Abstract

2-Carboxyethyl N, N-bis(2-chloroethyl)phosphorodiamidate and 4-ketocyclophosphamide (2-[bis(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorin-4-one 2-oxide) have been isolated and identified as urinary metabolites of dogs treated with the anticancer agent cyclophosphamide (2-[bis(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide). 2-Carboxyethyl N, N-bis(2-chloroethyl)phosphorodiamidate is the major urinary metabolite, whereas 4-ketocyclophosphamide is a minor metabolite and represents the first known product of cyclophosphamide which retains the ring structure. Another urinary metabolite yields β-hydroxypropionamide on hydrolysis, a further indication that the primary oxidative step in the metabolism of cyclophosphamide occurs on carbon 4 of the ring. Neither of the two isolated metabolites is highly cytotoxic to human epidermoid cancer cells in vitro or to Leukemia L1210 cells in vivo. Neither compound is on a pathway leading to an active form of the drug.