One downside of newer anticoagulants is that, unlike older drugs such as warfarin and heparin, there are no antidotes to reverse their effects when patients develop severe bleeds.
Recognising this, Boehringer Ingelheim has developed a humanised antibody called idarucizumab that blocks the effects of its big-selling direct thrombin inhibitor Pradaxa (dabigatran). Idarucizumab has successfully passed testing in healthy volunteers and will now start a pivotal trial in patients taking its anticoagulant.
In the initial trial, the antidote was found to be safe and effective in reversing dabigatran-induced anticoagulation and, importantly, did not appear to cause any bounce-back elevation in coagulation in the 145 volunteers enrolled.
Pradaxa has been a huge success since becoming the first of the novel oral anticoagulants to come onto the US market in 2011, with sales growing quickly to more than $1.6bn last year despite early concerns that the drug was associated with a higher risk of severe bleeding than warfarin.
An FDA drug safety communication issued in 2012 seemed to lay the matter to rest, suggesting that bleeding rates associated with Pradaxa were no worse than warfarin. Earlier this year however the FDA said it planned to start a large-scale study to compare the safety of the drug with warfarin in patients with atrial fibrillation (AF).
Pradaxa was also first to market in Europe in August 2011, followed by Bayer/Janssen’s Xarelto (rivaroxaban) and Bristol-Myers Squibb/Pfizer’s Eliquis (apixaban), which are both Factor Xa inhibitors. The three drugs have been steadily picking up new uses such as VTE and continue to battle for market share.
In 2013 Xarelto brought in over $2bn in global sales, giving it the lead in the market, while Eliquis was a distant third last year but appeared to be gaining ground. Daiichi Sankyo is also nearing the market with its Factor Xa inhibitor edoxaban.
Approval of an effective antidote could make doctors more comfortable prescribing Pradaxa and so give it a competitive edge in the marketplace.
“This is the first time that an antidote under development for a novel oral anticoagulant is investigated in a study in patients,” said Boehringer in a statement, adding that idarucizumab will be tested in hospital emergency rooms in more than 35 countries around the world.
Meanwhile, Portola Pharmaceuticals is developing a Factor Xa inhibitor antidote, called andexanet alfa, which could be used with both Xarelto and Eliquis and has been given breakthrough status by the US FDA. It is currently being tested in healthy volunteers administered Xarelto and Eliquis, with edoxaban studies at the planning stage.