I'm no fan of Merck (NYSE:MRK), but the sell-off of its shares yesterday seems a little overblown considering the lack of information.

What we know is that a trial comparing Merck's and Schering-Plough's (NYSE:SGP) cholesterol drug Zetia to Abbott Labs' (NYSE:ABT) Niaspan was ended early because of a "pre-specified, blinded interim analysis."

Let's break this down:

  • pre-specified -- the peek at the data was scheduled before the start of the trial
  • blinded -- a separate independent steering committee made the decision so that, if the trial continued, investigators wouldn't have seen the data
  • interim -- it was done before the trial was supposed to end
  • analysis -- analysis

See anything in there that suggests that Niaspan prevailed over Zetia? Me neither, but, judging by Merck's share decrease, it looks like that's what investors and some analysts are worried about.

It seems just as likely that the trial was ended because Zetia prevailed, or that finishing the trial was futile because it wouldn't show that either drug was better than the other. A trial testing Pfizer's (NYSE:PFE) Sutent against Roche's Avastin was stopped last month for just that reason.

Abbott contributed drugs and money to the trial, but it was run by an independent investigator, so the company doesn't have any control over the release of the data. The lead investigator plans to release the data after it's been peer-reviewed. Let's hope his peers can keep a secret.

Investors need to keep rumors and conspiracies in perspective. Sanofi-aventis (NYSE:SNY) was in a similar situation a few weeks ago, when rumors were flying over unpublished data about its insulin product, Lantus. It turns out the data wasn't as bad as the rumors led investors to think.

And until someone who's in the know talks, it's useless to speculate or trade. But some will do so anyway. Just be careful out there, Fools.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Rumor has it the Fool's disclosure policy likes to be printed on pink paper.