The Food and Drug Administration wants more information on data management and verification from a huge international study that examined stroke prevention in patients with an irregular heartbeat called atrial fibrillation, the drugmakers said Monday.
The companies said regulators did not ask for new studies in their response letter, and they plan to work quickly to address outstanding questions. Even so, a Bristol-Myers spokeswoman said the agency could take up to six months to review their response.
"We are already working with the agency, and we are hopeful that the review of our submission can be completed within a shorter timeframe," spokeswoman Laura Hortas said in an e-mail.
Pfizer Inc. shares fell 33 cents, or 1.5 percent, to $22.39 in Monday morning trading, and Bristol-Myers Squibb Co. shares dropped $1.22, or 3.5 percent, to $34.14.
The New York drugmakers said in February that the FDA had pushed back its deadline for deciding whether to approve Eliquis until June 28.
Eliquis, known chemically as apixaban, is one of three new drugs meant to prevent heart attacks and strokes better than the longtime standard treatment, warfarin. All three could become blockbusters, bringing their makers much-needed new revenue.
Doctors and patients have long wanted a better alternative to warfarin, an inexpensive generic drug also sold under brand names such as Coumadin. That's because getting the dose of warfarin correct is so tricky that patients must have frequent blood tests to ensure they're getting enough to prevent clots but not enough to cause internal bleeding.
Bristol-Myers discovered Eliquis and since 2007 has been testing it in partnership with Pfizer, the world's largest drugmaker.
The drug was approved in May by the European Union for preventing blood clots in patients who have had hip or knee replacement surgery. However, the companies ultimately are aiming for a much bigger market, the millions of U.S. and European patients with atrial fibrillation, an irregular heartbeat that raises risk of life-threatening blood clots.
The first of the new anticlotting drugs, Boehringer Ingelheim GmbH's Pradaxa, also known as dabigatran, was approved in October 2010 for patients with atrial fibrillation.
Another treatment, Johnson & Johnson's Xarelto, is approved for patients with atrial fibrillation and for preventing blood clots after hip or knee replacement surgery. But J&J said last week the FDA denied its request to expand approval of Xarelto to prevent life-threatening blood clots in patients with acute coronary artery disease.
J&J said regulators raised additional questions about the proposed new use, and it expects to work with them to address the questions as quickly as possible.