While everybody was busy covering the sour clinical-trial news surrounding Merck (NYSE: MRK) and Schering-Plough's (NYSE: SGP) cholesterol fighter Vytorin earlier in the week, AstraZeneca (NYSE: AZN) quietly announced heart-throbbing news for its own cholesterol-lowering drug, Crestor.

AstraZeneca announced on Monday that a data-monitoring board decided to halt a Crestor trial early, so that placebo-treated patients could get access to it as well. The study was using Crestor to help prevent cardiovascular-related deaths and ailments, and the efficacy data was coming in strong. This was no small study, either -- it had more than 15,000 participants.

The timing couldn't have been worse for AstraZeneca. Vytorin -- a combination of Merck's Zocor and Schering's Zetia -- stole all of the headlines this week, and investors shaved billions of dollars off both companies' market caps. But even so, AstraZeneca needed the good news it got, since generic competition against its Toprol-XL compound has eaten into its sales this year. And the study results should give the company new ammunition in its marketing battles against the other statins, including Pfizer's (NYSE: PFE) Lipitor and even Zocor, which has now gone generic.

Crestor won approval in the U.S. in 2003 and has since become AstraZeneca's top-selling drug, with sales of $2.8 billion last year. That's a 38% increase over 2006, and it's nearly twice as much as what it takes in for Toprol-XL, its next highest-grossing compound.

We didn't get any details on the Crestor study results yesterday, except for the top-line announcement. But we do know that AstraZeneca's guidance for adjusted earnings per share this year was in the range of $4.40 to $4.70, just pennies above the $4.38 it earned in 2007. The company is also still integrating last year's MedImmune acquisition into its operations. However, with the positive Crestor news and the negative results from its competitors, we could see AstraZeneca raise its earnings guidance for the year when it reports its first-quarter financial results later this month.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool's disclosure policy has perfect timing.