AtheroGenics

(AGIX)

said Monday that a clinical trial of its experimental treatment for clogged arteries produced positive results. But investors didn't appear to be impressed.

The company's stock fell $4.88, or 15.6%, to $26.49 in heavy trading. In less than an hour, trading volume was nearly 4.2 million shares, or more than twice the average daily trade over the past three months.

The company's drug AGI-1067 targets atherosclerosis, the process in which fatty substances build up in arteries to produce plaque. Over time the clogged arteries reduce blood flow, and the arteries can harden.

The company said a phase II clinical trial -- the second of three rounds of testing before a drug is submitted to regulators -- showed a statistically significant reduction (2.3%) in plaque volume over a 12-month period. However, when the AGI-1067 patients' plaque results were compared with those of patients receiving standard care, the results (0.8% reduction) were not statistically significant.

"We are pleased with the results ... and believe these data provide good evidence that, in contrast to current therapies, AGI-1067 has the ability to regress plaque in coronary arteries when dosed over a 12-month period," said Dr. Rob Scott, chief medical officer at AtheroGenics.

The company is in the midst of a phase III trial on the drug. "I consider these final

phase II data encouraging," said Dr. Jean-Claude Tardif of the Montreal Heart Institute, who is the principal investigator of the phase II trial. "I believe we have enhanced our chances of seeing positive results in the phase III trial."