Portola Pharmaceuticals Announces Phase 3 ANNEXA™-R Part 2 Study Results to be Presented at American Heart Association Scientific Sessions 2015

South San Francisco, Calif., Nov. 06, 2015 (GLOBE NEWSWIRE) -- Portola Pharmaceuticals (Nasdaq:PTLA) today announced that full data from the second part of its Phase 3 ANNEXA™-R (Andexanet Alfa a Novel Antidote to the Anticoagulant Effects of FXa Inhibitors – Rivaroxaban) study of the investigational agent andexanet alfa will be presented during a Late-Breaking Clinical Trial oral session at the upcoming American Heart Association (AHA) Scientific Sessions, which is taking place from November 7-11 in Orlando, Fla.

Andexanet alfa, a U.S. Food and Drug Administration (FDA)-designated breakthrough therapy, is a recombinant protein specifically designed to reverse the anticoagulant activity in patients treated with an oral or injectable Factor Xa inhibitor. Portola is developing it as a universal reversal agent for patients anticoagulated with an oral or injectable Factor Xa inhibitor who suffer a major bleeding episode or require emergency surgery.

The ANNEXA-R study evaluated the safety and efficacy of andexanet alfa in reversing the anticoagulant effect of the Factor Xa inhibitor rivaroxaban, as measured by anti-Factor Xa activity, in older healthy volunteers. Part 1 of the study demonstrated rapid reversal with an IV bolus infusion, and topline data from Part 2 showed the ability of andexanet alfa administered as an IV bolus followed by a continuous two-hour infusion to sustain that reversal for the duration of the infusion. In the study, andexanet alfa was well tolerated, with no serious or severe adverse events, no thrombotic events, and no antibodies to Factor X or Xa observed.

Following are details of the Late-Breaking oral presentation, which will include additional data beyond what has been previously announced.

Abstract Title: ANNEXA™-R Part 2: A Phase 3 Randomized, Double-Blind, Placebo-Controlled Trial Demonstrating Sustained Reversal of Rivaroxaban-Induced Anticoagulation in Older Subjects by Andexanet Alfa (PRT064445), a Universal Antidote for Factor XA (FXA) Inhibitors
Presenting Author: Mark Crowther, M.D., MSc., professor in the Department of Medicine, Hematology and Thromboembolism and Pathology and Molecular Medicine, McMaster University, Hamilton Ontario
Session Title: Novel Therapies for Common Problems
Date, Time and Location:Wednesday, November 11, at 10:45 a.m. ET, Chapin Theater

About Andexanet Alfa

Andexanet alfa is a modified human Factor Xa molecule that acts as a decoy to target and sequester with high specificity both oral and injectable Factor Xa inhibitors in the blood. Once bound, the Factor Xa inhibitors are unable to bind to and inhibit native Factor Xa, thus allowing for the restoration of normal hemostatic processes. Andexanet alfa is the only compound being studied as a reversal agent for Factor Xa inhibitors that directly and specifically corrects anti-Factor Xa activity – the anticoagulant mechanism of these agents.

Portola is currently evaluating andexanet alfa in ANNEXA-4, a Phase 4 single-arm confirmatory study in patients receiving apixaban, rivaroxaban, edoxaban or enoxaparin (a low molecular weight heparin and indirect Factor Xa inhibitor) who present with an acute major bleed. Data from a small number of patients from ANNEXA-4, as well as data from ANNEXA-A and ANNEXA-R, will serve as the clinical basis of a Biologics License Application (BLA), which Portola plans to submit to the FDA by the end of this year.

About Portola Pharmaceuticals, Inc.
Portola Pharmaceuticals is a biopharmaceutical company developing product candidates that could significantly advance the fields of thrombosis and other hematologic diseases. The Company is advancing its three wholly-owned programs using novel biomarker and genetic approaches that may increase the likelihood of clinical, regulatory and commercial success of its potentially life-saving therapies. These programs include betrixaban, an oral, once-daily Factor Xa inhibitor being evaluated in the APEX Phase 3 study for prophylaxis of venous thromboembolism (VTE); andexanet alfa, a recombinant protein designed to reverse the anticoagulant effect in patients treated with an oral or injectable Factor Xa inhibitor; and cerdulatinib, a Syk/JAK inhibitor in development to treat hematologic cancers. Portola's partnered program is focused on developing selective Syk inhibitors for inflammatory conditions. For more information, visit www.portola.com and follow the Company on Twitter@Portola_Pharma.

Forward-looking Statement
Statements contained in this press release regarding matters that are not historical facts are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Such statements include, but are not limited to statements regarding: andexanet alfa's potential as a reversal agent for patients anticoagulated with an oral or injectable Factor Xa inhibitor who suffer a major bleeding episode or require emergency surgery, Portola's plans for pursuit of regulatory approval of andexanet alfa, and the likelihood of clinical, regulatory and commercial success for andexanet alfa and Portola's other product candidates. Risks that contribute to the uncertain nature of the forward-looking statements include: the accuracy of Portola's estimates regarding its ability to initiate and/or complete its clinical trials; the success of Portola's clinical trials and the demonstrated efficacy of Portola's product candidates to the satisfaction of regulatory authorities; the accuracy of Portola's estimates regarding its expenses and capital requirements; Portola's ability to manufacture andexanet alfa; regulatory developments in the United States and foreign countries; Portola's ability to obtain and maintain intellectual property protection for its product candidates; and the loss of key scientific or management personnel. These and other risks and uncertainties are described more fully in Portola's most recent filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K, which was filed on March 2, 2015, and Quarterly Report on Form 10-Q, which was filed on August 5, 2015. All forward-looking statements contained in this press release speak only as of the date on which they were made. Portola undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

Investor Contact: Ana Kapor Portola Pharmaceuticals ir@portola.com Media Contact: Julie Normart W2O Group jnormart@w2ogroup.com

Source:Portola Pharmaceuticals, Inc.