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VIDEO: Andexanet alfa effectively reverses factor Xa anticoagulant

 

Key clinical point: An anticoagulant reversal drug showed efficacy, safety in its pivotal trial.

Major finding: Hemostatic efficacy of andexanet alfa was 83%, and thrombotic events occurred in 11%.

Study details: ANNEXA-4, a single arm cohort study with 227 patients.

Disclosures: ANNEXA-4 is sponsored by Portola Pharmaceuticals, the company developing andexanet alfa (AndexXa). Dr. Connolly has been a consultant to Portola and also to Bayer, Boehringer-Ingelheim, Bristol-Myers Squibb, and Sanofi-Aventis.

Source: Connolly S. ACC 2018.

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Andexanet alfa will boost factor Xa inhibitor use

Treatment with andexanet alfa produced good or excellent hemostasis in 83% of patients in the ANNEXA-4 study, which is what matters when patients are bleeding. Clinicians want to know that you can restore coagulation to a level where you can stop bleeding, and that’s what the results show.

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The lack of a reversal agent until now for direct-acting factor Xa inhibitor drugs has probably been a modest but real obstacle to widespread adoption of these agents. We can look at the example of another new oral anticoagulant, dabigatran (Pradaxa), which works by a different mechanism, specifically by inhibiting thrombin. After a reversal agent for dabigatran, idarucizumab (Praxbind) received Food and Drug Administration approval and became available in late 2015, an uptick in dabigatran prescriptions occurred. That experience shows that patients and providers want the safety net of a reversal agent. They want to know that, if there is bleeding or need for urgent surgery, there is a way to facilitate restoration of hemostasis.

It’s the same with direct factor Xa inhibitors: Some patients are concerned about the lack of a reversal agent, and having such an agent may help increase access to these agents for such patients. I think that, once andexanet becomes available for routine U.S. practice, we’ll see an uptick in prescribing of direct factor Xa inhibitors. Also, some patients who have opted for treatment with warfarin will switch to a safer class of drugs, the direct factor X a inhibitors. A myth exists that reversal agents can easily negate the anticoagulant effect of warfarin. The reality is that, despite having treatments that reverse warfarin’s effect, this is often not an easy process in actual practice.

On the safety side, there was no indication in the ANNEXA-4 results of rebound thrombosis with andexanet alfa treatment. Patients receiving a direct factor Xa inhibitor are prothrombotic – that’s why they are on an anticoagulant – so their risk for a thrombotic event is always there, especially when they are not fully anticoagulated, such as when a reversal agent is administered. We need to look to restarting treatment with an anticoagulant because these patients have a high thrombotic risk.

Gregory Piazza, MD , is a cardiologist at Brigham and Women’s Hospital in Boston. He has been an advisor to Portola Pharmaceuticals, the company developing andexanet alfa, as well as to Bayer and Pfizer, and he has received research funding from Bristol-Myers Squibb, Janssen, and Daiichi Sankyo. He made these comments in an interview .


 

REPORTING FROM ACC 18


Dr. Ajay J. Kirtane

Dr. Ajay J. Kirtane

“I use anticoagulants in high-risk PCI [percutaneous coronary intervention] patients with atrial fibrillation, and I expect to use more direct factor Xa inhibitor anticoagulants in light of the COMPASS findings, so having an agent that works for reversal – and these are very promising results – will be very important in our armamentarium. It will give us a safety net,” commented Ajay J. Kirtane, MD, director of the cardiac catheterization laboratory at Columbia University Medical Center in New York. (The COMPASS results, also presented at ACC 18, showed that peripheral artery disease patients on rivaroxaban plus aspirin had significantly fewer adverse peripheral vascular outcomes.)

The Prospective, Open-Label Study of Andexanet Alfa in Patients Receiving a Factor Xa Inhibitor Who Have Acute Major Bleeding (ANNEXA-4) enrolled 227 patients at any of 60 centers, with efficacy data available from 132 of the patients. About 60% of the patients had an intracranial bleed, and about 30% had a gastrointestinal bleed, and their average age was 77 years. Roughly three-quarters of patients were on an anticoagulant for atrial fibrillation, with the rest treated for venous thromboembolism, with 4% having both conditions. The most commonly used direct factor Xa inhbitors in these patients were apixaban (Eliquis) in 105 and rivaroxaban (Xarelto) in 75. The ANNEXA-4 study has not enrolled patients treated with a direct factor Xa inhibitor anticoagulant and undergoing surgery, a setting that will be the subject of a future study, Dr. Connolly said.

Clinicians administered andexanet alfa as a bolus followed by a 2-hour continuous infusion, with hemostatic efficacy assessed 12 hours after the start of treatment. The results showed that factor Xa inhibition fell by about 75%-90% within minutes of starting the bolus and remained depressed at that level during the infusion but then began recovering by 2 hours after the stop of infusion. Andexanet is a factor Xa “decoy” molecule that acts by latching onto the inhibitor molecules and thereby preventing them from interacting with actual factor Xa, but andexanet also has a short half life and hence the effect quickly reduces once treatment stops.

“There is no doubt that andexanet rapidly decreases anti–factor Xa activity,” he said.

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