Portola rolls toward approval for its 'breakthrough' anticoagulant antidote

Portola Pharmaceuticals' ($PTLA) anti-anticoagulant came through in a pair of Phase III trials, rapidly reversing the effects of blood thinners Xarelto and Eliquis and setting the stage for a final FDA submission.

The treatment, andexanet alfa, is designed to reverse the effects of drugs called Factor Xa inhibitors, which thin the blood by inhibiting the enzymes necessary for coagulation. Portola's drug works as a decoy, fooling such drugs into targeting it instead of the body's coagulation-regulating enzymes and thus reversing their effects and keeping patients safe in major bleeding events.

In late-stage studies published in The New England Journal of Medicine, Portola's therapy reversed anticoagulation within two to 5 minutes and sustained the effect throughout a two-hour infusion. To test andexanet alfa, Portola dosed patients with either Xarelto or Eliquis for four days and then randomized some to get the antidote and others to get placebo. In the end, Portola's treatment met its goals, charting a statistically significant effect on clotting, Factor Xa activity and thrombin generation, the company said.

Portola began a rolling FDA submission of andexanet alfa last quarter, planning to hand in the final part of its application by year's end. The treatment received the FDA's breakthrough-therapy designation, which has given Portola preferred access to agency officials and potentially puts andexanet alfa in line for an accelerated approval.

Antidotes like andexanet alfa have the potential to increase use of next-generation anticoagulants like Xarelto, marketed by Bayer and Johnson & Johnson's ($JNJ), and Eliquis, sold by Bristol-Myers Squibb ($BMY) and Pfizer's ($PFE). Boehringer Ingelheim's similar Pradaxa got a leg up on its rivals last month when the company won FDA approval for Praxbind, an in-house reversal agent for its Factor Xa blocker.

Beyond its antidote work, Portola is pressing forward with betrixaban, a proprietary anticoagulant in development for acute cases of venous thromboembolism. The drug has received the FDA's fast-track designation, and Portola expects to submit it for approval next year. The company also has a Phase I treatment for blood cancer and some preclinical projects focused on inflammation.

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