_Pfizer and Bristol-Myers Squibb have presented more detailed data on their new bloodthinner Eliquis which many analysts are claiming could become the drug of choice in the huge stroke market.

Having announced top-line data in June from a Phase III trial of Eliquis (apixaban), the firms put some meat on the bones at the European Society of Cardiology congress in Paris. The 18,201-patient study, called ARISTOTLE, showed that drug reduced the risk of stroke or systemic embolism by 21% in patients with atrial fibrillation when compared with the standard treatment warfarin.

The risk of major bleeding was cut by 31% and mortality by 11%. Pfizer and B-MS said ARISTOTLE showed that apixaban, a twice-daily direct Factor Xa inhibitor, is the first oral anticoagulant to significantly reduce all-cause death.

The companies expect to submit regulatory filings in AF in the USA and Europe in the third or fourth quarter of this year. Eliquis was approved in May by regulators in Europe for the prevention of venous thromboembolic events in adults who have undergone elective hip or knee replacement surgery.

The ARISTOTLE data has again ignited the debate as to which of the new bloodthinners will dominate the market. The race is currently being led by Boehringer Ingelheim's already-approved twice-daily oral direct thrombin inhibitor Pradaxa (dabigatran), and the German firm has just revealed that the drug already has been prescribed to more than 350,000 patients in the USA, Japan and Canada for stroke prevention in non-valvular AF.

The next entrant in the market is likely to be Bayer/Johnson & Johnson's once-daily Factor Xa inhibitor Xarelto (rivaraxoban), although studies have shown that the latter failed to beat warfarin on either efficacy or safety, but rather demonstrated equivalence. Some analysts believe that those weaker results could be due in part to dosing issues because Xarelto is taken once-daily, though the latter strategy could also be an advantage.

Aside from the new generation drugs, other observers note that warfarin is still appropriate for many patients and it also costs pennies, unlike its rivals.