Key Inclusion Criteria:

1. ≥18 years of age at time of informed consent.
2. Diagnosis of systemic lupus erythematosus (SLE) fulfilling the 2019 EULAR/ACR classification criteria.
3. Refractory active disease defined as inadequate response to, or relapse following, standard of care (SoC) therapy.
4. Patients on a stable dose of SoC for at least 4 weeks prior to enrollment.
5. Sufficient organ function as defined by the protocol.

Key Exclusion Criteria:

1. Active severe infection, including tuberculosis.
2. Severe hypogammaglobulinemia or IgA deficiency.
3. Active hepatitis or history of severe liver disease.
4. Severe cardiovascular diseases.
5. History of cancer within the past 5 years (with exceptions per protocol).
6. Receipt of B-cell-targeted therapies or other biologic therapies within the defined washout window prior to enrollment.
7. History of organ transplantation, bone marrow transplantation, or hematopoietic stem cell transplantation.
8. Known allergy to any active or inactive component of the study drug.