This Phase I, prospective, single-arm clinical study aims to evaluate the efficacy and safety of adjunctive methylene blue (MB) in patients experiencing cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS) following CAR-T cell therapy or bispecific antibody treatment. Preclinical studies demonstrated that MB alleviates CRS/ICANS-related symptoms, preserves the antitumor function of T cells, and modulates neuroinflammation without compromising immune efficacy. The study will employ a 3+3 dose-escalation design with three MB dosing cohorts, with treatment administered intravenously for 3-5 consecutive days. Vital signs, laboratory markers, and neurological status will be closely monitored, and concomitant standard supportive therapies will be permitted.