RecruitingBiological interventionT Cells and Pembrolizumab for Recurrent and Newly Diagnosed GlioblastomaThe goal of this clinical trial is to test a combined therapy approach (allogeneic cytomegalovirus \[CMV\]-specific T cells and pembrolizumab) in patients with brain cancer. The type of brain cancer being studied is glioblastoma multiforme/astrocytoma grade 4. The purpose of part 1 of this study is to determine the maximum-tolerated dose and/or recommended dose(s) for future exploration of allogeneic CMV-specific T cells as monotherapy or in combination with pembrolizumab in patients with recurrent GBM/astrocytoma grade 4. Part 2 of the study aims to investigate the anti-tumour activity of allogeneic CMV-specific T cells as monotherapy or in combination with pembrolizumab, assessed by magnetic resonance imaging and survival, in patients with recurrent or newly diagnosed GBM/grade 4 astrocytoma.