Inclusion Criteria:

- Phase I - Patients aged ≥12 months and <18 years, Phase II - Patients ≥12 months

- Phase I - Histologically confirmed diagnosis of medulloblastoma, rhabdomyosarcoma,
neuroblastoma, hepatoblastoma, high grade glioma, or osteosarcoma, that has
progressed despite treatment with standard therapies, or for which no standard
treatments are available (patients with brainstem gliomas are excluded). Phase II -
Histologically confirmed diagnosis of recurrent or relapsed medulloblastoma with at
least one measurable lesion.

- Performance Status: Karnofsky ≥60% for patients >10 yrs, Lansky ≥50 for patients less
than or equal to 10 yrs

- Protocol-defined renal , liver and bone marrow function

- Negative pregnancy test before starting study treatment. If of child bearing
potential must use 'highly effective' methods of contraception.

- All patients must consent to provide a tumor sample

Exclusion Criteria:

- Systemic anti-cancer treatment within 2 weeks prior to first dose (6 weeks for
nitrosourea, mitomycin and monoclonal antibodies).

- Focal radiotherapy within 4 weeks prior to first dose, or full spinal radiotherapy
within 3 months of first dose.

- Unresolved toxicity greater than CTCAE grade 1 from previous anti-cancer therapy or
radiotherapy (excluding neurotoxicity, alopecia, ototoxicity, lymphopenia or other
specifications in the eligibility criteria for this study), or incomplete recovery
from previous surgery, unless agreed by Novartis and the Principal Investigator (PI)
and documented.

- Major surgery, serious illness or traumatic injury within 2 weeks of starting study
therapy. Patients anticipated to require major surgery within the first 2 cycles of
treatment.

- Patients requiring a nasogastric tube for drug administration (G-tubes are permitted)

- Impaired cardiac function

- Pregnant or breast-feeding females

- Impairment of gastrointestinal (GI) function or GI disease

Other protocol-defined inclusion/exclusion criteria may apply