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Some doctors are raising concerns about the safety of andexanet alfa, the proposed reversal agent designed to control bleeding problems associated with side effects of Xarelto and Eliquis, two widely used, new-generation anticoagulants.
In letters to the editor published this week in the New England Journal of Medicine, doctors called for caution in enthusiasm for the factor xa inhibitor antidote, which, if approved by the FDA, could prevent numerous bleeding injuries linked to the new oral anticoagulants.
The drug is designed to reverse the blood thinning effects of the anticoagulants, allowing doctors to control and stop bleeding events that may occur among users of Xarelto, Eliquis and other similar blood thinners.
While warfarin has been the go-to anticoagulant treatment for decades, Xarelto, Eliquis and other new-generation anticoagulants have been introduced in recent years as a superior alternative, with the manufacturers claiming that they are easier to use and require less blood monitoring to maintain the proper dose. However, unlike warfarin, where the blood thinning effects of the drug can be reversed quickly with vitamin K and fresh frozen plasma if bleeding problems develop, no safe and effective antidote has been available for Xarelto or Eliquis.
Since the drugs have hit the market, thousands of reports involving uncontrollable Xarelto bleeding problems have plagued the new drugs, and there are currently more than 14,000 Xarelto lawsuits pending nationwide, alleging that the Bayer Healthcare and Janssen Pharmaceuticals sold an unreasonably dangerous and defective anticoagulant, without warning about the lack of an available reversal agent.
One letter, written by doctors from the McGill University Health Centre in Montreal, warned that a recent study heralding positive results for andexanet alfa may have overplayed its findings. The doctors said the methodologies used in the study may not provide reliable results.
“We understand the difficulty in conducting such studies but wonder how the efficacy of andexanet alfa can be reliably assessed without a comparator group,” the doctors wrote. “We also observed that the data on anti–factor Xa activity do not appear as a single pooled outcome. Consequently, the subgroup analyses of anti–factor Xa activity may be misconstrued as coprimary outcomes for rivaroxaban, apixaban, and enoxaparin and may lead readers to overestimate the importance of the results.”
The McGill doctors called for placebo-controlled trials to give a better assessment of the drug’s efficacy. However, another letter, by a group of doctors from Italy, warned that there were already signs of adverse side effects associated with the proposed reversal agent.
The doctors warn that 18% of patients given andexanet suffered an ischemic event, such as a stroke, within 30 days of receiving the drug. The doctors said that part of the problem may be that patients are not immediately put back on anticoagulants after being given the antidote, increasing their risk of stroke and other ischemic events. They suggested that a strategy of resuming blood thinners immediately after use of the antidote, or reserving it only for life-threatening bleeding events, may be possible solutions.
The proposed drug, given the brand name AndexXa, was developed by Portola Pharmaceuticals, and has been submitted to the FDA for approval. However, in September, the FDA indicated that it requires additional information regarding the manufacturing of the drug, and data on whether the drug can be used with the blood thinners Savaysa and Lovenox, before it can be approved.
The FDA did approve Praxbind in October 2015, which is a reversal agent for Pradaxa, which was the first member of this class to hit the market. However, Portola sought approval to market AndexXa as a reversal agent for Xarelto and Eliquis, which were the second and third members of this class, respectively.
The approval of a reversal agent for Xarelto and Eliquis has been sought by the drug makers, since it is widely acknowledged that this will make the drugs substantially safer.
According to allegations raised in product liability lawsuits filed against the drug makers, the new generation anticoagulants never should have introduced before a safe and effective reversal agent was available, seeking damages for severe bleeds and wrongful deaths caused by problems on Xarelto and Eliquis.
A series of Xarelto bellwether trials are expected to begin next year in the federal court system, which are designed to help parties gauge how juries may respond to certain evidence and testimony that is likely to be repeated throughout the litigation.
Thousands of Pradaxa lawsuits were filed against the makers of that competitor drug before the introduction of Praxbind, and the drug makers ultimately agreed to pay $650 million to settle about 4,000 cases.
It is widely expected that Xarelto settlements will require a substantially larger payment, given the larger market share and wider spread reports of problems among users of the controversial anticoagulant.