( SAN FRANCISCO July 10 2007 /PRNewswi...)Portola Pharmaceuticals Announces Positive Data from a Phase II,Study of its Factor Xa Inhibitor at the XXI Congress of the,International Society on Thrombosis and Haemostasis,Health

SAN FRANCISCO, July 10, 2007 /PRNewswire/ -- Portola Pharmaceuticals, Inc. announced positive Phase II data on its lead compound, PRT054021, an oral Factor Xa inhibitor, today at the XXI Congress of the International Society on Thrombosis and Haemostasis (ISTH) in Geneva, Switzerland. The EXPERT trial showed that PRT054021 was safe, effective, and well tolerated for the prevention of venous thromboembolic events (VTE) in patients undergoing total knee replacement (TKR) surgery. Portola expects to move PRT054021 into Phase III clinical development in VTE prevention in the first half of 2008.

EXPERT is a Phase II proof-of-concept study designed to examine the safety, efficacy and tolerability of two doses of PRT054021 versus enoxaparin event rates in recent comparable studies. EXPERT also included an enoxaparin group to compare the safety and antithrombotic activity of PRT054021 with that of enoxaparin. A steering committee of leading physicians and orthopedic surgeons concluded that EXPERT met its objectives and that PRT054021 was safe and effective at the doses studied.

In EXPERT, the incidence of VTE was 20% (95% Confidence Interval 12%-32%), 15% (8%-27%) and 10% (3%-23%) in the low dose group of PRT054021, the high dose group of PRT054021, and in the enoxaparin group, respectively. In recent comparable controlled trials the VTE rate for enoxaparin has been between 15% and 20%. No major bleeds were seen in the PRT054021 groups (0 out of 171, 0%), compared with 1 major bleed in the enoxaparin group (1 out of 43, 2.3%). No significant non-major bleeds were identified in the low dose group of PRT054021 (0 out of 87, 0%) and two in the high dose group of PRT054021 (2 out of 84, 2.4%), versus two significant non-major bleeds in the enoxaparin group (2 out of 43, 4.7%). No other significant safety concerns related to PRT054021 were identified.

"The EXPERT trial results are very encouraging," sai
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