Diagnostic and therapeutic indications

ATPace™, a novel injectable formulation of adenosine 5'-triphosphate (ATP), is developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extra- cellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio- cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunc- tion (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. The scientific rationale for the development of ATPace™ is discussed.