Safety and Tolerability of XmAb®5574 in Chronic Lymphocytic Leukemia

Inclusion Criteria: * relapsed or refractory CLL/SLL * at least 18 years of age * able to receive outpatient treatment and follow-up at the treating institution * completed all CLL therapies \> 4 weeks prior to first study dose Exclusion Criteria: * previously treated with an anti-CD19 antibody therapy * undergone prior allogeneic stem cell transplantation within 6 months or having active graft versus host disease * active Richter's syndrome * designated Class III or IV by the New York Heart Association (NYHA) criteria * history of myocardial infarction or stroke within the last 6 months * active viral, bacterial, or systemic fungal infection requiring treatment * HIV or Hepatitis C positive * Hepatitis B infection