The editorial, written by the journal's editor in chief, Dr. Jeffrey M. Drazen, executive editor Dr. Gregory D. Curfman and managing editor Stephen Morrissey, also alleges the study's authors deleted other relevant data before submitting their article for publication.
"Taken together, these inaccuracies and deletions call into question the integrity of the data on adverse cardiovascular events in this article," the doctors wrote. Excluding the three heart attacks "made certain calculations and conclusions in the article incorrect."
Adverse cardiovascular events include heart attacks, strokes and deaths.
CBS News medical correspondent Elizabeth Kaledin reports that in an unprecedented move, the journal published what it calls an "expression of concern," chastising the study's authors and saying "at least two of the authors knew about the three additional (heart attacks) at least two weeks before submitting… drafts of the study."
The findings of what became known as the VIGOR study have been a key part of testimony in the three product liability trials to date over the withdrawn drug, including one in which a federal jury in Texas began deliberations Thursday afternoon. Plaintiff attorneys claim the study showed Vioxx was dangerous, but the company disputed that.
Merck shares fell 61 cents, or 2 percent, to $29.68 in regular trading on the New York Stock Exchange, then fell an additional 85 cents, or 2.8 percent, to $28.85 in after-hours trading, after news of the journal editorial circulated.
In a statement issued late Thursday, Merck said the additional heart attacks "did not materially change any of the conclusions of the article," which was published in November 2000, more than a year after the Food and Drug Administration approved Vioxx. The company also said the information was not included because the heart attacks were reported after Merck's cut-off date for collecting information on the patients in the study.
"Nevertheless, these additional events were disclosed to the FDA in 2000, presented publicly at the FDA's Advisory Committee in February 2001, and included in numerous press releases subsequently issued by Merck," the company statement reads.
But Curfman said in an interview that Merck's arguments about the cut-off date "don't hold water" because journal articles are routinely updated with new data in the weeks before publication. "The health of the public, of many, many thousands of people, was at stake here," he said.
Data in Thursday's editorial show that 20 patients on Vioxx suffered heart attacks, instead of the 17 originally reported. Among patients in a comparison group taking the older, cheaper anti-inflammatory naproxen, there were four heart attacks.