Cyclophosphamide is a chemotherapy medication used in the treatment of breast cancer, lymphomas, leukemias, and certain autoimmune-related conditions. It is often used as part of combination chemotherapy regimens.

It is classified as an alkylating agent, a group of drugs that work by directly damaging DNA.

Cyclophosphamide works by adding alkyl groups to DNA molecules within cancer cells. This process may cause DNA strands to break or become unable to replicate properly, which can inhibit cancer cell growth and division.

Because it affects both cancerous and normal rapidly dividing cells, cyclophosphamide may also impact tissues such as bone marrow and the lining of the digestive tract. This may result in side effects such as reduced immunity, nausea, or hair loss.