PDCD1 and glioblastoma: Based on these promising preclinical results, a series of one-half of clinical trials exploring the combination immunotherapy of CAR T cells and PD-1 blockade agents for multiple malignancies are under investigation, including relapsed/refractory Hodgkin lymphoma (NCT04134325), classical Hodgkin lymphoma (NCT05352828), relapsed/refractory B-cell lymphoma (NCT04539444), HER2-positive sarcoma (NCT04995003), and glioblastoma (NCT03726515).