The present invention is related to arginine deiminase encapsulated into erythrocytes for use in therapy. It is in particular related to the use thereof in treating arginase-1 deficiency. Also, it relates to novel pharmaceutical compositions comprising arginine deiminase from M. arginini encapsulated into erythrocytes and the use thereof in treating diseases that may benefit from arginine depletion, such as arginine dependent cancers, in particular arginine-auxotrophic cancers, and arginase-1 deficiency.