Clinical Drug Experience Knowledgebase

Mibefradil is a calcium channel blocker, chemically unlike other compounds in the class, that was approved by the Food and Drug Administration (FDA), U.S.A. in June 1997 for the treatment of patients with hypertension and chronic stable angina. Shortly following its introduction, mibefradil was withdrawn from the market in the U.S.A. as well as in Europe. The reason for the voluntary withdrawal of the drug by Roche laboratories was claimed to be the result of new information about potentially harmful interactions with other drugs. Mibefradil is calcium channel blocker with moderate selectivity for T-type Ca2+ channels displaying IC50 values of 2.7 uM and 18.6 uM for T-type and L-type channels respectively. Mibefradil is a tetralol calcium channel blocking agent that inhibits the influx of calcium ions across both the T (low-voltage) and L (high-voltage) calcium channels of cardiac and vascular smooth muscle, with a greater selectivity for T channels. Vasodilation occurs in vascular smooth muscle, causing a decrease in peripheral vascular resistance and a resulting decrease in blood pressure. Mibefradil causes a slight increase in cardiac output during chronic dosing. Mibefradil slows sinus and atrioventricular (AV) node conduction, producing a slight reduction in heart rate and a slight increase in the PR interval. It has also been shown to slightly lengthen the corrected sinus node recovery time and AH interval and to raise the Wenckebach point. The mechanism by which mibefradil reduces angina is not known, but is thought to be attributed to a reduction in heart rate, total peripheral resistance (afterload), and the heart rate-systolic blood pressure product at any given level of exercise. The result of these effects is a decrease in cardiac workload and myocardial oxygen demand. Mibefradil has been repurposed from an abandoned antihypertensive to a targeted solid tumor treatment, and it has been rescued from drug-drug interactions by using short-term dose exposure. Tau is using the early success of mibefradil as a proof of concept to build a platform technology of Cav3 blockers for broad antitumor applications in combination with new targeted cancer therapies, well-established.   ^NCATS