Cyclophosphamide

Cyclophosphamide is a chemotherapy and immunosuppressant drug; it is also sold under the names Endoxan, Cyclonex and Cycloblastin. Cyclophosphamide is often used as an adjuvant drug with other chemotherapy medications especially for leukemia and lymphomas. (These cancers include Hodgkin’s and non-Hodgkin's lymphoma, Burkitt's lymphoma, chronic lymphocytic leukemia (CLL), chronic myelocytic leukemia (CML), acute myelocytic leukemia (AML), acute lymphocytic leukemia (ALL), T-cell lymphoma (mycosis fungoides), multiple myeloma, neuroblastoma, retinoblastoma, rhabdomyosarcoma, Ewing's sarcoma; breast, testicular, endometrial, ovarian, and lung cancers, and in conditioning regimens for bone marrow transplantation.)

Norwegian Study - Cyclo/ME
There is only limited evidence for the use of the drug to treat ME/CFS, and only for patients who meet the Canadian Consensus Criteria. In the study, Rekeland et al. (2020) found that intravenous cyclophosphamide improved symptoms in over 50% of patients, and this improvement was maintained in the long term. In the trial 55% of patients responded positively to the drug, with an improvement in fatigue and overall physical functioning, with 68% of the responders having sustained remission of ME/CFS after 4 years (15 of the 40 patients). The authors urged caution due to the lack of a control group. The presence of HLA genes HLA-DQB1*03:03 and/or HLA-C*07:04 was associated with patients who responded positively to the cyclophosphamide.

A Norwegian group, led by the researchers, Dr. Øystein Fluge and Professor Olav Mella, who have been studying Rituximab use in ME/CFS, also ran a clinical trial, called CycloME. The trial tested the effects of cyclophosphamide on ME/CFS patients that have been non-responders to Rituximab.

Risks & safety
Rekeland et al. 2020 reported a number of adverse effects, including one unexpected suspected serious adverse reaction - a worsening of POTS. Commonly reported side effects were nausea and constipation, and side effects affected 8 out of 40 patients.

Costs & availability
At present, only one clinical trial site, CycloME, is testing cyclophosphamide for use in ME/CFS.

Notable studies

 * 2020, Intravenous Cyclophosphamide in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. An Open-Label Phase II Study - (Full text)
 * 2021, Reduced Endothelial Function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome–Results From Open-Label Cyclophosphamide Intervention Study (Full text)

Learn more

 * - Cyclophosphamide - DrugBank Online
 * CycloME - Cyclophosphamide in ME/CFS