The group is seeking conditional approval for the drug's use when reversal of anticoagulation is needed due to life-threatening or uncontrolled bleeding and for patients requiring urgent or emergency surgery.

The submission is based on data from two Phase III ANNEXA studies that evaluated the safety and efficacy of IndexXa (andexanet alfa) in reversing the anticoagulant activity of the Factor Xa inhibitors rivaroxaban (Bayer's Xarelto) and apixaban (Pfizer/Bristol-Myers Squibb's Eliquis), showing in some cases reversal of the anticoagualant effect by 93.5 percent.

Annually, one to four percent of patients treated with Factor Xa inhibitors may experience major bleeding, and an additional one percent may require emergency surgery. In the EU, an estimated 73,000 oral Factor Xa inhibitor-treated patients will be hospitalised this year due to major bleeding or will require urgent surgery, but there are currently no reversal agents approved for use.

"These patients are critically ill and could potentially benefit from a Factor Xa inhibitor antidote," said Bill Lis, chief executive officer of Portola, and noted that the firm is "working diligently" to bring IndexXa to patients.

However, the firm's quest to secure US approval for the drug recently hit a setback after it was turned away by regulators.

The US Food and Drug Administration sent Portola a Complete Response Letter asking for more information, primarily related to manufacturing.

The agency also wants additional data to support inclusion of other Faxtor Xa inhibitors edoxaban and enoxaparin in the label, and indicated it needs to finalise its review of the clinical amendments to Portola's post-marketing commitments that recently were submitted.