Potent, selective intracellular neutrophil elastase (NE, alpha-1-proteinase) inhibitor (by covalently binding to NE). Inhibits human neutrophil elastase (HNE) and is selective over other human serine proteases with IC50 values of 22nM for HNE, >100µM for trypsin, cathepsin G and plasmin, >3µM for chymotrypsin and tissue plasminogen activator. Specific beta-cell proliferation promoter. Similar to SerpinB1, which functions through its inhibiting activity of several proteases including neutrophil elastase, cathepsin G and proteinase-3. Reverses insulin resistance and body weight gain in HFD-fed mice, suggesting that the SerpinA1-NE system regulates AMPK signaling, fatty acid oxidation (FAO) and energy expenditure. The imbalance between SerpinA1 (alpha1-antitrypsin; A1AT) and neutrophil elastase NE contributes to the development of obesity and related inflammation, insulin resistance and liver steatosis. Shown to inhibit tumor cell growth and proliferation and induce apoptosis in leukemia cell lines.