The Btk inhibitor AB‐95‐LH34 potently inhibits atherosclerotic plaque–induced thrombus formation and platelet procoagulant activity

• Published in: Journal of thrombosis and haemostasis 2022-12, Vol.20 (12), p.2939-2952
• Main Authors: Smith, Christopher W., Harbi, Maan H., Garcia‐Quintanilla, Lourdes, Rookes, Kieran, Brown, Helena, Poulter, Natalie S., Watson, Steve P., Nicolson, Phillip L. R., Thomas, Mark R.
• Format: Article
• Language: English
• Subjects: AB‐95‐LH34; Antiplatelet therapy; Arteriosclerosis; Atherosclerosis; Atherosclerosis - complications; atherosclerotic plaque; Bleeding; Blood clots; Blood platelets; Blood Platelets - metabolism; Cardiovascular disease; Collagen; Coronary artery disease; Fibrinolytic Agents - therapeutic use; Glycoprotein VI; Heart diseases; Hemorrhage - chemically induced; Humans; ibrutinib; Original; Phosphatidylserine; Phosphorylation; Plaque, Atherosclerotic - complications; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors - therapeutic use; Platelets; Protein Kinase Inhibitors - adverse effects; Src protein; Thrombin; THROMBOSIS; Thrombosis - drug therapy
• ISSN: 1538-7933; 1538-7836; 1538-7836
• DOI: 10.1111/jth.15899

Background New antithrombotic therapies with less effect on bleeding are needed for coronary artery disease. The Btk inhibitor ibrutinib blocks atherosclerotic plaque–mediated thrombus formation. However, it is associated with increased bleeding, possibly due to non–Btk‐mediated effects. Btk‐deficient patients do not have bleeding issues, suggesting selective Btk inhibition as a promising antithrombotic strategy. Objectives To compare the antithrombotic effects of the highly selective Btk inhibitor AB‐95‐LH34 (LH34) with ibrutinib. Methods Glycoprotein VI and G‐protein coupled receptor‐mediated platelet function and signaling were analyzed in healthy human donor platelets by lumi‐aggregometry, flow adhesion, and western blot following 1 h treatment with inhibitors in vitro. Results LH34 showed similar inhibition of Btk‐Y223 phosphorylation as ibrutinib, but had no off‐target inhibition of Src‐Y418 phosphorylation. Similar dose‐dependent inhibition of aggregation to atherosclerotic plaque material was observed for both. However, in response to Horm collagen, which also binds integrin α2β1, LH34 exhibited less marked inhibition than ibrutinib. Both LH34 and ibrutinib inhibited platelet adhesion and aggregation to plaque material at arterial shear. Ibrutinib demonstrated the most potent effect, with complete blockade at high concentrations. Platelet activation (P‐selectin) and procoagulant activity (phosphatidylserine exposure) in thrombi were inhibited by LH34 and completely blocked by ibrutinib at high concentrations. Furthermore, plaque‐induced thrombin generation was reduced by higher concentrations of LH34 and ibrutinib. Conclusions LH34 potently inhibits atherosclerotic plaque–induced thrombus formation and procoagulant platelet activity in vitro, with less off‐target inhibition of Src than ibrutinib, suggesting it is a promising antiplatelet therapy with the potential for reduced bleeding side effects.