Novartis Acquires Anthos Therapeutics for $925M, Reclaiming Promising Anticoagulant

Novartis has announced a $925 million upfront deal to acquire Anthos Therapeutics, bringing the phase 3 anticoagulant candidate abelacimab back into its pipeline. The Swiss pharmaceutical giant could pay up to an additional $2.15 billion in regulatory and sales milestones, with the deal expected to close in the first half of 2025.

Abelacimab: A Potential Game-Changer in Anticoagulation

Abelacimab, an anti-factor XI/XIa antibody, represents a new approach to preventing blood clots without increasing the risk of bleeding—a common side effect of current anticoagulants. Phase 2 trials have shown promising results, with abelacimab demonstrating an 80% reduction in venous thromboembolism compared to enoxaparin and a lower bleeding rate than Xarelto.

Anthos Therapeutics, formed in 2019 with a $250 million investment from Blackstone Life Sciences, has initiated three phase 3 trials for abelacimab. These studies, set to complete in 2026, focus on stroke prevention in atrial fibrillation patients unsuitable for current oral anticoagulants and the treatment of cancer-associated blood clots.

Competitive Landscape and Market Implications

The acquisition places Novartis back in competition with other pharmaceutical companies developing factor XI inhibitors. This class of drugs aims to improve upon non-vitamin K oral anticoagulants like Xarelto and Eliquis, which are facing upcoming generic competition.

However, the factor XI field has seen recent setbacks. Bayer's asundexian showed increased cardiovascular events compared to Eliquis, while Bristol Myers Squibb and Johnson & Johnson's milvexian failed a phase 2 trial before advancing to phase 3 studies. Regeneron is also in the race, developing two antibodies targeting different domains of factor XI.

Novartis CEO Vas Narasimhan had previously expressed interest in monitoring the factor XI space, particularly regarding study sizes and investment required to differentiate on safety. The acquisition of Anthos and abelacimab represents a significant commitment to this therapeutic area, with potential to address unmet needs in anticoagulation therapy.