Cyclophosphamide is a common drug used for chemotherapy and the treatment of certain autoimmune diseases. It is derived from the same compounds found in mustard gas. It is usually used to treat leukemia and lymphoma, and less often solid tumors. Among autoimmune diseases, it is most commonly used to treat granulomatosis with polyangiitis, and multiple sclerosis.

The actual drug does not affect the diseases, but the liver converts the drug into other compounds that have the actual therapeutic effect. Some of the benefits of cyclophosphamide is that because of its method of action, it has little effect on bone marrow, the liver or the cells that line the intestines. Recent studies have also shown that the dosage can be adjusted to modulate the body's immune system, increasing its utility for treating both autoimmune conditions and immunosuppression. It's side effects are generally mild as well, but include nausea, stomach ache, diarrhea, hair loss and lethargy. At higher doses, it can be toxic, and can also cause immunosuppression. It can also lead to long term cancer of the bladder.

Cyclophosphamide at Wikipedia