4-hydroperoxy cyclophosphamide (4-OOH-CY) is an active metabolite of Cyclophosphamide that induces hepatotoxicity.4-Hydroperoxy cyclophosphamide increases levels of glutaminase and aspartate aminotransferase, enhances inflammatory factors and oxidative markers, and Inhibits oxidoreductase activity.4-Hydroperoxy cyclophosphamide is used in the study of cancer and autoimmune diseases.

4-hydroperoxy cyclophosphamide mediates caspase-independent T cell apoptosis through oxidative stress-induced nuclear relocalization of mitochondrial apoptotic factors AIF and EndoG. [1]
The combination of 1 μg/mL 4-hydroperoxy cyclophosphamide and methotrexate inhibited IL-6/sil-6r-induced RANKL expression in fibroblast-like synoviocytes through inhibition of JAK2/STAT3 and p38MAPK signaling pathways. [2]

Intraperitoneal injection of 200 mg/kg 4-hydroperoxy cyclophosphamide resulted in caspase-independent T and B cell death in mice. [1]