Hematoporphyrin IX (I) is treated with an acetic acid solution of HBr to afford dibromide (II). Condensation of (II) with polyethyleneglycol 350 monomethyl ether, followed by alkaline hydrolysis of the ester groups generated during the reaction furnishes the polyethyleneglycol-conjugated porphyrin derivative (III). Then, complexation of the potassium salt of porphyrin diacid (III) with cis-[(trans-1,2-diaminocyclohexane)platinum(II)] sulfate (IV) by means of KOH in H2O gives rise to the title hematoporphyrin-platinum conjugate.