The "One-Step" approach for QT analysis increases the sensitivity of nonclinical QTc analysis.

Whether a compound prolongs cardiac repolarization independent of changes in beat rate is a critical question in drug research and development. Current practice is to resolve this in two steps. First, the QT interval is corrected for the influence of rate and then statistical significance is tested. There is renewed interest in improving the sensitivity of nonclinical corrected QT interval (QTc) assessment with modern studies having greater data density than previously utilized. The current analyses examine the effects of moxifloxacin or vehicle on the QT interval in nonhuman primates (NHPs) using a previously described one-step method. The primary end point is the statistical sensitivity of the assessment. Publications suggest that for a four animal crossover (4 × 4) in NHPs the minimal detectable difference (MDD) is greater than or equal to 10 ms, whereas in an eight animal crossover the MDD is ~6.5 ms. Using the one-step method, the MDD for the four animal NHP assessments was 3 ms. In addition, the one-step model accounted for day-to-day differences in the heart rate and QT-rate slope as well as drug-induced changes in these parameters. This method provides an increase in the sensitivity and reduces the number of animals necessary for detecting potential QT change and represents "best practice" in nonclinical QTc assessment in safety pharmacology studies.

Comparing the sensitivity of cross-over and parallel study designs for QTc assessment: An analysis based on a single large study of moxifloxacin in 48 nonhuman primates.

The cardiovascular safety pharmacology (SP) study conducted to satisfy ICH S7A and S7B has commonly used a cross-over study design where each animal receives all treatments. In an increasing number of cases, cross-over designs are not possible and parallel studies have to be used. These can seldom be as large as 8 animals/treatment to match an n = 8 cross-over. Animals in parallel designs receive only one treatment. Parallel studies will have a different sensitivity to detect changes. This sensitivity is a critical question in using nonclinical QTc evaluations to support an integrated proarrhythmic risk assessment under the newly released ICH E14/S7B Q&As. The current analysis used a study large enough (n = 48) to be analyzed both as a parallel and as a cross-over design to directly compare the performance of the two experimental designs coupled to different statistical models, while all other study conduct aspects were the same. A total of 48 nonhuman primates (NHP) received 2 different treatments twice: vehicle, moxifloxacin (80 mg/kg), vehicle, moxifloxacin (80 mg/kg). Post-dose QTc interval data were recorded for 48 h for each treatment. Data were analyzed using 12 animals randomly selected for each treatment in a parallel design or as an n = 48 animal cross-over study. Different statistical models were used. The primary endpoint was the residual deviation (sigma) from the models applied to hourly time intervals. The sigma was used to determine the minimal detectable difference (MDD) for the study design-statistical model combination. Two statistical models were applicable to either study design. They gave similar sigma and resulting MDD values. In cross-over designs, the individual animal identification (ID) can be used in the statistical model. This enabled the smallest MDD value. Simple statistical models for analysis were identified: Treatment + Baseline for parallel designs and Treatment + ID for cross-over designs. The statistical sensitivity of NHP parallel study designs is reasonable (MDD for n = 6 of 12.7 ms), and in combination with testing exposures higher than likely to be necessary in man could be used in an integrated risk assessment. Where sensitivity of the NHP in vivo QTc assessment is critical, the cross-over design enabled a higher sensitivity (MDD 12.2 ms for n = 4; 8 ms for n = 8).

The standardized functional observational battery: Its intrinsic value remains in the instrument of measure: The rat.

The International Conference on Harmonisation's (ICH) Tripartite Guideline on Safety Pharmacology Studies for Human Pharmaceuticals has adopted the requirement that each new test substance must be tested for effects on the central nervous system prior to "first dose in man". This assessment is required to measure, at a minimum, the effects of the substance on general motor activity, behavioral changes, coordination, sensory/motor reflex responses, and body temperatures. To achieve this goal, ICH S7A recommends a neurobehavioral assessment (usually a functional observational battery (FOB) or modified Irwin test), which is generally undertaken in the rat. There seems to be a growing lack of consensus on the value of the FOB to determine CNS safety. This review highlights the importance of the time, effort and cost of training technicians to familiarize with their instrument of measure, so that each observer is better able to identify and document very subtle changes in behavior that will serve to increase the reliability and validity of these assays with respect to CNS safety assessments.

Effects of telemetric epicardial leads and ventricular catheters on arrhythmia incidence in cynomolgus monkeys.

INTRODUCTION: Utilization of implantable bio-telemetry devices represents a common approach to contemporary cardiovascular safety assessment. Depending on the specific needs of the study design, and corresponding surgical methodologies employed, application of telemetry devices may have more or less liability to interact with ongoing physiology. The potential for intrathoracic procedures (epicardial/intracardiac ECG lead arrangements, left ventricular catheterization) to influence baseline cardiovascular function, and particularly arrhythmia status is currently an important topic of consideration. METHODS: Two experiments were performed to assess the post-surgical incidence of ventricular arrhythmias in cynomolgus monkeys instrumented with telemetry devices with 1) left ventricular pressure (LVP) transducers and epicardial lead array (N=67), and 2) epicardial lead array without LVP catheter placement (N=55). A third experiment (N=18) was performed to prospectively, and definitively, investigate the effect of chronic left ventricular catheterization on the observed incidences of arrhythmias by means of multiple (pre- and post-surgery) electrocardiographic evaluations conducted on ~24h of data per interval assessed up to ~12months post-implantation. RESULTS: The diversity and number of ventricular rhythm variants was considerably greater in animals instrumented with left ventricular catheters (62/67; 93%) compared to animals instrumented with epicardial leads only (21/55; 38.2%), and surgically naïve animals (9/18; 50%). Prior to surgery, the average frequency of all definitively characterized arrhythmias among experimentally naïve animals was 0.19/h; following surgical implantation of the telemetry device with epicardial leads and ventricular pressure catheter, the overall frequency of arrhythmia increased approximately 40-fold, to 7.19/h. DISCUSSION: Similar to prior investigations in canines, the present results confirm an increased incidence in the rate and variety of ventricular arrhythmias in cynomolgus monkeys when instrumented with telemetry devices equipped with LVP catheters. Instrumentation with epicardial leads was not associated with an increase in arrhythmias above that expected as a function of normal biological variation in experimentally naïve animals of this species.

A one-step approach to the analysis of the QT interval in conscious telemetrized dogs.

INTRODUCTION: To account for heart rate-induced changes in the QT interval, correction formulas are generally applied to normalize the QT interval for heart rate. None of these formulas is entirely accurate because correction or normalization of any parameter in biology may introduce an additional source of variation in estimating the parameter. In this article, a one-step approach for the statistical analysis of the QT interval was proposed based on modeling the functional relationship between the QT interval and heart rate. METHODS: The QT-HR relationship was incorporated into the statistical analysis to provide a model-based correction. This was accomplished by including HR as a covariate in the QT interval analysis. The approach was demonstrated using data generated from Lilly Research Laboratories. We compared the false positive rate and statistical power of QT, QTcF, and the proposed one-step method. RESULTS: We found the one-step method demonstrated the greatest sensitivity in detecting a QT interval change without an increase in the false positive rate. It was shown that the one-step QT analysis could detect a 5%-6% increment of the QT interval. This is approximately equivalent to an increase of 11-13 ms in QT interval in beagle dogs. DISCUSSION: Several advantages and unique features of the one-step method are discussed. These include evaluating treatment effect on QT without applying a heart rate correction formula and estimating QT difference flexibly at any selected heart rate. In addition to the linear QT-HR relationship, other functional relationships can be easily implemented to this approach.