Isomannide (1,4:3,6-Dianhydromannitol) is a common intermediate compound and derivative of Isosorbide (HY-B1469). Some derivatives of isomannide have potent inhibitory effects on KLK5 and KLK7. Isomannide can be used in the research of HCV infection and KLK5/KLK7-related diseases[1][2][3].