• The primary endpoint of this study is to evaluate the response rate of MS patients after high-dose cyclophosphamide therapy as determined by a sustained (greater than 6 months) decrease of greater than or equal to 1.0 in their EDSS score.
  

• The secondary endpoint of this study is to evaluate time to EDSS score progression.
  

Multiple sclerosis (MS) is the major disabling neurologic disease of young adults,and represents the most common immune-mediated inflammatory and demyelinating disorder of the central nervous system (CNS). Active inflammatory lesions contain components that include T cells, macrophages, and activated microglia. Within these lesions myelin is removed, axons are damaged and oligodendrocytes may be lost. In lesions undergoing inflammatory demyelination axonal injury also occurs. The disability MS produces is underscored by the nearly fifty percent of patients who will require ambulatory aids within 15 years after disease onset.

Currently, there is no cure for MS. Therapy is targeted at changing the short-term natural history of MS: to decrease attack rates and to postpone long-term disability. At present, interferon beta and glatiramer acetate form the foundation of therapy for relapsing MS. Mitoxantrone is approved for more severe cases of relapsing MS, such as those with rapidly accumulating neurologic impairments.

High-dose cyclophosphamide (HDC) is a non-bone marrow transplant treatment option for those afflicted by severe, refractory immune-mediated illnesses by pathologic autoreactive lymphocytes. The goal of this therapy is to induce immunoablation without myeloablation: that is, to eradicate offending B and T cells responsible for the illness while sparing the pluripotent blood stem cell of any ill effect. Since 1966, multiple publications on numerous immune-mediated illnesses have shown HDC without stem-cell rescue to decrease disease activity and improve quality of life

In this protocol we study HDC for severe, refractory MS. The primary goal is to assess the safety of HDC in this population, where no data exists regarding the tolerability of high-dose chemotherapy without stem-cell rescue. The treatment goal is not to induce disease regression (resolution of fixed neurologic deficits), but rather to stop disease progression without further remittive therapy.