Inclusion Criteria:

          1. Diagnosis of CLL in need of treatment according to the iwCLL guidelines

          2. Relapsed or refractory disease after at least one, but no more than 3 prior regimens
             for CLL

          3. Medically fit patients without relevant comorbidity, defined as total CIRS score ≤6
             (single score < 4 for one organ category)

          4. ECOG performance status of 0 - 2

          5. Hematology values within the following limits unless cytopenia is caused by the
             underlying disease, i.e. no evidence of additional bone marrow dysfunction (e.g.
             myelodysplastic syndrome (MDS), hypoplastic bone marrow due to toxicity of prior
             therapy):

               1. Absolute neutrophil count ≥1.5 x 109/L

               2. Platelets ≥50 x 109/L and more than 7 days since last transfusion

          6. Creatinine clearance >60 ml/min calculated according to the modified formula of
             Cockcroft and Gault or directly measured after 24 h urine collection

          7. Adequate liver function as indicated by a total bilirubin, AST, and ALT ≤2 the
             institutional ULN value, unless directly attributable to the patient's CLL

          8. Negative serological Hepatitis B test (i.e. HBsAg negative and anti-HBc negative,
             patients positive for anti-HBc may be included if PCR for HBV DNA is negative);
             negative testing of Hepatitis C RNA; negative HIV test within 6 weeks prior to
             registration

          9. 18 years of age or older

         10. Life expectancy >6 months

         11. Able and willing to provide written informed consent and to comply with the study
             protocol procedures

        Exclusion Criteria:

          1. Detected del(17p) or TP53 mutation

          2. Refractoriness to FCR / BR

          3. Transformation of CLL to aggressive NHL (Richter's transformation)

          4. Known central nervous system (CNS) involvement

          5. Evidence of significant uncontrolled concomitant disease

          6. Major surgery < 30 days before screening

          7. Decompensated hemolytic anemia 28 days before screening

          8. Hemolytic cystitis 28 days before screening

          9. Patients with a history of confirmed PML

         10. Prior treatment with GA101

         11. History of prior malignancy, except for conditions as listed below (a-d) and if
             patients have recovered from the acute side effects incurred as a result of previous
             therapy:

               1. Malignancies treated with curative intent and with no known active disease
                  present for ≥ 2 years before registration

               2. Adequately treated non-melanoma skin cancer or lentigo maligna without evidence
                  of disease at screening

               3. Adequately treated cervical carcinoma in situ without evidence of disease at
                  screening

               4. Surgically adequately treated low grade, early stage localized prostate cancer
                  without evidence of disease at screening

         12. Use of investigational agents or concurrent anticancer treatment within the last 4
             weeks before registration

         13. Patients with active infection requiring systemic treatment

         14. History of severe allergic or anaphylactic reactions to humanized or murine monoclonal
             antibodies and/ or known hypersensitivity to any constituent of the product

         15. Hypersensitivity to fludarabine, cyclophosphamide, bendamustine, GA101 and/ or to any
             of the excipients for example mannitol

         16. An individual organ/ system impairment score of 4 as assessed by the CIRS definition
             limiting the ability to receive an intensive therapy for CLL

         17. Legal incapacity

         18. Women who are pregnant or lactating

         19. Fertile men or women of childbearing potential unless:

               1. surgically sterile or ≥2 years after the onset of menopause

               2. willing to use a highly effective contraceptive method (Pearl Index <1) such as
                  those listed at section 4.2.2 Exclusion criteria during study treatment and for
                  12 months after end of study treatment

         20. Vaccination with a live vaccine within a minimum of 28 days before screening

         21. Participation in any other clinical trial which would interfere with the study drug

         22. Prisoners or subjects who are institutionalized by regulatory or court order

         23. Persons who are in dependence to the sponsor or an investigator