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Originally published in eMS News July 14, 2009

High-dose Cytoxan (cyclophosphamide or Revimmune), a chemotherapy drug, has demonstrated encouraging results in small scale studies. Along with cladribine, investigators are looking at the efficacy of high-dose Cytoxan as both a single and combination therapy, especially for those patients who do not respond to other treatment options.

Generally used to treat lymphomas and certain types of leukemia, Cytoxan is a nitrogen mustard alkylating agent that works by slowing or stopping cell growth. Chemotherapy treatments kill all rapidly dividing cells, which include cancer cells, hair cells, red cells, and white blood cells. Because the immune system is comprised of white blood cells, the thought behind Cytoxan as an MS treatment is that by reducing the number of white blood cells in the body, the therapy will slow immune activity and thus diminish or halt the autoimmune attacks that characterize MS. Lower doses of Cytoxan have been used to treat MS for many years, but it is only in the last two years that high-dose Cytoxan has gained momentum as an up-and-coming treatment option.

In 2006 and 2008, results from two small, uncontrolled clinical trials on high-dose Cytoxan were released. The more recent study, involving 9 relapsing-remitting MS patients, included four days of high-dose, intravenous Cytoxan (50 mg/kg per day). Eight of the participants had previously received immune-modulating therapies without success, and the ninth had refused approved treatments up to that point. After receiving the full dose of Cytoxan – the purpose of which was to kill the white blood cells – study participants were given a growth factor (granulocyte colony-stimulating factor) to encourage the growth of immune cells in the bone marrow. In 10 to 17 days, the study participants’ immune systems were reconstituted.
The primary endpoint – or goal – of this recent study was to evaluate the safety and tolerability of high-dose Cytoxan for MS patients. Investigators also looked at changes in gladolinium-enhancing lesions and disability as measured by the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Functional Composite (MSFC).

Although the study was quite small, investigators were pleased with the results. During the nearly 2-year follow-up, an average reduction in disability of 39.4% was seen, as well as an 87% average improvement in MSFC scores. The average number of brain lesions also decreased, from 6.5 at the start of the study to 1.2 at the follow-up stage. Additionally, during the 23-month study follow-up, 5 of the 9 study participants demonstrated no disease activity. The other four continued to show evidence of disease activity through brain lesions, but generally did not suffer any clinical episodes.

Other studies investigating high-dose Cytoxan combined with beta interferons are ongoing. Results from a study in Italy were released in 2005. During the study, thirty relapsing-remitting MS patients, all of whom had experienced significant relapse rates or disability progression in one year while on beta interferons, were treated with intravenous high-dose Cytoxan while continuing interferon treatment. All participants demonstrated a decrease in relapse rate; 70% of participants were relapse free. EDSS disability scores also improved. According to investigators, these encouraging results merit further exploration in larger, future studies.

High-dose Cytoxan, an immune suppressant, puts patients at risk for serious complications and toxic effects, specifically on organs such as the liver. Other side effects can include nausea and vomiting, diarrhea, hair loss, bladder damage, and temporary or permanent sterility. The therapy may also increase the risk of developing certain types of cancer. Larger studies are needed to better evaluate the safety and efficacy of high-dose Cytoxan as a single and combination treatment for MS.

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