Carboxyphosphamide is an inactive metabolite of the alkylating agent cyclophosphamide .1 It is formed from cyclophosphamide via oxidation 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)