Relying on the national and China Academy of Sciences' drug innovation system construction, scientists from Shanghai Institute of Pharmacology, China Academy of Sciences, from 1993, have made in-depth and systematic research on the synthesis methodology, structure-activity relationship, and pharmaceutical properties of fluoroquinolones. Supported by the National Special Program for New Drug Creation, the "863" Program, the National Natural Science Foundation and the Knowledge Innovation Project of the Chinese Academy of Sciences, researcher Yang Yushe, academician Ji Ruyun and their team adopted the strategy of structural optimization, devoted themselves to studying the gene structure-pharmacodynamic relationship, structure-metabolic characteristics relationship and structure-toxicity relationship of levofloxacin, synthesized a series of new compounds, and finally screened out a fluoroquinolone antibacterial drug with a new chemical structure-American National Hydrochloride. In August, 2008, when the drug was declared as a major scientific and technological project of "major new drug creation", it was highly recognized by the evaluation experts and ranked first among new chemical drugs.