The study is an open-labeled extension study to continue to assess the safety and tolerability of Epratuzumab in moderate to severe SLE subjects who have previously participated in SL0026 [NCT01449071] phase I/II trial.

Inclusion Criteria:

• Subject has completed the double-blind study SL0026 [NCT01449071] or terminated prematurely at Week 8 or later in SL0026 [NCT01449071] due to lack of efficacy
• Women of childbearing potential must agree to use an acceptable method of birth control/Written Informed Consent

Exclusion Criteria:

• Subjects with active, severe SLE disease activity which involves the renal system and active, severe, neuropsychiatric SLE, defined as any neuropsychiatric element scoring British Isles Lupus Assessment Group Index (BILAG) level A
• Subjects with concurrent relevant medical conditions like defined chronic infections or high risk of new significant infections
• Substance abuse or dependence
• Significant hematologic abnormalities
• History of malignant cancer
• Subjects with any other condition which, in the investigator's judgment, would make the subject unsuitable for inclusion