Cardiovascular Safety Pharmacology Studies Research Articles

A simple accurate method for concentration-QTc analysis in preclinical animal models

IntroductionIn preclinical cardiovascular safety pharmacology studies, statistical analysis of the rate corrected QT interval (QTc) is the focus for predicting QTc interval changes in the clinic. Modeling of a concentration/QTc relationship, common clinically, is limited due to minimal pharmacokinetic (PK) data in nonclinical testing. It is possible, however, to relate the average drug plasma concentration from sparse PK samples over specific times to the mean corrected QTc. We hypothesize that averaging drug plasma concentration and the QTc-rate relationship over time provides a simple, accurate concentration-QTc relationship bridging statistical and concentration/QTc modeling. MethodsCardiovascular telemetry studies were conducted in non-human primates (NHP; n = 48) and canines (n = 8). Pharmacokinetic samples were collected on separate study days in both species. Average plasma concentrations for specific intervals (CAverage0-X) were calculated for moxifloxacin in canines and NHP using times corresponding to super-intervals for the QTc data statistical analysis. The QTc effect was calculated for each super-interval using a linear regression correction incorporating QT and HR data from the whole super-interval. The concentration QTc effects were then modeled. ResultsIn NHP, a 10.9 ± 0.06 ms (mean ± 95% CI) change in QTc was detected at approximately 1.5× the moxifloxacin plasma concentration that causes a 10 ms QTc change in humans, based on a 0-24 h super-interval. When simulating a drug without QT effects, mock, no effect on QTc was detected at up to 3× the clinical concentration. Similarly, in canines, a 16.6 ± 0.1 ms change was detected at 1.7× critical clinical moxifloxacin concentration, and a 0.04 ± 0.1 ms change was seen for mock. ConclusionsWhile simultaneous PK and QTc data points are preferred, practical constraints and the need for QTc averaging did not prevent concentration-QTc analyses. Utilizing a 0-24 h super-interval method illustrates a simple and effective method to address cardiovascular questions when preclinical drug exposures exceed clinical concentrations.

In silico modelling of stroke volume, cardiac output and systemic vascular resistance in cardiovascular safety pharmacology studies by telemetry

The principle of proportionality of the systolic area of the central aortic pressure to stroke volume (SV) has been long known. The aim of the present work was to evaluate an in silico solution derived from this principle for modelling SV (iSV model) in cardiovascular safety pharmacology studies by telemetry. Blood pressure was measured in the abdominal aorta in accordance with standard practice. Central aortic pressure was modelled from the abdominal aortic pressure waveform using the N-point moving average (NPMA) method for beat-to-beat estimation of SV. First, the iSV was compared to the SV measured by ultrasonic flowmetry in the ascending aorta (uSV) after various pharmacological challenges in beagle dogs anaesthetised with etomidate/fentanyl. The iSV showed minimal bias (0.2 mL i.e. 2%) and excellent agreement with uSV. Then, previous telemetry studies including reference vasoactive and inotropic compounds were retrospectively reanalysed to model drug effects on stroke volume (iSV), cardiac output (iCO) and systemic vascular resistance (iSVR). Among them, the examples of nicardipine and isoprenaline highlight risks of erroneous or biased estimation of drug effects from the abdominal aortic pressure due to pulse pressure amplification. Furthermore, the examples of verapamil, quinidine and moxifloxacin show that iSV, iCO and iSVR are earlier biomarkers than blood pressure itself for predicting drug effect on blood pressure. This in silico modelling approach included in vivo telemetry safety pharmacology studies can be considered as a New Approach Methodology (NAM) that provides valuable additional information and contribute to improving non-clinical translational research to the clinic.

A comparison of the performance of contemporary, historical, and cross-lab controls in QTc assessment in conscious nonhuman primates

Cardiovascular safety pharmacology and toxicology studies include vehicle control animals in most studies. Electrocardiogram data on common vehicles is accumulated relatively quickly. In the interests of the 3Rs principles it may be useful to use this historical information to reduce the use of animals or to refine the sensitivity of studies.We used implanted telemetry data from a large nonhuman primate (NHP) cardiovascular study (n = 48) evaluating the effect of moxifloxacin. We extracted 24 animals to conduct a n = 3/sex/group analysis. The remaining 24 animals were used to generate 1000 unique combinations of 3 male and 3 female NHP to act as control groups for the three treated groups in the n = 3/sex/group analysis. The distribution of treatment effects, median minimum detectable difference (MDD) values were gathered from the 1000 studies. These represent contemporary controls.Data were available from 42 NHP from 3 other studies in the same laboratory using the same technology. These were used to generate 1000 unique combinations of 6, 12, 18, 24 and 36 NHP to act as historical control animals for the 18 animals in the treated groups of the moxifloxacin study. Data from an additional laboratory were also available for 20 NHP.The QT, RR and QT-RR data from the three sources were comparable. However, differences in the time course of QTc effect in the vehicle data from the two laboratories meant that it was not possible to use cross-lab controls. In the case of historical controls from the same laboratory, these could be used in place of the contemporary controls in determining a treatment's effect. There appeared to be an advantage in using larger (≥18) group sizes for historical controls. These data support the opportunity of using historical controls to reduce the number of animals used in new cardiovascular studies.

Technology and evaluation best practices for in vivo cardiovascular safety pharmacology studies

In vivo cardiovascular experiments as part of safety pharmacology studies have been developed for small molecule drug candidates to maximize detection power for potential undesirable pharmacodynamic effects of a drug candidate on physiological functions, and have been established with appropriate expertise. Conscious freely-moving telemeterized non-rodents are generally used for the in vivo cardiovascular experiments. The technology and evaluation best practices for the experiments have been optimized by multiple researchers and as a result, the experiments considerably contribute to the estimation of cardiovascular risks for humans. In addition, as described in ICH E14&S7B Q&A draft, non-clinical studies are gaining importance in the integrated risk assessment for QT prolongation in humans, and high quality data obtained in non-clinical studies are being required. This manuscript introduces actual technology and evaluation for in vivo cardiovascular safety pharmacology studies based on Japan activity for Improvement of Cardiovascular Evaluation by Telemetry system (J-ICET), which is one of the working groups hosted by Japanese Safety Pharmacology Society.

Echocardiographic and hemodynamic indices of myocardial contractility simultaneously evaluated in telemetered beagle dogs: A HESI-sponsored cross-company evaluation

IntroductionAlterations in cardiac contractility can have significant clinical implications, highlighting the need for early detection of potential liabilities. Pre-clinical methods to assess contractility are typically invasive and their translation to human measures of cardiac function are not well defined. Clinically, cardiac function is most often measured non-invasively using echocardiography. The objective of these studies was to introduce echocardiography into standard large animal cardiovascular safety pharmacology studies and determine the feasibility of this combination. MethodsA consortia of laboratories combined their data sets for evaluation. At each site, telemetered beagle dogs, in a 4 × 4 Latin square crossover study design (n = 4), were administered either pimobendan (positive inotrope) or atenolol (negative inotrope) orally at clinically relevant dose levels. Standard telemetry parameters were collected (heart rate, mean arterial blood pressure, etc.) continuously over 24 h, as well as derived contractility endpoints: QA interval and LV +dP/dtmax. At Tmax, echocardiography was performed in conscious dogs with minimal restraint to collect contractility parameters: ejection fraction (EF) and fractional shortening (FS). ResultsCorrelations between telemetry and echo contractility endpoints showed that, in general, a change in LV +dP/dtmax of 1000 mmHg/s translates to a 5.2% change in EF and a 4.2% change in FS. Poor correlations were shown between QA interval derived simultaneously, to both EF and FS. DiscussionComparing data from telemetry-only groups to those that included echocardiography collections showed no effect in the ability to interpret test article-related effects, providing the foundation for the inclusion of echocardiography without compromising standard telemetry data quality.

An Industry Survey With Focus on Cardiovascular Safety Pharmacology Study Design and Data Interpretation.

The Safety Pharmacology Society (SPS) conducted a membership survey to examine industry practices related mainly to cardiovascular (CV) safety pharmacology (SP). Questions addressed nonclinical study design, data analysis methods, drug-induced effects, and conventional and novel CV assays. The most frequent therapeutic area targeted by drugs developed by the companies/institutions that employ survey responders was oncology. The most frequently observed drug-mediated effects included an increased heart rate, increased arterial blood pressure, hERG (IKr) block, decreased arterial blood pressure, decreased heart rate, QTc prolongation, and changes in body temperature. Broadly implemented study practices included Latin square crossover study design with n = 4 for nonrodent CV studies, statistical analysis of data (eg, analysis of variance), use of arrhythmia detection software, and the inclusion of data from all study animals when integrating SP studies into toxicology studies. Most responders frequently used individual animal housing conditions. Responders commonly evaluated drug effects on multiple ion channels, but in silico modeling methods were used much less frequently. Most responders rarely measured the J-Tpeak interval in CV studies. Uncertainties relative to Standard for Exchange of Nonclinical Data applications for data derived from CV SP studies were common. Although available, the use of human induced pluripotent stem cell cardiomyocytes remains rare. The respiratory SP study was rarely involved with identifying drug-induced functional issues. Responders indicated that the study-derived no observed effect level was more frequently determined than the no observed adverse effect level in CV SP studies; however, a large proportion of survey responders used neither.

Preclinical to Clinical Translation of Hemodynamic Effects in Cardiovascular Safety Pharmacology Studies.

Cardiovascular (CV) safety-related attrition is an important contributor to the loss of promising drug candidates during development. CV safety pharmacology studies are conducted to identify these safety effects. Understanding translation of CV endpoints (specifically, heart rate [HR], and blood pressure [BP]) across preclinical animal models and to the clinic is critical in developing a robust CV derisking strategy. To this end, we investigated translation of HR and BP endpoints using data from 83 compounds that were tested in telemetry studies in rat and large animal (LA; dog or monkey) and 79 compounds that were tested in LA telemetry studies and human phase I clinical trials. Sensitivity, specificity as well as predictive values were calculated for rat to LA model comparison and for LA to human studies comparison. The rat CV model showed good concordance (sensitivity = 84% and specificity = 71%) for LA BP and HR changes. Similarly, LA CV measures of HR and BP showed good concordance (sensitivity = 78% and specificity = 79%) to clinical changes. The CV effects generally occurred within 0.3-3× free plasma concentration across species. Directionality of BP and HR change was conserved between LA to humans. However, for rat to LA comparisons the directionality of change was opposite for 23%-26% compounds. In conclusion, these data establish the translation of HR and BP from preclinical to clinical studies and emphasize the importance of preclinical animal models in the examination of CV safety of drugs.

Nonclinical Profile of BLZ-100, a Tumor-Targeting Fluorescent Imaging Agent.

BLZ-100 is a single intravenous use, fluorescent imaging agent that labels tumor tissue to enable more complete and precise surgical resection. It is composed of a chlorotoxin peptide covalently bound to the near-infrared fluorophore indocyanine green. BLZ-100 is in clinical development for intraoperative visualization of human tumors. The nonclinical safety and pharmacokinetic (PK) profile of BLZ-100 was evaluated in mice, rats, canines, and nonhuman primates (NHP). Single bolus intravenous administration of BLZ-100 was well tolerated, and no adverse changes were observed in cardiovascular safety pharmacology, PK, and toxicology studies in rats and NHP. The single-dose no-observed-adverse-effect-levels (NOAELs) were 7 mg (28 mg/kg) in rats and 60 mg (20 mg/kg) in NHP, corresponding to peak concentration values of 89 400 and 436 000 ng/mL and area-under-the-curve exposure values of 130 000 and 1 240 000 h·ng/mL, respectively. Based on a human imaging dose of 3 mg, dose safety margins are >100 for rat and monkey. BLZ-100 produced hypersensitivity reactions in canine imaging studies (lethargy, pruritus, swollen muzzle, etc). The severity of the reactions was not dose related. In a follow-up study in dogs, plasma histamine concentrations were increased 5 to 60 minutes after BLZ-100 injection; this coincided with signs of hypersensitivity, supporting the conclusion that the reactions were histamine based. Hypersensitivity reactions were not observed in other species or in BLZ-100 human clinical studies conducted to date. The combined imaging, safety pharmacology, PK, and toxicology studies contributed to an extensive initial nonclinical profile for BLZ-100, supporting first-in-human clinical trials.

Cardiovascular safety pharmacology studies in dogs enabled for a poorly soluble molecule using spray-dried dispersion: Impact on lead selection

The aim of this study was to identify an adequate formulation for a poorly soluble lead molecule (BI-A) that would achieve sufficiently high plasma concentrations after oral administration in dogs to enable a robust cardiovascular safety pharmacology assessment in telemetry-instrumented conscious dogs during lead optimization in drug discovery.A spray-dried dispersion of BI-A (BI-A-SDD) containing a 1:2 ratio of BI-A and hydroxypropyl methylcellulose acetate succinate-LF was prepared using a Büchi spray dryer B-90 (B-90). Physical form characterization, an in vitro dissolution test and a preliminary pharmacokinetic (PK) study following oral administration of BI-A-SDD were performed. Thereafter, effects on cardiovascular parameters in conscious, chronically-instrumented dogs were investigated for 24h after a single oral dose (5, 10, and 50mg/kg) using a modified Latin square cross-over study design.The BI-A-SDD powder was confirmed to be amorphous and was stable as an aqueous suspension for at least 4h. The BI-A-SDD suspension provided a greater rate and extent of dissolution than the crystalline BI-A suspension and the supersaturation was maintained for at least 4h. In PK studies the Cmax of the BI-A-SDD formulation (25.4μM; 77-fold the projected efficacious Cmax of 0.33μM) was 7.5-fold higher than the Cmax observed using oral administration of a 10% hydroxypropyl-β-cyclodextrin formulation at 100mg/kg in dogs (3.4μM). In conscious, chronically-instrumented dogs, the doses tested and plasma concentrations achieved were sufficient to enable a robust safety pharmacology evaluation. Multiple off-target hemodynamic effects were detected including acute elevations in aortic blood pressure (up to 22% elevation in systolic and diastolic blood pressure) and tachycardia (68% elevation in heart rate), results that were confirmed in other in vivo models. These results led to a deprioritization of BI-A.The study demonstrated that a spray-dried dispersion, prepared using the B-90 in drug discovery, enhanced the oral exposure of a poorly water-soluble molecule, BI-A, and thereby enabled its evaluation in safety pharmacology studies that ultimately resulted in deprioritization of BI-A from a pool of lead compounds.

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. MethodsData 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. ResultsPhentolamine 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. DiscussionBased 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.

Cardiovascular Safety Pharmacology of Sibutramine.

Sibutramine is an anorectic that has been banned since 2010 due to cardiovascular safety issues. However, counterfeit drugs or slimming products that include sibutramine are still available in the market. It has been reported that illegal sibutramine-contained pharmaceutical products induce cardiovascular crisis. However, the mechanism underlying sibutramine-induced cardiovascular adverse effect has not been fully evaluated yet. In this study, we performed cardiovascular safety pharmacology studies of sibutramine systemically using by hERG channel inhibition, action potential duration, and telemetry assays. Sibutramine inhibited hERG channel current of HEK293 cells with an IC50 of 3.92 μM in patch clamp assay and increased the heart rate and blood pressure (76 Δbpm in heart rate and 51 ΔmmHg in blood pressure) in beagle dogs at a dose of 30 mg/kg (per oral), while it shortened action potential duration (at 10 μM and 30 μM, resulted in 15% and 29% decreases in APD50, and 9% and 17% decreases in APD90, respectively) in the Purkinje fibers of rabbits and had no effects on the QTc interval in beagle dogs. These results suggest that sibutramine has a considerable adverse effect on the cardiovascular system and may contribute to accurate drug safety regulation.

Comparison of freely-moving telemetry Chinese Miniature Experiment Pigs (CMEPs) to beagle dogs in cardiovascular safety pharmacology studies

IntroductionTelemetry beagle dogs are the most frequently used species in cardiovascular telemetry assessments. However, beagle dogs may not be always suitable for all of the tests. Recently minipigs have received increased attention for these studies. Differences between the two species regarding the response of their cardiovascular systems to environmental stimuli are unclear. This study investigates how the telemetry minipig compares to beagle dog as a test subject and also refines the experimental protocols necessary to obtain accurate data. MethodsBeagle dogs and Chinese Miniature Experiment Pigs (CMEPs) were implanted with telemetry transmitters and the influences of gavage, feeding and the circadian cycle on various cardiovascular parameters were investigated. ResultsECG signal quality from CMEPs was superior to that of the beagle dogs. Poor ECG signal quality, elevated HR, BP and locomotor activity associated with gavage and feeding were observed in both species. ECG signal quality, BP and locomotor activity recovered more quickly in the CMEPs than in the beagle dogs. Residual elevation of HR found in CMEPs lasted approximately 4h post-feeding, which has a profound influence on the circadian cycle. A diurnal rhythm in CMEP with a significant increase of body temperature during the dark period and a clear circadian rhythm of locomotor activity in both species were observed. DiscussionThe present data demonstrated that gavage, feeding and circadian cycle were having an enormous influence on BP, HR and locomotor activity in both species. If drug-induced effects are expected rapidly after oral administration and feeding, CMEP seems to be a favorable choice. Also, due to the effects of feeding on HR, CMEPs should fast at least 5h before the start of recording or should not be fed during the study where the Tmax of a given compound might occur very late. It also should be taken into consideration when the test article has a potential effect on body temperature by using CMEPs. In summary, the telemetry CMEP is a valuable alternative to the beagle dog for cardiovascular telemetry studies.

Perspectives on Drug-induced Vascular Injury

Drug-induced vascular injury in nonclinical toxicity studies has been a difficult problem for the pharmaceutical industry for decades. Drugs associated with vascular injury include several classes of antibacterial agents, antimalarials, antivirals, antiinflammatory agents, and molecules manipulating multiple mechanisms for neurologic diseases, cardiovascular diseases, and diabetes mellitus. While some mechanisms of action (e.g., dopamine receptor agonists or antagonists, phosphodiesterase inhibitors, adrenergic agonists and antagonists, endothelin antagonists, and compounds that modulate endothelial nitric oxide synthase) would be expected to have vasoactive properties, other compounds can produce vascular injury with no obvious mechanism. Acute or multidose cardiovascular safety pharmacology studies in animals often show no systemic effects on blood pressure, heart rate, electrocardiographic data, or cardiac contractility for chemicals associated with vascular injury. Changes in vascular tone in regional arterial beds often are suspected but are difficult to demonstrate. The relevance of these findings in rats, dogs, or monkeys for human risk assessment is uncertain, and drug-induced vascular injury in humans related to vasoactive properties of chemicals is sparsely reported and poorly characterized. Human risk assessment is further complicated because vascular injury is difficult to detect or monitor in patients. Historically, drug-induced vascular injury has been a problem for small molecule pharmaceuticals, but more recently some monoclonal antibodies, other protein therapeutics, and oligonucleotide therapies have produced vascular injury in animal species through mechanisms that are likely different from those for small molecules. Further complicating risk assessment for vascular injury observed in nonclinical studies is the infrequent and sporadic nature of the findings in animals treated with some chemicals. Spontaneous arterial injury (arteriopathy) in control animals is uncommon, but not rare. The incidences of vascular injury in control rats, dogs, and cynomolgus monkeys from 2008 to 2013 in studies sponsored by Pfizer Inc. are shown in Table 1. Although the incidences vary considerably from year to year, it is unusual to find more than 1 control animal with vascular injury in any particular study, and very often the vascular injury in control animals is minimal in severity and limited to 1 or very few blood vessels. Unfortunately, vascular injury in the treated groups often is similarly limited to 1 or a few animals and only a few blood vessels. Based on the authors’ review of nonclinical toxicity studies over a 5-year period, vascular injury was reported in studies representing 114 small molecule drug candidates across many different mechanisms of action. Fifty-five of these compounds had vascular injury reported in only a single animal in just 1 study, and for 17 of these 55 molecules the vascular injury was limited to the nonrodent species with no vascular findings in rats. When the number of animals and number of blood vessels affected are very low in a study, the determination of whether these effects are test article related or incidental background noise can be difficult, particularly when there are limited historical data for the compound. When the interpretation of small exploratory studies is equivocal, one option is to move forward into larger studies to help provide more definitive information. However, due to the difficulties in differentiating spontaneous from drug-induced vascular injury, some sponsors may halt development of a drug candidate even though it may have benefit without causing vascular injury in patients. The pharmaceutical industry has been looking for decades for reliable noninvasive biomarkers of vascular injury in body fluids, other methods to detect or visualize vascular injury in humans, tools to identify mechanisms of vascular injury, and in vitro models that accurately predict human vascular injury. Progress has been frustratingly slow. Investigators representing many pharmaceutical companies are collaborating through the Vascular Injury Working Group within the Critical Path Institute’s Predictive Safety Testing Consortium (PSTC) to summarize the mechanisms of arterial injury in animals associated with vasodilation and vasoconstriction, establish a recommended histomorphologic lexicon based on anatomic site of vascular injury, propose a strategy to identify and qualify vascular injury biomarkers, and initiate early testing of multiple proposed biomarkers (see Mikaelian et al. in this issue). The Safer and Faster Evidence-based Translation (SAFE-T) collaboration within the Innovative Medicines Initiative sponsored by the European Commission and the The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article. Address correspondence to: Daniel Morton, Pfizer Inc., 200 Cambridge Park Drive, T4017C, Cambridge, MA 02140, USA; e-mail: dan.g.morton@pfizer.com. Abbreviations: EFPIA, European Federation of Pharmaceutical Industries and Associations; PSTC, Predictive Safety Testing Consortium; SAFE-T, Safer and Faster Evidence-based Translation.

Power spectral analysis of heart rate variability in cynomolgus monkeys in safety pharmacology studies: Comparative study with beagle dogs

IntroductionPower spectral analysis of heart rate variability is a tool known to provide information of interest on the autonomic control of heart rate in human. However, its use and its conditions of application and interpretation for safety purposes are not well defined for cardiovascular safety pharmacology studies. Likewise, data of power spectral analysis of heart rate variability in cynomolgus monkeys, a species often appropriate for use as second non rodent species in preclinical safety programmes, are not available. This study was designed to evaluate the relevance of this biomarker in this non human primate species, and to compare results with those from beagle dogs under the conditions of safety evaluation studies. MethodsPower spectral analysis of heart rate variability was performed on data collected in both species by telemetry following a standard design for cardiovascular safety pharmacology studies. Various pharmacological agents were tested in order to compare the profile of responses in both species after modifying the autonomic nervous balance. ResultsHeart rate variability in cynomolgus monkeys is mainly driven by the parasympathetic nervous system as in beagle dogs although vagal tone is less than in dogs. Power spectral analysis of heart rate variability allows detection of interaction with the autonomic nervous system in both species in all investigated situations, i.e. sympatholytic/sympathomimetic and parasympatholytic/parasympathomimetic drug induced effects. However, due to species difference in the autonomic control of heart rate, cynomolgus monkeys are likely to be more sensitive than beagle dogs for assessment of sympatholytic properties. DiscussionThis study confirms that power spectral analysis of heart rate variability from data derived from ECG recordings in telemetry studies is applicable in cardiovascular safety pharmacology studies and may provide relevant information about possible interaction with the autonomic nervous system when new drug entities are evaluated in either species. However, interspecies differences in autonomic control must be taken into account when interpreting possible drug effects.

Subchronic oral toxicity and cardiovascular safety pharmacology studies of resveratrol, a naturally occurring polyphenol with cancer preventive activity

To characterize the subchronic oral toxicity of resveratrol, CD rats received daily gavage doses of 0, 200, 400, or 1000mg resveratrol/kg/day, and beagle dogs received daily capsule doses of 0, 200, 600, or 1200mg resveratrol/kg/day for 90days. Resveratrol induced only minimal toxicity, consisting of dose-related reductions in body weight gain in female rats and both sexes of dogs, and a statistically significant increase in bilirubin levels in rats at the 1000mg/kg/day dose. Clinical observations, hematology, ophthalmology, neurotoxicity evaluations (functional observational batteries), organ weights, and gross pathology provided no biologically significant evidence of resveratrol toxicity in either species. In rats, the high dose of resveratrol reduced the incidence of cardiomyopathy; no other microscopic changes were seen. Histopathologic changes in dogs were limited to minimal inflammatory infiltrates in the kidney and urinary bladder, which were not considered toxicologically significant. A cardiovascular safety pharmacology (telemetry) study in dogs revealed no evidence of resveratrol toxicity. Based on body weight effects, the No Observed Adverse Effect Level (NOAEL) for resveratrol was 200mg/kg/day in rats and 600mg/kg/day in dogs. The apparent cardioprotective activity of resveratrol in rats demonstrates that its potentially beneficial activities may extend beyond efficacy in cancer prevention.

Validation of combined toxicology and cardiovascular safety pharmacology studies using JET technology

Validation of combined toxicology and cardiovascular safety pharmacology studies using JET technology

Evaluation of a novel ECG lead placement method in telemetered freely moving cynomolgus monkeys: Assessment of an intravascular biopotential lead

Introduction ECG is considered as a critical biomarker of cardiac safety pharmacology. ECG signal quality is essential for accurate interval quantification and automated arrhythmia detection. Methods We evaluated ECG signal quality over a 6 month period from 15 cynomolgus monkeys with radiotelemetry transmitters using biopotential leads where the negative lead was inserted in the jugular vein and advanced to the superior vena cava (intravascular lead) and the positive lead was placed on the diaphragm at the apex of the heart (diaphragmatic lead). Signal noise and signal-to-noise ratio from this implantation methodology were compared with signals obtained from animals with subcutaneous ECG lead. Macroscopic pathology and histopathology associated with the intravascular lead were evaluated at 6 months post-implantation in six monkeys. Results The ECG morphology obtained with the intravascular/diaphragmatic lead placement was comparable to conventional subcutaneous ECG (emulating Lead II) but presented higher amplitudes (P-wave + 50.0%; R-wave + 30.0%). Signal noise showed a circadian cycle of changes in magnitude for subcutaneous ECG leads that was not observed with this method. The intravascular/diaphragmatic lead placement presented a higher signal-to-noise ratio than subcutaneous ECG leads. No macroscopic abnormality was observed to be associated with the intravascular lead. Mild thickening of the intima/subintima with mild intimal proliferation of the cranial vena cava surrounding the intravascular lead were noted at histopathological examination. Discussion The intravascular/diaphragmatic ECG lead placement in cynomolgus monkeys provided reduced signal noise and elevated P–QRS–T amplitudes. The intravascular lead was well tolerated and appeared suitable for chronically instrumented cardiovascular safety pharmacology studies. Further assessments would be warranted to evaluate the potential of this methodology in other species.

Cardiovascular and respiratory safety pharmacology in Göttingen minipigs: Pharmacological characterization

IntroductionSimilarities between pigs and humans support the relevance of Göttingen minipigs for regulatory safety pharmacology. The minipig is the species of choice for cardiovascular safety pharmacology when pivotal repeat toxicology studies are conducted in this species. Methods4 male Göttingen minipigs with cardiovascular telemetry transmitters received intravenous saline, esmolol (0.5, 1, 2, 4 and 8mg/kg), medetomidine (0.04mg/kg), remifentanil (0.5, 1, 2, 4, 8 and 16μg/kg) and dopamine (2, 8, 10, 20, 30 and 50μg/kg/min) and oral sotalol (3 and 10mg/kg). Respiratory monitoring was conducted in 3 male and 3 female Göttingen minipigs receiving intravenous saline and methacholine (0, 3.4, 13.5 and 68μg/kg). ResultsHeart rate (HR) corrected QT was optimal with a method based on analysis of covariance (QTca) followed by Fridericia's standard formula. Esmolol induced a decrease in HR. Medetomidine was associated with an initial hypertension with bradycardia followed by sustained hypotension, bradycadia and prolonged QTc. Remifentanil induced a dose-dependent QTc shortening with an increase in arterial pressures. Sotalol caused a decrease in HR and systolic arterial pressure with an increase in PR and QTc intervals. Dopamine induced an increase in arterial and pulse pressures. Methacholine increased tidal volume, respiratory rate and minute volume. DiscussionThe results suggest that the minipig is a valid alternative to other non-rodent species for cardiovascular and respiratory safety pharmacology studies when this species is justified.

Statistical considerations on the power of cardiovascular safety pharmacology studies

Statistical considerations on the power of cardiovascular safety pharmacology studies

Arrhythmogenic liability screening in cardiovascular safety pharmacology: Commonality between non-clinical safety pharmacology and clinical thorough QT (TQT) studies

Multiple ECG analysis strategies are used in safety pharmacology in a framework focused on accurate ECG complex interval quantification and arrhythmia detection. Automated arrhythmia detection is commonly used in the clinic and adapted tools may be used to facilitate analysis of large non-clinical datasets in safety pharmacology. The ICH E14 guideline (for Thorough QT Studies (TQT) conducted in healthy volunteers) supports manual and semi-automated ECG evaluation by skilled readers with a single operator analyzing all the ECG recordings from a given subject to minimize observer bias. Both fully automated and semi-automated ECG analysis programs may be used in safety pharmacology studies. Based on power analysis, a group size of approximately n=18 per study arm is the minimal requirement in TQT studies to provide the sensitivity to detect a 5ms QT interval prolongation. This sample size differs markedly from common safety pharmacology non-clinical study designs. New technologies such as the jacketed external telemetry (JET) ECG system may facilitate achievement of a smaller group size in integrated cardiovascular safety pharmacology risk assessment. TQT and cardiovascular safety pharmacology studies share several common experimental and scientific limitations which may benefit from technological advances. Sensitivity expectations in non-clinical studies should be commensurate with sample size and further investigations including power analyses and comparison between fully automated and semi-automated ECG analysis may help better characterize detection thresholds. Reducing overall variability, increasing reproducibility of ECG interval measurements and enhancing arrhythmia detection strategies are the cornerstones of data analysis in cardiovascular safety pharmacology and will likely continue to attract considerable attention in the safety pharmacology community.