Efficacy and Safety Evaluation of Litifilimab in Adults with Active Systemic Lupus Erythematosus on Nonbiologic Standard of Care: A Phase 3 Randomized Controlled Trial

The primary objective of this study is to demonstrate the **efficacy** of litifilimab compared with placebo in participants with active systemic lupus erythematosus (SLE), who are receiving background lupus standard of care (SOC) therapy in reducing disease activity. This is clinically relevant as it aims to provide evidence for a potential new treatment option that could improve disease management and patient outcomes in SLE, a chronic autoimmune condition with significant morbidity.

Secondary objectives include:

• Demonstrating early onset of efficacy of litifilimab compared with placebo in reducing disease activity.
• Demonstrating organ-specific efficacy in reducing joint and skin disease activity.
• Evaluating the effect of litifilimab in reducing oral corticosteroid (OCS) use.
• Assessing the efficacy in reducing the occurrence of flare-ups up to Week 52.
• Evaluating additional efficacy with supplementary disease activity measures.
• Assessing the difference between litifilimab and placebo on participant-reported health-related quality of life (HRQoL), symptoms, and impacts of SLE.
• Evaluating the safety and tolerability of litifilimab.
• Evaluating the immunogenicity of litifilimab.

The clinical trial involves a total of **402 participants** diagnosed with **systemic lupus erythematosus** (SLE). The study population includes both male and female subjects, with an age range encompassing adults and adolescents. Participants were selected based on their active SLE status and are required to be on a stable regimen of standard of care (SOC) therapy for lupus, which may include antimalarials, oral corticosteroids (OCS), and/or a single immunosuppressant. The trial population includes individuals who meet the 2019 European League Against Rheumatism (EULAR) / American College of Rheumatology (ACR) classification criteria for SLE, with specific disease activity scores and organ system involvement as per the BILAG-2004 grading system. The study also considers vulnerable populations, ensuring a comprehensive assessment of the treatment's efficacy across diverse demographic groups.

The clinical trial is designed to evaluate the efficacy and safety of **litifilimab** (BIIB059) in adult participants with active **systemic lupus erythematosus** (SLE) who are receiving background nonbiologic lupus standard of care therapy. This is a multicenter, randomized, double-blind, placebo-controlled, Phase 3 study. The trial aims to demonstrate the efficacy of litifilimab compared to placebo in reducing disease activity. The study is expected to last until September 2025, with participant recruitment having commenced in May 2021.

Participants will be randomly assigned to receive either litifilimab or a placebo, both administered via subcutaneous injection. The placebo is a sterile liquid for injection with a formulation identical to that of the BIIB059 drug product minus the active ingredient. The trial will include several key visits: an initial screening visit to confirm eligibility based on criteria such as a diagnosis of SLE at least 24 weeks prior and specific disease activity scores, followed by regular follow-up visits to monitor progress and assess endpoints. The primary endpoint is the percentage of participants achieving a Systemic Lupus Erythematosus Responder Index of 4 (SRI-4) response at Week 52. Secondary endpoints include various measures of disease activity and quality of life improvements at different time points throughout the study.

Participants are expected to be involved in the study for a maximum of 52 weeks, with conditions for early termination including significant adverse events or withdrawal of consent. The study will also monitor the number of participants with treatment-emergent adverse events and the development of antibodies to litifilimab. The trial's design ensures that neither the participants nor the investigators know which treatment is being administered, maintaining the double-blind nature of the study. This methodology is crucial for minimizing bias and ensuring the reliability of the results.

The clinical trial involves the administration of **litifilimab**, marketed under the product name BIIB059, which is a recombinant monoclonal antibody. The pharmaceutical form of BIIB059 is an injection, specifically designed for **subcutaneous use**. The active substance, litifilimab, is a protein of other origin, developed by Biogen Idec Research Limited. The dosing regimen for BIIB059 is determined by the study protocol, with a maximum treatment period of 50 weeks. The exact dosage and frequency of administration are not specified in the provided data. Participant compliance with the dosing schedule will be monitored throughout the trial to ensure adherence to the protocol.

In addition to the experimental treatment, a placebo is utilized in this study. The placebo is a sterile liquid for injection, formulated to be identical to the BIIB059 drug product, minus the active ingredient. This ensures that the placebo mimics the physical and sensory characteristics of the experimental medication, allowing for a double-blind study design. The placebo is administered via the same route as BIIB059, which is subcutaneous injection. The use of a placebo is critical in evaluating the efficacy and safety of litifilimab by providing a comparator against which the effects of the active drug can be measured.

Participants in the trial will also continue to receive background nonbiologic lupus standard-of-care (SOC) therapy. This standard-of-care treatment is not specified in the provided data but typically includes medications such as corticosteroids, antimalarials, and immunosuppressants, which are commonly used in the management of **systemic lupus erythematosus** (SLE). The combination of SOC therapy with the investigational drug or placebo is intended to reflect real-world treatment scenarios and to assess the added benefit of litifilimab in reducing disease activity in patients with active SLE.

The efficacy of litifilimab (BIIB059) in the treatment of active systemic lupus erythematosus (SLE) will be assessed through a series of predefined endpoints. The primary endpoint is the percentage of participants who achieve a Systemic Lupus Erythematosus Responder Index of 4 (SRI-4) response at Week 52. Secondary endpoints include the percentage of participants achieving an SRI-4 response at Week 24, the percentage of participants with at least 4 swollen and tender joints at baseline who achieve a Joint-50 response at Week 52, and the percentage of participants with baseline oral corticosteroid (OCS) ≥10 mg/day who have an OCS reduction to ≤7.5 mg/day at Week 40, sustained through Week 52 without disease worsening.

Additional secondary endpoints involve the percentage of participants with a Cutaneous Lupus Erythematosus Disease Area and Severity Index Activity (CLASI-A) score ≥10 at baseline who achieve a 50% improvement at Week 16, annualized flare rate through Week 52, and changes from baseline in various health-related quality of life and functional assessment scores. The efficacy parameters will be measured and collected at specified timepoints, including Weeks 16, 24, 40, and 52, using validated scales and patient-reported outcomes. The analysis will focus on the time to onset of SRI-4 response sustained through Week 52, the percentage of participants achieving various response levels by visit, and the proportion of participants achieving low disease activity state (LLDAS) at Week 52.