Alan C. Cameron, MB ChB, BSc (Hons), MRCP

Georgi B, Mielke J, Chaffin M, Khera AV, Gelis L, Mundl H, et al. Leveraging Human Genetics to Estimate Clinical Risk Reductions Achievable by Inhibiting Factor XI. Stroke. 2019.

In this recent article, Georgi and colleagues highlight coagulation factor XI (FXI) as a promising new target for antithrombotic therapy to prevent ischemic stroke without an increased risk of major bleeding. The authors analyzed data from the UK Biobank and two large genome wide association studies to formulate a genetic score standardized to a 30% increase in relative activated partial thromboplastin time, which is equivalent to effects achieved by pharmacological FXI inhibition compared to enoxaparin for the prevention of venous thromboembolism after total knee arthroplasty. 

The results herald what could potentially be a game-changer in antithrombotic therapy for stroke prevention. The authors demonstrate that genetic predisposition to lower FXI levels is associated with a 53% reduction in risk of ischemic stroke (OR 0.47, 95% CI 0.36–0.61; p=1.5×10−8) and a 90% reduction in risk of venous thrombosis (OR 0.1, 95% CI 0.07–0.14; p=3.03×10−43) without an increase in major bleeding (OR 0.69, 95% CI 0.45–1.04; p=0.0739). The reductions in risk of ischemic stroke are similar in patients with or without a history of atrial fibrillation (AF), suggesting that absolute risk reductions are higher in patients with AF. The authors went on to apply a calibration factor to estimate the effects of genetically lower FXI levels compared to placebo and demonstrate an estimated risk reduction of 56% (OR 0.44, 95% CI 0.31–0.62); this is broadly comparable to relative risk reductions observed with warfarin compared to placebo.

If similar effects are observed in future clinical studies of pharmacological FXI inhibition, we could have a revolutionary new means of preventing ischemic stroke without increasing major bleeding. The study also highlights the advantages of using genetic studies to estimate the potential clinical benefits from novel therapeutic approaches to prevent stroke and associated cardiovascular disease, and sets the landmark for similar studies in the future. We eagerly await large-scale clinical studies investigating pharmacological FXI inhibition to define its role in stroke prevention.