Synthesis and evaluation of cationic polymeric micelles as carriers of lumbrokinase for targeted thrombolysis

To achieve targeted thrombolysis, a targeted delivery system of lumbrokinase(LK) was constructed using RGDfk-conjugated hybrid micelles. Based on the specific affinity of RGDfk to glycoprotein complex of GP Ⅱ b/Ⅲ a expressed on the surface of membrane of activated platelet, LK loaded targeted micelles(LKTM) can be delivered to thrombus. The hybrid micelles were composed of polycaprolactone-block-poly(2-(dimethylamino) ethyl methacrylate)(PCL-PDMAEMA), methoxy polyethylene glycol-block-polycaprolactone(mPEG-PCL)and RGDfk conjugated polycaprolactone-block-polyethylene glycol(PCL-PEG-RGDfk). PCLPDMAEMA was synthesized via ring open polymerization(ROP) and atom transfer radical polymerization(ATRP). PCL-PEG-RGDfk was synthesized via ROP and carbodiimide chemistry. The prepared LKTM was characterized by dynamic light scattering(DLS) and transmission electron microscope(TEM). Colloidal stability assay showed the prepared LKTM was stable. Biocompatibility assay was performed to determine the safe concentration range of polymer. The assay of fluorescent distribution in vivo demonstrated that LKTM can be efficiently delivered to thrombi in vivo. Thrombolysis in vivo indicated the thrombolytic potency of LKTM was optimal in all groups. Notably, the laboratory mice treated with LKTM exhibited a significantly shorter tail bleeding time compared to those treated with LK or LK-loaded micelles without RGDfk, which suggested that the targeted delivery of LK using RGDfk-conjugated hybrid micelles effectively reduced the bleeding risk.

Oral fibrinogen-depleting agent lumbrokinase for secondary ischemic stroke prevention： results from a multicenter, randomized, parallel- group and controlled clinical trial

Background Elevated fibrinogen （Fg） level is a known risk factor for ischemic stroke. There are few clinical trials on oral fibrinogen-depleting therapies for secondary ischemic stroke prevention. We aimed to assess the effects of one-year therapy with oral lumbrokinase enteric-coated capsules on secondary ischemic stroke prevention.

Preparation of pegylated lumbrokinase and an evaluation of its thrombolytic activity both in vitro and in vivo

Lumbrokinase(LK)is a group of serine proteases with strong fibrinolytic and thrombolytic activities.In clinical practice,LK can only be administered orally because of its antigenicity,iinmunogenicity and potential to produce anaphylactic reactions after injection.However,many useful drugs such as interferon,insulin,erythropoietin and interleukin have been modified with polyethylene glycol(PEG)to prepare injectable formulations.In this study,LK was modified with methoxy PEG succinimidyl carbonate(mPEG-SC)with molecular weights of 5000,10,000 and 20,000 and the pegylatcd products were isolated and purified using the Akta protein purification system.The extent of pegylation was detennined by HPLC.Fibrinolytic activities of pegylatcd and unmodified LK were measured both in vitro against urokinase on fibrin plates and in vivo using a mouse carageenan black tail model.Optimal pegylation was obtainal using mPEG-SC_(5000) in a buffer pH 8.0 with a reaction time of 5 h,reaction temperature of 0℃ and LK:mPEG-SC molar ratio of 1:25.The results show that mPEG modified LK has strong fibrinolytic and thrombolytic activities both in vitro and in vivo.It is suggested that the pegylatcd LK is a promising injectable thrombolytic agent for the treatment of thrombotic diseases in clinical practice.