UPDATED: Why Zetia Researchers' Silence on Ending of Niaspan Trial Is Unfair to Merck

Dr. Allen Taylor, an ARBITER-6 HALT trial investigator, should probably avoid talking to Merck investors for the next few weeks lest he get punched in the nose. It was Allen and his colleagues' unexplained announcement that they had stopped an Abbott Labs-funded comparison of Merck's Zetia with Abbott's Niaspan that sent Merck's stock plunging on the assumption that the test had been abandoned midway because Niaspan was proving superior.

As Forbes' Matt Herper points out, the trial was a small one and had only 180 patients enrolled. And no one knows what the data really say ... and so everyone is speculating.

Unfortunately for Merck, most speculators agree: Zetia was faring worst. That's unfortunate for Merck and its investors because we don't know whether that's true. Allen told Cardiology Today the study data will be published in a scientific forum at a later date:

We are consistently declining any further comment beyond what is posted on clinicaltrials.gov, ... There will be an opportunity for more substantive discussions in the future once the data are peer reviewed, published and presented. This is the decision from within the trial.
So let's get this straight: Allen et al have enough data on the study to stop the trial, but not enough to data to explain to the public why they stopped the trial. Does this make sense? Of course not. And yet Merck's holders must bear the brunt of Allen's refusal to explain what he's doing or why he did it.

Here's a selection of analyst comment. Note, they all have a different view:

Seamus Fernandez and Kathryn C. Alexander at Leerink Swann:

Bottom Line: Investor concern ... following a "prespecified, blinded interim analysis" by the independent steering committee may be warranted. ... we expect questions raised by ARBITER 6 to be an overhang for MRK/SGP and remain on the sidelines.
Jon Paul LeCroy of Natixis:
We are now assuming that this trial significantly favored Niaspan and, as a result, we are decreasing our sales estimates for both Zetia and Vytorin ... If this trial favors Niaspan, it would be the third blow against Zetia. We would expect Zetia and Vytorin prescriptions to show further declines.
Barbara Ryan of Deutsche Bank:
... believes it's "very unlikely" that Niaspan showed superiority. She said it was likely that "investigative futility" or enrollment problems, or both, were the reasons for the termination. She suggested that if Niaspan had shown superiority, that outcome would have been communicated by now. . .
UPDATE: For more background on why Allen declined to reveal the reasons for halting the trial, read this article in Circulation, "Preliminary Observations From Preliminary Trial Results; Have We Finally Had Enough?"