Patients with non-valvular atrial fibrillation receiving either 30 mg or 60 mg once-daily dose of DU-176b, an investigational oral Factor Xa inhibitor, experienced safety and tolerability as compared to those taking warfarin, according to new phase-II data presented at the 50th Annual Meeting of the American Society of Haematology in San Francisco.

These findings are the first results from a clinical study evaluating an oral Factor Xa inhibitor in atrial fibrillation patients. DU-176b is being developed solely by Daiichi Sankyo Company, Limited.

The objective of the multinational study was to assess the safety of four dose regimens of DU-176b in patients with non-valvular atrial fibrillation (AF), as compared to warfarin.

While the incidence of major and clinically relevant non-major bleeding events was significantly higher in the twice-daily DU-176b treatment groups (30 mg or 60 mg twice per day), compared with warfarin, the incidence reported in the once-daily DU-176b treatment groups (30 mg or 60 mg once per day) was similar to that in the warfarin-treated patient group. Bleeding events were evaluated using guidelines established by the International Society on Thrombosis and Haemostasis, the most sensitive scale of those currently used in clinical studies in cardiovascular disease.

"These results are noteworthy and encouraging because we observed significantly fewer adverse bleeding events in patients receiving one dose of DU-176b per day, versus two doses per day, suggesting with this compound, the most convenient dosing regimens also appear to be safer," said Jeffrey I. Weitz, professor of medicine and biochemistry, McMaster University and director, Henderson Research Centre, Hamilton, Ontario. "These data provide insight into the optimal dosing regimens for phase-III studies of DU-176b."

"Having clear results from a robust phase-II study among atrial fibrillation patients gives us confidence in evaluating the doses selected for our phase-III clinical trial," said Francis Plat, vice president, clinical development at Daiichi Sankyo Pharma Development. "We are hopeful that DU-176b may one day provide the community a safe and convenient treatment in the prevention of stroke in patients with non-valvular atrial fibrillation."

DU-176b is an oral anticoagulant that directly inhibits Factor Xa, a clotting factor in the blood. Daiichi Sankyo is developing DU-176b as a potential new treatment for the prevention of both arterial and venous thromboembolism.