N1-(3-Methoxypropyl)-2-(pyridylmethylidene)-hydrazine-1-carbothioamide (I) and its Cu2+, Pd2+ and Pt2+ complexes are effective anti-tumor agents. Also disclosed are compositions comprising (I) and its Cu2+, Pd2+ and Pt2+ complexes, and the use of the compositions in the treatment of malignant tumors.