this assumption distinct from a measured mixture or clinical outcome.
Reassess selected discordant literature drug profiles; compare new channel data with reported clinical ECG/proarrhythmia and evaluate major metabolites.
Multichannel panels generally 4–7 cells per concentration; verapamil 4–9 and ranolazine 4–6; parent–metabolite hERG measurements 3–9 cells per concentration.
Prior published channel pharmacology and clinical observations; parent-only exposure margins.
Vanoxerine preferentially inhibited hERG and lost 58% in its hERG rig; concentration correction shifted its IC50 from 6.7 to 2.2 nM. Combined hERG margins were 3 versus 210 parent-only for astemizole, 11 versus 160 for risperidone and 23 versus 29 for clarithromycin.
New patch-clamp measurements better aligned selected drug profiles with reported clinical electrical effects. Adding active metabolites substantially narrowed the hERG safety margins for astemizole and risperidone, under an explicit competitive-binding assumption.
