A Study to Evaluate the Efficacy and Safety of Dapirolizumab Pegol in Study Participants With Moderately to Severely Active Systemic Lupus Erythematosus

Inclusion Criteria:

1. Rescreening will be allowed once during the study in case there is new evidence for an inclusion criterion that was not fulfilled at the first screening or in case a study participant no longer meets an exclusion criterion or screening period exceeded the maximum duration due to delays in screening processes
2. Study participant must be ≥16 years of age, unless restricted by local regulation, at the time of signing the Informed Consent form (ICF)

Study participants who have moderate to severe disease activity due to either persisting active SLE or due to an acute worsening of SLE in the scope of frequent flaring/relapsing-remitting systemic lupus erythematosus (SLE) despite stable standard of care (SOC) medication defined as:

a. Diagnosed with SLE at least 24 weeks before the Screening Visit (Visit 1) study entry by a qualified physician b. Classified by 2019 SLE European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for SLE c. With serological evidence for SLE at Screening as demonstrated by at least 1 of the following: i) Evidence for anti-dsDNA (in central laboratory at Screening) ii) Either complement C3 < lower limit of normal (LLN) OR complement C4

1. Anti-Smith (anti-Sm) antibodies (central laboratory) 2. Anti-Sjögren's syndrome antibody A (Anti-SSA) (Ro)/Anti-Sjögren's syndrome antibody B (anti-SSB) (La) autoantibodies (central laboratory) 3. Historic evidence for anti-dsDNA antibodies

d. Moderately to severely active defined as

1. British Isles Lupus Assessment Group Disease Activity Index 2004 (BILAG 2004) Grade B in ≥2 organ systems and/or a BILAG 2004 Grade A in ≥1 organ systems at Screening and Baseline Visit AND
2. Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) ≥6 at Screening Visit AND

SLEDAI-2K without labs ≥4 at Baseline Visit

e. Receiving the following SOC medication at stable dose:

Antimalarial treatment in combination with corticosteroids and/or immunosuppressants or as stand-alone treatment if justified OR Treatment with corticosteroids and/or immunosuppressants if anti-malarial treatment is not possible

Exclusion Criteria:

1. Study participant has any medical or psychiatric condition (including conditions due to neuropsychiatric systemic lupus erythematosus (SLE)) that, in the opinion of the Investigator, could jeopardize or would compromise the study participant's ability to participate in this study. This includes study participants with a life threatening condition
2. Study participant has a history of an anaphylactic reaction to parenteral administration of contrast agents, human or murine proteins, or monoclonal antibodies
3. Study participant has a history of malignancy, except the following treated cancers: cervical carcinoma in situ, basal cell carcinoma, or dermatological squamous cell carcinoma
4. Study participant has an increased risk for thromboembolic events due to an ongoing heart disease or due to a medical device, including but not limited to vascular graft, valvular heart disease, atrial fibrillation, or a heart rhythm disorder
5. Study participant has evidence of human immunodeficiency virus (HIV) infection, agammaglobulinemias, T-cell deficiencies, or human T-cell lymphotropic virus-1 infection
6. Study participant had a reactivated latent infection (example, cytomegalovirus, herpes simplex virus, or herpes zoster infection) or opportunistic infection (including but not limited to, pneumocystis, cytomegalovirus, or severe herpes zoster infection) within 12 weeks prior to the first study medication infusion (Visit 2), or is currently receiving suppressive therapy for an opportunistic infection
7. Study participants who have received live/live attenuated vaccines within 6 weeks prior to the first study medication infusion
8. Study participant has clinically significant active or latent infection
9. Study participant has a mixed connective tissue disease, scleroderma, and/or overlap syndrome of these diseases with SLE
10. Study participant takes any protocol defined prohibited concomitant medication
11. Study participant has previously been randomized within this study or participant has previously been assigned to treatment with dapirolizumab pegol (DZP) in a study evaluating DZP
12. Study participant has participated in another study of an IMP within the previous 12 weeks or 5 half-lives of the investigational medicinal product (IMP) whatever is longer or is currently participating in another study of an IMP
13. Study participant has chronic kidney failure stage 4, manifested by estimated glomerular filtration rate <30mL/min/1.73m^2, or serum creatinine >2.5 mg/dL, or participant has proteinuria >3 g/day, or protein: creatinine ratio >340 mg/mmol at the Screening Visit