Inclusion Criteria:
1. Participants must be between 18 and 70 years of age, inclusive, at the time of signing the Informed Consent Form (ICF), with no restriction on gender.
2. Participants must have a history of chronic spontaneous urticaria (CSU) with a disease duration of at least 6 months prior to screening.
3. Participants must be diagnosed with H1-antihistamine-inadequately-controlled CSU at screening, defined as: having had persistent symptoms of pruritus and wheals for ≥6 weeks prior to screening, despite regular use of second-generation H1-antihistamines during that period.
4. At randomization, the UAS7 score must be ≥16 (range: 0-42) and the HSS7 score ≥ 8 (range: 0-21).
5. Participants must have been on a stable dose of the specified second-generation H1-antihistamine for at least 3 days prior to the first UAS score at screening.
6. Participants must be willing and able to complete logbook entries as required during the study and must have no missing daily UAS scores during the 7 days before randomization.
7. Participants must voluntarily sign the Informed Consent Form (ICF) before any study-related procedures, be able to communicate effectively with the investigator, and be willing to strictly adhere to the requirements of the study protocol.
8. Female participants of childbearing potential or male participants with a female partner of childbearing potential must agree to avoid donating sperm or ova and must agree to take highly effective contraceptive measures from the time of signing the ICF until 3 months after the last dose.
Exclusion Criteria:
1. Any skin disease that could interfere with study assessment (e.g., chronic inducible urticaria, urticarial vasculitis, atopic dermatitis, psoriasis).
2. Use of systemic or topical medications with therapeutic or immunomodulatory effects on the study disease during the relevant washout period prior to screening.
3. Use of investigational drugs or medical devices within 8 weeks or 5 half-lives (if known), whichever is longer, or within 30 days (for small molecules) prior to screening.
4. Vaccination or exposure to live or attenuated vaccines within 3 months prior to screening or participation in a vaccine-related clinical trial within 3 months prior to randomization.
5. History or current coagulation-related risk (e.g., bleeding diathesis, coagulopathy, GI bleeding with clinical significance, antiplatelet or anticoagulant use, history of thrombosis or thromboembolic events, or increased risk of thrombosis).
6. History of liver disease or current treatment for liver disease (e.g., hepatitis, cirrhosis, liver failure).
7. History of systemic antimicrobial use or presence of superficial skin infection (e.g., impetigo) within 4 weeks prior to screening.
8. History of malignancy or current malignancy (excluding completely resected and recurrence-free basal cell carcinoma, squamous cell carcinoma, or cervical intraepithelial neoplasia).
9. Major surgery performed within 3 months prior to randomization or planned during the study.
10. Serious concomitant disease or any condition judged by the investigator to make the participant unsuitable for study participation.
11. Abnormal findings in vital signs, physical examination, laboratory tests, ECG, chest X-ray/CT, or abdominal ultrasound during screening that have clinical significance and may affect study validity or participant safety.
12. Pregnant or breastfeeding women.
13. Allergy to the study drug or any of its components.
14. History of alcohol abuse within 6 months prior to screening (e.g., \> 14 units/week) or history of illicit drug abuse within 6 months prior to screening.
15. Any condition judged by the investigator that may affect the safety or efficacy evaluation of the study drug or participant compliance with the study procedures or diary.
