A Trial of the Safety of Escalating Doses of PRO131921 in Patients With Relapsed or Refractory Chronic Lymphocytic Leukemia

Inclusion Criteria: * Documented history of histologically confirmed B-cell CLL * Relapsed or refractory CLL with history of prior treatment with purine nucleoside analogue-containing regimen * Eligible for treatment of their CLL based on criteria adapted from the National Cancer Institute-Working Group (NCI-WG) Response Criteria for CLL * For patients of reproductive potential (males and females), use of a reliable means of contraception * For females of childbearing potential, a negative serum pregnancy test Exclusion Criteria: * Prior use of anti-CD20 monoclonal antibody therapy (other than rituximab) * Prior use of any non-CD20 targeted monoclonal antibody therapy within 6 months of enrollment * Current or recent CLL treatment * History of severe allergic or anaphylactic reactions to human, humanized, chimeric, or murine monoclonal antibodies * Evidence of acute/active autoimmune hemolytic anemia or other autoimmune complications of CLL * Use of hematopoietic growth factors or RBC and/or platelet transfusions * Evidence of significant uncontrolled concomitant diseases, such as cardiovascular disease, nervous system, pulmonary, renal, hepatic, endocrine, or gastrointestinal disorders * Evidence of myelodysplasia or myelodysplastic changes on bone marrow examination * History of cancer other than CLL) * Known active bacterial, viral, fungal, mycobacterial, or other infection or any major episode of infection requiring hospitalization or treatment with IV antibiotics or oral antibiotics * A major episode of infection requiring hospitalization or treatment with IV antimicrobials within 4 weeks of screening or oral antimicrobials within 2 weeks of screening * Positive hepatitis B or C serology * Positive human immunodeficiency virus (HIV) serology * Active cytomegalovirus (CMV) disease by antigen or polymerase chain reaction testing * Pregnancy or lactation * CNS leukemia * Recent major surgery, other than diagnostic surgery