title: Assessment of the proarrhythmic potential of the novel antiarrhythmic agent AZD7009 and dofetilide in experimental models of torsades de pointes.
abstract: BACKGROUND
  This study examined the proarrhythmic potential of the novel antiarrhythmic agent AZD7009 and dofetilide.
  
  
  RESULTS
  The electrophysiological and proarrhythmic effects of AZD7009 and dofetilide were assessed in the arterially perfused canine and rabbit left ventricular wedge preparation. The proarrhythmic potential of AZD7009, dofetilide, and azimilide was further assessed in the methoxamine-sensitized rabbit model of torsades de pointes (TdP) in vivo. AZD7009 lengthened the action potential duration (APD) and the QT interval in a bell-shaped manner (15.9 +/- 1.3% in canine wedge and 46.1 +/- 2.9% in rabbit wedge) occurring at 3 and 1 microM. In contrast, dofetilide did not show the bell-shaped concentration response and the QT interval was lengthened more extensively (27.7 +/- 1.6% and 100.8 +/- 10.0%). Furthermore, whereas dofetilide prolonged the midmyocardial and endocardial APD predominantly, resulting in an increased transmural dispersion of repolarization (TDR), AZD7009 prolonged the APD more homogenously in all cell layers. At 1 microM, AZD7009 produced phase 2 early afterdepolarizations (EADs) in 1/4 rabbit preparations but without ventricular R-on-T extrasystoles or TdP. In contrast, starting at 0.03 microM, dofetilide-induced EADs, R-on-T extrasystoles and TdP in 6/6, 5/6, and 4/6 preparations. Following intravenous infusion of AZD7009 (210 nmol/kg/minute), dofetilide (2 nmol/kg/minute) or azimilide (3.33 micromol/kg/minute), TdP was induced in 0/8, 5/8, and 5/8 rabbits (P = 0.026 vs AZD7009), respectively. In 5/5 rabbits, AZD7009 promptly suppressed TdP induced by dofetilide.
  
  
  CONCLUSIONS
  In animal models of TdP, AZD7009 delays ventricular repolarization in a self-limited way associated with a low risk of repolarization-related proarrhythmia.
authors.affiliation: Main Line Health Heart Center, Wynnewood, Pennsylvania, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Leif
authors.initials: L
authors.lastname: Carlsson
authors.forename: Tengxian
authors.initials: T
authors.lastname: Liu
authors.forename: Peter R
authors.initials: PR
authors.lastname: Kowey
authors.forename: Gan-Xin
authors.initials: GX
authors.lastname: Yan
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D005117:Cardiac Complexes, Premature / Q000139:chemically induced; D004195:Disease Models, Animal; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects; D006827:Hydantoins; D048289:Imidazolidines / Q000009:adverse effects; D008297:Male; D010627:Phenethylamines / Q000009:adverse effects*; D010879:Piperazines / Q000009:adverse effects; D011817:Rabbits; D013449:Sulfonamides / Q000009:adverse effects*; D016171:Torsades de Pointes / Q000139:chemically induced*
chemical_list: D000889:Anti-Arrhythmia Agents; D006827:Hydantoins; D048289:Imidazolidines; D010627:Phenethylamines; D010879:Piperazines; D013449:Sulfonamides; C086123:azimilide; C063533:dofetilide