The Toxicologist - Society of Toxicology

article. This is especially challenging when the test article is administered via inhalation.
This poster describes the method for achieving a successful outcome in
these types of studies, including the factors that must be considered in the design
and execution. Effects of proper habituation to equipment and carefully scheduled
study activities were assessed based on the overall character of cardiorespiratory response
from 3 different studies.
Prior to the first data collection, all animals were surgically implanted with DSI
telemetry transmitters and habituated to the exposure/data collection system.
Respiratory parameters were collected using respiratory inductance plethysmography
(RIP). Telemetry data were collected continuously while animals were in their
home cage, after transfer to the exposure suite but prior to either air or the vehicle,
during the exposure period, and for 24 hours post dose in 3 different studies. Each
study used a different vehicle and an air (sham) control was administered to assess
the vehicle effect.
Administration of the vehicle produced no effects on blood pressure, heart rate,
body temperature, respiratory rate, tidal volume and minute volume during predose,
exposure period and for the 24 hour post dose recording period when compared
to air (sham) control in all 3 studies. Very similar patterns in blood pressure
and heart rate were noted in all 3 studies; however, each study has a specific pattern
for body temperature and respiratory parameters, which was attributed to individual
variation in these parameters. This poster presents a consistent and reliable
method of collecting cardiorespiratory data from conscious beagle dogs prior to,
during and after inhalation exposure in our Testing Facility.
71 Assessment of QT-Interval Prolongation in Nonclinical
Safety Study Using External Telemetric Device in Conscious
Beagle Dogs: Application of QT Shift and Probabilistic
Methods.
L. Renaud 1 , P. Champeroux 2 , S. Ruillon 1 , N. Velasquez 1 , P. Desbois 1 ,
O. Wattrelos 1 and N. Claude 1 . 1 Drug Safety, Servier, Gidy, France; 2 Centre de
Recherches Biologiques, CERB, Baugy, France.
The detection of delayed ventricular repolarization, characterized by a QT interval
prolongation, is one of the main issues for the preclinical evaluation of potential
risk of pro-arrythmia for a new drug candidate. This study was designed to compare
different methods of QT interval prolongation assessment in conscious beagle dogs
using external telemetric device. The same 6 dogs (3/sex) were given vehicle or reference
compounds known to induce QT interval prolongation using a sequential
design (single oral dosing of Sotalol at 30 mg/kg and Moxifloxacin at 30 then 90
mg/kg or repeated oral dosing for 6 days of Thioridazine at 20 mg/kg/d and
Terfenadine at 30 mg/kg/d). Electrocardiograms were recorded during a treatmentfree
period and on day 1 and/or day 6 for approximately 20 h post dosing. QT intervals
were measured from a beat to beat analysis over 10-min periods centred on
selected timeslots and corrected according to the Van de Waters formula (QTvdw).
QT shift calculations and an analysis based on the principles of the Holzgrefe’s
probabilistic method (QTh, using a minimum 250 beats/timeslot) were also performed.
All methods allowed an accurate evidence of QT effect for Sotalol and
Moxifloxacin. The QT shift and QTh methods gave more evidences for
Terfenadine effect than QTvdw. As expected, the marked increase in heart rate
(HR) induced by Thioridazine resulted in no apparent effect on QT and a statistically
significant overcorrection for QTvdw whereas QT shift and QTh gave more
accurate and reliable results. The statistical sensitivity threshold detection of QT
prolongation was low, i.e. 10 to 15 ms for QT shift and QTh methods. Thus, external
telemetry in non-clinical safety dog studies allows new perspectives for a better
assessment of QT prolongation when associated to QT shift and Holzgrefe’s
probabilistic methods, especially in case of slight drug-induced QT effect or
marked changes in HR.
72 Integration of Automated Patch Clamp Systems and Logistic
Models in the Cardiochannelgramtm (CCGTM) for Better
Prediction of Cardiac Risk.
J. W. Kramer 1 , G. J. Myatt 2 , C. A. Obejero-Paz 1 , A. Bruening-Wright 1 ,
Y. A. Kuryshev 1 and A. M. Brown 1 . 1 ChanTest Corporation, Cleveland, OH;
2 Leadscope Inc., Columbus, OH.
Drug-induced inhibition of the cardiac hERG potassium channel is recommended
by ICH and FDA to predict delayed cardiac repolarization (DR) and cardiac risk.
The consequent QTc prolongation is a surrogate marker of Torsade de Pointes
(TdP), a rare but potentially lethal iatrogenic outcome. Drugs with effective therapeutic
plasma concentrations (ETPC) within 30-fold of their hERG IC50s are
thought to be dangerous despite the fact that multiple ion channel effects (MICE)
14 SOT 2013 ANNUAL MEETING
can mitigate DR. Here we demonstrate that logistic regression models, which integrate
MICE, predict TdP with much greater certainty than the hERG safety ratio
(hERG IC50/ETPC or safety margin (SM)) alone. To this end we measured hERG,
Nav1.5,Cav1.2, Kir2.1 and KvLQT1/minK IC50 values of 56 drugs (33 +TdP and
23 -TdP) from multiple classes using automated patch clamp systems including
Qpatch and PatchXpress. The sensitivity of the automated patch clamp platforms
was evaluated in a comparison to manual patch clamp. ETPC values and the torsadogenic
liability of drugs was obtained from the literature, package inserts and
Arizona CERT. Eleven logistic regression models were constructed; one using the
hERG SM alone, the others integrating hERG SM, Nav1.5 SM and/or Cav1.2 SM
data. The predictive power of each model was evaluated using the likelihood ratio
test. Leave-one-out cross validations were performed and each model’s accuracy was
determined by comparing receiver–operating characteristics (ROC, sensitivity vs.
1-specificity). Models that include Nav1.5, Cav1.2 or both variables are statistically
significant better predictors of TdP liability than the model that contains only
hERG (Model 1). Model 1 had a ROC area under the curve (AUC) of 0.80 and
Model 11, that includes hERG, Nav and Cav1.2 SMs, significantly improved accuracy
showing a ROC AUC of 0.94. Thus, Model 11 that incorporates the concept
of MICE in the CardioChannelGramTM (CCGTM) is a robust nonclinical predictor
of cardiac risk.
73 Characterization of Jacketed External Telemetry with Blood
Pressure in Conscious Nonhuman Primates in Pen-Style
Housing Administered Etilefrine, Sotalol, or Hydralazine.
L. Kreckler, J. Kopshinsky, J. Schneider, G. Hanson, D. Morris and C. Foley.
Covance Laboratories, Inc., Madison, WI.
An important component of nonclinical safety assessment is the evaluation of electrocardiography
(ECG) and hemodynamic parameters. Jacketed external telemetry
with an implanted telemetry blood pressure transmitter (JET-BP) is a minimally invasive
technology being utilized in general toxicology studies to assess ECG and
blood pressure measurements in conscious, unrestrained animals. We characterized
JET-BP in nonhuman primates (NHPs) housed in pen-style caging with three reference
compounds with known effects on blood pressure or ECG parameters.
Thirty-six male NHPs were implanted with a telemetry blood pressure device and
group-housed in pen-style caging (3 animals/pen). Four animals per group were
given reference material or a concurrent control article. Etilefrine, a sympathomimetic,
was given at 1 or 10 mg/kg; hydralazine, a vasodilator, at 1 or 10 mg/kg;
and sotalol, a non-specific β-blocker, at 3 or 30 mg/kg. JET-BP measurements were
recorded for at least 90 minutes prior to dosing and continuously for at least 20
hours postdose. The following ECG and hemodynamic parameters were determined
as one (light phase) or two-hour (dark phase) averages: PR, QT and rate-corrected
QT; systolic, diastolic, and mean arterial pressures; heart rate; and arterial
pulse pressure. In addition, blood was collected at seven postdose timepoints for
each test article for pharmacokinetic analysis. Etilefrine significantly increased
mean arterial pressure, systolic blood pressure and pulse height, while diastolic
blood pressure remained unchanged. Sotalol significantly prolonged QT with no
significant change in blood pressure. Administration of hydralazine did not significantly
change blood pressure at the dose levels administered. In summary, ECG
and blood pressure changes caused by three different reference compounds were detectable
using JET-BP technology in group-housed NHPs.
74 Differential Cardiovascular Physiology and Pathology in
Selected Lineages of Miniature Swine.
A. Stricker-Krongrad 1 , T. J. Madsen 1 , B. C. Hanks 1, 2 , D. Brocksmith 2 , J. Liu 1 ,
L. D. Brown 1, 2 and G. F. Bouchard 1, 2 . 1 Sinclair Research Center, LLC, Columbia,
MO; 2 Sinclair BioResources LLC, Auxvasse, MO.
The miniature swine has been increasingly recognized as a valid alternative to canine
and non-human primates in regulatory toxicity. This poster presents the results
of cardiovascular assessments in the Yucatan, Hanford, and Sinclair miniature
swine conducted during clinical investigations and control toxicity testing.
Anatomic parameters were obtained at necropsy. Blood vessels diameter, velocity,
and flow were obtained by Doppler ultrasonography. Cardiac electrophysiology was
obtained using clinical ECG and surgical monitor units. Macroscopic lesions and
histopathology assessments were conducted on heart and kidneys. Data were compared
to published measurements of adult human illustrating similarities or differences
(for practicality, male data are reported here). Across the three lineages, heartto-body
weights ratio ranged from 0.41 to 0.50 and were higher than human
(0.42). The geometric corrections for heart rate adjustment to body size ranged
from 215 to 297 and were comparable to human (241), indicating that heart volume
and function were well adjusted to the reduction in body size. The miniswine