Anthos’ ABP-959 outperforms Xarelto in preventing bleeding events in phase 2 trial

Anthos abelacimab trial, Blackstone ex-Novartis drug, Xarelto bleeding comparison, Anti-Factor XI/XIa antibody, Thrombosis without hemostasis, Novartis MAA868 history, Anthos phase 3 studies,

Blackstone Life Sciences’ substantial $250 million investment in an ex-Novartis drug candidate has yielded yet another positive outcome in its Phase 2 trials. The data from Anthos Therapeutics reveals that their candidate, abelacimab, has significantly reduced bleeding when compared to Xarelto, a product from Bayer and Johnson & Johnson. This achievement adds to the mounting evidence supporting the biotech’s potential to treat thrombosis effectively without impacting hemostasis.

Originally, Novartis initiated Phase 2 trials for the anti-Factor XI/XIa antibody, previously known as MAA868, back in 2018. These trials were designed to evaluate the molecule’s ability to inhibit FXI in patients with atrial fibrillation and to prevent clots in individuals undergoing knee replacement surgery. However, Novartis withdrew these trials before any patients were enrolled, leading Blackstone to license the asset the following year.

Since then, Anthos, the biotech entity formed by Blackstone to advance this candidate, has been accumulating compelling evidence suggesting that Novartis may have relinquished a valuable asset. In 2021, Anthos reported an 80% reduction in venous thromboembolism compared to enoxaparin, and now, they have presented data on bleeding.

Existing drugs used to combat venous thromboembolism, which involves the formation of blood clots in veins, often come with an increased risk of bleeding. Anthos envisions abelacimab as a means to separate thrombosis treatment from the risk of excessive bleeding. The recent Phase 2 trial, which involved 1,287 patients with atrial fibrillation at moderate to high risk of stroke, administered Xarelto or two different doses of the investigational antibody subcutaneously once a month. The trial demonstrated that the drug candidate was associated with a reduction in major or clinically relevant non-major bleeding events. This outcome prompted Anthos to halt the study and offer patients on Xarelto the opportunity to switch to abelacimab.

While Anthos has not yet released specific data from the Phase 2 trial, they have described the reduction in bleeding as “overwhelming” and “unprecedented.” The biotech plans to unveil the complete dataset at an upcoming scientific congress.

“The largest and longest head-to-head study of a Factor XI inhibitor to provide definitive evidence of a highly significant reduction in bleeding as compared to a standard-of-care anticoagulant. The study had a median of 21 months of follow-up.”

– Marc Sabatine, M.D., Brigham and Women’s Hospital 

Anthos has already progressed abelacimab into three Phase 3 clinical trials, enrolling patients with atrial fibrillation and cancer patients at risk of venous thromboembolism. The biotech is one of several developers targeting FXI, with Bristol Myers Squibb and J&J collaborating on milvexian and Bayer working on asundexian, both of which are administered orally. This latest achievement underscores the potential for abelacimab to bring about a significant shift in the field of thrombosis treatment.

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