Inclusion Criteria

Inclusion criteria

1. Patients > 3 years of age.

2. Diagnosis of neurofibromatosis type 1 (NF1).

3. Presence of clinically significant plexiform neurofibromas (biopsy proven if possible
with tissue blocks available); defined as tumors that are potentially life
threatening or are impinging on vital structures or significantly impair the quality
of life from pain or other symptoms.

4. Patients must have measurable disease by magnetic resonance imaging (MRI).

5. Patients must have a Karnofsky of > 70% or Lansky of > 50% and a life expectancy of
> 2 months.

6. Adequate end organ function, defined as the following:

total bilirubin < 1.5 x ULN, SGOT and SGPT < 2.5 x UNL, creatinine < 1.5 x ULN, ANC >
1.5 x 109/L, platelets > 100 x 109/L.

7. Patients must be able to swallow whole pills.

8. Female patients of childbearing potential must have negative pregnancy test within 7
days before initiation of study drug dosing. Postmenopausal women must be amenorrheic
for at least 12 months to be considered of non-childbearing potential. Male and
female patients of reproductive potential must agree to employ an effective barrier
method of birth control throughout the study and for up to 3 months following
discontinuation of study drug.

9. Written, voluntary informed consent.

Exclusion criteria

1. Patient has received any other investigational agents within 28 days of first day of
study drug dosing, unless the disease is rapidly progressing.

2. Patient is < 5 years free of another primary malignancy except: if the other primary
malignancy is not currently clinically significant nor requiring active intervention,
or if other primary malignancy is a basal cell skin cancer or a cervical carcinoma in
situ. Existence of any other malignant disease is not allowed.

3. Patient with Grade III/IV cardiac problems as defined by the New York Heart
Association Criteria. (i.e., congestive heart failure, myocardial infarction within 6
months of study)

4. Female patients who are pregnant or breast-feeding.

5. Patient has a severe and/or uncontrolled medical disease (i.e., uncontrolled
diabetes, chronic renal disease, or active uncontrolled infection).

6. Patient has a known brain metastasis. Non-specific CNS changes on MRI/CT
characteristic of NF1 are allowed, but not known CNS malignancies.

7. Patient has known chronic liver disease (i.e., chronic active hepatitis, and
cirrhosis).

8. Patient has a known diagnosis of human immunodeficiency virus (HIV) infection.

9. Patient received chemotherapy within 4 weeks (6 weeks for nitrosourea or mitomycin-C)
prior to study entry, unless the disease is rapidly progressing.

10. Patient previously received radiotherapy to greater than or equal to 25 % of the bone
marrow

11. Patient had a major surgery within 2 weeks prior to study entry.

12. Patient with any significant history of non-compliance to medical regimens or with
inability to grant reliable informed consent.

13. Patients who have or anticipate receiving permanent (or semi-permanent) metallic
structures attached to their body. (e.g., braces on teeth, body piercings), which
their physicians believe will interfere with the MRI.