Calpeptin is a potent, cell penetrating calpain inhibitor, with an ID₅₀ of 40 nM for Calpain I in human platelets^[1]. Calpeptin is also an inhibitor of cathepsin K^[2]. IC50 & Target: ID50: 40 nM (Calpain I in human platelets)^[1].
Cthepsin K^[2] In Vitro: Calpeptin (0-100 nM, 24 hours) treatment suppresses the proliferation of both WI38 VA13 and IMR90 cells in a dose-dependent manner. Calpeptin (1000 pg/ml, 24 hours) inhibits IL-6-induced cell proliferation of lung fibroblasts^[3]. In Vivo: Calpeptin with Bleo (0.04 mg/mouse, i.p., 3 times weekly, 28 days) administration significantly inhibits the collagen deposition and increases of calpain activity in the NSC-125066 treated mouse lung tissues^[3].