A Combined Study in Pediatric Cancer Patients for Dose Ranging and Efficacy/Safety of Plerixafor Plus Standard Regimens for Mobilization Versus Standard Regimens Alone

Inclusion Criteria: * Age 2 to \< 18 years during stage 1 and 1 to \< 18 years during stage 2 * Ewing's sarcoma, soft tissue sarcoma, lymphoma, neuroblastoma, brain tumors or other malignancy (excluding any form of leukemia) requiring treatment with high dose chemotherapy and autologous transplant as rescue therapy * Eligible for autologous transplantation * Recovered from all acute significant toxic effects of prior chemotherapy * Adequate performance status (for patients ≥16 years of age, defined as Karnofsky score \>60 and for patients \<16 years of age, defined as Lansky score \>60) * Absolute neutrophil count \>0.75 × 10\^9/L * Platelet count \>50 × 10\^9/L * Calculated creatinine clearance (using the Schwartz method): during study Stage 1, \>80 mL/min/1.73m\^2 and during study Stage 2, \>60 mL/min/1.73m\^2 * Aspartate aminotransferase(AST)/serum glutamic oxaloacetic transaminase(SGOT), alanine aminotransferase(ALT)/serum glutamic pyruvic transaminase (SGPT) and total bilirubin \<3 × upper limit of normal * The patient and/or their parent/legal guardian is willing and able to provide signed informed consent * Patients who are sexually active must be willing to abstain from sexual intercourse or agree to use an approved form of contraception while receiving plerixafor and/or standard mobilization treatment and for at least 3 months following any plerixafor treatment Exclusion Criteria: * Any form of leukemia * A co-morbid condition which, in the view of the Investigator, renders the patient at high-risk from treatment complications * Previous stem cell transplantation * Persistent high percentage marrow involvement prior to mobilization will be prohibited. * On-going toxicities (excluding alopecia) Grade ≥2 resulting from prior chemotherapy * Acute infection * Fever (temperature \>38.5°C) - if fever is between 37°C and 38.5°C, infection must be excluded as a cause * Known HIV seropositivity, AIDS, hepatitis C or active hepatitis B infections * Positive pregnancy test in post pubertal girls * History of clinically significant cardiac abnormality or arrhythmia * Use of an investigational drug which is not approved in any indication either in adults or pediatrics within 2 weeks prior to the first dose of G-CSF to be administered as part of the patient's planned standard mobilization regimen, and/or during the study up until engraftment of the transplant. If patients are on investigational drugs as part of their anti-cancer regimen, this should be discussed with the Sponsor before screening. Drugs approved for other indications that are being used in a manner considered standard of care for this transplant procedure are allowed * The patient (and/or their parent/legal guardian), in the opinion of the Investigator, is unable to adhere to the requirements of the study