A pilot trial of microplasmin in patients with long-term venous access catheter thrombosis

Background Microplasmin, a truncated form of plasmin, degrades fibrin and reacts with the circulating inhibitor α₂-antiplasmin. We investigated the safety and efficacy of intra-catheter microplasmin bolus administration for the restoration of catheter function in long-term venous access catheter thrombosis. Methods This open-label, ascending-dose, pilot study enrolled 31 subjects. Two doses of microplasmin were evaluated, (5 mg and 8 mg) administered via a 2 ml intra-catheter bolus injection in 10 and 21 patients respectively. Catheter function was evaluated 30 min after the first bolus administration. In case of incomplete catheter function restoration, a second bolus was administered with reassessment of catheter function 30 min thereafter. Results After the first bolus, complete restoration of catheter withdrawal function was observed in 5 out of 10 (50%) and 14 of out 21 (66%) subjects treated with 5 mg and 8 mg respectively and in 8 out of 10 (80%) and 18 out of 21 (86%) subjects after a second administration of microplasmin. No bleeding complications nor other adverse events were related to microplasmin. Conclusions In this pilot trial, microplasmin restored catheter function in a safe and effective way.