The purpose of this study is evaluating the efficacy and safety of SC antifrolumab in adult patients with moderate -to-severe SLE despite receiving standard therapy

This is a Phase 3, multicentre, multinational, randomised, double-blind, placebo-controlled study to evaluate the efficacy and safety of a subcutaneous treatment regimen of anifrolumab versus placebo in participants with moderately to severely active, autoantibody-positive systemic lupus erythematosus (SLE) while receiving standard of care (SOC) treatment. Participants must be taking either 1 or any combination of the following: oral glucocorticoids, antimalarial, and/or immunosuppressants. The study will be performed in adult participants of 18 to 70 years of age.

Approximately 360 participants receiving SOC treatment will be randomised in a 1:1 ratio to receive a fixed subcutaneous dose of anifrolumab or placebo administered once weekly via an accessorized prefilled syringe and with the primary endpoint evaluated at Week 52. Subjects who complete Week 52 may enter into open-label extension (OLE). All patients who enter the OLE Period will receive a fixed subcutaneous dose of anifrolumab for up to 52 weeks. Study intervention will be administered SC via an accessorised prefilled syringe (aPFS).

Inclusion Criteria:

1. Patients who have a diagnosis of pediatric or adult SLE according to the ACR 1997 revised criteria for ≥ 24 weeks prior to signing the ICF

2. To be eligible a patient must have SLEDAI-2K ≥ 6 points and "Clinical" SLEDAI-2K score ≥4 points at screening

3. BILAG2004 with at least 1 of the following:

   1. BILAG2004 level A disease in ≥ 1 organ system
   2. BILAG2004 level B disease in ≥ 2 organ systems

4. Physician's Global Assessment (PGA) score ≥ 1.0 on a 0 to 3 VAS at Screening

5. Antinuclear antibody, and/or Anti-dsDNA and/oranti-Smith positive at Screening,

6. Must be on stable background standard therapy with DMARD, glucocorticoids or anti-malarials alone or in combinations.

   Exclusion Criteria:

7. Active severe or unstable neuropsychiatric SLE

8. Active severe SLE-driven renal disease

9. History of any non-SLE disease that has required treatment with oral or parenteral corticosteroids for more than a total of 2 weeks within the last 24 weeks prior to signing the ICF.

10. History of recurrent infection requiring hospitalization and IV antibiotics (eg, 3 or more of the same type of infection over the previous 52 weeks).

11. Known history of a primary immunodeficiency, splenectomy, or any underlying condition that predisposes the patient to infection, or a positive result for human immunodeficiency virus (HIV) infection confirmed by central laboratory at Screening.

12. At Screening, confirmed positive test for hepatitis B serology and positive test for hepatitis C antibody

13. Any severe case herpes zoster infection at any time prior to Week 0 (Day 1),

14. Opportunistic infection requiring hospitalization or IV antimicrobial treatment within 3 years of randomization.

15. History of cancer, apart from:

    1. Squamous or basal cell carcinoma of the skin treated with documented success of curative therapy ≥ 3 months prior to Week 0 (Day 1)
    2. Cervical cancer in situ treated with apparent success with curative therapy ≥ 1 year prior to Week 0 (Day 1).

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the de-identified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

Double Blind (Participant, Care Provider and Investigator) and OLE