Antidote for Factor Xa Inhibitors Goes to Phase 2 Study

December 12, 2012

SOUTH SAN FRANCISCO, California — A so-called "universal antidote" for factor Xa inhibitors has entered phase 2 studies in which the drug, currently called PRT4445 (Portola Pharmaceuticals), will be given to healthy volunteers who had been given a factor Xa inhibitor, the company has announced [1].

Oral anticoagulants with an antidote would have an important advantage in the clinical landscape over those that don't have one; they are useful for managing episodes of uncontrolled bleeding during anticoagulation or for emergency surgery, Portola notes.

Antidotes for the current wave of approved and investigational oral anticoagulant alternatives to warfarin are a hot research area. The lack of an antidote was one of the first cautions to be sounded when the first of these new agents to be approved, the direct thrombin inhibitor dabigatran etexilate (Pradaxa, Boehringer Ingelheim), became available.

PRT4445 by its nature works with all factor Xa inhibitors, the company says, and in fact the upcoming phase 2 study will have cohorts taking apixaban (Eliquis, Bristol-Myers Squibb/Pfizer) and others taking Portola's own oral factor Xa inhibitor, betrixaban. That drug, which can be given once daily, Portola notes, is currently in trials for extended-duration prophylaxis for venous thromboembolism (VTE).