Because hirudin has important development value, and the source of leech is limited, the medical circles at home and abroad focus on obtaining recombinant hirudin through genetic engineering. After 1986, the recombinant hirudin was successfully expressed in Escherichia coli and zymogen respectively. Compared with natural hirudin, the 63rd amino acid (tyrosine) of recombinant hirudin is not sulfated, and its activity is slightly lower, and other properties are basically the same. Intravenous injection has no toxic and side effects at therapeutic dose. At present, some large foreign biotechnology companies have entered various clinical studies of hirudin. Every year, at least a dozen patents about hirudin peptides are published, including hirudin-like peptides, and there are always dozens of research papers every year. 199 was officially listed in Germany at the end of 1998, and199 was approved to be listed in Britain. Registered countries are the United States, Europe, Australia, New Zealand, South Africa and other countries 10.
The serum half-life of hirudin is too short to play an antithrombotic role. Processing hirudin and PEG into coupling agents can greatly prolong the serum half-life of hirudin, thus improving its antithrombotic effect in vivo (PEG modification is a common method to improve the plasma half-life of protein and polypeptide drugs).