The latest safety data for Merck & Co.’s (MRK) withdrawn Vioxx drug show an increased risk of strokes, highlighting a lesser-noticed aspect of the Vioxx litigation that has been dominated primarily by claims the painkiller caused heart attacks.

The new data, which the drug maker released Thursday, could bolster the cases of people who claim in lawsuits that Vioxx caused their strokes, and might even spur new lawsuits, analysts said.

Merck hasn’t said how many of the 11,500 Vioxx lawsuits it faces involve stroke cases, but one plaintiff’s lawyer estimated it was about a third.

If they’re showing a statistically significant relationship with stroke and it wasn’t there before, they can downplay it if they want to, but it sounds like bad news to me,” said David Stahl, a corporate-defense attorney in Chicago who is not involved in the case.

But Merck officials say the new data should be kept in perspective because previous studies didn’t suggest a meaningful increase in risk for strokes among Vioxx users. They added it won’t change their litigation strategy of fighting each case individually, potentially over many years. The company is 3-3 in jury verdicts so far, all involving claims of heart-related events.

“We have extensive data from other studies showing no difference in the risk” for stroke, Merck general counsel Kenneth Frazier said on a conference call with reporters Thursday. “So, when you look at the extensive data that we’ve published, we still believe there is no evidence of an increased risk of stroke for purposes of the litigation.”

Studies have, however, at least suggested the possibility of an increased stroke risk because strokes were part of a so-called “composite endpoint” of various cardiovascular events. Some studies showed a greater incidence in the composite endpoint in Vioxx users than those taking placebo or another type of medication.
The first stroke-related Vioxx lawsuit could come to trial later this year. U.S. Judge Eldon Fallon in New Orleans has indicated he intends to try a series of cases through 2006 including a stroke case. The only federal case decided by a jury so far was a heart-attack case, which Merck won.

Merck withdrew Vioxx from the market in September 2004 after halting a three-year study of the drug because it showed an elevated risk of cardiovascular events in people taking the pill for at least 18 months.
Based on data from that study of nearly 2,600 patients, people taking Vioxx were 1.92 times as likely as those taking a placebo, or fake pill, to have adverse thrombotic events. That composite endpoint included cardiac events, stroke and peripheral vascular events.

Broken down further, the three-year data also showed the Vioxx group was 2.8 times as likely to have a cardiac event as those in the placebo group, which also had statistical significance.

But while the three-year data, as reported in the New England Journal of Medicine in March 2005, showed Vioxx users were more likely to have a stroke than in the placebo group, the increase wasn’t statistically significant, meaning it could have been due to chance.

The new data from Merck come from the same study but include a one-year follow-up period during which no one took Vioxx or placebo. Combining the three-year “on-drug” period with the one-year “off-drug” period, the risk of overall cardiovascular events was still higher among Vioxx users than placebo, at 1.74, a statistically significant increase. The four-year data also show a statistically significant increase in risk for cardiac events.

Broken down further, the four-year combined data showed a higher risk of stroke among Vioxx users. There were 17 Vioxx users who had ischemic strokes, compared with six in the placebo group. And during the one-year “off-drug” follow-up period, there were 7 strokes among former Vioxx users and none in the placebo group. An ischemic stroke is one caused by a blood clot or embolism such as an air bubble in the blood.

In one sense, the new stroke data aren’t a complete surprise. Garret Fitzgerald, a professor at University of Pennsylvania’s School of Medicine who has studied Vioxx, said he didn’t think “there is anything mysterious or novel about the stroke end of things.”

He noted in an email message that the combined endpoint of stroke and heart attack showed an increased risk for Vioxx users in previous studies. And he suggested the mechanism of how Vioxx might increase the risks of both heart attack and stroke “would be expected to be linked.”

J.P. Morgan analyst Chris Shibutani said the new stroke data might be an aberration “but could still be cause for some concern.” He added in a research note that he expects plaintiffs’ attorneys to file new claims on the basis of the stroke data, though most cases will still involve heart attacks.
But Shibutani didn’t expect the new data to change Merck’s case-by-case legal strategy, which he called “sensible.”

The latest analysis also showed that people who stopped taking Vioxx had a higher risk of cardiovascular events than placebo during the one-year off-drug period. The increase wasn’t statistically significant, but the finding could prompt people who had cardiovascular events after taking Vioxx to now file lawsuits against Merck.

Citigroup analyst George Grofik said in a research note “they do not appear to be strong cases at this time.” But there may be new data on additional patients that could change the status of the increased risk during the off-drug period to “statistically significant.”
Grofik said his estimate of Merck’s Vioxx liability of $2 billion to $10 billion is under review in light of the new data.

Merck shares fell 23 cents to $34.28 Friday afternoon.

Shibutani doesn’t own Merck shares; J.P. Morgan has performed investment-banking services for Merck in the past 12 months. Citigroup or its affiliates beneficially owns at least 1% of Merck shares and the firm has received investment-banking compensation from Merck in the past 12 months.

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