Boehringer Ingelheim has presented “groundbreaking results” from a huge late-stage study which show that its oral anticoagulant Pradaxa significantly reduced the risk of stroke compared with warfarin, without raising the risk of bleeding.

The Phase III data presented at the European Society of Cardiology meeting in Barcelona and published in the New England Journal of Medicine involved over 18,000 patients in 44 countries. The study, called RE-LY, demonstrated that patients taking 150mg of Pradaxa (dabigatran etexilate) enjoyed a 34% lower risk of stroke and systemic embolism, compared with those taking warfarin, the blood thinner derived from rat poison sold by Bristol-Myers Squibb as Coumadin but now available generically.

Boehringer also noted that patients on 110mg of Pradaxa experienced similar reductions in stroke and systemic embolism compared to warfarin, but also had a 20% reduced risk of major bleeding. The drug also demonstrated superior reductions in haemorrhagic strokes and vascular mortality.

The response to RE-LY from clinicians was overwhelmingly positive. Stuart Connolly of the McMaster University in Hamilton, Canada, and co-principal investigator of the study, said the results “exceeded all our expectations”. He added that “we now have an oral treatment which offers superior protection from stroke with less bleeding and without the need for routine monitoring”.

Even more enthusiastic was Michael Ezekowitz of the Lankenau Institute in Philadelphia and US lead researcher of RE-LY, who hailed the results as “the first breakthrough in 60 years for preventing stroke in patients with atrial fibrillation.” He added that “the magnitude of these results cannot be understated”, noting that Coumadin, while “highly effective” is “very difficult to control” and Pradaxa is “potentially more effective and safer”.

Dr Ezekowitz pointed out that warfarin takes four days to work, while dabigatran acts within two hours, has very few drug-to-drug interactions and does not require patient monitoring. He added that if the dosage of a blood thinner is too high, the patient can experience bleeding and if it is too low, a stroke can occur, but “this trial not only identified a drug that is more effective than Coumadin, it also revealed the precise dosage that needs to be administered”.

The German drugmaker’s chairman, Andreas Barner, said Pradaxa could “revolutionise anticoagulant treatment” and “we look forward to expeditiously submitting these results to regulatory authorities around the world”. The treatment is available in over 40 countries for the primary prevention of venous thromboembolic events in adults who have undergone elective total hip or total knee replacement surgery; an approval in AF should push it into blockbuster territory.

The RE-LY study puts Pradaxa closer to approval in this indication than rival drugs, notably Bayer/Johnson & Johnson's Xarelto (rivaroxaban) and, further down the line, Pfizer/Bristol-Myers Squibb's apixaban and Merck & Co's betrixaban.