Inclusion Criteria:

- Patients in all parts of the study must have histological verification of malignancy
at either original diagnosis or relapse.

- For Part A, patients must have recurrent or refractory solid tumours, lymphoma
or CNS tumours (excluding diffuse intrinsic pontine gliomas).

- For Part B, patients must have recurrent or refractory leukemia.

- For Part C, patients must have one of the following diagnoses: neuroblastoma, or
medulloblastoma / CNS primitive neuroectodermal tumour (PNET).

Disease Status

- Patients with solid tumours must have either measurable or evaluable disease (defined
by a positive nuclear scan such as bone scan or metaiodobenzylguanidine (MIBG) scan.
For part C only, in the case of neuroblastoma, if a lesion is isolated and /or
previously irradiated and stable, a proven positive biopsy will be required to be
eligible.

- Patients with refractory or relapsed leukemia must have greater than 25% blasts in
bone marrow (M3 bone marrow); active extramedullary disease may also be present.
Patients with leptomeningeal disease are not eligible.

Therapeutic Options:

The patient's current disease state must be one for which there is no known curative
therapy or therapy proven to prolong survival with an acceptable quality of life.

Prior Systemic Therapy

Patients must have recovered from the acute effects of prior chemotherapy, immunotherapy
or radiotherapy prior to study entry as follows:

- At least 3 weeks from completion of myelosuppressive chemotherapy, biologic agents or
other investigational cancer treatment

- At least 7 days from completion of therapy with a growth factor

- At least 6 weeks from hematopoietic stem cell rescue following myeloablative therapy

- Post allogeneic hematopoietic transplant patients are eligible, but must have no
evidence of active graft vs. host disease

- At least 2 weeks from completion of local palliative XRT (small port)

- At least 3 months must have elapsed if prior total body irradiation, craniospinal XRT
or if ≥ 50% radiation of pelvis

- At least 6 weeks must have elapsed if other substantial bone marrow irradiation

- At least 6 weeks from prior MIBG therapy Age > 12 months and ≤ 18 years at the time
of study entry. Performance Status: Karnofsky ≥ 60% for patients > 10 years; Lansky ≥
50 for patients ≤ 10 years.

For Patients with Solid Tumours (Parts A and C):

- Absolute neutrophil count (ANC) ≥ 1.0 x 10 (power of 9)/L

- Platelets ≥100 x 10(power of 9)/L

- Hemoglobin ≥ 80 g/L

For Patients with Leukemia (Part B only)

- No minimum absolute neutrophil count

- Platelet count ≥ 20 x 10 (power of 9)/L (may receive transfusion)

- Hemoglobin ≥ 80 g/L (may receive transfusion)

- serum creatinine ≤ 1. 5 x upper limit of normal for age or

- measured GFR ≥ 70 mL/min/1.73 m2

- LVEF by ECHO or MUGA Scan within normal institutional limits

- QTc ≤ 450 msec

- AST and ALT ≤ 5.0 x upper limit normal for age

- bilirubin ≤ 1.5 x upper limit normal for age

Additional Criteria For Part C Of The Study

- Skin toxicity (excluding alopecia) ≤ Grade 1

- Serum triglycerides (fasting) < 3.4 mmol/L

- Negative urine dipstick for protein OR < 1000 mg protein/24 hour urine collection

- No evidence of gross hematuria

Patient or guardian consent must be obtained on all patients according to local
Institutional and/or University Human Experimentation Committee requirements.

Patients registered on this trial must be treated and followed at the participating
centre.

Protocol treatment to begin within five working days of patient registration.

Exclusion Criteria:

- Cardiac Exclusions. Patients with a pathologic cardiac arrhythmia requiring active
treatment. Patients with a history of arrhythmia must be > 12 months since last
treatment with no recurrence of arrhythmia in the interval.

- Inability To Take Oral Medication. Patients must be able to take oral medication and
have no gastrointestinal abnormalities (e.g. bowel obstruction or previous gastric
resection) which would lead to inadequate absorption of SB939.

- Known HIV, hepatitis B or hepatitis C infections.

- Current treatment with agents with a known risk of Torsades de Pointes
http://torsades.org (list #1).

- Pre-existing peripheral neuropathy ≥ grade 3.

- There is no available information regarding human fetal or teratogenic toxicities
related to SB939. 13-cis-retinoic acid is known to be teratogenic. Pregnancy tests
must be obtained in girls who are post menarchal. Males or females of reproductive
potential may not participate unless they have agreed to an effective contraceptive
method. Pregnant or breast feeding females will not be entered on this study due to
the potential fetal and teratogenic adverse events.