Imetelstat Sodium in Treating Younger Patients With Recurrent or Refractory Brain Tumors

INCLUSION CRITERIA: * MOLECULAR BIOLOGY STUDY * Tumor: Histologically confirmed Dx of ependymoma or HGG (such as anaplastic astrocytoma, glioblastoma, gliosarcoma, or anaplastic oligodendroglioma) that is recurrent or refractory to conventional therapy. * Subjects must have clinical indications for surgical resection and be amenable to receiving imetelstat prior to tumor resection. Subjects who require emergent surgery are not eligible for the Molecular Biology study. * Subjects must provide, fresh flash frozen tumor samples (target 50 mg tissue; as low as 20 mg is adequate) from the time of diagnosis or previous recurrence for the assessment of tumor telomerase activity by the TRAP assay. * PHASE II STUDY * Tumor: Subjects must have recurrent or refractory disease with a histological Dx from either the initial presentation or at the time of recurrence. The requirement for histologic verification is waived for subjects with DIPG (stratum D). The following diagnoses are eligible and will be treated in separate strata (B-D): (B) recurrent or refractory high-grade glioma, (such as anaplastic astrocytoma, glioblastoma multiforme, gliosarcoma, anaplastic oligodendroglioma); (C) recurrent or refractory ependymoma; (D) recurrent or refractory DIPG (diagnosis by imaging characteristics acceptable; no histologic confirmation required) * Slides from either initial Dx or relapse must be available for central pathology review for Strata B-C. Tissue slides must be sent per Se…