11/13/2012 08:00 am ET Updated Jan 13, 2013

Xarelto: Blood Clot Pill To Be Tested For Heart Attack Prevention

FRANKFURT, Nov 13 (Reuters) - German drugmaker Bayer will start the largest drug trial so far involving blood-thinner Xarelto in a bid to widen its use to become a treatment for preventing repeat heart attacks.

As part of the trial with 20,000 participants, called Compass, Bayer will try to show Xarelto can complement or possibly replace Aspirin as the standard treatment for people who have suffered a heart attack due to atherosclerosis, or clogging of arteries.

The pill, jointly developed with Johnson & Johnson, is already approved to prevent blood clots after major orthopaedic surgery and to prevent strokes caused by a form of irregular heartbeat common among the elderly.

Bayer expects to generate peak annual sales from Xarelto of more than 2 billion euros ($2.5 billion), with stroke prevention as the main contributor.

It stuck to that forecast on Tuesday, even when taking into account the new targeted patient group, which is sizable.

About 100 million people in Western countries are currently at a higher risk of suffering a heart attack because of atherosclerosis, according to Bayer.

The Compass trial - in the third and last phase of testing required for regulatory approval - will see participants in more than 25 countries take Aspirin or Xarelto, or a combination of the two.

"It's a three-arm study ... We hope that the combination in particular will show a synergetic or complementary effect," Frank Misselwitz, Bayer's head of cardiovascular drug development, told Reuters.

The trial will start in the first quarter of next year and should last for about five years.

The yardstick will be which study arm has the fewest incidents of heart attack, stroke or cardiovascular death. The main side effect to be monitored will be major bleeding.

In a separate indication, Bayer and J&J have already been trying to get approval for adding Xarelto to standard treatment with Aspirin to prevent heart attacks and strokes in patients with acute coronary syndrome (ACS).

In September it filed a response to U.S. regulators after advisors expressed concern about bleeding risks.

($1 = 0.7868 euros) (Reporting by Frank Siebelt and Ludwig Burger; Editing by Mark Potter)