Adebrelimab Plus Temozolomide ± Hyperbaric Oxygen for Primary Glioblastoma

Inclusion Criteria: * Age 18-70 years, male or female. * Newly-diagnosed primary glioblastoma histologically-confirmed; received maximal safe resection or biopsy, and completed standard concurrent chemoradiotherapy with temozolomide. * Dexamethasone dose ≤4 mg/day at initiation of adjuvant study treatment. * Karnofsky Performance Status(KPS) ≥70. * Expected survival ≥3 months. * Adequate bone marrow: ANC ≥1.5×10\^9/L; Hb ≥90 g/dL; PLT ≥100×10\^9/L; WBC ≥3.0×10\^9/L. * Adequate liver function: ALT/AST/ALP ≤2.5×ULN (≤5×ULN if liver metastasis); total bilirubin \<1.5×ULN. * Adequate coagulation function: PT, APTT, INR ≤1.5×ULN. * Female not pregnant / lactating; effective contraception required for fertile females and males during study and 6-month after last study treatment. * Signed written informed consent, willing to comply with study procedures. * Not participating in other interventional clinical trials. Exclusion Criteria: * Prior anti-angiogenic, targeted, immunotherapy (anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, CTLA-4 antibody etc.). * Progressive disease according to iRANO criteria. Suspicious pseudo-progression should be further evaluated by advanced imaging. * Multifocal glioblastoma (separate tumor lesions without overlapping T2/FLAIR signal), or leptomeningeal metastasis. * Prior interstitial brachytherapy, implanted chemotherapy, local injection, convection-enhanced delivery; prior Gliadel wafer placement; prior Optune device usage. * Tumor completely located in infratentorial region. * Known hypersensitivity to temozolomide or adebrelimab components. * Dexamethasone \>4 mg/day at adjuvant treatment initiation. * History of immunodeficiency, or receiving immunosuppressive agents within 7 days before first study drug (except dexamethasone ≤4 mg daily). * Uncontrolled concurrent severe disease: active infection, symptomatic congestive heart failure, unstable angina, arrhythmia, uncontrolled hypertension or psychiatric condition interfering with study compliance. * Active systemic autoimmune disease requiring systemic therapy within past 2 years; physiological replacement therapy (thyroxine, insulin etc.) are allowed. * Medical conditions unsuitable for hyperbaric oxygen therapy or immunotherapy. * Severe anemia or concomitant medications interfering temozolomide absorption. * Uncontrolled major psychiatric disorder including depression with CESD-R score ≥16. * Cognitive impairment preventing neuro-oncology assessment. * Pregnant or lactating women. * Participated in other relevant clinical trials within prior 3 months. * Life-threatening complication or vegetative state after chemoradiotherapy. * Other malignant tumor within past 5 years (except cured carcinoma in-situ, basal-cell skin carcinoma). Poor compliance unable to follow protocol. * Substance-use disorder (DSM-V criteria: alcohol or drug addiction). * Active cardiac disease within 6 months prior to screening: myocardial infarction, unstable angina; LVEF\<50%, poorly controlled arrhythmia. * Active infection or unexplained fever\>38.5℃ at screening / before first dosing (fever attributed to tumor is permitted). * Immunodeficiency including active hepatitis; HBV-DNA ≥1000 IU/ml; HCV-RNA ≥1000 IU/ml. Chronic HBV carrier with HBV-DNA\<2000 IU/ml must receive concurrent antiviral treatment to be eligible. * Investigator's judgment that subject is inappropriate for this trial.