High definition oscillometry (HDO): A novel methodfor non-invasive blood pressure measurements incynomolgus monkeys

Andrea MitchellCovance Laboratories, Madison, WI, United States

Cynomolgus monkeys are commonly used in toxicologicalresearch including the determination of drug effects on thecardiovascular system. Accurate and reproducible determination ofblood pressure (BP) in conscious, manually restrained or chemicallyrestrained animals is a challenge with current non-invasive cufftechniques. The HDO technique enables real time measurements thatare visible on a computer screen for immediate determination if themeasurement is valid. Further, the HDO measurement is considerablyfaster (up to15 s) than other cuff methods. Measurements taken withHDO and Cardell BP Monitor Model 9401 were compared for accuracyand reliability with simultaneously recorded direct blood pressuredata from telemetry implants. Six animals, implanted with atelemetry transmitter, were used and data were compared undermanual constraint, with or without administration of a BP loweringdrug (hexamethonium) or ketamine sedation. For each animal,systolic, diastolic, mean arterial pressure, and pulse rate (PR; HDOand Telemetry only) were determined. Simple linear regressionrevealed substantially larger R2 values for HDO-Telemetry thanCardell-Telemetry comparisons. R2 values were up to 0.69 for HDOand up to 0.15 for Cardell for BP data. For PR, R2 values were up to 0.98for HDO. In conclusion, HDO data revealed a close correlation withtelemetry data indicating that this novel, non-invasive techniqueproduces reliable blood pressure data in manually or chemicallyrestrained monkeys for a wide blood pressure range.

doi:10.1016/j.vascn.2009.04.077

Evaluation of the pro-thrombotic effect of COX-2 inhibitorrofecoxib in dog model of arterial thrombosis

Aliaksandr Bulhaka,⁎, Jan-Arne Björkmanb, Helen Zachrissonb,Ahmad Al-Saffara, Tomas ForsbergaaDepartment of Safety Pharmacology, Safety Assessment,AstraZeneca R&D, Södertälje, SwedenbDepartment of Bioscience, AstraZeneca R&D, Mölndal, Sweden

In vivo models of arterial thrombosis are widely used forevaluation of potential anti-thrombotic effects of existing and newlysynthesized drugs, but whether or not they can reveal pro-thrombotic effects is unclear. COX-2 inhibitors increase the incidenceof cardiovascular events in patients due to enhanced arterialthrombosis resulting from a disruption of the balance between theprostaglandins PGI2 and TXA2. The aim of the study was to investigatethe utility of a dog model of arterial thrombosis for the evaluation ofpro-thrombotic effects using a COX-2 inhibitor rofecoxib.

In anaesthetized beagle dogs femoral artery thrombosis wasinduced by stenosis following mechanical damage. Animals weregiven a single dose of vehicle followed by three consecutive doses ofrofecoxib 1, 3, 10 mg/kg (n=6) or continuous vehicle (n=6). Eachdose consisted of i.v. bolus+infusion over 30 min. Mean arterialblood pressure (MAP), heart rate (HR), femoral artery blood flow,ADP-induced platelet aggregation, bleeding time, blood loss, andplasma concentration were evaluated.

The mean plasma concentration after 1, 3 and 10 mg/kg rofecoxibwas 2.5±0.005, 13.7±0.008 and 51.3±0.01 µM. At 10 mg/kg,rofecoxib decreased MAP by 33% (P<0.01) compared to pre-dose.

Rofecoxib 3 and 10 mg/kg decreased volume blood flow and time toocclusion in stenosed artery to 67% and 38% (P<0.05, P<0.01 vs. pre-dose; P<0.001 vs. vehicle), and 72% and 50% (P<0.05–P<0.01),respectively. Mean bleeding time and blood loss were decreased at10 mg/kg dose (63%, P<0.01 and 69%, P<0.05). No changes werefound in ADP-induced platelet aggregation.

The COX-2 inhibitor rofecoxib induced a dose-dependent pro-thrombotic effect in an in vivo dog model of arterial thrombosisverified by decreased volume blood flow and time to occlusion. Thus,the present study demonstrates the utility of this model forevaluation of potential pro-thrombotic effects of drugs.

doi:10.1016/j.vascn.2009.04.078

IKs: Another cardiovascular liability besides hERG, and use of anovel IKs blocker to screen for IKs blockade

Rob TowartJohnson & Johnson PRD, Beerse, Belgium

Screening for hERG inhibition has become an essential part of thepre-clinical profiling of new compounds. Another ion channel, IKs, isalso important in the repolarisation of cardiac cells, and blockade ofIKs can cause or contribute to TdP in vivo (e.g., Gallacher et al.,Cardiovasc. Res. 76, 247–56, 2007).

A novel experimental compound, “JNJ303”, had little effect onhERG or sodium channels, and did not affect APD or TRIaD inLangendorff rabbit hearts. However, “JNJ303” exhibited a pro-nounced QT-prolongation effect in anaesthetised guinea pigs, andcaused spontaneous TdP in 2 of 4 anaesthetised dogs at 0.63–1.25 mg/kg iv. This compound turned out to be a selective andpotent inhibitor of KvLQT1/minK (IC50=64 nM) which mediatesthe IKs current. Using tritiated “JNJ303”, we developed a bindingassay for IKs, which correlated well with activity observed in the IKspatch clamp assay. We tested a series of analogues of “JNJ303” in thebinding assay, and demonstrated a strong structure–activity rela-tionship (SAR) for the series. The most potent analogue, “JNJ282”,selectively inhibited IKs current with IC50 <<10 nM, and causedspontaneous TdP in 3 of 4 anaesthetised dogs at doses as low as0.16–0.32 mg/kg iv.

Despite little effect on hERG or other cardiac ion channels (e.g., Na,Ca, Ito, IK1), potent blockade of IKs may therefore prolong QT, andcause spontaneous TdP in vivo at low doses. These findingsdemonstrate the cardiovascular danger of IKs blockade, and empha-size the advantages of early screening for this potentially dangerousproperty.

doi:10.1016/j.vascn.2009.04.079

A HESI consortium approach to assess the human predictive valueof non-clinical repolarisation assays

Jean-Pierre Valentin⁎, Syril PettitHESI, Washington, DC, United States

Drug-induced QT interval prolongation and Torsades de Pointesremain serious public health issues in bringing safe new pharma-ceuticals to the market place. Under the auspices of ILSI Health andEnvironmental Sciences Institute (HESI), a consortium involvingrepresentatives from pharmaceutical companies, regulatory agenciesand opinion leaders from the scientific and medical research

Abstracts / Journal of Pharmacological and Toxicological Methods 60 (2009) 210–258226