Study of YK012 in Moderate to Severe Systemic Lupus Erythematosus

Inclusion Criteria: * Aged 18 to 75 years (inclusive) at screening, regardless of sex * Meet the 2019 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for SLE, with a confirmed SLE diagnosis for at least 24 weeks at screening * Positive for anti-dsDNA antibody and/or antinuclear antibody (ANA) and/or anti-Smith antibody at screening, as determined using the local laboratory's reference ranges at the study site * Medium to high disease activity at screening, defined as: Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score ≥7 * Receiving stable background therapy at screening * Capable of understanding and voluntarily participating in this clinical trial, having provided written informed consent, and able to comply with scheduled visits, treatments, examinations, and other study procedures. Exclusion Criteria: * Known allergy to monoclonal antibodies or exogenous human immunoglobulins, or hypersensitivity to the investigational drug or any of its components * Received any anti-CD19/CD20 therapy or any B-cell depleting agents within 6 months prior to enrollment, or B-cell stimulatory factor inhibitors within 3 months or 5 half-lives prior to enrollment * Received TNF inhibitors, interleukin receptor blockers, other small molecules or biologics within 3 months or 5 half-lives prior to enrollment * Received intravenous immunoglobulins or plasmapheresis within 3 months prior to enrollment * Used traditional Chinese medicines/herbal preparations for SLE treatment containing within 2 weeks prior to enrollment * Received live or attenuated vaccines within 1 month prior to enrollment * Has other autoimmune diseases, inflammatory joint diseases, or skin disorders (other than SLE) that may interfere with disease activity assessment * History of malignancy within 5 years before screening, except for cured cases with no recurrence for at least 5 years, such as basal cell or squamous cell skin cancer, cervical carcinoma in situ, ductal carcinoma in situ of breast, or papillary thyroid cancer * Clinically significant cardiovascular/cerebrovascular diseases within 6 months prior to screening * Presence of QTcF interval prolongation on electrocardiogram (ECG) * Presence of poorly controlled hypertension at screening * History of non-SLE conditions requiring oral/intravenous/intramuscular/subcutaneous corticosteroid therapy (\>2 weeks) within 6 months prior to enrollment * Active tuberculosis at screening or untreated latent tuberculosis * History of solid organ or bone marrow transplantation * Presence of active infections * Lupus nephritis requiring protocol-prohibited medications as assessed by the investigator * Uncontrolled lupus crisis within 8 weeks prior to screening * History of central nervous system (CNS) disorders * Presence of clinically unstable or uncontrolled medical conditions at screening * Presence of clinically significant abnormal laboratory test results * Presence of active viral infections (e.g., hepatitis B, hepatitis C, HIV, or active syphilis) * Had major surgery within 4 weeks prior to enrollment or planned during study; * Participation in other interventional clinical trials within 4 weeks prior to enrollment * Pregnant or lactating women, or individuals with pregnancy plans during the study and within a specified period after treatment who are unwilling to use effective contraception * Other conditions deemed by investigators to preclude study participation.