Testing the Combination of Anti-cancer Drugs Actimab-A and Cemiplimab (REGN2810) to Improve Outcomes for Patients With Recurrent Glioblastoma

Inclusion Criteria: * Patients must have histologically or cytologically confirmed glioblastoma isocitrate dehydrogenase wild type (IDH-WT) World Health Organization (WHO) grade 4 inclusive of gliosarcoma (Louis et al., 2021) * Note: Isocitrate dehydrogenase (IDH) status confirmed by immunohistochemistry (IHC) for IDH1 R132H + next-generation sequencing (NGS) for IDH1 and IDH2 hotspots * Evidence of recurrent disease (RD) that is measurable (1 x 1cm) at first or second relapse demonstrated by disease progression using Response Assessment in Neuro-Oncology 2.0 (RANO 2.0) criteria, unless the recurrence is outside the radiation field or has been histologically documented * Tumor O-6-methylguanine-deoxyribonucleic acid (DNA) methyltransferase (MGMT) methylation status must be available from any prior GBM tumor specimen; results of routinely used methods for MGMT methylation testing (e.g., mutagenically separated polymerase chain reaction \[MSPCR\] or quantitative polymerase chain reaction \[PCR\] are acceptable) * Previous first-line treatment with at least radiotherapy (prior dose ≥ 40 gray \[Gy\]) * Note: Prior temozolomide, prior tumor-treatment fields and/or Gliadel wafer (if placed at initial tumor resection) are allowed, but none of these are required * Last radiation ≥ 6 months (182 days) prior to enrollment if received ≥ 60 Gy or ≥ 3 months (84 days) if received \< 60 Gy to limit the risk of radiation necrosis * No previous treatment with anti PD1, PDL1, CTLA-4, o…