This rather toxic anti-cancer drug has the advantage of being taken orally rather than by injection only, unlike most anti-cancer agents. In multiple sclerosis, cyclophosphamide has mostly been used for the chronic progressive form.
Unfortunately this cyclophosphamide MS treatment has major side effects, both short and long term. In the longer term, it can cause a variety of cancers in its own right. These side effects limit its usefulness for people with MS.