Abelacimab Significantly Reduces Bleeding

Anthos Therapeutics celebrated its Phase II results showing that its novel Factor XI inhibitor abelacimab significantly reduced bleeding among AFib patients compared to the immensely popular blood thinner rivaroxaban (Xarelto).

  • Abelacimab is an investigational monoclonal antibody that locks the Factor XI blood clotting protein in its inactive state, potentially allowing thrombosis treatment without affecting hemostasis.
  • The drug was originally developed by Novartis, before being acquired by Blackstone Life Sciences (Anthos’ parent company) for $250M in 2019.
  • We haven’t yet confirmed how abelacimab measures up to rivaroxaban for reducing stroke risks, but if it proves non-inferior for stroke prevention it could significantly expand anticoagulant treatment options for older and more frail patients.

The AZALEA-TIMI 71 trial included 1,287 global AFib patients with moderate-to-high stroke risks, following them for a median of 21 months before the trial was halted due to “an overwhelming reduction” in bleeding events.

  • The study had abelacimab patients receive either 90 mg or 150 mg subcutaneously each month, or 20mg of rivaroxaban orally every day. 

Actual data on the abelacimab arm’s reduction in bleeding events won’t come out for several months. However, study authors give plenty of reasons to have high expectations, calling the reductions in major or clinically relevant bleeding events “overwhelming,” “unprecedented,” and “highly significant” versus standard-of-care treatment with rivaroxaban.  

  • Anthos also initiated an extension study evaluating patients who were originally in the rivaroxaban arm and switched to abelacimab after the original trial was halted.

Although abelacimab’s immediate next steps are to release full AZALEA-TIMI 71 results and complete its extension study, most attention will be on an ongoing Phase III study confirming its effectiveness with stroke reduction.

The Takeaway

It’s been a while since we’ve seen the medical community get this excited about trial results that didn’t include actual data, highlighting how much clinical demand exists for anticoagulants that don’t pose significant bleeding risks. Abelacimab still has a lot to prove, but if it matches rivaroxaban on stroke prevention it could be well positioned to meet that demand.

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