An anti-clotting pill from Bayer and Johnson & Johnson offers a new way of preventing stroke although further studies will be needed to refine treatment options, according to a review in a top medical journal.
Wednesday's editorial in the New England Journal of Medicine (NEJM) will be read closely by doctors and industry analysts, who have been grappling with results from a difficult-to-interpret clinical trial of Xarelto.
Gregory Zoppo of the University of Washington, and Misha Eliasziw of the University of Calgary, said the mix of statistical analyses used to assess the once-daily drug had "muddied the waters" over its benefits.
Xarelto, known generically as rivaroxaban, was hailed last November as being 21 percent better at preventing stroke in patients with a form of irregular heartbeat called atrial fibrillation (AF) than the standard treatment, warfarin.
But this conclusion was based on an analysis that excluded certain patients. When all those who entered the trial were evaluated, no superiority was established for Xarelto.
"I think we can say safely that rivaroxaban is not inferior to warfarin. I don't think we can say it is superior," Zoppo said in a telephone interview. "Non-inferiority is not a bad thing."
The editorial also highlighted the fact warfarin, which requires patients to have regular blood tests to ensure correct dosing, was not used as effectively as it might have been in the study.
And the authors said an "important concern" was that new anti-coagulants such as Xarelto did not have antidotes to rapidly reverse their anti-coagulation effects in the event of serious bleeding. Patients on warfarin can be given vitamin K.
The full results of the so-called ROCKET-AF study were published in the NEJM alongside the editorial.
The Food and Drug Administration has approved Xarelto for preventing blood clots after knee and hip surgery, and it is expected to decide whether to approve it in the much larger stroke-prevention market later this year.
A similar drug called Pradaxa, or dabigatran, from Boehringer Ingelheim, is on the market and several others are under development, including apixaban from Bristol-Myers Squibb and Pfizer.
All aim to replace warfarin, a problematic drug, in the lucrative market for millions of mainly elderly patients with AF. Zoppo said their arrival was a notable advance.
"What's really exciting about rivaroxaban and dabigatran is now we have some alternatives to warfarin that are relatively easy to take and their control seems to be pretty straightforward," he said.
"Is everybody going to switch from warfarin? I think the answer is 'no'. Patients who are managed very well on warfarin should stay on it."
He said there was scope for further trials looking at the relative merits of existing drugs and other, even newer ones still in earlier stages of development.
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