Shares in Germany’s Bayer jumped 4% yesterday after the company revealed its once daily oral clotbuster Xarelto (rivaroxaban) was superior to the gold standard warfarin, with less risk of bleeding, in protecting against stroke among patients with atrial fibrillation.

Data from the ROCKET AF trial - at more than 14,000-plus individuals enrolled it is the largest ever conducted among this patient population - showed a 21% reduction in the risk of stroke. Additionally, while overall rates of bleeding were similar to warfarin, they were significantly lower for the major complications of intracranial haemorrhage, critical organ bleed and bleeding-related death.

Xarelto looks set to be a real challenger to warfarin - offering superior efficacy and simplified dosing without the need for routine monitoring of bloods - and has already won a clutch of plaudits. But it will have to compete with Boehringer Ingelheim’s recently approved Pradaxa (dabigatran etexilate), which also has strong data but must be taken twice daily. Though a recent entrant onto the US market after its approval for stroke prevention in October, Pradaxa has been approved in Europe since 2008 for use as a clotbuster following orthopaedic surgery.

Patients with atrial fibrillation have a five-fold increased risk of stroke and a high percentage cannot tolerate warfarin; indeed the main complication of AF is stroke and about one-third of the 8-plus million AF patients in the USA and Europe are expected to suffer from a stroke.

Bayer and partner Johnson & Johnson are believed to be ready to file for approval of Xarelto in Europe and the USA, respectively, before the end of the year. And observers expect the news could spur analysts’ revenue forecasts for Xarelto beyond the $3-$4 billion already on the table.