Dive Brief:

  • An experimental blood thinner dramatically cut the risk of major bleeding versus the widely used drug Xarelto in a mid-stage study of nearly 1,300 people with atrial fibrillation, results presented Sunday at the American Heart Association’s meeting showed.
  • The new blood thinner, called abelacimab and developed by biotechnology company Anthos Therapeutics, reduced major or clinically relevant non-major bleeding by 67% over Xarelto. Anthos’ therapy also lowered the risk of gastrointestinal bleeding — a known concern with Xarelto — by 93%, according to the data.
  • Abelacimab is one of a promising new class of anticoagulants known as a Factor XI or Factor XIa inhibitors. Bristol Myers Squibb and Bayer have bet big on Factor XIa inhibitors of their own, launching late-stage trial programs set to enroll tens of thousands of participants.

Dive Insight:

Direct oral anticoagulants like Xarelto and Eliquis unseated warfarin as go-to choices for blood thinning in people at risk of stroke and clotting more than a decade ago. But these drugs, which earn their makers billions of dollars in annual sales, carry bleeding risks that make them unsuitable or undesirable for some people.

Anthos, as well as Bristol Myers and Bayer, are attempting to fill that gap with Factor XI inhibitors. The drugs are meant to stop thrombosis — the formation of blood vessel-blocking clots — while sparing hemostasis, the process used by the body to respond to injuries.

All three companies have already advanced into Phase 3 testing, although Bristol Myers and Bayer are planning much larger trials than Anthos, which first focused on smaller late-stage studies in cancer-associated thrombosis. (Bristol Myers is partnered with J&J on Factor XI inhibitor development.)

Sunday’s results support the biotech’s recently begun Phase 3 trial in people with atrial fibrillation who can’t take existing anticoagulants. That study will pit abelacimab against a placebo to compare rates of stroke or systemic embolism.

“By providing patients with the possibility of continuous protection against blood clots, the potential for enhanced adherence and a placebo-like bleeding profile, abelacimab could represent the ‘holy grail’ of hemostasis-sparing anticoagulation,” said Anthos’ Chief Medical Officer Dan Bloomfield, in a statement on the data.

Anthos’ drug differs from Bristol Myers’ and Bayer’s in an important respect: As a monoclonal antibody, the drug is given by subcutaneous injection, while its pharmaceutical competitors are oral pills.

Abelacimab originated with Novartis, which teamed up with Blackstone Life Sciences to launch Anthos in 2019.

Editor’s note: This story has been updated to note J&J’s participation in Factor XI inhibitor development with Bristol Myers.