Inclusion Criteria:

          -  Are ≥ 18 years of age by initiation of study treatment.

          -  Have B-cell NHL proven by histology, with histological subtypes limited to follicular
             lymphoma (FL) (except FL3B), MCL and marginal zone lymphoma (MZL).

          -  Have measureable nodal disease

          -  Are willing to undergo lymph node biopsies or biopsies of other involved tissue

          -  Have relapsed disease or disease refractory to conventional treatment or for which no
             standard therapy exists.

          -  Have received at least one line of conventional previous therapy which must include at
             least one rituximab-based regimen.

          -  Have a life expectancy of at least 12 weeks

          -  Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.

          -  Have CD20+ malignancy

          -  Have hematological and biochemical indices within prespecified ranges

        Exclusion Criteria:

          -  Have had an allogenic bone marrow or stem cell transplant within 12 months

          -  Have presence of active chronic graft versus host disease

          -  Have current leptomeningeal lymphoma or compromise of the central nervous system.

          -  Have transformed lymphoma from a pre-existing indolent lymphoma.

          -  Have Waldenstrom's Macroglobulinemia or FL3B,

          -  Need systemic doses of prednisolone >10 mg daily (or equipotent doses of other
             corticosteroids) while on the study trial other than as pre-medication.

          -  Have known or suspected hypersensitivity to rituximab or BI-1206.

          -  Have cardiac or renal amyloid light-chain amyloidosis.

          -  Have received the following:

          -  Chemotherapy or small molecule products with 2 weeks of first dose of BI-1206

          -  Radiotherapy (except for focal symptomatic control of lymphadenopathy) within 4 weeks

          -  Immunotherapy within 8 weeks

          -  Have ongoing toxic manifestations of previous treatments.

          -  Have the ability to become pregnant (or already pregnant or lactating/breastfeeding).

          -  Have had major surgery from which the subject has not yet recovered.

          -  Are at high medical risk because of non-malignant systemic disease including active
             infection on treatment with antibiotics, antifungals or antivirals.

          -  Are serologically positive for hepatitis B, hepatitis C or human immunodeficiency
             virus (HIV).

          -  Have an active, known or suspected autoimmune disease.

          -  Have concurrent congestive heart failure, prior history of class III/ IV cardiac
             disease (New York Heart Association [NYHA]),

          -  Have current malignancies of other types