Another setback in the lab. This time, Bristol-Myers Squibb and Pfizer say apixaban failed to meet its goal in a Phase III test for preventing venous thromboembolism (VTE) in patients undergoing total knee replacement. Although research for other uses will continue, a regulatory filing next year to seek approval to market the drug for preventing blood clots won’t take place.

Early evaluation of a study comparing two daily doses of apixaban with two of an older blood thinner, enoxaparin, found they worked about the same. Why? The drugmaker sayenoxaparin was more effective than it had been in previous patient studies. The new study, called ADVANCE-1, also found similar rates of side effects such as bleeding in the two drugs. Full results will be revealed in December.

Bristol-Myers and Pfizer said they are considering further testing of apixaban for preventing clots in knee surgery patients, but with different study parameters. Meanwhile, other tests will continue, with no changes needed, according to the drugmakers. Those include testing the drug to treat venous blood clots, to prevent them in patients having major orthopedic surgery, and to prevent stroke in patients with atrial fibrillation. Here is the statement.

Apixaban is an oral drug from a new class of medicines that evidence indicates can inhibit a blood-clotting substance called factor Xa. The drug is being tested in several late-stage studies in tens of thousands of people around the world.

Enoxaparin is a version of the Heparin blood thinner that is given as an injection just under the skin. Sanofi-Aventis sells it under the brand names Lovenox.