ORLANDO, Fla. (Reuters) - A drug developed by Portola Pharmaceuticals to rapidly reverse the effect of new blood thinning agents in cases of major bleeding or other emergencies proved highly effective in a late stage study, according to data presented on Wednesday that should help make the case for its approval.
Portola's andexanet alfa reversed the anticoagulant effect of the new drugs, known as factor Xa inhibitors, within minutes of being administered, with no reported serious side effects, researchers said.
The factor Xa drugs, Xarelto (rivaroxaban) and Eliquis (apixaban) were approved as effective and safer alternatives to the decades-old drug warfarin to prevent blood clots and strokes. But there is no approved antidote should the effect of the drugs need to be stopped in a hurry, if for example, emergency surgery is required.
The final stage of Portola's Phase III program tested the reversal drug against placebo in 39 healthy volunteers aged 50 to 68 who were given Xarelto.
Andexanet alfa significantly reduced anti-Factor Xa activity by 97 percent compared with placebo, with reversal persisting for one to two hours after completion of its infusion, which was deemed highly statistically significant.
The Portola drug "was able to almost immediately, almost completely reverse the affect of the drug," said Dr. Mark Crowther, the study leader who presented the data at the American Heart Association's scientific meeting in Orlando.
Similarly effective data on andexanet alfa's ability to reverse Eliquis previously had been presented. Results of both also were reported in the New England Journal of Medicine.
Portola said it plans to file for U.S. approval before the end of this year.
While major bleeding episodes are more rare with the new medicines than with warfarin, they still occur. And patients taking them also could seriously injure themselves in falls, car accidents or other incidents of trauma that cause extensive bleeding, researchers said.
"Having knowledge that there is an effective reversal agent will increase provider comfort in using these drugs for sure," said Crowther, a professor at McMaster University in Hamilton, Ontario.
A reversal agent for Boehringer Ingelheim's anticoagulant Pradaxa recently won U.S. approval.
Dr. Jerrold Levy of Duke University, who discussed the study at the AHA meeting but was not involved in the trial, said safe and effective reversal agents for the new anticoagulants "are critical for emergencies when they occur."
When the Portola drug is approved, "it will be stocked in all hospitals," Levy predicted.
Reporting by Bill Berkrot; Editing by Paul Simao