This is a multi-center, open-label, phase 1 study.

The purpose of this study is to evaluate the pharmacokinetics (PK) of multiple doses of Telitacicept in subjects with childhood-onset systemic lupus erythematosus (cSLE) on a background of standard of care therapy and explore the safety and efficacy of Telitacicept in patients with cSLE.

Main Inclusion Criteria:

1. Fulfills SLICC 2012 or 2019 EULAR/ACR classification criteria for SLE.
2. 5-17 years of age when signing the informed consent.
3. Suject and/or legal guardian or parent provided written informed consent.
4. SELENA SLEDAI score ≥ 8 at screening.
5. Serum autoantibodies (ANA and/or anti ds-DNA) tested positive at screening.
6. Have been on a stable standard of care for SLE for at least 30 days prior to randomization.
7. Female patients are required to be non-pregnant, non-lactating or sterile.

Main Exclusion Criteria:

1. Have received Telitacicept at any time.
2. Have received any of the following therapies within 6 months of baseline: B-cell targeted treatment, e.g., belimumab, rituximab, abatacept, other investigational biologicals.
3. Have received any of the following therapies within 90 days of baseline: anti-TNF or anti-IL-6 therapy, interleukin-1 receptor antagonist, intravenous immunoglobulin (IVIG), plasmapheresis.
4. Have received any of the following therapies within 30 days of baseline: Intravenous cyclophosphamide, non-biological investigational agents (within 30 days of baseline or 5 half-lives, whichever is longer), newly added immunosuppressive/immunomodulatory agent, anti-malarial, NSAID, high-dose prednisone or equivalent (> 1.5 mg/kg/day) or any intramuscular or intravenous steroid.
5. Have received live vaccine within 30 days of baseline.
6. Participated in an interventional clinical trial within 6 months of screening.
7. Active CNS lupus requiring treatment within 60 days of baseline, including seizure, psychosis, organic brain syndrome, cerebrovascular accident, cerebritis or CNS vasculitis.
8. Currently on kidney replacement therapy (hemodialysis, peritoneal dialysis) or in need of such therapy within 90 days of baseline.
9. eGFR<30 mL/min/1.73m2.
10. Acute severe nephritis.
11. History of vital organ transplant (e.g., heart, lung, kidney, liver) or hematopoietic stem cell/marrow transplant.
12. Significant unstable or uncontrolled acute or chronic diseases (cardiovascular, lung, hematology, gastrointestinal, liver, renal, neurologic, malignancy or infectious disease) that could be explained by causes other than SLE.

13 Have planned surgery, laboratory abnormalities, other diseases or conditions that, in the opinion of the investigator, makes the subject unsuitable for the study.

14. History of malignant neoplasm in the past 5 years. 15. Primary immune deficiency. 16. Acute or chronic infections requiring treatment. 17. HIV or HCV positive. 18. Tuberculosis. 19.HBsAg/HbcAb positive. 20.HBcAb positive. 21.History of COVID-19 within 4 weeks prior to screening. 22.History of hospitalization due to severe Covid-19 within 12 months prior to screening.

23.History of allergy to parenteral administration of contrast agents, human or murine proteins or monoclonal antibodies.

24.History of drug or alcohol abuse or dependence within 364 days prior to baseline.

25.Investigators believe that there are other factors that are not suitable for participating in the experiment.