A new, small molecule drug from Bayer AG was approved by the US Food and Drug Administration on 9 November to reduce the risk of secondary stroke in patients who have already experienced a disorder. The drug, Sunharbo (asundexian) inhibits factor XIa – an enzyme that plays a key role in blood clotting. According to Bayer, Sunharbo is the first drug of its kind to be approved for patients. When given in combination with an antiplatelet therapy, it has been shown to reduce stroke risk in two specific instances.
These are in adults that have experienced a non-cardioembolic ischaemic stroke, a type of stroke caused by a clot that did not originate in the heart, and transient ischaemic attack, which is a temporary disruption of blood flow to part of the brain.
According to two papers presented at a 2025 conference of the European Stroke Organisation, approximately one in five stroke survivors who have had a non-cardioembolic ischaemic stroke will have another one within five years. These secondary strokes are often more serious than the first.
“Stroke is a leading cause of disability and death in the US, and survivors are at risk of having another stroke,” Hylton Joffe of the FDA’s Center for Drug Evaluation and Research, said in a prepared statement.
Sunharbo works by blocking FXIa, a clotting factor in the intrinsic coagulation pathway. Within this pathway it triggers the production of thrombin which then activates more protein and amplifies the formation and stability of blood clots, By blocking FXIa, Sunharbo interrupts this process and reduces excess thrombin generation and clot growth. In a Phase 3 study, 12,327 adult patients were assigned to the drug or to a placebo. Sunharbo significantly reduced the risk of ischaemic stroke by 26% compared with the placebo over a median treatment of 14.2 months, the FDA said.
Copyright 2026 Evernow Publishing Ltd.