Comparative studies on biological activity of /+/R and /-/S enantiomers of cyclophosphamide and ifosfamide. II. Antiproliferative activity of cyclophosphamide and ifosfamide enantiomers.

The present studies on antiproliferative activity of cyclophosphamide and ifosfamide /+/R and /-/S enantiomers followed the earlier described differences in their antitumour activity. P-388 leukemic cells in LCFU (Leukemic Colony Forming Units) assay and Lewis lung cells in experimental metastasis assay were used as models of tumour cells. Bone marrow stem cells were applied as models of normal proliferating cells in NCFU-(Normal Colony Forming Units) and RPNCFU (Rapidly Proliferating Normal Colony Forming Units) tests. In all four models /-/S enantiomers exerted higher antiproliferative effect, than their counterparts. Antiproliferative activity of /+/RS cyclophosphamide and ifosfamide appeared to be exactly intermediate between /+/R and /-/S forms. These data, precisely differentiating the effect of /+/R, /-/S and / +/- /RS forms, confirmed the earlier described, higher antitumour effect of /-/S enantiomers of cyclophosphamide and ifosfamide.