This multi-site Phase II study will enroll adults with histologically confirmed diagnosis of World Health Organization (WHO) Grade IV glioblastoma (GBM), isocitrate dehydrogenase (IDH)-wildtype consistent with WHO central nervous system (CNS) 2021 criteria who have received prior first-line treatment including with at least radiotherapy and temozolomide, with a Karnofsky performance status (KPS) ≥60, adequate organ function, and at least one measurable lesion according to the response assessment in neuro-oncology (RANO) 2.0 criteria.