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 Shortly following its introduction, mibefradil was withdrawn from the market in the U.S.A. as well as in Europe.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.

Levalmodipine (S-amlodipine) is an active enantiomer of amlodipine, a calcium antagonist that inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle. Experimental data suggest that S-amlodipine binds to both dihydropyridine and nondihydropyridine binding sites. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. S-Amlodipine inhibits calcium ion influx across cell membranes selectively, with a greater effect on vascular smooth muscle cells than on cardiac muscle cells. Enantiomerically pure S-amlodipine is marketed in some countries worldwide, while racemate, containing active S-enantiomer an inactive R-enantiomer is marketed in the USA and indicated for the treatment of hypertension and coronary artery disease.

Bepridil is a calcium channel blocker that has well characterized anti-anginal properties and known but poorly characterized type 1 anti-arrhythmic and anti-hypertensive properties. It has inhibitory effects on both the slow calcium and fast sodium inward currents in myocardial and vascular smooth muscle, interferes with calcium binding to calmodulin, and blocks both voltage and receptor operated calcium channels. It is used to treat hypertension (high blood pressure), angina (chest pain), sustained atrial fibrillation and tachyarrhythmia. The most common side effects were upper gastrointestinal complaints (nausea, dyspepsia or GI distress), diarrhea, dizziness, asthenia and nervousness. Certain drugs could increase the likelihood of potentially serious adverse effects with bepridil hydrochloride. In general, these are drugs that have one or more pharmacologic activities similar to bepridil hydrochloride, including anti-arrhythmic agents such as quinidine and procainamide, cardiac glycosides and tricyclic anti-depressants. Anti-arrhythmics and tricyclic anti-depressants could exaggerate the prolongation of the QT interval observed with bepridil hydrochloride. Cardiac glycosides could exaggerate the depression of AV nodal conduction observed with bepridil hydrochloride.

Pinaverium, known under the brand name DICETEL, is a spasmolytic agent used for functional gastrointestinal disorders. It is a quaternary ammonium compound that acts as an atypical calcium antagonist to restore normal bowel function. It is shown to relieve GI spasm and pain, transit disturbances and other symptoms related to motility disorders and may be considered as effective first-lline therapy for patients with irritable bowel syndrome (IBS). Pinaverium is also used to help relieve symptoms caused by certain disorders of the gallbladder associated with secretion of bile. Pinaverium bromide is the common ingredient in formulations, mostly as oral tablets. Although it is not a currently approved drug by the FDA, pinaverium is available in over 60 countries including Canada. DICETEL® (pinaverium bromide) is a calcium antagonist which inhibits the calcium influx by blocking the voltage-dependent calcium channel at the smooth muscle cell level. It possesses a high degree of selectivity for the intestinal smooth muscle.

Tetrandrine, isolated from the root of Stephania tetrandra S Moore, is a traditional Chinese clinical agent for silicosis, autoimmune disorders, inflammatory pulmonary diseases, cardiovascular diseases and hypertension. Tetrandrine is a potent MDR-reversing agent and is an ABCB1/ABCC1 inhibitor. Tetrandrine (CBT-1) is being developed by CBA Pharma, as an adjunctive therapy to chemotherapy in various cancer types with multiple drug resistance (MDR), including acute myelogenous leukemia , Breast, Non-Hodgkin’s Lymphoma, Hodgkin’s disease, Non-Small Cell Lung Cancer, Multiple Myeloma, Gallbladder, Pancreatic, Gastrointestinal Tract, Small Cell Lung Cancer, Bladder, Head & Neck, and Sarcoma.

Caroverine is a spasmolytic drug used in tinnitus treatment improves mechanosensitivity and mechanotransduction phenomenon and otoneuroprotective agent. Caroverine acts as an N-type calcium channel blocker, competitive AMPA receptor antagonist, and non-competitive NMDA receptor antagonist. When excessive glutamate binds to NMDA receptors, the receptor opens and allows calcium and sodium to enter the neuron, abnormal levels of calcium disturbs ionic balance causing spontaneous depolarization state. Pathological spontaneous depolarization state is reversed back to physiological polarization state by antagonistic property of Caroverine.

Gallopamil is a L-type calcium channel blocker designed for the treatment of coronary heart diseases: angina pectoris, prinzmetal angina and hypertonia.

Efonidipine is a 1,4-dihydropyridine derivative for the treatment of hypertension and angina. Efonidipine exerts its antihypertensive and antianginal effects through blocking L- and T-type calcium channels.

Lercanidipine is antihypertensive drugs which acts by blocking L-type calcium channels, allowing relaxation and opening of blood vessels. Lercanidipine exists as a racemate, with anti-hypertensive activity residing primarily in S-enantiomer. NDA for lercanidipine was submitted to FDA in 2002 by Forest Laboratories, but FDA refused to approve the drug, and lercanidipine is not marketed in USA. Lercanidipine is also investigated in preclinical models of epilepsy and ischemic stroke.

Bencyclane, a cycloheptane, is a vasodilator, antiplasmodic and a platelet aggregation inhibitor found to be effective in a variety of peripheral circulation disorders. Bencyclane has various other potentially useful pharmacological effects such as smooth muscle relaxation. Under the trade name Halidor it is used in several European countries to treat the symptoms of atherosclerosis, occlusive arterial disease. Its mechanism may involve block of calcium channels. However as was shown in vitro it does not act by a direct influence on the Ca2+ pumps of vascular smooth muscle cells. In in vitro biochemical assays related to smooth muscle excitation-contraction coupling, binding to beta 1-, beta 2-, and alpha-adrenergic receptors, inhibition of phosphodiesterase activity, and antagonism of calcium accumulation bencyclane bound to alpha- and beta-receptors. Bencyclane appeared to be a promising anti-sickling agent that can be used orally in sickle cell anaemia (SCD).