Abstract Number: PB0989
Meeting: ISTH 2021 Congress
Theme: Platelets and Megakaryocytes » Platelet Function and Interactions
Background: Spleen tyrosine kinase (Syk) and Bruton’s tyrosine kinase (BTK) play critical roles in platelet physiology, facilitating GPVI-mediated platelet signaling. Small molecule tyrosine kinase inhibitors (TKIs) targeting Syk and BTK have been developed as anti-neoplastic and anti-inflammatory therapeutics, and have also gained interest as anti-platelet agents. However, no studies to date have systematically examined multiple Syk and BTK inhibitors simultaneously to uncover and compare the mechanisms by which these agents affect platelet signaling and function.
Aims: Determine the effects of 12 TKIs (Bay 61-3606, R406/fostamatinib, entospletinib, TAK-659, ibrutinib, acalabrutinib, ONO-4059/tirabrutinib, AVL-292/spebrutinib, CG-806, BMS-935177, BMS-986195, fenebrutinib) on platelet functional responses.
Methods: Platelets were isolated from human donors’ whole blood and treated with the selected TKIs. Platelets were stimulated and assessed for P-selectin exposure, PAC-1 binding, ATP secretion, adhesion on collagen and fibrinogen surfaces under static and physiological flow conditions, protein phosphorylation levels, and PI3K/tubulin colocalization to evaluate the effect of each inhibitor on platelet function.
Results: The selected TKIs significantly reduced GPVI-mediated platelet adhesion on collagen (27-70% reduction) and integrin-mediated platelet spreading on fibrinogen (7-45% reduction in average surface area). Under physiological flow, platelet aggregate volume was reduced by 32-51% on collagen surfaces when treated with selected TKIs. Downstream of GPVI-mediated activation, selected TKIs reduced platelet ATP secretion (53-67% reduction), the percentage of platelets exposing P-selectin (to 1.37-6.64%), and percentage of platelets binding PAC-1 (to 0.91-9.09%) in response to GPVI agonist, cross-linked collagen-related peptide (CRP-XL) activation. All TKIs inhibited GPVI-mediated phosphorylation of PLCγ2, PKCδ and Akt, but differentially affected the phosphorylation of PI3K p85 regulatory subunit. Fluorescence imaging of PI3K found co-localization with tubulin when untreated, but is disrupted in platelets treated with the selected TKIs.
Conclusions: Clinically relevant TKIs targeting Syk and BTK inhibit platelet functional responses, but may differentially alter PI3K signaling and organization in an inhibitor class specific manner.
To cite this abstract in AMA style:
Zheng T, Lofurno E, Melrose A, Lakshmanan H, Pang J, Phillips K, Fallon M, Kohs T, Ngo A, Shatzel J, Hinds M, McCarty O, Aslan J. Assessment of the Effects of Syk and BTK Inhibitors on GPVI-mediated Platelet Signaling and Function [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/assessment-of-the-effects-of-syk-and-btk-inhibitors-on-gpvi-mediated-platelet-signaling-and-function/. Accessed March 22, 2024.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/assessment-of-the-effects-of-syk-and-btk-inhibitors-on-gpvi-mediated-platelet-signaling-and-function/