Recombinant Neorudin for the Prevention of Deep-Vein Thrombosis After Spinal-Cord Injury.

Background: Whether anticoagulant therapy should be used after spinal-cord injury (SCI) surgery was controversial. The anticoagulation characteristics of a newly developed anticoagulant, recombinant neorudin (EPR-hirudin (EH)), were explored using a rat model of SCI to provide a basis for clinical anticoagulation therapy of SCI. Methods: A rat model of SCI was developed by Allen's method. Then, thrombosis in the inferior vena cava was induced by ligation. The low-bleeding characteristics of EH were explored by investigating dose-response and time-effect relationships, as well as multiple administration of EH, on thrombus formation complicated with SCI. Results: EH inhibited thrombosis in a dose-dependent manner by reducing the wet weight and dry weight of the thrombus. An inhibiting action of EH on thrombosis was most evident in the group given EH 2 h after SCI. After multiple intravenous doses of EH, thrombosis inhibition was improved to that observed with low molecular weight heparin (LMWH) (87% vs 90%). EH administration after SCI neither increased bleeding in the injured spine nor damaged to nerve function. Bleeding duration and activated partial thromboplastin time were increased in the high-dose EH group compared with that in the normal-saline group, but were lower than those in the LMWH group. Conclusion: EH can reduce thrombus formation in a rat model of SCI, and bleeding is decreased significantly compared with that using LMWH. EH may prevent thrombosis after SCI or spinal surgery.

The toxicity assessment of neorudin in cynomolgus monkeys.

In this study, the toxicity effects on circulatory system and respiratory system, and the acute toxicity test of recombinant neorudin (EPR-hirudin, EH) in cynomolgus monkeys were evaluated to provide reference information for clinical studies. Eighteen cynomolgus monkeys were randomly divided into three groups for single intravenous administration of 3, 30 mg/kg EH and normal saline, respectively. The changes of respiratory frequency, respiratory intensity, blood pressure and electrocardiogram before and after administration were recorded. In acute toxicity test, six cynomolgus monkeys were intravenously received EH at a single dose of 171, 257, 385, 578, 867 and 1300 mg/kg respectively. The vital signs, hematology, serum biochemistry, coagulation indexes and electrocardiogram indexes of the animals were determined before administration and on the 7th and 14th day after administration. As the results showed that there were no significant abnormal changes in respiratory frequency, respiratory intensity, blood pressure or electrocardiogram in cynomolgus monkeys after receiving EH at 3 mg/kg and 30 mg/kg, and there was no statistical difference between the treated groups and normal saline group. In the acute toxicity test, no significant abnormalities were observed in vital signs, hematology, serum biochemistry, coagulation indexes and electrocardiogram indexes of six cynomolgus monkeys at day 7 and 14 after EH administration. Furthermore, autopsies of all cynomolgus monkeys showed no abnormalities. The results of toxicokinetics showed that AUClast of the drug increased in proportion to the EH dose in the range of 171-578 mg/kg, and increased in over proportion to the EH dose in the range of 578-1300 mg/kg. The variation of Cmax was basically consistent with AUClast. In a sum, A single intravenous injection of 3 and 30 mg/kg of EH did not affect the circulatory system and respiratory system in cynomolgus monkeys and the maximum tolerated dose of EH in cynomolgus monkey is over 1300 mg/kg (equivalent to 619-1300 times of the proposed clinical equivalent dose).