Safety Study of Nifurtimox for Relapsed or Refractory Neuroblastoma

Inclusion Criteria: 1. Age: 0-21 years at the time of study entry. 2. Diagnosis: Histologic verification of neuroblastoma at original diagnosis or relapse. 3. Disease Status: Refractory or first or multiple relapsed neuroblastoma with measurable disease by radiographic scan (CT or MRI and MIBG), abnormal urinary catecholamine levels, or positive bone marrow biopsy/aspirate. MIBG not required if subject's neuroblastoma is previously determined to not uptake MIBG isotope (not MIBG avid). 4. Current disease state must be one for which there is currently no known curative therapy. 5. A negative urine pregnancy test is required for female participants of child bearing potential (\>13 years of age). 6. Patients must have adequate liver function as defined by AST or ALT \<10x normal and a bilirubin \<1.5mg/dl 7. Informed Consent: All patients and/or legal guardians must sign informed written consent. Assent, when appropriate, will be obtained according to institutional guidelines Exclusion Criteria: 1. Life expectancy \<3 months 2. Investigational Drugs: Patients who are currently receiving another investigational drug. 3. Anti-cancer Agents: Patients who are currently receiving other anticancer agents. 4. Infection: Patients who have an uncontrolled infection. 5. Patients who in the opinion of the investigator may not be able to comply with the safety monitoring requirements of the study. 6. Patients may not receive bisphosphonates (i.e. Zometa) within 7 days of start of therapy.