March 7 (Bloomberg) -- CV Therapeutics shares fell 24 percent after the drugmaker's chest-pain treatment, Ranexa, didn't help people with acute heart disease in a study.

Shares of the Palo Alto, California-based company fell $2.90 to $9.40 as of 4 p.m. New York time in Nasdaq Stock Market trading of 22.2 million, almost 16 times its three-month daily average. It was biggest one-day drop since December 2003, wiping out $172 million in market value.

The drug didn't show a statistically significant benefit in treating heart attacks or unstable angina, the company said yesterday. Ranexa was approved in January 2006 for chronic angina -- chest pain that develops after exertion when the heart needs more oxygen -- and accounted for $9 million in fourth- quarter sales.

The clinical trial was intended to test the drug's safety, allowing removal of restrictions on its use. The treatment didn't appear to increase deaths or irregular heartbeats, meaning it may win approval for other uses. Based on the results, the company doesn't plan to continue studying Ranexa for heart attacks or unstable angina, spokesman John Bluth said.

Ranexa could be reinvented as a diabetes drug if the company can show a significant reduction in glucose levels in diabetics, according to a report today by Piper Jaffray analyst Thomas Wei.

``We have historically viewed and continue to view the diabetes data as a possible game changer for Ranexa,'' Wei said, citing previous studies that showed a reduction.

To contact the reporter on this story: Tom Randall in New York at trandall6@bloomberg.net.

Last Updated: March 7, 2007 16:38 EST