Portola Pharmaceuticals Initiates Phase II Trial of Betrixaban, its Novel Oral Factor Xa Inhibitor for Stroke Prevention in Atrial Fi...( SOUTH SAN FRANCISCO Calif. Nov. 3...)

SOUTH SAN FRANCISCO, Calif., Nov. 3 /PRNewswire/ -- Portola Pharmaceuticals, a biopharmaceutical company developing innovative drugs that provide significant advances in cardiovascular and inflammatory diseases, and cancer, today announced that it has begun patient enrollment in a large Phase II clinical trial of betrixaban, the Company's novel oral Factor Xa inhibitor anticoagulant, for stroke prevention in patients with atrial fibrillation (SPAF).

"This is a major milestone achievement to advance the first of our two highly differentiated Phase II product candidates that address the unmet needs of the more than 50 million patients worldwide requiring hospital or chronic antithrombotic therapy," said Charles Homcy, M.D., president and chief executive officer of Portola. "Betrixaban's unique profile has the promise to deliver reliable efficacy administered once-daily without the excess bleeding associated with other anticoagulants."

The Phase II trial, called EXPLORE Xa, is a multi-national, double-blind, dose-finding study that will enroll approximately 500 patients and assess three once-daily doses of betrixaban (40 mg, 60 mg, and 80 mg) administered for at least three months compared to dose-adjusted warfarin (given open label), the current standard of care, in patients with non-valvular atrial fibrillation. The goal of the study is to assess long-term safety and tolerability of betrixaban and provide key dosing information for Phase III studies. The Company expects to complete enrollment of this trial by the end of 2009.

Potential Best in Class Therapy

"We are thrilled to have the opportunity to evaluate what we believe is a truly unique anticoagulant in an exciting new class," said Stuart Connolly, M.D., director of the Division of Cardiology at McMaster University, Hamilton, Ontario, Canada, and principal investigator. "Because betrixaban may provide predictable anticoagulation combined with a lower risk of bleeding, and beca
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