JY231 Injection for the Treatment of Active Systemic Lupus Erythematosus (SLE)

Inclusion Criteria:

1. Diagnosed with SLE according to the 2019 European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria or the 2012Systemic Lupus Erythematosus International Clinical Collaboration (SLICC) criteria.

2. Must have been treated with glucocorticoids in combination with immunosuppressantsand/or biologics for at least 2 months prior to screening and have been dose stablefor >2 weeks, with the disease remaining active (i.e., prior glucocorticoid +immunosuppressant or glucocorticoid + immunosuppressant + biologics, any of theabove medications alone do not qualify). Oral corticosteroids must meet thefollowing requirements: 1) Prednisone (or equivalent) ≥ 7.5 mg/day; 2) When used incombination with immunosuppressants and/or biologics, there is no minimum daily doserequirement for corticosteroids.

3. positive anti-nuclear antibody (ANA), and/or positive anti-ds-DNA antibody, and/orpositive anti-Smith antibody at screening.

4. Screening Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score >6 and 'clinical' SLEDAI-2K score ≥4.

1)Note: 'Clinical' SLEDAI-2K is a SLEDAI-2K score that excludes scores attributable to any urine or laboratory findings, including immunological indicators: 2)-Includes scores for the following clinical items: arthritis, myositis, rash, alopecia, mucosal ulcers, pleurisy, pericarditis, or vasculitis; 3)-excludes scores attributable to fever, SLE headache and organic brain syndromes.

5.British Isles Lupus Assessment Group 2004 (BILAG2004) score of at least one of the following:

1. ≥1 organ system BILAG2004 grade A disease

2. ≥2 organ system BILAG2004 Grade B disorders 6.Physician's General Assessment (PGA)score of ≥1.0 (0-3 visual analogue scale VAS) at screening.

Exclusion Criteria:

1. Combination of other autoimmune diseases requiring systemic therapy.

2. SLE patients: the presence of still uncontrolled lupus crisis within 8 weeks priorto screening, including acute progressive lupus nephritis, severe neuropsychiatriclupus, severe haemolytic anaemia, severe immune thrombocytopenia, granulocytedeficiency, severe cardiac damage, severe lupus pneumonitis, severe lupus hepatitis,severe vasculitis, etc., which were assessed as unsuitable for participation in thestudy by the investigator.

3. Pre-screening comorbidity with clinically significant central nervous system diseaseor pathological changes not due to lupus, including but not limited to: cerebralvascular accident, aneurysm, epilepsy, convulsions/convulsions, aphasia, stroke,severe brain injury, dementia, Parkinson's disease, cerebellar disease, organicbrain syndromes, or psychosis.

4. History of allogeneic bone marrow or stem cell transplantation or solid organtransplantation (e.g., kidney, lung, heart, liver) or future plans for suchtransplantation.

5. Presence of clinically significant cardiovascular dysfunction in the 12 months priorto screening, including, but not limited to: class III or IV heart failure asdefined by the New York Heart Association (NYHA), myocardial infarction, unstableangina pectoris, uncontrolled or symptomatic atrial arrhythmia, any ventriculararrhythmia.

6. Presence of significant pulmonary or cardiac manifestations such as pericarditis,pleural effusion at the time of screening, assessed by the investigator to beunsuitable for participation in this study.

7. Patients with severe asthma or chronic obstructive pulmonary disease (COPD), mild ormoderate asthma or COPD on stable therapy may be enrolled.

8. History of malignancy within 5 years prior to signing the Informed Consent Form (ICF), except adequately treated or surgically resected, non-melanoma skin cancersor carcinoma in situ (e.g., cervical cancer, bladder cancer, breast cancer) withoutresidual disease.

9. Women who are pregnant or breastfeeding.

10. History of recurrent infections requiring hospitalisation and intravenousantibiotics (e.g. 3 or more episodes of the same type of infection in the past 1year).

11. Active infection requiring systemic treatment, such as infectious pneumonia,tuberculosis, etc., within 2 weeks prior to clearance.

12. Hepatitis B surface antigen (HBsAg) positive, or Hepatitis B core antibody (HBcAb)positive and peripheral blood Hepatitis B Virus (HBV) DNA test positive; Hepatitis CVirus (HCV) antibody positive and peripheral blood HCV RNA positive; humanimmunodeficiency virus (HIV) antibody positive; syphilis antibody positive.

13. Have received a live attenuated vaccine within 4 weeks prior to clearance or plan toreceive a live attenuated vaccine during the course of the study.

14. Have received high-dose corticosteroids (prednisone ≥ 60 mg/day or equivalent)within 4 weeks prior to clearance, or are unable to taper prednisone to ≤ 10 mg/day 5 days prior to clearance.

15. Inability to taper or elute background therapy prior to clearing chemotherapy asdescribed in Table 3.

16. Receiving renal replacement therapy within 3 months prior to screening oranticipating the need for renal replacement therapy during the study.

17. History of drug or alcohol abuse within 1 year prior to screening.

18. History or evidence of suicidal thoughts within 6 months prior to screening or anysuicidal behaviour within the previous 12 months that the investigator considers tobe a significant risk of suicide.

19. Use of another study drug within 4 weeks or 5 half-lives (whichever is longer) priorto screening.

20. History of hypersensitivity or life-threatening reaction to the study drug or anycomponent or preparation of the study treatment (including clear chemotherapy). Seethe Investigator's Brochure (IB) for more information about the components of thestudy drug.

21. Any condition that, in the opinion of the investigator, may affect participation inthe study, pose a safety risk to patients, or may confound the interpretation ofstudy results.