A dopamine decarboxylase inhibitor; inhibits conversion of L-DOPA to dopamine in the periphery; increases the plasma concentration of L-DOPA by 186% and prolongs the half-life in plasma by 48% and skeletal muscle extracellular fluid by 66% in dog when administered at a dose of 100 mg/kg; potentiates the activity of AhR; inhibits proliferation of pancreatic cancer cells in vitro and tumor growth in vivo