Inclusion Criteria:

          1. Be at least 18 years of age.

          2. Must sign an informed consent form prior to any screening procedures.

          3. Has histologically or cytologically confirmed relapsed and/or refractory B-cell NHL
             with no available standard therapy or is not a candidate for available standard
             therapy, and for whom, in the opinion of the investigator, experimental therapy with
             GEN3009 may be beneficial. All subjects must have received at least two prior lines of
             systemic therapy.

          4. Has one of the specified subtypes for B-cell NHL for the Dose Escalation and Dose
             Expansion parts of the study.

          5. Has measurable disease for B-cell NHL or has active disease for Chronic Lymphocytic
             Leukemia (CLL).

          6. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.

          7. Has adequate hepatic, renal, and bone marrow functions.

          8. Before the first dose of GEN3009, during the trial, and for 12 months after the last
             dose of GEN3009, a woman must be either not of childbearing potential or of
             childbearing potential and practicing a highly effective method of birth control, and
             must have a negative serum beta-human chorionic gonadotropin (beta-hCG) and urine
             pregnancy test at screening.

          9. A man who is sexually active with a woman of childbearing potential and has not had a
             vasectomy must agree to use a barrier method of birth control.

        Exclusion Criteria:

          1. Prior treatment with a CD37-targeting agent.

          2. Prior allogeneic Hematopoietic Stem Cell Transplantation (HSCT).

          3. Autologous HSCT within 3 months before the first dose of GEN3009.

          4. Treatment with an anti-cancer biologic including anti-CD20 therapy, radio-conjugated
             or toxin-conjugated antibody or chimeric antigen receptor (CAR) T-cell therapy within
             4 weeks or 5 half-lives, whichever is shorter, before the first dose of GEN3009.

          5. Chemotherapy or radiation therapy within 2 weeks of the first dose of GEN3009.

          6. Treatment with an investigational drug or an invasive investigational medical device
             within 4 weeks or 5 half-lives, whichever is shorter, prior to the first dose of
             GEN3009.

          7. Autoimmune disease or other diseases that require permanent or high-dose
             immunosuppressive therapy.

          8. Received a cumulative dose of corticosteroids more than the equivalent of 250 mg of
             prednisone within the 2-week period before the first dose of GEN3009.

          9. Has uncontrolled intercurrent illness.

         10. Toxicities from previous anti-cancer therapies have not resolved to baseline levels or
             to Grade 1 or less except for alopecia and peripheral neuropathy.

         11. Primary central nervous system (CNS) lymphoma or known CNS involvement at screening.

         12. Known past or current malignancy other than inclusion diagnosis,

         13. Has had major surgery within 3 weeks before screening or will not have fully recovered
             from surgery, or has major surgery planned during the time the subject is expected to
             participate in the trial (or within 4 weeks after the last dose of GEN3009).

         14. Known history/positive serology for hepatitis B.

         15. Known medical history or ongoing hepatitis C infection that has not been cured.

         16. HIV tested positive at screening.

         17. Is a woman who is pregnant or breast-feeding, or who is planning to become pregnant
             while enrolled in this trial or within 12 months after the last dose of GEN3009.

         18. Is a man who plans to father a child while enrolled in this trial or within 12 months
             after the last dose of GEN3009.