This study is to evaluate the safety of AMG 623 in subjects with systemic lupus erythematosus. All subjects will receive 4 weekly doses of study drug over a 3 week period, and then will be followed for an additional 28 weeks, for total study duration of 31 weeks.

Inclusion Criteria:

• Men and women between the ages of 18 and 65 years old
• Diagnosis of SLE
• Stable disease; defined as no change in SLE therapy within the previous 30 days. Up to 5 mg/day incremental changes of prednisone therapy is allowed during the 30 days prior to randomization
• SLE disease duration of at least 1 year, as diagnosed by a physician

Exclusion Criteria:

• Current renal disease
• Signs or symptoms of viral or bacterial infection within 30 days of enrollment
• Any disorder (including psychiatric), condition or clinically significant disease (other than a diagnosis of SLE) that would interfere the study evaluation, completion and/or procedures per the investigator's discretion
• Administration of more than 10 mg/day prednison (or equivalent) in the 30 days prior to randomization