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.