Positive Ph III results for Portola's Xarelto antidote andexanet alfa

USA-based Portola Pharmaceuticals (Nasdaq: PTLA) saw its shares jump 7.2% to $40.83 after it announced positive results from a Phase III study of andexanet alfa, which is being developed as a anticoagulant antidote to German pharma major Bayer’s (BAYN: DE) Xarelto (rivaroxaban).

Portola announced full results from the first part of the Phase III ANNEXA-R (Andexanet Alfa a Novel Antidote to the Anticoagulant Effects of fXa Inhibitors -- Rivaroxaban) study, which is evaluating the safety and efficacy of andexanet alfa with the Factor Xa inhibitor Xarelto in healthy volunteers. Results showed the first part of this registration-enabling study met all primary and secondary endpoints with high statistical significance (p<0.0001 compared with placebo).

Andexanet alfa administered as an intravenous (IV) bolus produced rapid and significant reversal of the anticoagulant effect of Xarelto as measured by anti-Factor Xa activity (>90% reduction of mean anti-Factor Xa activity within five minutes of the end of administration). Additionally, there was a significant reduction in the level of free (unbound) Xarelto in the plasma, and thrombin generation was rapidly restored to within the normal baseline range following administration of andexanet alfa. In the study, andexanet alfa was well tolerated. There were no serious or severe adverse events, no thrombotic events, and no antibodies to Factor X or Xa observed.