Presentation Details
| UNC9426, a selective TYRO3 inhibitor, decreases human platelet activation and increases survival in a murine pulmonary embolism model Samantha Judd1, Stephanie Springborn1, Adam Kidwell1, Deborah DeRyckere2, Douglas K.Graham2, Xiaodong Wang3, Brian Branchford1. 1Versiti Blood Research Institute, Wauwatosa, WI, USA.2Aflac Cancer and Blood Disorders Center and Children's Healthcare of Atlanta, Atlanta, GA, USA.3Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC, USA |
Abstract
Introduction: Platelet activation is necessary for physiologic hemostasis, but unchecked activation can lead to pathologic thrombosis. Recent clinical studies of pediatric thrombosis etiology have identified inflammation as an independent risk factor for hospital-acquired venous thromboembolism. GAS6, an acute phase reactant that increases during inflammation, signals through TYRO3, AXL, and MERTK (TAM) receptors to induce a signal transduction cascade resulting in an activating conformational change in the aIIb/b3 integrin, thus allowing fibrinogen binding and subsequent activation of the platelets. Methods: Following informed consent, human whole blood was drawn into sodium citrate and platelet rich plasma (PRP) was generated via differential centrifugation. Animal studies were performed in wild type C57BL/6 mice under supervision of the Institutional Animal Care and Use Committee. The TYRO3-specific small molecule inhibitor UNC9426 was reconstituted in DMSO prior to incubation with human PRP, or with a permeability-enhancing buffer prior to injection into mice. Light transmission aggregation was performed using collagen and ADP as agonists for human PRP incubated with either UNC9426 or DMSO control. Thrombin and convulxin were used to stimulate platelets prior to flow cytometry, in which fluorescent antibodies were used to detect P-selectin and bound PAC-1 on the surface of activated platelets in human whole blood samples. PRP incubated with either UNC9426 or DMSO control. Male and female 8-14-week-old mice were anesthetized and underwent intravenous injection with UNC9426 or buffer control, followed by intravenous injection of a collagen/epinephrine solution to induce systemic venous thrombosis. Results: Compared to DMSO controls, UNC9426-treated human PRP samples exhibited decreased maximum aggregation after addition of collagen or ADP. The UNC9426-treated human whole blood samples demonstrated a reduction in P-selectin expression and PAC-1 binding to activated aIIb/b3 integrin compared to DMSO controls. Mice treated with UNC9426 demonstrated dose-dependent protection from collagen/epinephrine-induced pulmonary embolism model, with three-quarters of them surviving, compared to one-half of controls. Conclusion: UNC9426 is a novel TYRO3-specific small molecule inhibitor that decreases human platelet activation and demonstrates a protective effect in a murine pulmonary embolism model. This compound, and others like it, may represent an alternative strategy to decrease platelet activation and thrombosis risk.
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