early discontinuation based on strategic sponsor decision not driven by any safety concern

The objective is to evaluate whether once weekly subcutaneous (SC) injection of idrabiotaparinux sodium (biotinylated idraparinux) is at least as efficient to prevent clots in brain and in the other organs than oral international normalized ratio (INR) adjusted-dose warfarin in patients with atrial fibrillation (AF).

The end of the study is defined by a common study end date for all participants, defined as 9 months (39 weeks) after the last participant randomized.

All participants will receive oral warfarin (or matching placebo) and weekly SC injections of idrabiotaparinux sodium (or matching placebo) up to 6 months before the common study end date. All participants are expected to be treated for at least 6 months.

All participants will have then an 6-month observational period after cessation of study treatment.

Inclusion Criteria:

• Non valvular atrial fibrillation (AF)
• Indication for long-term Vitamin-K antagonist (VKA) therapy based on the presence of previous ischemic stroke, transient ischemic attack (TIA) or systemic embolism and/or at least two of the following risk factors: hypertension requiring drug treatment, moderately or severely impaired left ventricular function and/or congestive heart failure, age > or = 75 years, diabetes mellitus.

Main exclusion Criteria:

• Indication for VKA other than AF
• Stroke or TIA within previous 5 days
• Transient AF caused by a reversible disorder
• Planned major surgery/trauma or cardioversion within 30 days
• INR > 3 at baseline
• Active bleeding or high risk of bleeding
• Uncontrolled hypertension
• Pregnancy or childbearing potential without proper contraceptive measures or breast feeding.