A Study to Learn About the Safety of Litifilimab (BIIB059) Injections and Whether They Can Improve Symptoms of Adult Participants Who Have Systemic Lupus Erythematosus

SRI-4 response is a composite endpoint defined by the following criteria:

• Reduction from baseline of ≥4 points in systemic lupus erythematosus disease activity index 2000 (SLEDAI-2K).
• No new organ system affected, as defined by no new organ system with British isles lupus assessment group-2004 (BILAG-2004) grade A and no more than 1 new organ system with BILAG-2004 grade B compared with Baseline.
• No worsening from baseline in lupus disease activity as defined by <0.3-point increase on 3-point Physician's Global Assessment (PGA) - Visual Analog Scale (VAS).
• No violation to protocol-specified medication rules.

The BILAG disease activity index evaluates SLE activity in number of organ systems, using a separate alphabetic score (A to E) assigned to each organ system defined as follows, BILAG A: severe disease activity; BILAG B: moderate disease activity; BILAG C: Stable mild disease; BILAG D: System previously affected but now inactive; BILAG E: System never involved. BICLA is a composite endpoint defined as BILAG-2004 improvement, defined as all BILAG-2004 grade A at Baseline improved to grade B, C, or D, and all BILAG-2004 grade B at baseline improved to grade C or D, no BILAG-2004 worsening in other BILAG-2004 organ systems such that there are no new BILAG-2004 grade A or greater than 1 new BILAG-2004 grade B, no worsening in the SLEDAI-2K total score compared with Baseline, no worsening from Baseline in lupus disease activity defined by < 0.3-point increase on 3-point PGA-VAS and no violation to protocol-specified medication rules.

Joint-50 response is 50% reduction in total active joint count from baseline. An active joint is defined as a joint with pain and signs of inflammation (e.g., tenderness, swelling or effusion). A 28-joint assessment will be performed to determine the active joint count, which is defined as the sum of tender and swollen joint counts.

No worsening of the disease is defined as no new BILAG-2004 grade A or less than 2 new BILAG-2004 grade B since the last visit during the Week 40 to Week 52.

Cutaneous Lupus Erythematosus Disease Area and Severity Index - Activity (CLASI-A) score is used to evaluate lupus skin manifestations. CLASI-A scores of 0 to 9, 10 to 20, and 21 to 70 represent disease severity of mild, moderate, and severe, respectively. CLASI-50 is 50% of improvement from baseline in CLASI-A.

Annualized flare rate will be calculated as the total number of flares divided by the flare exposure time in days, and the ratio multiplied by 365.25.

The PGA is an Investigator-administered assessment used to quantify disease activity and is measured using an anchored VAS. The PGA asks the Investigator to assess the participant's current disease activity from a score of 0 (none) to 3 (severe), with the assessment made relative to the most severe state of SLE.

The BILAG disease activity index evaluates SLE activity in number of organ systems, using a separate alphabetic score (A to E) assigned to each organ system defined as follows, BILAG A: severe disease activity; BILAG B: moderate disease activity; BILAG C: Stable mild disease; BILAG D: System previously affected but now inactive; BILAG E: System never involved. BICLA is a composite endpoint defined as BILAG-2004 improvement, defined as all BILAG-2004 grade A at Baseline improved to grade B, C, or D, and all BILAG-2004 grade B at baseline improved to grade C or D, no BILAG-2004 worsening in other BILAG-2004 organ systems such that there are no new BILAG-2004 grade A or greater than 1 new BILAG-2004 grade B, no worsening in the SLEDAI-2K total score compared with Baseline, no worsening from Baseline in lupus disease activity defined by < 0.3-point increase on 3-point PGA-VAS and no violation to protocol-specified medication rules.

SRI-4 response is a composite endpoint defined by the following criteria:

• Reduction from baseline of ≥4 points in SLEDAI-2K.
• No new organ system affected, as defined by no new organ system with British isles lupus assessment group-2004 (BILAG-2004) grade A and no more than 1 new organ system with BILAG-2004 grade B compared with Baseline.
• No worsening from baseline in lupus disease activity as defined by <0.3-point increase on 3-point PGA -VAS.
• No violation to protocol-specified medication rules.

SRI-4 response is a composite endpoint defined by the following criteria:

• Reduction from baseline of ≥4 points in SLEDAI-2K.
• No new organ system affected, as defined by no new organ system with British isles lupus assessment group-2004 (BILAG-2004) grade A and no more than 1 new organ system with BILAG-2004 grade B compared with Baseline.
• No worsening from baseline in lupus disease activity as defined by <0.3-point increase on 3-point PGA -VAS.
• No violation to protocol-specified medication rules. The SRI-5 and SRI-6 are computed with a minimal five-point or six-point improvement in SLEDAI-2K being required, respectively.

Joint-50 response is 50% reduction in total active joint count from baseline. An active joint is defined as a joint with pain and signs of inflammation (e.g., tenderness, swelling or effusion). A 28-joint assessment will be performed to determine the active joint count, which is defined as the sum of tender and swollen joint counts.

Cutaneous Lupus Erythematosus Disease Area and Severity Index - Activity (CLASI-A) score is used to evaluate lupus skin manifestations. CLASI-A scores of 0 to 9, 10 to 20, and 21 to 70 represent disease severity of mild, moderate, and severe, respectively. CLASI-20, -50, -70 and -90 represent 20%, 50%, 70% or 90% improvement from baseline in CLASI-A score, respectively.

Cutaneous Lupus Erythematosus Disease Area and Severity Index - Activity (CLASI-A) score is used to evaluate lupus skin manifestations. CLASI-A scores of 0 to 9, 10 to 20, and 21 to 70 represent disease severity of mild, moderate, and severe, respectively. CLASI-A ≤1 represent the absolute score ≤1 in CLASI-A by visit.

A SFI severe flare is defined as any of the following:

• Change in SLEDAI instrument score to > 12.
• New or worse: central nervous system SLE; vasculitis; nephritis; myositis; platelets < 60,000/mL; or hemolytic anemia with hemoglobin < 7 g/dL or decrease in hemoglobin >3 g/dL AND requiring: doubling prednisone dose, increase to > 0.5 mg/kg/day or hospitalization.
• Increase in prednisone dose to > 0.5 mg/kg/day.
• New requirement for cyclophosphamide, azathioprine, methotrexate, or mycophenolate for SLE activity.
• Hospitalization for SLE activity.
• Increase in PGA score to > 2.5.

BILAG-2004 severe flare is defined as an A score for items recorded as worse or new. BILAG-2004 is evaluated by scoring each item of a list of signs and symptoms given as 4 = new; 3 = worse; 2 = same; 1 = improving; 0 = not present; and ND = not done.

SFI severe flare is defined any of the following: change in SLEDAI instrument score to >12; or new or worse: central nervous system SLE; vasculitis; nephritis; myositis; platelets <60,000 per milliliter (/mL); or hemolytic anemia with hemoglobin <7 grams per deciliter (g/dL) or decrease in hemoglobin >3 g/dL and requiring: doubling prednisone dose; or increase to >0.5 milligrams per kilogram per day (mg/kg/day) or hospitalization; or increase in prednisone dose to >0.5 mg/kg/day; or new requirement for cyclophosphamide, azathioprine, methotrexate, or mycophenolate for SLE activity; or hospitalization for SLE activity; or increase in PGA score to >2.5.

LLDAS is a composite endpoint defined as:

• SLEDAI-2K score ≤ 4, with no activity in a major organ system (renal, central nervous system, cardiopulmonary, vasculitis, fever); and
• No new features of lupus disease activity compared with the previous assessment; and
• Safety of Estrogens in Lupus Erythematosus National Assessment - Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI) PGA ≤ 1; and
• Current prednisone (or equivalent) dose ≤ 7.5 mg/day; and
• Standard maintenance doses of immunosuppressive drugs and approved biological agents.

LLDAS is a composite endpoint defined as:

• SLEDAI-2K score ≤ 4, with no activity in a major organ system (renal, central nervous system, cardiopulmonary, vasculitis, fever); and
• No new features of lupus disease activity compared with the previous assessment; and
• SELENA-SLEDAI PGA ≤ 1; and
• Current prednisone (or equivalent) dose ≤ 7.5 mg/day; and
• Standard maintenance doses of immunosuppressive drugs and approved biological agents.

LLDAS is a composite endpoint defined as:

• SLEDAI-2K score ≤ 4, with no activity in a major organ system (renal, central nervous system, cardiopulmonary, vasculitis, fever); and
• No new features of lupus disease activity compared with the previous assessment; and
• SELENA-SLEDAI PGA ≤ 1; and
• Current prednisone (or equivalent) dose ≤ 7.5 mg/day; and
• Standard maintenance doses of immunosuppressive drugs and approved biological agents.

The SLEDAI-2K is a reliable, valid, simple, 1-page activity index that measures disease activity and records features of active lupus as present or not. It uses a weighted checklist to assign a numeric score based on the presence or absence of 24 symptoms at the time of assessment or during the previous 28 days. Each symptom present is assigned between 1 and 8 points based on its usual clinical importance, yielding a total score that ranges from 0 points (no symptoms) to 105 points (presence of all defined symptoms), where higher scores represent increased disease activity. SLEDAI-2K improvement is defined as a reduction from Baseline of ≥ 4 points in SLEDAI-2K score.

The BILAG disease activity index evaluates SLE activity in number of organ systems, using a separate alphabetic score (A to E) assigned to each organ system defined as follows, BILAG A: severe disease activity; BILAG B: moderate disease activity; BILAG C: Stable mild disease; BILAG D: System previously affected but now inactive; BILAG E: System never involved. No worsening of BILAG is defined as no new organ system affected, as defined by no new organ system with BILAG-2004 grade A and no more than 1 new organ system with BILAG-2004 grade B compared with Baseline.

The PGA is an investigator-administered assessment used to quantify disease activity and is measured using an anchored VAS. PGA asks the investigator to assess the participant's current disease activity from a score of 0 (none) to 3 (severe), with the assessment made relative to the most severe state of SLE. No worsening from Baseline in lupus disease activity is defined by < 0.3-point increase on 3-point PGA-VAS. No worsening from Baseline in lupus disease activity as defined by < 0.3-point increase on 3-point PGA-VAS.

The SLEDAI-2K uses a weighted checklist to assign a numeric score based on the presence or absence of 24 symptoms at the time of assessment or during the previous 28 (+2) days. Each symptom present is assigned between 1 and 8 points based on its usual clinical importance, yielding a total score that ranges from 0 points (no symptoms present) to 105 points (presence of all defined symptoms). No worsening of SLEDAI-2K is defined as no increase in the SLEDAI-2K total score from baseline.

The BILAG disease activity index evaluates SLE activity in number of organ systems, using a separate alphabetic score (A to E) assigned to each organ system defined as follows, BILAG A: severe disease activity; BILAG B: moderate disease activity; BILAG C: Stable mild disease; BILAG D: System previously affected but now inactive; BILAG E: System never involved. BILAG-2004 improvement, defined as all BILAG-2004 grade A at Baseline improved to grade B, C, or D, and all BILAG-2004 grade B at Baseline improved to grade C or D. BILAG-2004 improvement, defined as all BILAG-2004 grade A at Baseline improved to grade B, C, or D, and all BILAG-2004 grade B at Baseline improved to grade C or D. BILAG-2004 improvement, defined as all BILAG-2004 grade A at Baseline improved to grade B, C, or D, and all BILAG-2004 grade B at Baseline improved to grade C or D.

No worsening of the disease is defined as no new BILAG-2004 grade A or less than 2 new BILAG-2004 grade B since the last visit between Week 40 and Week 52.

The LupusQoL is a participant-reported, lupus-specific, Health-Related Quality-of-Life Questionnaire (HRQoL) consisting of 34 items grouped in 8 domains: physical health, pain, planning, intimate relationships, burden to others, emotional health, body image and fatigue. Participants indicate their responses on a 5-point Likert response format, where 4 = never, 3 = occasionally, 2 = a good bit of the time, 1 = most of the time, and 0 = all the time. A LupusQoL score for each domain will be reported on a 0 to 100 scale, with greater values indicating better HRQoL.

The SF-36 determines participant's overall quality of life by assessing 1) limitations in physical functioning due to health problems; 2) limitations in usual role because of physical health problems; 3) bodily pain; 4) general health perceptions; 5) vitality; 6) limitations in social functioning because of physical or emotional problems; 7) limitations in usual role due to emotional problems; and 8) general mental health. Items 1-4 primarily contribute to the physical component summary (PCS) score of the SF-36. Items 5-8 primarily contribute to the mental component summary (MCS) score of the SF-36. Scores on each item are summed and averaged (range: 0=worst to 100=best). Increases from baseline indicate improvement.

The FACIT-Fatigue is a participant-administered HRQoL questionnaire that evaluates participant's fatigue in the 5 broad categories: physical well-being, social/family well-being, emotional well-being, functional well-being and additional concerns. The level of fatigue is measured by questions assessed on a 5-point scale (0 = not at all; 1 = a little bit; 2 = somewhat; 3 = quite a bit; 4 = very much). The responses for each item are added to obtain a total score which ranges from 0 to 52, with a higher score indicating less fatigue.

The PHQ-9 is a participant-administered HRQoL questionnaire to screen for the presence and severity of depression. The PHQ-9 is a participant-reported outcome (PRO) that is used to measure depression in adults. It contains 9 questions. The PHQ-9 yields an overall severity score that can range from 0 to 27 with the following severity scores: 0-4 = none; 5-9 = mild; 10-14 = moderate; 15-19 = moderate-to-severe; and 20-27 = severe.

WPAI questionnaire is a validated instrument to measure impairments in work and activities. The WPAI yields four types of scores: 1. Absenteeism (work time missed) 2. Presenteesism (impairment at work / reduced on-the-job effectiveness) 3. Work productivity loss (overall work impairment / absenteeism plus presenteeism) 4. Activity Impairment. Each score ranges from 0 to 100, with higher numbers indicating greater impairment and less productivity

An adverse event (AE) is any untoward medical occurrence in a patient or clinical investigation participant administered a pharmaceutical product and that does not necessarily have a causal relationship with this treatment. A TEAE is an AE that started or worsened in severity after the first dose of study treatment through 28 days after the last dose of study treatment or end of study (EOS) date, whichever comes earlier. An SAE is any untoward medical occurrence that at any dose results in death (a life-threatening event), in the view of the investigator, places the participant at immediate risk of death, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, results in a birth defect, or is a medically important event.