The present invention provides a 3-iodo-L-phenylalanine or 4-iodo-L-phenylalanine for the preparation of a pharmaceutical composition for thetreatment of malignant neoplasia. Moreover, the invention provides a methodfor the treatment of malignant neoplasia, the method comprising the steps ofadministering 3-iodo-L-phenylalanine or 4-iodo-L-phenylalanine to a subject inneed thereof and a pharmaceutical composition comprising 3-iodo-L-phenylalanine or 4-iodo-L-phenylalanine.