Methods for screening compounds for proarrhythmic risk and antiarrhythmic efficacy

1. A method for screening compounds for their potential to induce or inhibit a cardiac arrhythmia in a subject, comprising determining the ratio of the time constant (τ) of I Ca, L recovery in tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel treated with a test compound to the ventricular repolarization time of cardiac tissue treated with the test compound.

2. The method of claim 1 , wherein determining the ratio comprises measuring the ventricular repolarization time of cardiac tissue treated with the test compound, measuring the recovery of the L-type calcium channel current (I Ca,L ) in tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel treated with the test compound, calculating the time constant of (τ) of I Ca,L recovery in the tissue expressing the L-type calcium channel or any subunit or combination of subunits of the L-type calcium channel, and calculating the ratio of the time constant (τ) of I Ca,L recovery to the ventricular repolarization time.

3. The method of claim 2 , wherein the ventricular repolarization time is measured by electrogram, glass microelectrode, or monophasic action potential electrode and concurrent transmural electrocardiogram.

4. The method of claim 2 , wherein the cardiac tissue is freshly isolated ventricular myocytes, freshly isolated Purkinje fibers, freshly isolated ventricular myocardial layer, freshly isolated papillary muscle, freshly isolated atrial tissue, freshly isolated ventricular wedge, or freshly isolated atrial wedge.

5. The method of claim 2 wherein the L-type calcium channel current recovery is measured by voltage clamping.

6. The method of claim 1 , wherein the tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium is cardiac tissue.

7. The method of claim 1 , wherein the tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium is a stable cell line.

8. The method of claim 6 , wherein the cardiac tissue is freshly isolated ventricular myocytes, freshly isolated Purkinje fibers, freshly isolated ventricular myocardial layer, freshly isolated papillary muscle, freshly isolated atrial tissue, freshly isolated ventricular wedge, or freshly isolated atrial wedge.

9. The method of claim 2 , wherein the tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium is cardiac tissue.

10. The method of claim 2 , wherein the tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium is a stable cell line.

11. The method of claim 9 , wherein the cardiac tissue is freshly isolated ventricular myocytes, freshly isolated Purkinje fibers, freshly isolated ventricular myocardial layer, freshly isolated papillary muscle, freshly isolated atrial tissue, freshly isolated ventricular wedge, or freshly isolated atrial wedge.

12. The method of claim 1 , wherein the cardiac tissue and tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel are treated with multiple doses of the test compound wherein the doses range from the rest compound's free therapeutic plasma C max to a concentration equal to or greater than 100-times higher than the free therapeutic plasma C max .

13. The method of claim 1 , wherein the cardiac tissue and tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel are treated with multiple doses of the test compound wherein the doses range from the test compound's free therapeutic plasma C max to a concentration equal to or greater than 30-time higher than the free therapeutic plasma C max .

14. The method of claim 2 , wherein the cardiac tissue and tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel are treated with multiple doses of the test compound wherein the doses range from the test compound's free therapeutic plasma C max to a concentration equal to or greater than 100-times higher than the free therapeutic plasma C max .

15. The method of claim 2 , wherein the cardiac tissue and tissue expressing the L-type calcium channel or any subunit or combination thereof of the L-type calcium channel are treated with multiple doses of the test compound wherein the doses range from the test compound's free therapeutic plasma C max to a concentration equal to or greater than 30-times higher than the free therapeutic plasma C max .

16. The method of claim 1 , further comprising determining a TdP risk score for a specified dose of the test compound in a specified species by comparing said ratio of said time constant (τ) of I Ca,L recovery to said ventricular repolarization time for said test compound to the ratio of said time constant (τ) of I Ca,L recovery to said ventricular repolarization time of a standard having an established negative, low, moderate, or high risk of inducing TdP in said species.

17. The method of claim 16 , wherein the standard having an established negative risk of inducing TdP is LORATADINE, CIPROFLOXACIN, CLOMIPRAMINE, FLUXETINE or VERAPAMIL.

18. The method of claim 16 , wherein the standard having an established low risk of inducing TdP is AMIODARONE, CITALOPRAM, FLECAINIDE, or MOXIFLOXACIN.

19. The method of claim 16 , wherein the standard having an established moderate risk of inducing TdP is BEPRIDIL, HALOPERIDOL, SPARFLOXACIN, or TERFENADINE.

20. The method of claim 16 , wherein the standard having an established high risk of inducing TdP is DOFETILIDE, SOTALOL, QUINIDINE, or CISAPRIDE.