Comparative studies on biological activity of /+/R and /-/S enantiomers of cyclophosphamide and ifosfamide. I. Antitumour effect of cyclophosphamide and ifosfamide enantiomers.

The differences in antitumour effect of /+/R and /-/S enantiomers of both cyclophosphamide and ifosfamide were detected. In the case of ifosfamide in all five tested tumour models (Leukemia L1210, P388, Lewis lung carcinoma, 16/C mammary adenocarcinoma and B16 melanoma) the /-/S form exerted not only higher antitumour effects than /+/R form, but revealed higher therapeutic indices as well. The same appeared to be true for /-/S enantiomer of cyclophosphamide in three models of solid tumours. In L1210 and P-388 ascitic leukemia models /+/R and /-/S cyclophosphamide exerted the same antitumour effect.