Bayer ends large blood thinner trial for ‘inferior efficacy’

Bayer is stopping a large clinical trial testing its experimental blood thinner asundexian in people with irregular heartbeats because it didn’t work as well as Bristol Myers Squibb’s Eliquis, the company said Monday.

Shares in the German drugmaker fell by about one-fifth in trading on the Frankfurt stock exchange following the news. Earlier this year, Bayer executives had said they expect asundexian — one of an emerging class of drugs called Factor XIa inhibitors — to eventually earn in excess of $5 billion in annual sales, making Monday’s trial setback a major blow to the company.

Called OCEANIC-AF, the study was evaluating how well asundexian prevents strokes in people with atrial fibrillation, the primary reason people now receive Eliquis or Bayer’s own Xarelto. Companies developing Factor XIa inhibitors believe the drugs can be safer than Factor Xa medicines like Eliquis and Xarelto by reducing the risk of bleeding.

Xarelto, which Johnson & Johnson markets in the U.S., arrived on the market before Eliquis, but hasn’t achieved the same annual sales. In clinical trials, Bayer was only able to prove that Xarelto wasn’t inferior to an older drug called warfarin, while Eliquis proved both safer and more effective.

Combined, Bayer and Johnson & Johnson reported Xarelto annual sales of about $6 billion in 2022, compared with nearly $12 billion for Eliquis. Both drugs are set to lose patent protection in the middle of the 2020s, however, meaning those sales could be eroded by generic competition. Success with Factor XIa drugs could help the drugmakers offset expected losses from generic Factor Xa drugs.

Asundexian was ahead in development of a Bristol Myers Squibb Factor XIa called milvexian, which isn’t set to complete the Phase 3 trials necessary to seek Food and Drug Administration approval until 2026 or 2027.

Bayer decided to halt the trial, which began just nine months ago, based on “ongoing surveillance which showed an inferior efficacy of asundexian versus the control arm.” It is an unusually early termination for a Phase 3 study in cardiovascular disease, which typically enrolls tens of thousands of patients and last several years to detect a benefit from new drugs.

According to the company, safety results were “consistent” with previously reported trial data.

A trial in people who have already experienced a stroke or transient ischemic attack will continue, Bayer said. However, the company will reassess a planned study in atrial fibrillation patients who can’t take other oral anticoagulants, which Bayer announced two weeks ago.

The trial halt may also raise doubts about the promise of milvexian, which like asundexian reported mixed Phase 2 data in stroke prevention. Bristol Myers shares fell 3% this morning. The company, with its partner J&J, has outlined a major Phase 3 program to prove milvexian’s effectiveness.

In a July note to clients initiating coverage on Bristol Myers Squibb, SVB Securities analyst David Risinger described milvexian as the company’s “biggest pipeline opportunity” that could potentially reach more than $5 billion in annual sales, a total company executives also believe is possible.

Umer Raffat, an analyst at Evercore ISI, said in a client note that Bayer’s announcement will have “very significant implications” for other companies in the field.

Bristol Myers said in an emailed statement that it remains confident in its trial plans and that it believes milvexian is different from other oral Factor XI inhibitors.

Editor’s note: This story has been updated with comment from Bristol Myers Squibb.

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