The tumor-inhibiting effect of isomeric dichloro(diphenylethylenediamine)platinum(II) complexes

Ring unsubstituted dichloro(diphenylethylenediamine)platinum(II) complexes show a dependence of their antitumor activity on the configuration and position of phenyl rings in ethylenediamine ligand. Dichloro(1,1-diphenylethylenediamine)platinum(II) (1d) and meso-dichloro(1,2-diphenylethylenediamine)-platinum(II) (meso-2d) have a weaker effect on the human breast-cancer cell line MDA-MB 231 and on rat leukemia L 5222 than (+/-)-dichloro(1,2-diphenylethylenediamine)platinum(II)((+)-2d) and its enantiomers (+)-2d and (-)-2d which cause marked and comparable inhibition of both tumors; (+/-)-2d is also active on ADJ/PC 6 plasmacytoma of the mouse and on cisplatin-, daunomycin-, and cisplatin/daunomycin-resistant Ehrlich ascites tumors of the mouse. The differences in activity of the diastereomers (+/-)-2d and meso-2d, for which distinct influences on the DNA secondary structure can be demonstrated CD spectroscopically may be explained by a steric hindrance of the drug-DNA interaction.