The goal of this clinical trial is to learn the safety of OT-C001 and decide a good dose in treating relapsed or refractory diffuse large B-cell lymphoma patients. It will also learn about the preliminary activity of OT-C001.

Participants will:

Receive a short course of chemotherapy before OT-C001 treatment. During the study treatment, participants will recieve weekly dose of OT-C001 for 3 or 6 weeks. During the study period, participants will also receive another two drugs, rituximab and IL-2, to support OT-C001 treatment.

Participants need to visit the clinic or may be hospitalized according to the study plan.

Inclusion Criteria:

• ≥18 years of age
• histologically confirmed diagnosis of R/R DLBCL-NOS without further standard treatment options including those relapsing after or ineligible for CAR T-cell therapy
• with evaluable disease
• with adequate biological parameters at baseline
• ECOG performance status ≤1
• life expectancy >3 months as assessed by the investigator

Exclusion Criteria:

• Receive concomitantly any antitumor-directed drug therapy
• Any vaccination with live virus vaccines before or during treatment
• With severe atopic predisposition who need a treatment with monoclonal antibodies, allergen immunotherapy, or long-term systemic corticosteroids
• Major surgery within 3 weeks
• With rapidly progressing disease that includes massive uncontrolled pleural, pericardial, or peritoneal effusions, pulmonary lymphangitis, and over 50% liver involvement
• Ongoing immune-related tocivities or adverse events grade >1 not resolved from previous therapies except vitiligo, stable neuropathy up to grade 2, hair loss, and stable endocrinopathies with substitutive hormone therapy
• Documented history of active autoimmune disorders requiring systemic immunosuppressive therapy within the last 12 months
• Primary or secondary immune deficiency
• Active and uncontrolled infections requiring intravenous antibiotic or antiviral treatment
• Seropositive (except after vaccination or confirmed cure for hepatitis) for HIV, HBV, or HCV
• Clinically significant cardiac disease including heart failure, uncontrolled hypertension, pre-existing arrhythmia, uncontrolled angina pectoris, or myocardial infarction within 12 months
• Dementia or altered mental status that would prohibit informed consent
• Other malignancy within the last 3 years except adequately treated nonmelanoma skin cancer, in situ carcinoma of the uterine cervix, or myelodysplastic syndromes