Sotrastaurin is a protein kinase C (PKC) inhibitor that displays immunosuppressive activity, blocking T cell activation through the disruption of downstream NF-κB signaling. In cell-free assays, sotrastaurin was reported to inhibit PKCα, βI, δ, ε, η, and θ with Ki values of 0.95, 0.64, 2.1, 3.2, 1.8, and 0.22 nM, respectively. Sotrastaurin can prevent the production of various cytokines by activated T cells, macrophages, and keratinocytes in vitro and has been shown to inhibit an acute allergic contact dermatitis response in rats when dosed orally at 30 mg. However, clinical investigation of sotrastaurin for its potential to prevent renal transplant rejection was halted during phase II testing due to high incidence of rejection. Sotrastaurin is also reported to activate Wnt/β-catenin signaling via the inhibition of glycogen synthase kinase 3 (IC50s = 229 and 172 nM for α and β isoforms, respectively), which is essential for embryogenesis and adult stem cell maintenance.
