Trastuzumab-Induced Negative Chronotropic and Lusitropic Effects in Cynomolgus Monkeys

Treatment with trastuzumab, an antihuman epidermal growth factor receptor type 2 humanized monoclonal antibody, has been associated with heart failure in certain patients with cancer; however, the mechanism underlying trastuzumab-induced cardiac dysfunction remains unclear. This study was conducted to clarify the cardiac effects of trastuzumab in cynomolgus monkeys, which are commonly used as cross-reactive species in preclinical safety evaluation. Monkeys were treated with trastuzumab weekly for 1 month (5 doses in total). At first and fifth doses for pressure-volume loop analysis, trastuzumab at 20 mg·kg-1·10 min-1, equivalent to the human therapeutic dose, was administered intravenously to isoflurane-anesthetized animals, followed by 60 mg·kg-1·10 min-1 at a 30-minute interval. The other doses were fixed at 80 mg·kg-1·10 min-1 under unanesthetized conditions. After the first dose, reduced heart rate, decreases in maximal rate of fall of left ventricular pressure, and prolonged time constant for isovolumic relaxation, which are predictors of drug-induced changes in lusitropy, were observed at 20 and 60 mg·kg-1. The changes after the fifth dose were comparable with those after the first dose, indicating trastuzumab did not show exacerbation of cardiac function during the 1-month trial. No significant changes in slope of preload recruitable stroke work, which is a load-independent inotropic parameter, were observed at either dose. In conclusion, trastuzumab-induced little inotropic effect but induced negative chronotropic or lusitropic effects in monkeys, which might be associated with impaired left ventricular diastolic function.