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