A Combination Therapy of Cyclophosphamide and Immunomodulating Agents in Cancer

Cyclophosphamide is a precursor of alkylating nitrogen mustard and was initially claimed to have antineoplastic and immunosuppressive properties. However, the role of cyclo-phosphamide as an immune activator has also been reported, depending on the dosage used. The application of lower-dose cyclophosphamide has emerged as a potential approach to cancer treatment. Cyclophosphamide selectively depletes regulatory T cells (Tregs), which dampens the immunological response, thereby rebalancing the immune system to allow other immune cells to act more efficiently. Cyclophosphamide can be either a friend or a foe in cancer treatment, de-pending on the therapeutic regime. The following questions remain to be answered: Can the cy-clophosphamide be used in the presence of other agents? Is there any single immunotherapeutic agent that acts synergistically with cyclophosphamide to effectively alter the immunosuppres-sive tumor microenvironment? This review emphasizes the role of cyclophosphamide as an im-mune modulator, both alone and in combination with other immunotherapeutic agents, for effec-tive cancer treatment in preclinical and clinical settings.