Cyclophosphamide

Cyclophosphamide is a chemotherapy and immunosuppressant drug. It 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