LONDON (Dow Jones) - Anglo-Swedish pharmaceutical AstraZeneca said Monday that its blockbuster anti-cholesterol treatment Crestor has passed a key scientific trial.

AstraZeneca (AZN) said that Crestor reversed plaque build-up in the arteries of patients with evidence of coronary artery disease, the first time a statin has demonstrated regression of atherosclerosis in a major clinical study.

The landmark trial, entitled Asteroid, was conducted over two years using a 40 miligram once-a-day dosage.

Analysts immediately turned to the significance of the trial results for AstraZeneca's statin competitors.

Pondering whether the data could threaten the dominance of market-leader Pfizer's (PFE) Lipitor drug or erode the position of the Vytoroin drug from Schering-Plough (SGP) and Merck (MRK) in the $20 billion market for cholesterol- lowering drugs, analysts at Bear Stearns said "not exactly."

"Rather, it reaffirms a growing body of evidence that says lower LDL cholesterol levels are better. To that end, Vytorin should benefit handsomely," the broker said.

Crestor has been dogged by safety concerns aftera Food and Drug Administration official told a Senate Finance Committee in late 2004 that it was one of five drugs which could raise safety concerns.

David Graham, associate director for science and medicine in the FDA Office of Drug Safety, warned about the possible risk of renal failure associated with Crestor.

Bear Stearns said that this overhang on the product hasn't gone away.

"We think the brand will continue to suffer from the negative perception of the drug's safety. Vytorin lowers LDL as well as Crestor, yet has no safety issues," said Bear Stearns.

AstraZeneca shares gained 3.1% at 29.67 pounds, adding to recent sharp gains made amid a sector rife with bid speculation.

In fact, Germany's Mercksaid on Monday that it has offered to buy Schering ( SHR) .

Another reason for a relatively subdued price rise could be that investors were mulling a weekend report in The Sunday Times that suggested AstraZeneca will in two years' time have to pay an estimated 2.6 billion pounds to its U.S. rival Merck .

The payment stems from the partial unwinding of a long-standing royalty agreement dating back to 1998, the report says without citing sources. (END) Dow Jones Newswires 03-13-06 0528ET Copyright (c) 2006 Dow Jones & Company, Inc.