Effects of group housing on ECG assessment in conscious cynomolgus monkeys.

INTRODUCTION: Assessing the cardiovascular safety of new chemical or biological entities is important during pre-clinical development. Electrocardiogram (ECG) assessments in non-human primate (NHP) toxicology studies are often made using non-invasive telemetry systems. We investigated whether ECG recording was feasible during group housing of NHPs, rather than the usual single housed arrangement, and whether it would impact the data collected or affect the ability to detect drug-induced changes in QTc interval. METHODS: Following a period of acclimatisation to jackets, cynomolgus monkeys (3 males and 3 females) were housed in same sex groups of 3. Female monkeys were administered 4 doses of vehicle while male monkeys were administered vehicle, 15, 45, and 135mg/kg moxifloxacin. Each dose was administered on a separate dosing day. The same dosing protocol was repeated with the animals singly housed and the results from the two phases were compared including assessment of statistical power. RESULTS: Heart rate (HR) was significantly lower, and PR and QT intervals were significantly higher, at multiple time points when the animals were group housed compared with the singly housed phase. QRS duration and QTc interval were less affected. Moxifloxacin increased QT and QTc intervals but had no consistent effect on HR, QRS duration or PR interval under group housed or singly housed conditions. Power analysis suggested that group housing did not adversely affect the magnitude of detectable changes of ECG parameters. In general, detection of slightly smaller changes was achieved under conditions of group housing. DISCUSSION: The current study shows group housing to be technically possible during non-invasive ECG recording, resulting in lower resting heart rates and small improvements in sensitivity of detection of drug-induced effects. Given the psychological benefits of group housing for NHPs, it is a refinement that should be considered when conducting ECG assessments in NHP toxicology studies.

Reducing attrition in drug development: smart loading preclinical safety assessment.

Entry into the crucial preclinical good laboratory practice (GLP) stage of toxicology testing triggers significant R&D investment yet >20% of AstraZeneca's potential new medicines have been stopped for safety reasons in this GLP phase alone. How could we avoid at least some of these costly failures? An analysis of historical toxicities that caused stopping ('stopping toxicities') showed that >50% were attributable to target organ toxicities emerging within 2 weeks of repeat dosing or to acute cardiovascular risks. By frontloading 2-week repeat-dose toxicity studies and a comprehensive assessment of cardiovascular safety, we anticipate a potential 50% reduction in attrition in the GLP phase. This will reduce animal use overall, save significant R&D costs and improve drug pipeline quality.

Evaluation of a homemade SYBR green I reaction mixture for real-time PCR quantification of gene expression.

Real-time PCR is an accurate method that can be used for the quantification of specific DNA molecules. Here we provide a protocol for SYBR Green I in real-time PCR applications using plastic reaction tubes. We report that SYBR Green I is alkali labile and once degraded inhibits the PCR. In our optimized protocol, diluted aliquots of SYBR Green I remain stable for at least two weeks. We also evaluated different cDNA synthesis protocols for the quantification of multiple genes from the same cDNA preparation. The best result was obtained with cDNAs synthesized by OmniScript reverse transcriptase from 2.5 microg total RNA using oligo d(T)18 primers. The cDNA reactions could be diluted 1:25, allowing the quantification of up to 125 different medium expressed genes of Arabidopsis. Extension times ranged between 20 and 40 bp/s for accurate quantification of PCR products up to approximately 400 bp in the Rotor-Gene 2000 system. Using our optimized real-time PCR protocol, the reproducibility and amplification efficiency was high and comparable to a commercially available SYBR Green I kit. Furthermore, the sensitivity allowed us to quantify 10-20 copies of mRNA and dsDNA. Thus, the protocol eliminates the need for expensive pre-made kits.