This study is a multicenter, randomized, double-blind, placebo-controlled phase III clinical trial aimed at evaluating the efficacy and safety of MG-K10 humanized monoclonal antibody injection in CSU trial participants with poor control of second-generation H1 antihistamines.

This study is a multicenter, randomized, double-blind, placebo-controlled phase III clinical trial aimed at evaluating the efficacy and safety of MG-K10 humanized monoclonal antibody injection in CSU trial participants with poor control of second-generation H1 antihistamines. A total of 226 patients with chronic spontaneous urticaria (CSU) are planned to be enrolled in this study and randomly assigned to either the experimental group or the control group at a 1:1 ratio. The study consists of a screening period (1-4 weeks), a double-blind treatment period (24 weeks), a continuous treatment period (24 weeks), and a follow-up period (8 weeks).

Inclusion Criteria:

1. Aged ≥12 and ≤75 years, body weight ≥30 kg, voluntarily sign ICF.
2. Diagnosed with CSU for ≥6 months, with pruritus and wheals for >6 weeks despite using second-generation H1 antihistamines.
3. Within 7 days prior to randomization: UAS7 score ≥16, ISS7 score ≥8, and at least one UAS ≥4.

3.Willing to maintain stable background antihistamine dose during the study (up to 4 times standard dose allowed).

4.Agree to use effective contraception during the study and for 6 months after last dose.

Exclusion Criteria:

1. Inducible urticaria (e.g., dermographism, cold, heat, cholinergic) or other chronic pruritic skin diseases (e.g., atopic dermatitis) affecting study assessment.
2. Active tuberculosis, or untreated latent TB; serious active infections.
3. Known or suspected immunodeficiency, or history of invasive opportunistic infections.
4. Known allergy to study drug or excipients.
5. Prior use of MG-K10 or other biologics (anti-IL-4Rα, anti-IgE, etc.) within 16 weeks or 5 half-lives.
6. Use of immunosuppressants, systemic corticosteroids, phototherapy, or Chinese herbal medicine within 4 weeks prior to first UAS assessment.
7. Clinically significant laboratory abnormalities at screening: ANC <1.2×10⁹/L, platelets <90×10⁹/L, ALT/AST/total bilirubin >2×ULN, creatinine >1.5×ULN.
8. Positive for HBsAg, or HBcAb positive with HBV-DNA ≥1×10³ copies/ml; HCV-Ab positive with HCV-RNA positive; HIV antibody positive.
9. QTcF >500 msec or other clinically significant ECG abnormalities.
10. Pregnant, breastfeeding, or planning pregnancy during the study.
11. History of malignant tumors within 5 years (except adequately treated non-melanoma skin cancer or cervical carcinoma in situ).
12. Participated in another clinical study and used investigational drug within 12 weeks or 5 half-lives prior to first UAS assessment.