By Chris Delporte

CV Therapeutics Inc. said it is initiating a Phase III trial of CVT-510 in patients with paroxysmal supraventricular tachycardia (PSVT), seeking to reduce rapid heart rates during atrial arrythmias in those patients.

The multicenter, randomized, double-blind, placebo-controlled trial is designed to determine the safety and efficacy of CVT-510 in the conversion of PSVT to normal sinus rhythm. The target enrollment for the study is 180 patients. Atrial arrythmias happen when electrical signals in the atria cause the heart to beat too rapidly or uncontrollably. The most common atrial arrythmias are atrial fibrillation, atrial flutter and PSVT.

¿This is a program for all atrial arrythmias,¿ Dan Spiegelman, senior vice president and chief financial officer at CV Therapeutics, told BioWorld Today. ¿There are about 2.5 million cases diagnosed each year. Approximately 2.2 million are atrial fibrillation, 220,000 are atrial flutter, and between 160,000 and 200,000 are PVST.¿

The AV node controls the transmission of electrical impulses from the atria to the ventricles. When the frequency of signals passing through the AV node is too high, the ventricles, in turn, begin to beat too rapidly. The resulting insufficient time for filling and emptying the left ventricle can result in hypotension and reduced blood flow to the brain and other vital organs, the company said. As a result, heart rate must be controlled as quickly as possible.

The current standard of care for PVST is either Adenocard (pure adenosine), manufactured by Medco Research Inc., of Research Triangle Park, N.C., and marketed by Fujisawa USA Inc., of Deerfield, Ill., or an intravenous calcium channel blocker. Both treatments lower heart rate, but they also lower blood pressure. Lower blood pressure keeps current treatments from becoming effective long-term therapies.

¿CVT-510 is a selective A1 adenosine receptor agonist and the A1 receptor should lower heart rate,¿ Spiegelman explained. ¿But it doesn¿t affect the A2 receptor, which lowers blood pressure.¿

Intravenous CVT-510 is designed to slow the speed of AV nodal conduction by selectively stimulating the A1 adenosine receptor. Selective stimulation could avoid blood pressure lowering that can be caused by stimulation of the A2 adenosine receptor. Therefore, according to CV Therapeutics, it should be possible to quickly control arrythmias without lowering blood pressure.

The company released positive data last November from its Phase II study showing that 32 of 37 patients converted from PSVT to normal sinus rhythm.

During the upcoming trial, patients will be given either a dose of CVT-510 or placebo. If it doesn¿t convert them in a minute or two, they will be given another dose. If the second dose fails, they will be treated with the current standard of care.

Spiegelman speculated that the revenues for CVT-510 could be anywhere from $200 million to $300 million.

CVT-510 joins the company¿s ranolazine for the treatment of angina as cardiovascular products in Phase III studies. Spiegelman said the company just finished enrollment for its second Phase III trial of ranolazine and expects to be able to release data by the end of the fourth quarter.

Palo Alto, Calif.-based CV Therapeutics entered into an agreement with Innovex, a subsidiary of Quintiles Transnational, of Research Triangle Park, N.C., to market ranolazine. Spiegelman said no marketing alliances have been made for CVT-510, a product to which the company owns all rights.

CV Therapeutics¿ stock (NASDAQ:CVTX) gained $4.22 Friday to close at $57.

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