Journal: Frontiers in Pharmacology

Article Title: Integrating drug effects on individual cardiac ionic currents and cardiac action potentials to understand nonclinical translation to clinical ECG changes

doi: 10.3389/fphar.2025.1674861

Figure Lengend Snippet: Prior patch clamp data interpreted to indicate selective inhibition of I NaL by mexiletine or lidocaine, and selective block of Ca V 1.2 channels by diltiazem. This figure shows prior patch clamp data from Crumb et al., 2016 that were used to select drug pairs and doses for testing in the clinical trial by Johannesen et al., 2016. The data were generated using manual whole cell patch clamp method at 36 °C and recombinant cell lines stably expressing hERG, Ca V 1.2, or Na V 1.5 channels. See Crumb et al., 2016 for details. Concentration-inhibition plots for dofetilide (A) , lidocaine (B) , mexiletine (C) , and diltiazem (D) . The Y-axis shows fractional inhibition; the X-axis, nominal drug concentrations. Error bars denote ±SE. The gray shaded region corresponds to the concentration range evaluated in the human trabeculae recordings . The dashed line represents free clinical C max from : dofetilide, 1.2 nM; lidocaine, 2.9 µM; mexiletine, 3.6 µM; and diltiazem, 53.1 nM. Free C max are calculated using the following information: dofetilide (molecular weight or MW: 441.6 g/mol; percent protein binding or PB: 65%), lidocaine (MW: 234.3 g/mol; PB: 70%), mexiletine (179.26 g/mol; PB: 55%), and diltiazem (MW: 414.5 g/mol; PB: 75%). In these plots, black symbols and curves denote data for hERG; blue, I NaL ; and green, I Ba or Ba 2+ current through Ca V 1.2 channels.

Article Snippet: Dofetilide, lidocaine, moxifloxacin, tetracaine, and verapamil were purchased from Sigma; diltiazem, mexiletine, nifedipine, and tetrodotoxin citrate, from Tocris.

Techniques: Patch Clamp, Inhibition, Blocking Assay, Generated, Recombinant, Stable Transfection, Expressing, Concentration Assay, Molecular Weight, Protein Binding

Journal: Frontiers in Pharmacology

Article Title: Integrating drug effects on individual cardiac ionic currents and cardiac action potentials to understand nonclinical translation to clinical ECG changes

doi: 10.3389/fphar.2025.1674861

Figure Lengend Snippet: Lidocaine or mexiletine, but not diltiazem, reduced hERG block-induced QT C and J-T peakC prolongation. Data used to generate this figure have been published . The plasma drug concentration-dependent analysis for QT C (A,C) and J-T peakC (B,D) for dofetilide co-administered with lidocaine (orange) or mexiletine (blue) (A,B) , and for moxifloxacin co-administered with diltiazem (green) (C,D) . The solid line as well as shaded area reflects the fit of a linear model between drug concentration (dofetilide in panels (A,B) and moxifloxacin in panels (C,D) and placebo and baseline-corrected changes in each ECG interval. The points with error bars (95% CI) reflect the maximum change when dofetilide is combined with lidocaine or mexiletine (A,B) , or when moxifloxacin is combined with diltiazem (C,D) . LIDO, lidocaine; MEX, mexiletine; DIL, diltiazem.

Article Snippet: Dofetilide, lidocaine, moxifloxacin, tetracaine, and verapamil were purchased from Sigma; diltiazem, mexiletine, nifedipine, and tetrodotoxin citrate, from Tocris.

Techniques: Blocking Assay, Clinical Proteomics, Concentration Assay

Journal: Frontiers in Pharmacology

Article Title: Integrating drug effects on individual cardiac ionic currents and cardiac action potentials to understand nonclinical translation to clinical ECG changes

doi: 10.3389/fphar.2025.1674861

Figure Lengend Snippet: Present patch clamp data that showed diltiazem to be a multi-ion channel blocker and nifedipine to be a selective Ca V 1.2 channel blocker. The new patch clamp experiments for dofetilide (A) , lidocaine (B) , mexiletine (C) , diltiazem (D) , and nifedipine (E) . The Y-axis shows fractional inhibition and the X-axis, nominal drug concentrations. Error bars denote ±SE. For Hill fits to estimate potency, fractional inhibition data for individual cells (not shown here) were used. For dofetilide (A) , 29 cells were recorded (4-10 cells for each concentration). For lidocaine (B) , 14 cells were recorded for hERG (4-9 cells for each concentration except 3 µM which was recorded in one cell), 18 cells were recorded for I NaL (4-5 cells per concentration), and 11 cells were recorded for I CaL (4-6 cells per concentration). For mexiletine (C) , nine cells were recorded for hERG (4-5 cells per concentration), 18 cells were recorded for I NaL (4-5 cells per concentration), and 11 cells were recorded for I CaL (5-6 cells per concentration). For diltiazem (D) , eight cells were recorded for hERG (4 cells per concentration), 17 cells were recorded for I NaL (4 cells per concentration, except for 100 µM which was recorded in one cell), and 10 cells were recorded for I CaL (4 cells per concentration). For nifedipine (E) , 11 cells were recorded for hERG (4-5 cells per concentration), 17 cells were recorded for I NaL (4-6 cells per concentration), and 11 cells were recorded for I CaL (4-6 cells per concentration). The shaded regions correspond to the regions evaluated in human action potentials ; the dashed line represents clinical concentration. HERG data for dofetilide and I CaL data for diltiazem had been published previously by this laboratory.

Article Snippet: Dofetilide, lidocaine, moxifloxacin, tetracaine, and verapamil were purchased from Sigma; diltiazem, mexiletine, nifedipine, and tetrodotoxin citrate, from Tocris.

Techniques: Patch Clamp, Inhibition, Concentration Assay

Journal: Frontiers in Pharmacology

Article Title: Integrating drug effects on individual cardiac ionic currents and cardiac action potentials to understand nonclinical translation to clinical ECG changes

doi: 10.3389/fphar.2025.1674861

Figure Lengend Snippet: Shortening of dofetilide-induced APD prolongation by mexiletine or lidocaine. Changes from vehicle control recordings in APD parameters in panel (A) and in triangulation (left Y-axis) and STV (right Y-axis) in panel (B) for dofetilide with increasing concentrations of mexiletine. Panels (D) and (E) show similar plots for dofetilide and lidocaine. For panels (A,B,D,E) , data are presented as mean change from vehicle ±SE. Representative AP traces in (C) and (F) for vehicle, dofetilide, and dofetilide with increasing concentrations of mexiletine or lidocaine recorded at 1 Hz. DOF, Dofetilide; LIDO, lidocaine; MEX, mexiletine.

Article Snippet: Dofetilide, lidocaine, moxifloxacin, tetracaine, and verapamil were purchased from Sigma; diltiazem, mexiletine, nifedipine, and tetrodotoxin citrate, from Tocris.

Techniques: Control

Journal: Frontiers in Pharmacology

Article Title: Integrating drug effects on individual cardiac ionic currents and cardiac action potentials to understand nonclinical translation to clinical ECG changes

doi: 10.3389/fphar.2025.1674861

Figure Lengend Snippet: AP changes by diltiazem, but not nifedipine, suggest multi-ion channel block. Change from vehicle in panels (A,B) for diltiazem 38.4 µM with increasing concentrations of dofetilide and nifedipine 1 µM with increasing concentrations of dofetilide in panels (D,E) . In panels (B,E) the left y-axis corresponds to triangulation and the right y-axis correspond to STV. For panels (A,B,D,E) data is presented as mean change from vehicle and ±SE. Representative AP traces in (C) and (F) for vehicle, diltiazem or nifedipine with increasing concentrations of dofetilide at 1 Hz.

Article Snippet: Dofetilide, lidocaine, moxifloxacin, tetracaine, and verapamil were purchased from Sigma; diltiazem, mexiletine, nifedipine, and tetrodotoxin citrate, from Tocris.

Techniques: Blocking Assay