Abstract 36: Concurrent Ultrasound Diagnosis and Treatment of Thrombosis Using Activated Platelet Targeted Theranostic Microbubbles

Abstract

Molecular ultrasound imaging is an attractive non-invasive technology widely available for rapid clinical diagnosis. We hypothesized that thrombolytic drugs loaded microbubbles (MBs), which are selectively targeted to activated platelets, will allow high-resolution, real-time imaging of thrombosis, and at the same time offer potent thrombolytic efficacy without bleeding complications, and enable the immediate monitoring of success or failure of thrombolysis. Our therapeutic agents/imaging particles, targeted theranostic microbubbles (TT-MB), consist of a fusion construct that combines the fibrinolytic drug urokinase, echo-enhancing microbubbles for visualization by ultrasonography, and an activated-platelet-specific single-chain antibody for targeting specifically to thrombi. In the ferric-chloride induced carotid artery thrombosis mouse model, treatment with TT-MB significantly reduced thrombus size after 45 min, while no significant difference was observed in the MB that were targeted but without urokinase (37.09 ± 5.6 vs. 97.16 ± 4.3, mean % change ± SEM, normalized to baseline thrombus size, p<0.001). The same degree of efficient thrombolysis was only achievable using a high dose of urokinase (NS). We also show that the targeting and thus clot-enrichment effect of TT-MBs results in a highly potent fibrinolysis that could only be matched using high doses of non-targeted urokinase. However, the latter is associated with a highly prolonged bleeding time (79.25 ± 6.5 vs. 1079.25 ± 260.7, seconds ± SEM, p<0.001). In contrast, TT-MB does not prolong bleeding time (NS). In conclusion, activated platelet targeted microbubbles conjugated with recombinant urokinase represent a novel and unique theranostic approach to simultaneously diagnose and treat thrombosis as well as to immediately monitor success or failure of thrombolysis. This unique technology holds promise for major progress towards rapid diagnosis and bleeding-free, potent therapy of the vast number of patients suffering from thrombotic diseases.