Carboxyphosphamide is an inactive metabolite of the alkylating agent cyclophosphamide .1It is formed from cyclophosphamideviaoxidation of the intermediate metabolite aldophosphamide by aldehyde dehydrogenase. 1.Manthey, C.L., and Sladek, N.E.Kinetic characterization of the catalysis of activated cyclophosphamide (4-hydroxycyclophosphamide/aldophosphamide) oxidation to carboxyphosphamide by mouse hepatic aldehyde dehydrogenasesBiochem. Pharmacol.37(14)2781-2790(1988)