Study of How Safe and Effective Tarlatamab is in Brain Cancers

Inclusion Criteria: * Provision of informed consent prior to any study specific procedures. * Must be 18 years of age or older. * Body weight \> 40 kg. * Patients must have histologically or cytologically confirmed diffuse astrocytic or oligodendroglial tumors by World Health Organization 2016 classification which are IDH mutant. * Patients could have received up to 2 regimens of systemic therapy after relapse. * For Cohort 1: Patient must be clinically deemed resectable and a resection is clinically indicated. * For Cohort 2: Patient must be unresectable or a resection is not clinically indicated at the time of enrollment. * Patients must have normal organ and bone marrow function measured within 14 days prior to administration of study treatment * Eastern Cooperative Oncology Group (ECOG) performance status 0-1. * Patients must have a life expectancy ≥ 12 weeks. * Patients of childbearing potential must have a negative serum pregnancy test within 28 days prior to start of therapy and Day 1 prior to start of therapy. * All participants must agree to use 2 acceptable methods to prevent pregnancy for study required duration. * Patients are willing and able to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations. * All patients in Cohort 1 and Cohort 2 are required to submit archival tissue. In addition, * Patients in Cohort 1 must be willing to provide fresh tumor samples at the time of clinically indicate…