Fragment E1 labeled with I-123 in the detection of venous thrombosis

Fragment E1, which has been shown to have specific binding affinity for thrombi in an animal model, was investigated in humans for its safety and ability to bind to venous thrombi. Human Fragment E1 was labeled with I-123 and administered intravenously to patients with proved or suspected deep vein thrombosis. The vascular distribution of radioactivity was documented by obtaining gamma camera images of the patients' legs for 30 minutes following administration of I-123-Fragment E1. All patients (n = 5) with documented venous thrombi had rapid localization of labeled Fragment E1 in the area of thrombus. Patients without evidence of thrombi (n = 5) showed no focal localization, although two of these patients showed diffuse uptake along the length of the veins, due to superficial phlebitis. Analysis of blood samples in four patients indicated that disappearance of Fragment E1 from the circulation was more rapid in individuals with thrombosis (t 1/2 = 20 min) than in individuals without thrombosis (t 1/2 = 90 min), and a radiolabeled species of high molecular weight was found in patients with thrombosis but was absent from patients without thrombosis. These early results suggest that radiolabeled Fragment E1 is a safe and potentially valuable agent for the rapid detection of venous thrombosis.