Another breakthrough in anticoagulation therapy appears to be on the horizon with the new oral factor Xa inhibitor, apixaban, having shown a clinically important reduction in stroke and systolic embolism compared with aspirin in high-risk atrial fibrillation (AF) patients unsuitable for treatment with warfarin in the AVERROES (Apixaban Versus Acetylsalicylic Acid to Prevent Stroke) trial.

Patients with AF but unable to take warfarin were randomised to aspirin or apixaban. The 5,600-patient trial was terminated earlier this year following an interim analysis showing a reduced rate of stroke/systolic embolism in apixaban-treated patients compared with those on aspirin, without a significant increase in major bleeding.

The annual stroke or systemic embolism rate was 1.7% in apixaban-treated patients compared to 3.9% in aspirin-treated patients, without an increase in major haemorrhage (1.6% and 1.4% respectively). The rate of haemorrhagic stroke was 0.2% per year in both treatment groups and there was no evidence of hepatic toxicity or other major adverse events.

Principal investigator, Dr Stuart Connolly (McMaster University, Hamilton, Ontario, Canada), described the results of the trial as “truly impressive”. He added: “The reduction in stroke and systemic embolism is very important and the increased risk of haemorrhage is small. It appears that apixaban will be an excellent treatment for the many patients with atrial fibrillation who are unsuitable for warfarin. These findings will reduce the burden of stroke in society.”

Apixaban has already been investigated for the prevention of deep vein thrombosis, following orthopaedic surgery, and is also being studied against warfarin in AF patients suitable for warfarin. It does not as yet have a licence for use for AF in the UK.