Portola reports positive data for Factor Xa inhibitor antidote; shares rise

Shares in Portola rose as much as 11 percent Friday on news that its investigational therapy andaxanet alfa met the primary endpoint of reversing the effect of Bayer and Johnson & Johnson's anticoagulant Xarelto (rivaroxaban). In October, the drugmaker disclosed that the drug also effectively reversed the anticoagulation activity of Pfizer and Bristol-Myers Squibb's Eliquis (apixaban).

In the study, 41 healthy volunteers aged 50 to 75 were administered Xarelto once daily for four days and then randomised to receive andaxanet alfa or placebo. The company stated that efficacy was evaluated using biomarker ebdpoints, with anti-Factor Xa levels as the primary endpoint, while the secondary endpoints of the study included the plasma levels of plasma-unbound of Xarelto and thrombin generation levels.

Top-line results for the first part of the Phase 3 ANNEXA-R study illustrated that andaxanet alfa immediately and significantly reversed the anticoagulating effects of Xarelto, while the product was found to be well tolerated. Portola said that full results of the study will be presented later this year at the American College of Cardiology annual meeting.

"The statistically significant Phase 3 ANNEXA-R study data, together with results presented previously with [Eliquis], provide compelling evidence that this groundbreaking agent could serve as a universal antidote for Factor Xa inhibitor anticoagulants," remarked Portola executive vice president of R&D John T. Curnutte.

Meanwhile, Portola is conducting a second part of the study in which healthy volunteers will be administered Xarelto for four days followed by randomisation to receive andaxanet alfa, administered as an intravenous bolus followed by a continuous infusion for 120 minutes, or placebo. Results from the second phase of the study are anticipated in mid-2015.

Andaxanet alfa was granted breakthrough therapy status by the FDA in 2013.

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