Strategic Integration of In Vivo Cardiovascular Models During Lead Optimization

Abstract

The strategic integration of in vivo cardiovascular models is important during lead optimization to enable a wide therapeutic index for cardiovascular safety. However, under what conditions (eg, species, route of administration, anesthesia) studies should be performed to drive go/no-go is open to interpretation. Two compounds, torcetrapib and a novel steroid hormone mimetic (SHM-1121X), both with off-target cardiovascular liabilities, were profiled in 4 in vivo cardiovascular models. Overlapping plasma concentrations of torcetrapib were achieved in all models tested; values ranged from therapeutic to supratherapeutic. In anesthetized rats, intravenous torcetrapib elicited dose-dependent increases in mean arterial pressure (MAP; 2-18 mm Hg above vehicle during the low- and high-dose infusion), and in anesthetized dogs, torcetrapib increased MAP from 4 to 22 mm Hg. In conscious rats, a single oral dose of torcetrapib increased MAP from 10 to 18 mm Hg in the low-dose and high-dose groups, respectively, whereas in conscious dogs, MAP increased from 3 to 12 mm Hg. SHM-1121X produced marked hypotension in the same models. Pharmacokinetic-pharmacodynamic analysis demonstrated strong correlation across the models tested for both compounds. Results suggest that equivalency across models allows for flexibility to address key issues and enable go/no-go during lead optimization without concern for discordant results. The predictive value of each model was validated with torcetrapib and, when put into practice, led to a decisive no-go for SHM-1121X.