Background: Inorganic polyphosphate (polyP) is a procoagulant and pro-inflammatory polyanion, known to be released by platelets. PolyP promotes thrombin generation through several mechanisms in vitro,
including activation of the contact pathway, activation of Factor XI, and subsequent triggering of the intrinsic pathway. Accelerated thrombin generation kinetics are a predictor of venous thromboembolism (VTE) development up to 90 days after trauma. The contribution of polyP to accelerated thrombin generation after trauma is presently unknown, and polyP levels are difficult to measure directly. This study aimed to assess the impact of polyP inhibition on thrombin generation after injury using two novel agents: UHRA-8, a polyP and nucleic acid antagonist, and MPI-8, a selective polyP antagonist. Methods: Whole blood was collected from trauma patients upon arrival to the Emergency Department and from healthy volunteers by venipuncture. Samples were promptly processed to platelet poor plasma and stored in multiple aliquots at -80o
C until analysis. Thrombin generation (calibrated automated thrombogram, CAT) was expressed as lag time (LT, minutes), peak height (PH, nM), time to peak (ttPeak, minutes), and endogenous thrombin potential (ETP, nM*minute). Thrombin generation was initiated using a PPP Low reagent (Diagnostica Stago, Parsippany NJ), containing 1 pM tissue factor and 4.2 M phospholipids. CAT was performed for each patient +/- MPI-8 and UHRA-8 (50 g/mL for each). Wilcoxon matched-pairs test was used to detect differences with and without each antagonist. Results are expressed as median and quartiles [Q1, Q3]; P <0.05 is considered significant. Results: Fifty-six trauma patients and 39 healthy volunteers were enrolled in this study. Trauma patients had a median age of 53 years and 46.4% were male. Median injury severity score was 14 [10, 23], 91% were blunt injuries, and there were two (3.6%) mortalities. Volunteers had a median age of 29 years, and 51.3% were female. At baseline, trauma patients had greater PH (182.9 nM [121.0, 255.2] vs. 120.5 nM [62.1, 174.8], p <0.001) and greater ETP (1224 nM*min [1017, 1631] vs. 1097 nM*min [695, 1475], p = 0.046) than volunteers. Treatment of trauma patient plasma with UHRA-8 resulted in a more hypocoagulable profile on CAT assays (longer LT and ttPeak, and decreased PH and ETP than in untreated plasma [Table 1]). Treatment of trauma patient plasma with MPI-8 resulted in longer LT and ttPeak than untreated plasma, but greater ETP compared to untreated plasma (Table 2). In volunteers, treatment of plasma with either UHRA-8 or MPI-8 also led to a more hypocoagulable thrombin generation profile, but to a significantly greater degree as compared to trauma patients (ΔLT and Δ ttPeak were both significantly greater in volunteers, p <0.001). Conclusion: Treatment of trauma patient plasma with two novel polyP inhibitors, MPI-8 and UHRA-8, result in attenuation of hyperocoagulable thrombin generation in response to injury. This attenuation was less profound in the injured patients, suggesting that increased circulating polyP may contribute to accelerated thrombin generation following traumatic injury, and may represent a future novel target for chemoprophylaxis in these complex, high risk patients.