GERMANY — Bayer faced a substantial setback and it has abruptly terminated the OCEANIC-AF clinical trial, evaluating the efficacy of its experimental blood thinner, asundexian, in individuals with irregular heartbeats.

The trial’s premature end was attributed to the drug’s inferior performance compared to Bristol Myers Squibb’s Eliquis, sending Bayer’s stock plummeting by approximately one-fifth on the Frankfurt stock exchange.

Asundexian, part of the emerging class of Factor XIa inhibitors, was anticipated to generate over US$5 billion in annual sales, according to earlier projections by Bayer executives. The trial’s failure deals a significant blow to Bayer’s revenue expectations.

The OCEANIC-AF study focused on assessing asundexian’s ability to prevent strokes in patients with atrial fibrillation, a condition for which Eliquis and Bayer’s Xarelto are commonly prescribed.

The Factor XIa inhibitors, including asundexian, were developed with the aim of providing a safer alternative to Factor Xa medicines like Eliquis and Xarelto, with a reduced risk of bleeding.

Bayer’s Xarelto, marketed in the U.S. by Johnson & Johnson, had entered the market before Eliquis but failed to match its annual sales.

Eliquis demonstrated both superior safety and efficacy in clinical trials, leading to its higher market adoption and nearly US$12 billion in sales in 2022, compared to Xarelto’s US$6 billion.

The setback with asundexian raises concerns about the future sales prospects for Bayer and Johnson & Johnson’s Xarelto, as both drugs are set to lose patent protection in the mid-2020s, exposing them to potential erosion from generic competition.

The premature termination of the trial comes just nine months after its initiation, based on ongoing surveillance indicating the inferior efficacy of asundexian compared to the control arm.

While the safety results were consistent with previous trial data, such an early halt is uncommon in Phase 3 cardiovascular studies, which typically involve extensive patient enrollment and multiple years to detect benefits from new drugs.

Bayer stated that a trial focused on individuals who have experienced a stroke or transient ischemic attack will continue, but a planned study in atrial fibrillation patients unable to take other oral anticoagulants will be reassessed.

The impact of Bayer’s decision may extend to other players in the field, including Bristol Myers Squibb, which is developing a Factor XIa inhibitor called milvexian.

Although milvexian is ahead in development compared to asundexian, the trial halt may cast doubts on its promise, especially as it reported mixed Phase 2 data in stroke prevention. Bristol Myers’ shares experienced a 3% decline following Bayer’s announcement.

Despite the setback, Bristol Myers remains confident in its trial plans for milvexian, emphasizing its differentiation from other oral Factor XI inhibitors.

Analysts anticipate that Bayer’s announcement will have substantial implications for the broader landscape of companies in this therapeutic field.

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