Ofatumumab is a fully-human monoclonal antibody that exhibits high binding affinity to an antigen on the surface of B lymphocytes. Antigen engagement by ofatumumab results in maximal B-cell killing through complement-dependent cytotoxicity and antigen-dependent cellular cytotoxicity in both antigen high- and low-expressing cells. Recent research has shown that ofatumumab-dependent B-cell depletion provides clinical benefit to subjects with CD20-positive cancers such as chronic lymphocytic leukemia (CLL). The purpose of the current study is to assess the impact of ofatumumab on electrocardiographic parameters with particular focus on cardiac repolarization (QTc interval duration) in subjects with refractory CLL. Subjects enrolled in this open-label, single-arm trial will receive ofatumumab at the highest clinical dose (2000 mg) studied or planned for study. Ofatumumab will be administered as eight weekly intravenous (IV) infusions followed by four monthly infusions, beginning in Week 13, across a 25-week treatment period. Cardiovascular effects will be evaluated during treatment through routine 12-lead electrocardiographic (ECG) monitoring. The pharmacokinetic relationship between plasma concentration of ofatumumab and its effect on QTc interval duration will be examined. Specifically, ECG assessments will be collected in triplicate at baseline, at the time of maximum ofatumumab concentrations periodically on-therapy, and at the end of treatment. After completion of the final ofatumumab infusion, subjects will continue to be followed for safety and efficacy for six months relative to the last ofatumumab dose.