Preclinical QT safety assessment: cross-species comparisons and human translation from an industry consortium.

INTRODUCTION: In vivo models have been required to demonstrate relative cardiac safety, but model sensitivity has not been systematically investigated. Cross-species and human translation of repolarization delay, assessed as QT/QTc prolongation, has not been compared employing common methodologies across multiple species and sites. Therefore, the accurate translation of repolarization results within and between preclinical species, and to man, remains problematic. METHODS: Six pharmaceutical companies entered into an informal consortium designed to collect high-resolution telemetered data in multiple species (dog; n=34, cynomolgus; n=37, minipig; n=12, marmoset; n=14, guinea pig; n=5, and man; n=57). All animals received vehicle and varying doses of moxifloxacin (3-100 mg/kg, p.o.) with telemetered ECGs (≥500 Hz) obtained for 20-24h post-dose. Individual probabilistic QT-RR relationships were derived for each subject. The rate-correction efficacies of the individual (QTca) and generic correction formulae (Bazett, Fridericia, and Van de Water) were objectively assessed as the mean squared slopes of the QTc-RR relationships. Normalized moxifloxacin QTca responses (Veh Δ%/µM) were derived for 1h centered on the moxifloxacin Tmax. RESULTS: All QT-RR ranges demonstrated probabilistic uncertainty; slopes varied distinctly by species where dog and human exhibited the lowest QT rate-dependence, which was much steeper in the cynomolgus and guinea pig. Incorporating probabilistic uncertainty, the normalized QTca-moxifloxacin responses were similarly conserved across all species, including man. DISCUSSION: The current results provide the first unambiguous evidence that all preclinical in vivo repolarization assays, when accurately modeled and evaluated, yield results that are consistent with the conservation of moxifloxacin-induced QT prolongation across all common preclinical species. Furthermore, these outcomes are directly transferable across all species including man. The consortium results indicate that the implementation of standardized QTc data presentation, QTc reference cycle lengths, and rate-correction coefficients can markedly improve the concordance of preclinical and clinical outcomes in most preclinical species.

Characterization of the human QT interval: novel distribution-based assessment of the repolarization effects of moxifloxacin.

The authors have previously demonstrated rate-independent QT variability in the dog and cynomolgus monkey, where the QT associated with any RR was a normally distributed value that was accurately evaluated as the distribution mean. The present study investigated the rate-independent characteristics of the human QT. Digital electrocardiographs (1000 Hz) were collected for 24 hours in 51 patients (thorough QT study) and analyzed by computer. Distribution-based analysis was applied to the placebo and moxifloxacin (400 mg) arms to characterize the nature of the QT interval and to assess the efficacy of distribution-based analysis for QTc determination. Novel statistics using continuous means and bootstrapped 95% confidence intervals were developed to facilitate QT analysis. Machine-read QT values were compared with core laboratory semiautomated values for verification. RR intervals demonstrated repetitive protocol-dependent variations (50-250 milliseconds); QT intervals were normally distributed, spanning 60 to 100 milliseconds for each RR interval. Distribution-based analysis detected a moxifloxacin response identical to semiautomated analysis, but with reduced variability and improved statistical power, where n = 12 satisfied the ICH E14 criteria for a positive control. Distribution-based analysis has the potential to provide a universal method for clinical QT heart rate correction, enabling accurate detection of QT changes when limited numbers of volunteers are exposed to drug.