Bristol-Myers Squibb Co. announced that its blood thinner apixaban failed in a late-stage study. Apixaban acts by inhibiting coagulation factor Xa and was put through phase III trials in the prevention of venous thromboembolism, in patients having knee replacement surgery, together with a number of related competing compounds, such as rivaroxaban.

However, apixaban proved no better than older drug enoxaparin, marketed by Sanofi-Aventis as Lovenox. Bristol-Myers and its partner Pfizer Inc. had been planning to apply late next year for Food and Drug Administration approval to sell the drug to patients undergoing knee replacement surgery.

Full results of the phase III trial, dubbed ADVANCE-1, are to be presented in December at a medical conference. The two companies are currently evaluating future studies with different parameters. The companies are also testing the drug to treat venous blood clots, to prevent them in patients having major orthopedic surgery, and to prevent stroke and other problems caused by clots in patients with atrial fibrillation. The drug may prove its effectiveness in any of these areas and thus may become a viable alternative to competing products. Eight late-stage studies are currently undergoing, involving a total of about 45,000 people around the world.