Safety Study to Assess AFM11 in Patients With Relapsed and/or Refractory CD19 Positive B-cell NHL

Inclusion Criteria: * Patients with CD19+, relapsed or refractory histologically (WHO classification) confirmed follicular lymphoma, marginal zone lymphoma, lymphoplasmocytic lymphoma, mantle cell lymphoma, diffuse large B-cell lymphoma, mediastinal B-cell lymphoma, or transformed B-cell lymphomas. * Patients with either indolent or aggressive NHL. * Patients who relapsed or were refractory to the approved standard therapy, which must have included 1 treatment line with rituximab plus chemotherapy, and who are not candidates for bone marrow transplant (including both peripheral blood and hematopoietic stem cell transplants with a curative intent. * Measurable disease (at least 1 lesion ≥ 1.5 cm) documented by CT scan. * Disease progression requiring therapy. * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2. * Life expectancy of at least 6 months. * Ability to understand the patient information and informed consent form. * Signed and written informed consent Exclusion Criteria: * Total number of B-cells (healthy and malignant combined) in the peripheral blood exceeds the upper physiological limit (as per institutional guidance) of total B-cell counts in healthy individuals. * Autologous Hematopoietic stem cell transplant (HSCT) within 12 weeks prior to start of AFM11 treatment. * Abnormal hematological laboratory values as defined below: 1. Peripheral lymphocyte count \> 20 × 10\^9/L 2. Platelet count ≤ 75,000/µL 3. Hemoglobin level ≤ 9 g/dL. * Known or suspected central nervous system (CNS) involvement. 1. History of or current relevant CNS pathology as epilepsy, seizure, paresis, aphasia, apoplexia, severe brain injuries, cerebellar disease, organic brain syndrome, and/or psychosis. 2. Evidence for presence of malignant disease, inflammatory lesions, and/or vasculitis on cerebral MRI. 3. Infiltration of the cerebrospinal fluid by malignant B-cells, confirmed by lumbar puncture. * Cancer chemotherapy within 4 weeks prior to start of AFM11 treatment, or at least 4 times the respective half-lives, whichever is longer. * Radiotherapy within 4 weeks prior to start of AFM11 treatment. * Therapy with antibody, or antibody constructs within 4 weeks prior to start of AFM11 treatment, or at least 4 times the respective half-lives, whichever is longer. * Prior treatment with alemtuzumab (Campath®) within 12 weeks prior to start of AFM11 treatment. * Treatment with any investigational agent within 4 weeks prior to start of AFM11 treatment, or at least 4 times the respective half-life, whichever is longer. * Contraindication for any of the concomitant medications. * Abnormal renal or hepatic function as follows: aspartate aminotransferase (AST or serum glutamic oxaloacetic transaminase \[SGOT\]) and/or alanine aminotransferase (ALT or serum glutamic pyruvic transaminase \[SGPT\]) ≥ 2.5 × upper limit of normal (ULN); total bilirubin ≥ 1.5 × ULN; serum creatinine ≥ 2 × ULN; creatinine clearance \< 50 mL/minute. * History of malignancy other than B-cell lymphoma within 5 years prior to study entry, with the exception of basal cell carcinoma of the skin or carcinoma in situ of the cervix. * Active autoimmune disease requiring systemic immunosuppressive treatment. * Uncontrolled infections; known bacteremia. * Any concurrent disease or medical condition that is deemed to interfere with the conduct of the study as judged by the Investigator. * Regular dose of corticosteroids during the 4 weeks prior to start of AFM11 treatment or anticipated need of continuous corticosteroids exceeding prednisone 20 mg/day or equivalent, or any other immunosuppressive therapy within 4 weeks prior to start of AFM11 treatment. * Known infection with human immunodeficiency virus (HIV) or chronic infection with hepatitis B or hepatitis C virus. * Pregnant or nursing women or women of childbearing potential not willing to use an effective form of contraception during participation in the study and at least 12 weeks thereafter. Male patients not willing to ensure that during the study and at least 12 weeks thereafter no fathering takes place. Effective methods of contraception include intrauterine device 8(IUD), combined (estrogen- and progesterone-containing) hormonal contraception (oral, vaginal ring or transdermal patch) with an ethinylestradiol dose of at least 30 µg, plus use of male condoms (preferably with spermicides), female condoms, female diaphragm, or cervical cap. * Prior treatment with blinatumomab or any other CD19 targeting T-cell engager, including CD19 CAR-T cells. * Clinically relevant coronary artery disease (New York Heart Association \[NYHA\] functional angina classification III/IV), congestive heart failure (NYHA III/IV), or high risk of, or known, uncontrolled arrhythmia.