JH013 Injection in Patients With Primary Sjögren's Syndrome

Inclusion Criteria: * Patients with primary Sjögren's syndrome (pSS) who meet the 2016 ACR/EULAR classification criteria for primary Sjögren's syndrome; 18 to 65 years of age (inclusive) for Part A and 18 to 75 years of age (inclusive) for Part B; * EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) score ≥6 during the Screening Period; * EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI) score ≥5 during the Screening Period; * Elevated serological markers during the Screening Period, defined as an antinuclear antibody (ANA) titer ≥1:160 and positive rheumatoid factor (RF), or positive anti-SSA antibody (with or without anti-SSB antibody); * Stimulated whole salivary flow rate ≥0.05 mL/min or unstimulated whole salivary flow rate ≥0.01 mL/min during the Screening Period; * Women of childbearing potential must have a negative serum β-human chorionic gonadotropin (β-hCG) pregnancy test within 72 hours prior to dosing. Postmenopausal women (defined as amenorrhea for at least 12 months) and women with a known history of hysterectomy, bilateral oophorectomy, bilateral salpingectomy, or tubal ligation are considered not to be of childbearing potential and are not required to undergo a pregnancy test; * Participants must understand and comply with the study procedures, voluntarily participate in the study, and provide written informed consent. Exclusion Criteria: * Secondary Sjögren's syndrome, defined as Sjögren's syndrome overlapping with another autoimmune disease or systemic inflammatory disease (e.g., rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, or idiopathic inflammatory myopathy); * Use of another investigational medicinal product within 5 half-lives or 30 days prior to Screening, whichever is longer, or within a period during which the expected pharmacodynamic effect has not returned to baseline, whichever is longer; or for a longer period if required for the investigational medicinal product; * Use of B-cell-depleting therapies within 24 weeks prior to Screening (e.g., VAY736, rituximab, other anti-CD20 monoclonal antibodies, anti-CD22 monoclonal antibodies, or anti-CD52 monoclonal antibodies), or B-cell counts have not recovered to the lower limit of normal or baseline following prior B-cell-depleting therapy, whichever is lower; * Receipt of any of the following prior treatments before Screening: 1. Within 24 weeks: iscalimab (anti-CD40 monoclonal antibody), belimumab (anti-BAFF monoclonal antibody), telitacicept, abatacept (CTLA4-Fc-Ig), anti-tumor necrosis factor-alpha (TNF-α) biologics, intravenous or subcutaneous immunoglobulin (IVIG/SCIG), or plasma exchange; 2. Within 12 weeks: intravenous or oral cyclophosphamide, mycophenolate mofetil (MMF), intravenous or oral cyclosporine A, or any other immunomodulatory/immunosuppressive medication (e.g., JAK inhibitors or other kinase inhibitors); * Prednisone dose \>10 mg/day, or any adjustment to the prednisone dose within 2 weeks prior to Screening; * Currently receiving azathioprine, or use of azathioprine within 3 months prior to Screening. Patients who have been receiving a stable dose of hydroxychloroquine or methotrexate for ≥3 months prior to Screening and who will maintain the same dose throughout the study may be eligible; * Use of traditional Chinese medicines (TCM) or proprietary Chinese medicines for the treatment of primary Sjögren's syndrome within 4 weeks prior to Screening, including Tripterygium wilfordii polyglycosides and total glucosides of paeony; * Use of sialagogues within 7 days prior to Screening, such as anethole trithione or pilocarpine; * Severe systemic involvement of Sjögren's syndrome, as assessed by the Investigator, including but not limited to: 1. Severe vasculitis involving the kidneys, gastrointestinal system, heart, lungs, or central nervous system (excluding cutaneous vasculitis); 2. Active central or peripheral nervous system involvement requiring high-dose glucocorticoid therapy; 3. Severe renal involvement, such as estimated glomerular filtration rate (eGFR) \<60 mL/min, serum creatinine \>2 mg/dL, or urinary protein \>3 g/day; 4. Severe pulmonary involvement, such as dyspnea at rest, or pulmonary function test results showing forced vital capacity (FVC) \<60% or diffusing capacity of the lung for carbon monoxide (DLCO) \<40%; 5. Myositis requiring high-dose glucocorticoid therapy; 6. Lymphoma; * Abnormal laboratory parameters: 1. Hematology: hemoglobin \<8.0 g/dL, white blood cell (WBC) count \<2.0 × 10⁹/L, platelet count \<75 × 10⁹/L, or absolute neutrophil count (ANC) \<1.0 × 10⁹/L; 2. Clinical chemistry: total bilirubin \>1.5 × ULN, or alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \>3 × ULN; * Active viral, bacterial, or other infection requiring systemic treatment, or a clinically significant history of recurrent infections; * Known hypersensitivity to any component of JH013 or its excipients, including histidine, dilute hydrochloric acid, arginine hydrochloride, or sucrose; * History of organ, hematopoietic stem cell, or bone marrow transplantation; * Requirement for regular use of medications known to cause dry mouth or dry eyes, including but not limited to beta-blockers, antihistamines, pseudoephedrine, selective antidepressants, anticholinergic agents, sedatives, antipsychotics, antiparkinsonian medications, and diuretics; * Use of topical ophthalmic prescription medications, excluding artificial tears, gels, and lubricants, with no stable dose for at least 90 days prior to Screening, or any anticipated change in the treatment regimen during the study; * Receipt of a live or live-attenuated vaccine within 30 days prior to Screening; * History of malignancy in any organ system within the past 5 years, whether treated or untreated and regardless of evidence of local recurrence or metastasis, except for locally treated basal cell carcinoma of the skin, carcinoma in situ of the cervix, or Sjögren's syndrome-associated lymphoma; * History of sarcoidosis; * Any condition considered by the Investigator to be unsuitable for participation in the study, including surgery, medical conditions (e.g., inadequately controlled hypertension, heart failure, or diabetes), psychiatric disorders, or other conditions; * Positive test results for human immunodeficiency virus (HIV) antibodies; positive hepatitis B virus (HBV) surface antigen (HBsAg), or positive HBV core antibody (anti-HBc) with positive HBV DNA; positive hepatitis C virus (HCV) antibody; or positive syphilis serology; * History of tuberculosis (TB) or a positive interferon-gamma release assay (IGRA) at Screening. An IGRA result obtained within 3 months prior to Screening is acceptable; * Known history of poor medication adherence, or inability or unwillingness to complete the study questionnaires; * Pregnancy or breastfeeding; planned pregnancy; or women of childbearing potential or sexually active men who are unwilling to use reliable contraception during the study and for 3 months after the last dose of study drug, or who intend to donate sperm during the same period.