This is a multicenter, randomized, double-blind, placebo-controlled phase III clinical study aimed at evaluating the efficacy and safety of stapokibart in adolescent patients with seasonal allergic rhinitis, and observing the quality of life, Pharmakokinetics(PK), Pharmacodynamics (PD) characteristics, and immunogenicity of subjects.

Allergic rhinitis (AR) is a non infectious chronic inflammatory disease of the nasal mucosa that is mainly mediated by immunoglobulin E (IgE) in atopic individuals exposed to allergens.

All participants will receive standard of care treatment as concomitant medications. Stapokibart or placebo will be administered as add-on therapy.

Inclusion Criteria:

• Age range: ≥12 years to <18 years
• Voluntarily sign the informed consent form.
• Seasonal allergic rhinitis has been prevalent for at least 2 years.Positive for allergens associated with seasonal allergic rhinitis.
• Poor control of seasonal allergic rhinitis with nasal glucocorticoids or other therapeutic agents during the same pollen season in the past.
• Weight≥40kg.
• Symptom severity scores for the season met the enrollment criteria.

Exclusion Criteria:

• Subjects who received anti-interleukin-4 receptor alpha(anti-IL-4Rα), anti-thymic stromal lymphopoietin(anti-TSLP), anti-immunoglobulin E(anti-IgE) monoclonal antibodies or other biologics within 10 weeks or 5 half-lives prior to screening (whichever is longer), or have a history of inadequate therapeutic response or intolerance to prior anti-IL-4Rα monoclonal antibody treatment for seasonal allergic rhinitis.
• Subjects with known hypersensitivity to stapokibart, any anti-IL-4Rα monoclonal antibody, or any ingredients of background concomitant medications.
• Subjects who newly initiate allergen-specific immunotherapy within 3 months before screening or intend to receive such therapy during the trial, or whose allergen exposure at home or workplace is expected to change significantly throughout the study period.
• Subjects with poorly controlled recent asthma or concomitant severe asthma with percent predicted Forced Expiratory Volume in one second(FEV1) ≤50% at screening.
• Subjects presenting other active nasal comorbidities at screening (chronic rhinitis, drug-induced rhinitis, chronic rhinosinusitis with or without nasal polyps, severe nasal septal deviation, etc.) that may interfere with efficacy determination.
• Subjects with current or past history of infections of special concern (active tuberculosis, helminthic infections, severe herpes virus infections, etc.), or diagnosed with malignant tumors within 5 years before screening, excluding fully cured cervical carcinoma in situ and non-metastatic cutaneous squamous or basal cell carcinoma.
• Subjects with severe underlying medical conditions including severe hepatic and renal impairment, autoimmune diseases, cardiovascular and cerebrovascular disorders, HIV infection, active hepatitis B/C, immunosuppression, or history of solid organ/hematopoietic stem cell transplantation which, in the investigator's opinion, may pose safety risks via trial participation.
• Have a serious underlying medical condition that, in the opinion of the investigator, may pose a risk to subject safety by participation in a clinical trial.