CM336 for Active Sjogren's Syndrome Study

Inclusion Criteria: * Male or female, aged 18 to 75 years (inclusive) at the time of signing the informed consent form (ICF), and willing to comply with the study protocol requirements. * Body weight ≥ 45 kg at screening. * Voluntary compliance with the protocol requirements for permitted/prohibited concomitant therapies. * Definitive diagnosis of primary Sjögren's disease (SjD) according to the 2016 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria, and meeting all of the following requirements: 1. Seropositive for at least one SjD-related autoantibody. 2. Prior treatment with at least two systemic therapies for SjD symptoms. 3. Active disease at screening, defined as Clinical EULAR Sjögren's Syndrome Disease Activity Index(ClinESSDAI) ≥ 5. * No better therapeutic alternative available for the study participant. Exclusion Criteria: * Presence of other systemic autoimmune diseases besides primary Sjögren's disease. * Presence of other autoimmune or inflammatory diseases. * Presence of any other medical condition with clinical manifestations overlapping with primary Sjögren's disease or that may interfere with result interpretation. * Presence of active, life-threatening, or organ-threatening SjD complications at screening. * History of severe allergic reactions (as judged by the investigator), or history of hypersensitivity to monoclonal antibodies or any component of CM336. * Presence of congenital immunodeficiency, or acquired immunodeficiency not related to the participant's autoimmune disease or its medical treatment. * Positive HIV antibody, positive Treponema pallidum antibody, or history of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. * History of tuberculosis infection. * Active infection requiring intravenous anti-infective treatment within 3 months before first dose of study drug, or oral anti-infective treatment within 2 weeks before first dose of study drug. * History of disseminated herpes zoster, or ocular/Central Nervous System herpes zoster, or systemic herpes simplex or symptomatic herpes zoster infection within 3 months before first dose of study drug. * Deep vein thrombosis or pulmonary embolism within 6 months before first dose of study drug. * History of severe cardiovascular or cerebrovascular disease, including but not limited to: 1. Unstable arrhythmia, unstable angina pectoris. 2. New York Heart Association (NYHA) functional class III or IV. 3. Uncontrolled hypertension (average systolic blood pressure ≥160 mmHg or diastolic blood pressure ≥100 mmHg on two measurements despite optimal treatment). 4. Fridericia-corrected QT interval(QTcF) \>450 ms for males or \>470 ms for females * History of pulmonary arterial hypertension with WHO functional class II or above. * Presence of uncontrolled asthma or chronic obstructive pulmonary disease (COPD); uncontrolled diabetes mellitus; uncontrolled thyroid or other endocrine disorders; uncontrolled psychiatric disorders. * Presence of any of the following during screening: 1. Neutrophil count \<1×10⁹/L, platelet count \<100×10⁹/L, or hemoglobin \<80 g/L (applicable only to patients without hematologic involvement). 2. Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) \>2× upper limit of normal (ULN). 3. estimated Glomerular Filtration Rate(eGFR) \<40 mL/min/1.73m² (2021 Chronic Kidney Disease Epidemiology Collaboration formula). 4. Prothrombin time (PT) or activated partial thromboplastin time (APTT) \>1.5×Upper Limit of Normal. * Major surgery within 3 months before screening or planned during the study period (requiring hospitalization and general anesthesia, excluding diagnostic procedures). * History of malignancy within 5 years before first dose of study drug (except cured basal cell carcinoma, squamous cell carcinoma of the skin, and cervical carcinoma in situ without evidence of recurrence). * Prior treatment with any anti-B-cell maturation antigen targeted therapy (including cell therapy or antibody therapy, etc.). * Receipt of prohibited medications within the corresponding timeframes.