Study of the Trifunctional Antibody FBTA05 and Donor Lymphocyte Infusion in B-cell Lymphoma After Allogeneic Stem Cell Transplantation

Inclusion Criteria: * Patient´s written informed consent * ≥ 18 years of age; male and female * Confirmed CLL, low grade NHL or high grade NHL on standard histological or immunophenotypical criteria described in the WHO classification of lymphoid malignancies * CD20 positivity (if not already confirmed) * Adequate haematological, liver and kidney functions * Platelet count ≥25,000mm³ (=25 x 10\^9/l) * Patients with active disease (relapsed/refractory) that survived at least 60 days after allogeneic transplantation * Eastern Cooperative Oncology Group (ECOG) performance status \<=2 (Appendix IV) * Negative pregnancy test (no more than 2 days before enrolment) and adequate contraception during the study in women of child bearing potential (pre- menopausal, \<2 years post-menopausal or not surgically sterile) Exclusion Criteria: * Any anti-CD20 and / or any other anti-T cell directed antibody treatments \< 3 months before application of FBTA05 * Positivity for human anti-mouse antibodies (HAMAs) * History of GvHD ° III or IV, or GvHD requiring steroid therapy with more than 10 mg/day * Known or suspected hypersensitivity to recombinant, murine or rat proteins * AST/SGOT greater than 10 x ULN (grade 3, CTCAE) * Bilirubin greater than 5 x ULN (grade 3, CTCAE) * Creatinine greater than 3.5 mg/dl (grade 3, CTCAE) * Acute or uncontrolled chronic infections, viral infections at risk of reactivation (e.g.HCV, HBV, HIV) * Unable or unwilling to comply fully with the protocol * Any condition which in the judgement of the Investigator would place the subject at undue risk or interfere with the results of the study