Study to Evaluate Safety and Tolerability of XmAb13676 in Patients With CD20-expressing Hematologic Malignancies

Inclusion Criteria:

- Able to provide written informed consent

- Diagnosis of either Non-CLL B cell malignancy or CLL/SLL

- Ineligible for or have exhausted standard therapeutic options

- Last dose of anti-CD20 antibody therapy must have been >4 weeks before the first dose
of XmAb13676

- ECOG performance status 0-2

- Not a candidate for or refusing treatment with hematopoietic stem cell transplantation

- Fertile patients must agree to use effective contraception during and for 4 weeks
after completion of study

- Able and willing to complete the entire study

Exclusion Criteria:

- Cytotoxic chemotherapy, radiotherapy, or immunotherapy within 4 weeks, or small
molecule or investigational agents within 6 elimination half-lives of the first dose
of XmAb13676

- Prior allogeneic stem cell or solid organ transplantation

- Failure to recover from Grade 3 or 4 toxicity from previous treatment

- Multiple myeloma/plasma cell leukemia or B cell acute lymphoblastic leukemia

- Known intolerance to CD20 monoclonal antibody therapy

- History of primary central nervous system lymphoma or neoplastic central nervous
system disease

- Platelet count < 50 x 10^9/L

- Absolute neutrophil count < 1.0 x 10^9/L

- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) at screening > 3x
upper limit of normal (ULN)

- Bilirubin > 1.5 mg/dL

- Estimated creatinine clearance < 50 mL/min

- Active/uncontrolled autoimmune disease

- Clinically significant cardiac/cardiovascular disease, or pulmonary compromise

- Seizure disorder

- History of stroke with the past year

- History or evidence of a clinically unstable/uncontrollable disorder, condition or
disease other than primary malignancy, that in the opinion of the Investigator would
pose a risk to the patient safety or interfere with the study evaluation, procedures
or completion

- Evidence of any serious bacterial, viral, parasitic or systemic fungal infections
within the 30 days prior to study entry

- Positive test for human immunodeficiency virus (HIV) or hepatitis C (HCV) antibodies
(unless HCV viral load test by PCR is negative)

- Positive test for HbsAg, or positive test for HBcAb (unless serology is positive due
to recent intravenous immunoglobulin therapy). HBcAb positivity will be allowed if
HBsAb is present.

- Patient is pregnant or breast feeding, or planning to become pregnant while enrolled
in the study, up to the End of Study visit