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Andexanet alfa achieved primary, secondary efficacy endpoints in phase 3 trial
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Portola Pharmaceuticals announced that a phase 3 trial assessing the factor Xa inhibitor antidote andexanet alfa has achieved its primary and secondary endpoints with a high degree of statistical significance and favorable safety results.
According to a press release, results from the first of two planned ANNEXA-A studies indicated that IV treatment with andexanet alfa led to the immediate and significant reversal of anticoagulation activity following administration of apixaban (Eliquis; Bristol-Myers Squibb and Pfizer).
The randomized, double blind, placebo-controlled trial included 33 older, healthy volunteers treated with apixaban 5 mg twice daily for 4 days. Participants were randomly assigned in a 3:1 ratio to receive either placebo or a 400 mg IV bolus of andexanet alfa. The primary endpoint was anti-factor Xa levels, with secondary endpoints including levels of plasma unbound apixaban and thrombin generation. Andexanet alfa was well-tolerated, and no participants experienced serious adverse events, according to the release.
"Andexanet alfa represents a potential important advance to the field of anticoagulation for factor Xa inhibitor patients who suffer a major bleeding event or those requiring emergency surgery," William Lis, chief executive officer of Portola, said in the release. “…These highly statistically significant phase 3 ANNEXA-A data demonstrate that andexanet alfa has the potential to be the first agent approved as a universal factor Xa inhibitor antidote.”
The full results from the trial will be presented during the Clinical Science: Special Reports session at the American Heart Association Scientific Sessions in November.
The second ANNEXA-A trial will include 32 healthy volunteers who will receive apixaban followed by IV andexanet alfa similarly to the first trial, and will be randomly assigned at a 3:1 ratio to receive either placebo or a continuous 4 mg/min infusion of andexanet alfa for 120 minutes. Results from this trial are anticipated for early next year, the company stated in the release.
The company intends to file a Biologics License Application with the FDA for Accelerated Approval by the end of 2015. Additional study of andexanet alfa will also assess its efficacy for other factor Xa inhibitors, including betrixaban, edoxaban, enoxaparin and rivaroxaban, John T. Curnutte, MD, PhD, executive vice president of research and development for Portola, said in the release.