Oral direct thrombin inhibitor AZD0837 for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation: a randomized dose-guiding, safety, and tolerability study of four doses of AZD0837 vs. vitamin K antagonists

Aims: Oral anticoagulation with vitamin K antagonists (VKAs) for stroke prevention in atrial fibrillation (AF) is effective but has significant limitations. AZD0837, a new oral anticoagulant, is a prodrug converted to a selective and reversible direct Thrombin Inhibitor (AR-H067637). We report from a Phase II randomized, dose-guiding study (NCT00684307) to assess safety, tolerability, pharmacokinetics, and pharmacodynamics of extended-release AZD0837 in patients with AF.

Methods and results: Atrial fibrillation patients (n = 955) with > or =1 additional risk factor for stroke were randomized to receive AZD0837 (150, 300, or 450 mg once daily or 200 mg twice daily) or VKA (international normalized ratio 2-3, target 2.5) for 3-9 months. Approximately 30% of patients were naïve to VKA treatment. Total bleeding events were similar or lower in all AZD0837 groups (5.3-14.7%, mean exposure 138-145 days) vs. VKA (14.5%, mean exposure 161 days), with fewer clinically relevant bleeding events on AZD0837 150 and 300 mg once daily. Adverse events were similar between treatment groups; with AZD0837, the most common were gastrointestinal disorders (e.g. diarrhoea, flatulence, or nausea). d-Dimer, used as a biomarker of thrombogenesis, decreased in all groups in VKA-naïve subjects with treatment, whereas in VKA pre-treated patients, d-dimer levels started low and remained low in all groups. As expected, only a few strokes or systemic embolic events occurred. In the AZD0837 groups, mean S-creatinine increased by approximately 10% from baseline and returned to baseline following treatment cessation. The frequency of serum alanine aminotransferase > or =3x upper limit of normal was similar for AZD0837 and VKA.

Conclusion: AZD0837 was generally well tolerated at all doses tested. AZD0837 treatment at an exposure corresponding to the 300 mg od dose in this study provides similar suppression of thrombogenesis at a potentially lower bleeding risk compared with dose-adjusted VKA. This study is registered with ClinicalTrials.gov, number NCT00684307.