4-hydroperoxy Cyclophosphamide (4-OOH-CY) is the active metabolite form of the prodrug Cyclophosphamide. 4-OOH-CY crosslinks DNA and induces T cell apoptosis independent of death receptor activation, but activates mitochondrial death pathways through production of reactive oxygen species (ROS).[1] Formulations containing the prodrug Cyclophosphamide are used to treat lymphomas and autoimmune disorders.[2],[3]

Reference:
[1]. Strauss, G., Westhoff, M.-A., Fischer-Posovszky, P., et al. 4-hydroperoxy-cyclophosphamide mediates caspase-independent T-cell apoptosis involving oxidative stress-induced nuclear relocation of mitochondrial apoptogenic factors AIF and EndoG. Cell Death Differ. 15(2), 332-343 (2008).
[2]. Ahmed, A.R., and Hombal, S.M. Cyclophosphamide (Cytoxan). A review on relevant pharmacology and clinical uses. J. Am. Acad. Dermatol. 11(6), 1115-1126 (1984).
[3]. Appel, G.B. New and future therapies for lupus nephritis. Cleve. Clin. J. Med. 79(2), 134-140 (2012).