A clinical trial comparing Abbott Laboratories' (ABT) cholesterol drug Niaspan with Zetia from Merck & Co. (MRK) and Schering-Plough Corp. (SGP) was terminated last month.

An independent steering committee stopped the trial based on results of a "pre-specified, blinded interim analysis," but not due to safety concerns, according to a notice posted on a U.S. National Institutes of Health online registry of clinical trials in mid-June.

It wasn't immediately clear whether the early termination was a negative sign for one or both of the drugs.

Abbott, of Abbott Park, Ill., and the Walter Reed Army Medical Center in Washington are listed as the trial's sponsors and collaborators.

The trial's lead investigator, cardiologist Allen Taylor of Washington Hospital Center in Washington, declined to elaborate on why the trial was terminated, beyond the reason posted on the NIH site. He said more information might be provided at a later date. Taylor said Abbott indirectly funded the trial but wasn't involved in its design or conduct.

An Abbott spokeswoman declined immediate comment, and a Walter Reed spokesman couldn't immediately be reached Wednesday afternoon.

Skip Irvine, a spokesman for the Merck/Schering-Plough venture said: "We have no insight into why this action was taken, other than the statement on [the NIH registry] that said the trial 'was not stopped due to safety concerns.'"

Abbott's Niaspan sales rose 19% to $786 million in 2008.

Zetia generated about $2.2 billion in sales last year, down nearly 9% from the year before due to studies released during 2008 that raised questions about Zetia's efficacy and safety. Zetia also is a component of the combination cholesterol drug Vytorin, also marketed by Merck/Schering-Plough.

The trial of 400 people at risk for heart attacks began in November 2006 and was expected to be completed later this year. In the trial, patients already taking so-called statin cholesterol drugs were given either Niaspan or Zetia. Niaspan is commonly used to raise good cholesterol levels, while Zetia is used primarily to lower bad cholesterol, though each has additional uses. Each drug works by a different mechanism, and can be used in combination with a statin.

Researchers tracked the drugs' effects on artery thickening after 14 months, using an ultrasound technique known as carotid intima-media thickness, or CIMT. The primary goal was to assess whether one drug provided a greater benefit.

Some doctors - and defenders of Vytorin and Zetia - have previously suggested that CIMT monitoring isn't very useful in detecting significant changes in artery thickness in certain patients. It was a CIMT trial that first raised questions about the efficacy of Vytorin and Zetia.

Taylor, the lead investigator, worked at Walter Reed when the trial began but has since moved to Washington Hospital Center. Walter Reed was one of the trial's locations.

Taylor declined to identify members of the steering committee that decided to end the trial.

Abbott shares rose 97 cents to $46.31 Wednesday. Merck rose 42 cents to $28.04, while Schering-Plough rose 17 cents to $25.27.

Information about the trial can be found at: http://www.clinicaltrials.gov/ct2/show/NCT00397657

-By Peter Loftus, Dow Jones Newswires; 215-656-8289; peter.loftus@dowjones.com