Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed supratentorial malignant primary glioma
Glioblastoma multiforme (closed to accrual as of 05/31/2001) Gliosarcoma (closed to
accrual as of 05/31/2001) Anaplastic astrocytoma Anaplastic oligodendroglioma Mixed
malignant gliomas Original histological diagnosis of low-grade glioma allowed if a
subsequent histological diagnosis of malignant glioma is confirmed Prior treatment for no
more than 2 prior relapses allowed Disease progression documented by at least 2 pre-study
brain scans Recent prior tumor resection of recurrent or progressive tumor allowed if
recovered from the effects of prior surgery

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life
expectancy: More than 8 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3
Platelet count at least 100,000/mm3 Hemoglobin at least 10 g/dL (may be transfusion
dependent) Hepatic: Bilirubin less than 2 times upper limit of normal (ULN) SGOT less than
2 times ULN Renal: Creatinine less than 1.5 mg/dL Creatinine clearance at least 60 mL/min
Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective
barrier contraception during and for at least 2 months after study Able to swallow
capsules No active infection No disease or other serious concurrent medical illness that
would preclude study

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 1 week since prior interferon At
least 1 week since prior thalidomide Chemotherapy: Recovered from prior chemotherapy At
least 4 weeks since prior cytotoxic therapy (2 weeks for vincristine, 3 weeks for
procarbazine, or 6 weeks for nitrosoureas) Endocrine therapy: At least 1 week since prior
tamoxifen Prior steroids allowed if on stable or decreasing dose for at least 5-7 days
before baseline MRI If steroid dose is increased between date of baseline MRI and
initiation of study drug, a new baseline MRI is required Radiotherapy: Not specified
Surgery: See Disease Characteristics No concurrent surgery Other: At least 1 week since
any prior noncytotoxic agents (e.g., isotretinoin) No other concurrent anticancer therapy,
including other investigational drugs