Angiotensin converting enzyme 2 protein or nucleic acid is used to treat or prevent fibrosis or liver disease. ACTIVITY : Cytostatic Hepatotropic. MECHANISM OF ACTION : Collagen production inhibitor. After bile duct ligation, mice were treated with recombinant angiotensin converting enzyme 2 protein by intravenous injection at a dose of 2 mg/kg once a day for 14 days. Collagen-producing cells were monitored by smooth muscle actin (SMA) assay. The numbers of such cells increased greatly in the damaged livers of untreated mice, whereas SMA was not detectable in the livers of the treated mice.