MB-CART20.1 Lymphoma

Inclusion Criteria: * Refractory/relapsed CD20+ B-NHL (including malignant transformation like Richter's transformation) with no curative treatment option. * At least 18 years of age * Estimated life expectancy of more than 3 months * ECOG performance status (Eastern cooperative oncology group) of 0-2 * Negative serological HBV (Hepatitis B virus) test, negative testing of HCVAb (Hepatitis C virus Antibody), negative HIV1/2 (Human immunodeficiency virus 1/2 ) test within 6 weeks prior to enrollment * No childbearing potential or negative pregnancy test at screening and before chemotherapy in women with childbearing potential. * Signed and dated informed consent before conduct of any trial-specific procedure Exclusion Criteria: * Participation in another interventional trial that could interact with this trial * Any evidence 0f CNS (Central nervous system) involvement * Known history or presence of clinically relevant CNS pathology * Patients with history of primary immunodeficiency, * Patients with any history of auto-immune induced condition such as those caused by checkpoint inhibitors, MEK inhibitors or BRAF inhibitors, for example pituitary hypophysitis must be excluded * Patients with Chronic Lymphocytic Leukemia unless suffering from malignant transformation * Active systemic fungal, viral or bacterial infection * Serious cardiac functional incapacity (class III or IV as defined by the New York Heart Association Classification) * Severe pulmonary disease (DLCO (Transfer factor of the lung for carbon monoxide) and/or FEV1 (Forced expiratory volume in 1 second) \< 65%, dyspnea at rest) * Liver dysfunction as indicated by a total bilirubin, AST (Aspartate Aminotransferase), and ALT (Alanine aminotransferase) ≥ 2 the institutional ULN (Upper limit of normal) value, unless directly attributable to the patient's tumor * Creatinine clearance \<50 ml/min calculated according to the modified formula of Cockcroft and Gault * Pregnant or lactating women * Active secondary malignancy requiring treatment (except basal cell carcinoma or malignant tumor curatively treated by surgery) within the last 5 years before enrollment. * Medical condition requiring prolonged use of systemic corticosteroids (\> 1 month) * Prior therapy with genetically modified substances * Use of anti-CD20 antibodies within 4 weeks before leukapheresis * Chemotherapy within 4 weeks prior to leukapheresis * Other treatment within 4 weeks or two half-lives, whichever is longer before MB-CART20.1 infusion. This pertains to immunomodulatory therapies such as checkpoint inhibitors because of the influence on the immune system * Concurrent systemic radiotherapy * Hypersensitivity against any drug or its ingredients/impurities that is scheduled or likely to be given during trial participation e.g. as part of the mandatory lymphodepletion protocol, pre-medication for infusion, rescue medication/salvage therapies for treatment of related toxicities * Patients in which such medication is contraindicated for other reasons than hypersensitivity (e.g. live vaccines and fludarabine) * Patients in which trial related procedures are contraindicated as judged by the investigator, e.g. lumbar punctures for CSF (Cerebrospinal fluid) sampling * Patient's lack of accountability, inability to appreciate the nature, meaning and consequence of the trial and to formulate his/her own wishes correspondingly * Patients who have a relationship of dependence or employer employee relationship to the sponsor or the investigator * Committal to an institution on judicial or official order * Cerebral dysfunction, legal incapacity * Other investigational treatment within 4 weeks before IMP (Investigational Medicinal Product) infusion * Clinically relevant autoimmune diseases or history of autoimmune disease