Statistical power analysis for hemodynamic cardiovascular safety pharmacology studies in beagle dogs

Preclinical evaluation of general toxicity and safety pharmacology of a receptor-binding domain-based COVID-19 subunit vaccine in various animal models

The coronavirus disease 2019 pandemic has resulted in the introduction of several naïve methods of vaccine development, which have been used to prepare novel viral vectors and mRNA-based vaccines. However, reluctance to receive vaccines owing to the uncertainty regarding their safety is prevalent. Therefore, rigorous safety evaluation of vaccines through preclinical toxicity studies is critical to determine the safety profiles of vaccine candidates. This study aimed to evaluate the toxicity profile of HuVac-19, a subunit vaccine of SARS-CoV-2 utilizing the receptor-binding domain as an antigen, in rats, rabbits, and dogs using single- and repeat-dose study designs. Repeat-dose toxicity studies in rats and rabbits showed transient changes in hematological and serum biochemical parameters in the adjuvant and/or vaccine groups; however, these changes were reversed or potentially reversible after the recovery period. Moreover, temporary reversible changes in absolute and relative organ weights were observed in the prostate of rats and the thymus of rabbits. Gross examination of the injection sites in rats and rabbits treated with the adjuvant- and HuVac-19 showed discoloration and foci, whereas histopathological examination showed granulomatous inflammation, inflammatory cell infiltration, and myofiber degeneration/necrosis. This inflammatory response was local, unassociated with other toxicological changes, and resolved. In a pharmacological safety study, no toxicological or physiological changes associated with HuVac-19 administration were observed. In conclusion, HuVac-19 was not associated with any major systemic adverse effects in the general toxicity and safety pharmacology evaluation, demonstrating that HuVac-19 is a vaccine candidate with sufficient capacity to be used in human clinical trials.

Statistical power analysis of cardiovascular safety pharmacology studies in conscious rats

Cardiovascular (CV) toxicity and related attrition are a major challenge for novel therapeutic entities and identifying CV liability early is critical for effective derisking. CV safety pharmacology studies in rats are a valuable tool for early investigation of CV risk. Thorough understanding of data analysis techniques and statistical power of these studies is currently lacking and is imperative for enabling sound decision-making.

METHODS

Data from 24 crossover and 12 parallel design CV telemetry rat studies were used for statistical power calculations. Average values of telemetry parameters (heart rate, blood pressure, body temperature, and activity) were logged every 60s (from 1h predose to 24h post-dose) and reduced to 15min mean values. These data were subsequently binned into super intervals for statistical analysis. A repeated measure analysis of variance was used for statistical analysis of crossover studies and a repeated measure analysis of covariance was used for parallel studies. Statistical power analysis was performed to generate power curves and establish relationships between detectable CV (blood pressure and heart rate) changes and statistical power. Additionally, data from a crossover CV study with phentolamine at 4, 20 and 100mg/kg are reported as a representative example of data analysis methods.

RESULTS

Phentolamine produced a CV profile characteristic of alpha adrenergic receptor antagonism, evidenced by a dose-dependent decrease in blood pressure and reflex tachycardia. Detectable blood pressure changes at 80% statistical power for crossover studies (n=8) were 4-5mmHg. For parallel studies (n=8), detectable changes at 80% power were 6-7mmHg. Detectable heart rate changes for both study designs were 20-22bpm.

DISCUSSION

Based on our results, the conscious rat CV model is a sensitive tool to detect and mitigate CV risk in early safety studies. Furthermore, these results will enable informed selection of appropriate models and study design for early stage CV studies.

The evaluation of drug-induced changes in cardiac inotropy in dogs: Results from a HESI-sponsored consortium

INTRODUCTION

Drug-induced effects on the cardiovascular system remain a major cause of drug attrition. While hemodynamic (blood pressure (BP) and heart rate (HR)) and electrophysiological methods have been used in testing drug safety for years, animal models for assessing myocardial contractility are used less frequently and their translation to humans has not been established. The goal of these studies was to determine whether assessment of contractility and hemodynamics, when measured across different laboratories using the same protocol, could consistently detect drug-induced changes in the inotropic state of the heart using drugs known to have clinically relevant positive and negative effects on myocardial contractility.

METHODS

A 4×4 double Latin square design (n=8) design using Beagle dogs was developed. Drugs were administrated orally. Arterial blood pressure, left ventricular pressure (LVP) and the electrocardiogram were assessed. Each of the six laboratories studied at least 2 drugs (one positive inotrope (pimobendan or amrinone) and one negative inotrope) (itraconazole or atenolol) at 3 doses selected to match clinical exposure data and a vehicle control. Animals were instrumented with an ITS telemetry system, DSI's D70-PCTP system or DSI's Physiotel Digital system. Data acquisition and analysis systems were Ponemah, Notocord or EMKA.

RESULTS

Derived parameters included: diastolic, systolic and mean arterial BP, peak systolic LVP, HR, end-diastolic LVP, and LVdP/dtmax as the primary contractility index. Blood samples were drawn to confirm drug exposures predicted from independent pharmacokinetic studies. Across the laboratories, a consistent change in LVdP/dtmax was captured despite some differences in the absolute values of some of the hemodynamic parameters prior to treatment.

DISCUSSION

These findings indicate that this experimental model, using the chronically instrumented conscious dog, can accurately and consistently detect changes in cardiac contractility, across multiple sites and instrumentation systems, and that data obtained in this model may also translate to clinical outcomes.

Preclinical safety evaluation of intravenously administered SAL200 containing the recombinant phage endolysin SAL-1 as a pharmaceutical ingredient

Phage endolysins have received increasing attention as potent antibacterial agents. However, although safety evaluation is a prerequisite for the drug development process, a good laboratory practice (GLP)-compliant safety evaluation has not been reported for phage endolysins. A safety evaluation of intravenously administered SAL200 (containing phage endolysin SAL-1) was conducted according to GLP standards. No animals died in any of the safety evaluation studies. In general toxicity studies, intravenously administered SAL200 showed no sign of toxicity in rodent single- and repeated-dose toxicity studies. In the dog repeated-dose toxicity test, there were no abnormal findings, with the exception of transient abnormal clinical signs that were observed in some dogs when daily injection of SAL200 was continued for more than 1 week. In safety pharmacology studies, there were also no signs of toxicity in the central nervous and respiratory system function tests. In the cardiovascular function test, there were no abnormal findings in all tested dogs after the first and second administrations, but transient abnormalities were observed after the third and fourth administrations (2 or 3 weeks after the initial administration). All abnormal findings observed in these safety evaluation studies were slight to mild, were apparent only transiently after injection, and resolved quickly. The safety evaluation results for SAL200 support the implementation of an exploratory phase I clinical trial and underscore the potential of SAL200 as a new drug. We have designed an appropriate phase I clinical trial based on the results of this study.

ILSI–HESI cardiovascular safety subcommittee dataset: An analysis of the statistical properties of QT interval and rate-corrected QT interval (QTc)

INTRODUCTION

The Health and Environmental Sciences Institute of the International Life Sciences Institute (ILSI/HESI) Cardiovascular Safety Subcommittee outlined a set of in vivo telemetry studies to determine how well this preclinical model identified compounds known to cause torsades de pointes (TdP) and prolong QT interval in humans. In the original analysis of these data, QT, QTcB (Bazett model), QTcF (Fridericia model), and QTcQ (animal-specific model) were evaluated. We further evaluate the statistical properties of these measurements, using a method that can properly account for the sources of variability in the dataset.

METHODS

The ILSI/HESI telemetry studies were conducted as a double Latin square design where eight dogs each received a vehicle control and three dose levels of a compound on four separate dosing days. We statistically analyzed the QT/QTc intervals using a repeated measures analysis of covariance and evaluate the powers for QT, QTcF and QTcQ based on simulations.

RESULTS

The analyses for QTcF and QTcB intervals show that all six compounds which were known to cause TdP in humans were identified as positive and all six compounds known to be free of TdP events in their clinical use had no statistically significant treatment-related effects, while the analyses for QTcQ identified all positive compounds except pimozide. The power analysis shows that the method can detect a 7% increment of QT, a 5% increment of QTcF, and a 4% increment of QTcQ, with greater than 80% of power when n=8.

DISCUSSION

We describe a repeated measures procedure to perform statistical analysis of covariance on Latin square designs and show that it can be used to detect meaningful changes in the analysis of QT/QTc intervals.

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.