The purpose of the OBSErve-LN study is to assess the real-world use and effectiveness of belimumab in routine practice for the treatment of adults with active LN in multiple countries of interest. This study aims to provide the first long-term (up to 5 years) assessment of renal function preservation in belimumab treated participants.

This is a Phase 4 study and will involve both prospective and retrospective data collection from participants.

Inclusion Criteria:

• Participants to provide a signed informed consent at the time of enrollment per protocol,
• Male or female aged 18 or over at initiation of belimumab,
• Participants received belimumab in any formulation (subcutaneous or intravenous) for the treatment of active LN prescribed as per local label in combination with standard immunosuppressive therapy/ies at initiation of belimumab,
• Participants initiated belimumab 6 to 24 months prior to study enrollment,
• Accessibility of medical records starting at belimumab initiation (including accessibility of medical records for the prior 12 months and confirmatory biopsy at any time prior to belimumab initiation),
• Biopsy-confirmed LN diagnosis at any time prior to belimumab initiation for treatment of LN
• Class III (focal LN) with or without Class V (membranous LN),
• Class IV (diffuse LN) with or without Class V,
• Class V.

Exclusion Criteria:

• Participants receiving renal replacement therapy (i.e., dialysis, kidney transplant, or those in end-stage kidney disease) at initiation of belimumab,
• Participant is concomitantly receiving another SLE targeted monoclonal antibody (MAb), or a MAb expected to compromise immune responses, at initiation of belimumab,
• Participants in a clinical trial during the observation period (with the exception of allowing participation in other non-interventional studies),
• Participant is pregnant at the initiation of belimumab,
• Participant with a kidney transplant at the initiation of belimumab,
• Participants will be excluded from the study if they are planning to become pregnant or are pregnant at study enrollment.

The study will include participants with lupus nephritis who initiated belimumab prescribed as per local label alongside standard therapy/ies under routine care conditions in the countries of interest.