Study to Evaluate the Efficacy and Safety of Pemigatinib in Participants With Previously Treated Glioblastoma or Other Primary Central Nervous System Tumors Harboring Activating FGFR1-3 Alterations

Inclusion Criteria:

* Histological, cytological, or molecular confirmation of recurrent GBM or other glioma, circumscribed astrocytic glioma, or glioneuronalor neuronal tumors that has recurred.
* Radiographically measurable disease.

  . -Karnofsky performance status ≥ 60.
* Life expectancy ≥ 12 weeks.
* Documentation of an actionable FGFR1-3 gene mutation or fusion/rearrangement from tissue : FGFR1-3 fusions or other rearrangements (FGFR1-3 in-frame fusions, any FGFR2 rearrangement, or FGFR1/3 rearrangement with known partner) or a defined FGFR1-3 activating mutation or in-frame deletion. Only participants with FGFR fusions or rearrangements with an intact kinase domain are eligible.
* MRI-documented objective progression after prior therapy and must have no therapy available that is likely to provide clinical benefit.
* Most recent archival tumor specimen must be a tumor block or a minimum of 15 unstained slides from biopsy or resection of primary tumor or metastasis.
* Willingness to avoid pregnancy or fathering children.

Exclusion Criteria:

* Prior receipt of an FGFR inhibitor.
* Receipt of anticancer medications or investigational drugs for any indication or reason within 28 days before first dose of study drug.
* Participants may have had treatment for an unlimited number of prior relapses but must not have had prior bevacizumab or other VEGF/VEGFR inhibitors (exception: prior bevacizumab is allowed if it was administered for the treatment of radiation necrosis rather than progressive tumor and was stopped at least 12 weeks prior to MRI showing tumor progression).
* Concurrent anticancer therapy
* Candidate for potentially curative surgery.
* Dexamethasone (or equivalent) \> 4 mg daily at the time of study registration
* Current evidence of clinically significant corneal or retinal disorder as confirmed by ophthalmologic examination.
* Diffuse leptomeningeal disease.
* Radiation therapy administered within 12 weeks before enrollment/first dose of study drug.
* Known additional malignancy that is progressing or requires active systemic treatment.