The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and efficacy of CM336 in adult participants with active primary Sjogren's Syndrome.

An open-label, multicenter, multiple ascending dose study evaluating safety, tolerability,PK/ADA profile and efficacy of CM336 administered subcutaneously in active primary Sjogren's Syndrome.

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.