A Study to Investigate Safety of INT2104 Infusions in Participants Aged 18 Years of Age and Older Who Have B-cell Cancers That Came Back After Previous Treatment

The purpose of this first-in-human study is to evaluate the safety and tolerability of INT2104 when administered to humans in a broad population of participants with refractory/relapsing B-cell malignancies. Preliminary efficacy information may also be obtained. INT2104 is a gene therapy delivering a transgene for a chimeric antigen receptor (CAR) specific for CD20 (CAR20). The lentiviral vector is designed to generate CAR T and CAR Natural Killer (NK) cells inside the body following intravenous (IV) administration. Study details include the following: * The study duration will be 5 years * The treatment duration will be a one-time intravenous (IV) infusion of INT2104

Inclusion Criteria: * Diagnosed with relapsed/refractory (R/R) B-NHL (Burkitt's lymphoma are eligible for Part B only) confirmed by histology or flow cytometry Note: Bone Marrow involvement is allowed * B-NHL must have CD20 antigen positive tumour confirmed from a tumour biopsy taken at screening * Measurable disease at the time of enrolment * Progression after at least 2 lines of systemic therapy * Has not received more than one prior marketed CAR-T cell therapy (including tandem or bispecific CAR-T) or other genetically modified T-cell therapy. * Sex and Contraceptive/Barrier Requirements consistent with local regulations for clinical trials Females: must have negative serum pregnancy test at screening and on Day -1 prior to INT2104 infusion Both sexes: must agree to use highly effective methods, including a barrier method after INT2104 infusion * Haematological criteria: * Absolute lymphocyte count (ALC) ≥300/µL * Platelet count ≥50,000/mL * Absolute neutrophil count (ANC) ≥500/µL * Eastern Cooperative Oncology Group (ECOG) score of 0 or 1 * Adequate renal, cardiac, hepatic, and lung function Key Inclusion Part B only * Diagnosed with relapsed/refractory B-ALL, and with exceptions as detailed in exclusion criteria. Participants with Philadelphia chromosome positive (Ph+) B-ALL disease are eligible. * B-ALL participants must have CD20 antigen positive leukaemia * Measurable disease at the time of enrolment * Participants with Burkitt's lymphoma are eligible for Part B only Exclusion Criteria: * Central Nervous System (CNS)-only B-cell malignancy, or B-cell malignancy with R/R secondary CNS involvement. * Diagnosis or history of chronic lymphocytic leukaemia (CLL) (including large cell \[Richter\] transformation of CLL) or small lymphocytic lymphoma (SLL) * Diagnosis or history of cutaneous lymphoma * History of another primary malignancy that has not been in remission for at least 3 years before signing informed consent (except for: non-melanoma skin cancer, low grade prostate cancer or carcinoma in situ (e.g., cervix, bladder, breast)) * Acute or chronic graft-versus-host disease * Participant has received donor lymphocyte infusion within 6 weeks prior to INT2104 infusion * History of autoimmune disease requiring systemic immunosuppression/ systemic disease modifying agents within 2 years before enrolment * History or presence of CNS disorder * History of myocardial infarction, cardiac angioplasty or stenting, unstable angina, or other clinically significant cardiac disease within 12 months before signing informed consent * Participants has active syphilis, cytomegalovirus (CMV), acute or chronic active hepatitis B, or untreated hepatitis C. * Participant is Human immunodeficiency virus (HIV) positive. * Any medical condition likely to interfere with assessment of safety or efficacy of the study treatment * A vaccine within 4 weeks prior to INT2104 infusion * Intolerance or severe hypersensitivity reaction to any excipients of the INT2104 product. * An active fungal, bacterial, viral, or other infection that is uncontrolled or requires antimicrobials at the time of INT2104 infusion. * Participant is pregnant or nursing. * In the investigator's judgment, the participant is unlikely to complete all protocol-required study visits or procedures, including follow-up visits, or comply with the study requirements for participation Note: Other protocol defined Inclusion/Exclusion criteria may apply.