Efficacy and Safety of Ofatumumab Retreatment and Maintenance Treatment in Patients With B-cell Chronic Lymphocytic Leukemia (CLL)

Inclusion Criteria:

* Has responded to ofatumumab treatment (CR, nPR, PR) or has had SD at least up to and including visit number 14 (24 weeks after first infusion) in the Hx-CD20-406 trial.
* Has disease progression after visit number 14 (24 weeks after first infusion) in the Hx CD20 406 trial.
* Received at least eight ofatumumab infusions.
* Has active CLL with an indication for treatment.
* Has Eastern Cooperative Oncology Group (ECOG) performance status grade 0, 1 or 2.
* Provides signed informed consent, following receipt of verbal and written information about the trial, before any trial related activity is carried out.
* If previously treated in GEN416 (this trial), the patient must have achieved CR with subsequent disease progression 24 weeks or later after the first infusion in the GEN416 trial.

Exclusion Criteria:

* The disease has transformed to more aggressive B-cell malignancies (e.g. diffuse large B-cell lymphoma, Richter's syndrome or prolymphocytic leukemia).
* Has a suspected treatment requiring malignancy other than CLL.
* Has received treatment other than ofatumumab within two weeks prior to visit 2.
* Has clinically significant cardiac disease including unstable angina, acute myocardial infarction within six months from visit 1, congestive heart failure (NYHA III IV), and arrhythmia requiring therapy, with the exception of clinically non-significant extra systoles or minor conduction abnormalities.
* Has significant concurrent, uncontrolled medical condition including, but not limited to, renal, hepatic, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral or psychiatric disease.
* Has a history of significant cerebrovascular disease.
* Is known HIV positive.
* Has positive serology for hepatitis B, defined as a positive test for HBsAg and/or positive tests for both anti-HBs and anti-HBc.
* Has known or suspected hypersensitivity to components of the IMP.
* Has received treatment with any non-marketed drug substance or experimental therapy other than ofatumumab within four weeks prior to visit 2.
* Currently participates in any other interventional clinical trial other than Hx-CD20-406.
* Known or suspected to not being able to comply with a trial protocol (e.g. due to alcoholism, drug dependency or psychiatric disorder).
* Is breast feeding (women only).
* Has a positive pregnancy test at screening (women only).
* Is not willing to use adequate contraception during the trial and one year after last dose of ofatumumab (women only). Adequate contraception is defined as hormonal birth control or intrauterine device. For patients in the US the use of double barrier method is considered adequate.