Inclusion Criteria:
1. Age 18 to 70 years, male or female.
2. Diagnosis of primary Sjögren's Syndrome meeting the 2016 ACR/EULAR classification criteria.
3. Confirmed diagnosis of Interstitial Lung Disease by High-Resolution Computed Tomography (HRCT).
4. Stable doses of corticosteroids and immunosuppressants (e.g., mycophenolate mofetil) for at least 1 week prior to enrollment.
5. Willing and able to provide written informed consent
Exclusion Criteria:
1. Allergy: Known allergy or hypersensitivity to Telitacicept or any of its excipients.
2. Concomitant Autoimmune Diseases: Diagnosis of other systemic autoimmune diseases besides Sjögren's Syndrome, such as Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Systemic Sclerosis (SSc), Mixed Connective Tissue Disease (MCTD), or ANCA-associated vasculitis. (Note: Secondary Sjögren's Syndrome is not excluded on this basis alone, but the primary condition must be considered).
3. Laboratory Abnormalities (at Screening):
Hematology:
Hemoglobin (Hb) \< 85 g/L. White Blood Cell count (WBC) \< 3.0 × 10\^9/L. Neutrophil count (NEUT) \< 1.5 × 10\^9/L. Platelet count (PLT) \< 80 × 10\^9/L.
Liver Function:
Alanine aminotransferase (ALT) or Aspartate aminotransferase (AST) \> 2.5 × the upper limit of normal (ULN).
Total bilirubin (TBIL) \> 1.5 × ULN.
Kidney Function:
Estimated glomerular filtration rate (eGFR) \< 45 mL/min/1.73m². Or serum creatinine (Cr) \> 1.5 × ULN.
4. Significant Organ Diseases or Comorbidities:
Cardiovascular: Myocardial infarction or unstable angina within the past 6 months; uncontrolled hypertension (systolic ≥160 mmHg or diastolic ≥100 mmHg); pulmonary arterial hypertension with evidence of right heart failure.
Respiratory: Presence of other significant lung diseases (e.g., COPD, asthma, pulmonary embolism, active pulmonary tuberculosis).
Gastrointestinal: Active peptic ulcer, gastrointestinal bleeding, or pancreatitis.
Malignancy: History of any malignancy within the past 5 years (excluding successfully treated basal cell carcinoma of the skin or in-situ cervical carcinoma).
Psychiatric: Severe mental illness (e.g., severe depression, schizophrenia) or cognitive impairment that may interfere with compliance.
5. Prior/Concomitant Medications:
Use of rituximab, belimumab, TNF inhibitors (e.g., etanercept, adalimumab), or ther biologic agents (e.g., IL-6, IL-17, IL-23 inhibitors) within 3 months prior to screening.
Participation in another interventional clinical trial (receiving investigational drug or device) within 4 weeks prior to screening.
6. Active Infection:
Presence of an active infection requiring systemic anti-infective treatment at screening.
Active tuberculosis (positive T-SPOT.TB or TST with chest X-ray/CT findings suggestive of active disease).
Positive HIV antibody. Positive Hepatitis B surface antigen (HBsAg), or positive Hepatitis B core antibody (HBcAb) with detectable HBV DNA.
Positive Hepatitis C antibody with detectable HCV RNA.
7. Special Populations:
Women who are pregnant or breastfeeding. Women of childbearing potential who are unwilling or unable to use highly effective contraceptive methods from screening until at least 3 months after the last dose of study drug.
Patients planning to undergo major surgery during the study period.
8. Other Situations:
Inability to cooperate with pulmonary function tests (e.g., due to severe cognitive impairment or dyspnea).
Any condition that, in the opinion of the investigator, makes the patient unsuitable for participation in this study (e.g., poor compliance, inability to understand study procedures).
