Project Title: Effect on Platelet Function of Von Willebrand Factor Inhibition by DTRI-031 and Targeted Reversal by DTRI-025 in Canine Circulation
Project Mentor: Dr. Shahid Nimjee MD, PhD – Neurological Surgery
Please click the link below to access my project for the 2021 Autumn Undergraduate Research Festival:
Cerebral ischemic stroke is the leading cause of combined death and disability worldwide (1). Despite its prevalence, only one FDA-approved thrombolytic exists. Recombinant tissue plasminogen activator (rTPA) works by converting plasminogen to plasmin, which breaks down fibrin found within a clot. However, rTPA is limited by its hemorrhagic side effects and irreversibility (2). Von Willebrand Factor is a clotting factor that maintains blood hemostasis. In thrombosis, VWF binds to glycoprotein Ibα at the A1 platelet domain to create an endothelial lattice allowing for platelet aggregation. We have developed an RNA aptamer (DTRI-031) that specifically targets and effectively inhibits VWF, which is heavily implicated in small and large animal occlusion models (3). Additionally, DTRI-031 can be paired with an antidote (DTRI-025) that rapidly reverses the aptamer, offering a new degree of control not available with rTPA. In this study, we investigated the dose-response of 0.5 mg/kg DTRI-031 with varying concentrations of DTRI-025 by collecting canine blood samples at various timepoints following infusion. To measure different dimensions of DTRI-025 performance, whole blood was analyzed in three ways. Protein analysis demonstrated consistent levels of VWF throughout, suggesting ELISA kit insensitivity to the A1 domain, where VWF binds to the platelet. Chronolog impedance analysis and platelet function analysis (PFA) both exhibited consistent reversal activity across all treatment groups. Notably, all treatment groups demonstrated PFA platelet closure in under ten minutes. The consistency across all three tests – ELISA, Chronolog, and PFA – suggests no specific dose-response to DTRI-031, rather general inhibitory action.
- Facts and Figures about Stroke. 2019. (Accessed May 2021, 2021, at https://www.worldstroke. org/component/content/article/16-forpatients/84-facts-and-figures-about-stroke.)
- Lansberg MG, Bluhmki E, Thijs VN. Efficacy and safety of tissue plasminogen activator 3 to 4.5 hours after acute ischemic stroke: a metaanalysis, Stroke 2009;40:2438-41.
- Oney S, Nimjee SM, Layzer J, et al. Antidote-controlled platelet inhibition targeting von Willebrand factor with aptamers. Oligonucleotides 2007;17:265-74
I would like to thank the Office of Undergraduate Research and Creative Inquiry for their support in this project and for allowing me to be a part of the Undergraduate Research Apprenticeship Program in the Summer of 2021. I would also like to thank my Principal Investigator and mentor, Dr. Shahid Nimjee M.D./Ph.D., and other lab members for their continued support over the past two years. I am honored to be a part of this project and a member of this lab.