title: Cardiovascular monkey telemetry: sensitivity to detect QT interval prolongation.
abstract: BACKGROUND
  Preclinical evaluation of delayed ventricular repolarization manifests electrocardiographically as QT interval prolongation and is routinely used as an indicator of potential risk for pro-arrhythmia (potential to cause Torsades de Pointes) of novel human pharmaceuticals. In accordance with ICH S7A and S7B guidelines we evaluated the sensitivity and validity of the monkey telemetry model as a preclinical predictor of QT interval prolongation in humans.
  
  
  METHODS
  Cardiovascular monitoring was conducted for 2 h pre-dose and 24 h post-dosing with Moxifloxacin (MOX), with a toxicokinetic (TK) evaluation in a separate group of monkeys. In both studies, MOX was administered orally by gavage in 0.5% methylcellulose at 0, 10, 30, 100, 175 mg/kg. Each monkey received all 5 doses using a dose-escalation paradigm. Inherent variability of the model was assessed with administration of vehicle alone for 4 days in all 4 monkeys (0.5% methylcellulose in deionized water).
  
  
  RESULTS
  MOX had no significant effect on mean arterial pressure, heart rate, PR or QRS intervals. MOX produced significant dose-related increases in QTc at doses of 30 (Cmax=5.5+/-0.6 microM), 100 (Cmax=16.5+/-1.6 microM), and 175 (Cmax=17.3+/-0.7 microM) mg/kg with peak increases of 22 (8%), 27 (10%), and 47 (18%) ms, respectively (p<or=0.05; compared to vehicle).
  
  
  CONCLUSIONS
  In conclusion, we have developed a reproducible, sensitive and reliable primate telemetry model in rhesus monkeys, which exhibits low inherent intra-animal variability and high sensitivity to detect small but significant increases in QT/QTc interval (approximately 4%) with MOX in the same range of therapeutic plasma concentrations attained in humans. Therefore, the primate telemetry model should be considered an important preclinical predictor of QT prolongation of novel human pharmaceuticals.
authors: Safety Assessment, Merck Research Laboratories, P.O. Box 4, West Point, PA 19486, United States.
authors: A A
authors: AA
authors: Chaves
authors: W J
authors: WJ
authors: Keller
authors: S
authors: S
authors: O'Sullivan
authors: M A
authors: MA
authors: Williams
authors: L E
authors: LE
authors: Fitzgerald
authors: H E
authors: HE
authors: McPherson
authors: D
authors: D
authors: Goykhman
authors: P D
authors: PD
authors: Ward
authors: C M
authors: CM
authors: Hoe
authors: L
authors: L
authors: Mixson
authors: R J
authors: RJ
authors: Briscoe