Enzastaurin in Treating Young Patients With Refractory Primary CNS Tumors

DISEASE CHARACTERISTICS: * Histologically confirmed primary CNS malignancy including low-grade glioma * All tumors, except intrinsic brain stem and diffuse optic pathway tumors, must have histological verification at either the time of diagnosis or recurrence * Patients with intrinsic brain stem or diffuse optic pathway tumors must have clinical and/or radiographic evidence of progression * Recurrent or progressive disease or disease refractory to standard therapy and for which there is no known curative therapy PATIENT CHARACTERISTICS: Inclusion Criteria: * Karnofsky performance scale (for \> 16 years of age) or Lansky performance score (for ≤ 16 years of age) ≥ 60% assessed within two weeks prior to registration * Peripheral absolute neutrophil count (ANC) ≥ 1,000/μL * Platelet count ≥ 100,000/μL (transfusion independent) * Hemoglobin ≥ 8.0 g/dL (may receive RBC transfusions) * Creatinine clearance or radioisotope GFR ≥ 70 mL/min OR maximum serum creatinine based on age as follows: * 0.8 mg/dL (≤ 5 years of age) * 1.0 mg/dL (6 to 10 years of age) * 1.2 mg/dL (11 to 15 years of age) * 1.5 mg/dL (≥ 16 years of age) * Total bilirubin ≤ 1.5 x upper limit of normal (ULN) for age * ALT ≤ 5 x ULN for age * Serum albumin ≥ 2.5 g/dL * Patients of childbearing or child-fathering potential must be willing to use a medically acceptable form of birth control, which includes abstinence, while being treated on this study * Negative pregnancy test * Patients must have a normal QTc for age and no evidence of a clinically significant arrhythmia on ECG * No evidence of active graft-versus-host disease Exclusion Criteria: * Pregnant or lactating * Body surface area \< 0.5 m\^2 * Clinically significant unrelated systemic illness that would compromise the patient's ability to tolerate protocol therapy or would likely interfere with the study procedures or results * Known hypersensitivity to enzastaurin hydrochloride or its components * Inability to return for follow-up visits or obtain follow-up studies required to assess toxicity to therapy PRIOR CONCURRENT THERAPY: Inclusion Criteria: * Must have recovered from the acute toxic effects (grade ≤ 2) of all prior therapy before entering this study * Must not have received myelosuppressive chemotherapy within 3 weeks of entry onto this study (6 weeks for prior nitrosourea) * At least 7 days since the completion of therapy with a hematopoietic growth agent (i.e., filgrastim \[G-CSF\], sargramostim \[GM-CSF\], or erythropoietin) * At least 14 days since long-acting formulations * Therapeutic use of myeloid growth factors in patients with serious neutropenic conditions, such as sepsis, may be considered at the investigator's discretion * At least 7 days since the completion of therapy with a biologic agent * At least 2 weeks since prior local palliative radiotherapy (small port) * At least 6 months must have elapsed after prior total body irradiation (TBI) or craniospinal radiotherapy * At least 6 weeks must have elapsed after other substantial bone marrow irradiation * At least 6 months since prior allogeneic bone marrow transplantation * At least 3 months since prior autologous bone marrow or stem cell transplantation * Patients who are receiving dexamethasone must be on a stable or decreasing dose for at least 1 week prior to registration * Corticosteroids should be used at the lowest dose to control symptoms of edema and mass effect Exclusion Criteria: * Routine concurrent use of growth factors (i.e., G-CSF, GM-CSF, or erythropoietin) * Any other concurrent anticancer or investigational drug therapy * Concurrent enzyme-inducing anticonvulsants (EIACDs) * Concurrent gents that prolong the QTc * Concurrent drugs that are substrates or inhibitors of CYP3A4 or CYP2C9 * Other concurrent drugs that are sensitive substrates of CYP2C8, CYP2C9, or CYP2C19 and/or have a narrow therapeutic window