A European pharmaceutical company initiative challenging the regulatory requirement for acute toxicity studies in pharmaceutical drug development.

Regulatory guidelines indicate acute toxicity studies in animals are considered necessary for pharmaceuticals intended for human use. This is the only study type where lethality is mentioned as an endpoint. The studies are carried out, usually in rodents, to support marketing of new drugs and to identify the minimum lethal dose. A European initiative including 18 companies has undertaken an evidence-based review of acute toxicity studies and assessed the value of the data generated. Preclinical and clinical information was shared on 74 compounds. The analysis indicated acute toxicity data was not used to (i) terminate drugs from development (ii) support dose selection for repeat dose studies in animals or (iii) to set doses in the first clinical trials in humans. The conclusion of the working group is that acute toxicity studies are not needed prior to first clinical trials in humans. Instead, information can be obtained from other studies, which are performed at more relevant doses for humans and are already an integral part of drug development. The conclusions have been discussed and agreed with representatives of regulatory bodies from the US, Japan and Europe.

QT interval measurement in the dog: chest leads versus limb leads.

INTRODUCTION: An accurate measurement of the QT interval is dependent on the accurate identification of the end of the T wave. Although chest leads have been recommended in dog toxicology studies, their use has not been widely put into practice, as shown by a recent survey on methodology for ECG collection in the pharmaceutical industry. Therefore, there is little published data on dog QT measurement from chest leads. METHODS: Electrocardiograms (ECGs) were taken from 100 beagle dogs (50 males, 50 females), with the dogs restrained in a sling. On the day of recording, measurements were performed at time zero and 1 h later. Recordings were repeated 7 to 10 days later. QT interval measurements were taken simultaneously from Lead II and the chest Lead CV5RL. Heart rate was taken from Lead II. Statistical analyses included the calculation of a QT correction formula, comparison of the mean values and variability of QT and QTc measurements from Leads II and CV5RL, the comparison of T-wave polarity from both leads, and a power analysis for QT and QTc. RESULTS: The T wave was positive in almost all dogs (99/100) in the Lead CV5RL at all measurement periods, while it was either positive or negative in Lead II (64-75/100), and the incidence of positive T wave varied between measurement periods. The QT interval was significantly shorter (194+/-11 to 197+/-12 vs. 197+/-13 to 200+/-12 ms) when measured from the CV5RL lead at all recording periods and in both sexes. In addition, the standard deviation for QT measurement within each individual ECG record demonstrates less intra-animal variation when QT is measured from Lead CV5RL compared with Lead II (3.8 vs. 13.2 ms). The linear regression between QT and heart rate was improved when QT measurements were taken from CV5RL, as shown by the percentage of variability R2. DISCUSSION: Estimates of the sample sizes showed that fewer animals would be required to detect a change at both the high and the mid-doses when using the chest Lead CV5RL. Using Lead II, we are able to detect within-animal changes of 10% in either QT or QTc; with Lead CV5RL, we are able to detect 10% change in QT and 5% change in QTc.

Electrocardiographic monitoring in the Göttingen minipig.

The purpose of the study reported here was to determine conditions for electrocardiographic monitoring in the Göttingen minipig in view of its use as a second non-rodent species in toxicology studies. Electrocardiograms were recorded from conscious minipigs (6/sex) maintained in a sling. The three standard bipolar limb leads (I, II, III), the three augmented unipolar limb leads (aVR, aVL, aVF), the triangular Nehb-Spöri leads (dorsal, axial, ventral) and their corresponding unipolar leads were recorded, and automated analysis of amplitudes and intervals was made. Major QRS patterns were not observed for any of the bipolar and unipolar leads. For triangular leads, the amplitude of waves was higher than that for limb leads, and the rS pattern dominated for dorsal, axial ventral and aV(F)-Ventral leads. The qR pattern dominated in the aV(R)-dorsal lead, whereas consistency and dominant patterns were not observed for the aV(L)-axial lead. For limb leads, the position of the electrode affected the ECG. Electrodes placed on the cubital and stifle joints were the preferred positions since the P- and R-waves were clearly identifiable with amplitudes > 0.2 mV. Also, the T-wave amplitude was (positive or negative) > 0.2 mV in at least two leads, making the determination of the QT-interval accurate. For the triangular leads, the position of the electrode had less influence on the amplitude of deflections. However, if the axial lead is to be used for calculation of intervals and amplitudes, the xyphoid process is the preferred position. In conclusion, the triangular lead system is recommended for recording ECGs in minipigs. Limb leads could be used in connection. The cubital and stifle joints for standard limb leads and the neck, sacrum, and xyphoid process for triangular leads are the preferred positions for electrodes.

Type B Ventricular Preexcitation With Abnormal Contraction of the Ventricular Septum in a Dog.

A 14monthold female beagle had ventricular preexcitation (VP).The finding was characterized by a wide positive QRS complex with a tall notched R wave in leads I, II, III, and aVF, an inverted QRS complex in leads aVR and aVL, a Q wave in lead I, and a short PR interval. Compression of the carotid sinus caused an anticipated marked decrease in heart rate, but did not reveal latent electrocardiographic abnormalities. We did not detect evidence of ventricular hypertrophy during echocardiography. Examination of the M-mode image indicated abnormal movements of the septum. There were 2 sharp waves at each systole instead of a single wider wave that is seen for clinically normal dogs. To further characterize this ECG finding, the affected dog and 2 clinically normal female beagles (positive control dogs) were given atropine (0.025 mg/kg of body weight, i. v.) Increases in heart rate, relative to values obtained before atropine administration, were evident in all 3 dogs. Increase in heart rate in the dog with VP appeared sooner after injection than in the clinically normal dogs; it was evident at the conclusion of the atropine injection. When the increase in heart rate was maximal in the affected dog (3 min after atropine administration), notching of the R wave disappeared, and the QRS duration decreased to about 60 ms. Echocardiographically, atropine produced a decrease in end diastolic, end systolic and stroke volumes in all treated dogs, which was similar between clinically normal dogs and the dog with VP. Atropine administration also was associated with a decrease in the percentage of thickening of the septum in the dog with VP, but not in the clinically normal dogs. We did not detect histopathologic abnormalities in the heart of the dog with VP.