Federal officials issued a complete response letter late Thursday, which means they want more information from the drug manufacturer before making a final decision.
Xarelto (rivaroxaban) entered the market last summer and is already approved for the prevention of blood clots that form in the blood vessels of the legs and lungs during knee or hip replacement surgery. It is also approved to reduce stroke risk in patients with certain abnormal heart rhythms.
But manufacturer Janssen, which is a division of Johnson & Johnson, sought to expand its use to include patients with a common heart condition known as acute coronary syndrome (ACS), which occurs when blood flow to the heart is restricted because of blood clots that form in the heart arteries.
The company stands behind its drug and still hopes for a future approval. "We are confident in the robust study results of the ATLAS ACS ... trial and the positive benefit-risk profile of rivaroxaban in patients with ACS. We will continue to work with the FDA to fully address their questions as quickly as possible," said Paul Burton, MD, PhD, vice president, Cardiovascular Franchise Medical Leader at Janssen R&D.
More than 1 million people in the U.S. are hospitalized for heart attacks, strokes, and other events linked to ACS each year.
New-Generation Blood Thinners
Patients taking warfarin must be closely monitored because of the risk for brain hemorrhages and other potentially life-threatening bleeding events.
Safety questions have still plagued both drugs since they entered the U.S. market.
In the months after Pradaxa was approved to lower stroke and blood clot risk in patients with atrial fibrillation, about 500 cases of hemorrhaging were reported, according to the nonprofit drug monitoring group Institute for Safe Medication Practices.
And in a surprise move late last month, an FDA panel set the stage for Thursday's action by voting 6 to 4 against recommending the approval of Xarelto to treat patients with ACS.
At the time, the panel cited concerns about bleeding risk and missing data from the pivotal ATLAS trial of the drug.
Missing Data Cited by Panel
In that trial, Xarelto was found to reduce the risk of death or stroke by 15% among patients recently hospitalized for acute coronary syndrome.
But panel members were concerned that the researchers had incomplete outcome data on 12% of the study participants.
The FDA is scheduled to rule on whether or not to approve the third new blood thinner, Bristol-Myers Squibb's and Pfizer's Eliquis, by the end of the month.
While the new blood thinners are easier to take than warfarin, there have been concerns that dangerous bleeding episodes linked to the use of the drugs may also be harder to control.
In patients taking warfarin, which works by blocking vitamin K, doctors can reverse the blood thinning effects if they need to in a few hours by administering the vitamin or by giving patients blood clotting agents.
It is not clear if blood clotting drugs work as well to reverse the blood thinning action of the new medications.
Early laboratory studies suggest that some of the strategies used to reverse the blood thinning action of warfarin may also work with the new drugs.
But Elmhurst, Ill., cardiologist and American Heart Association spokesman Vincent Bufalino, MD, tells WebMD that these trials are preliminary and there is, as yet, no consensus on how to best reverse the actions of the new drugs in emergency situations.