This is a single-center, open-label, phase Ib clinical study to evaluate the safety, pharmacokinetics and pharmacodynamic characteristics of LP-003 injection in adolescent subjects aged 12-18 years.

Inclusion Criteria:

• Adolescent subjects aged ≥12 years and <18 years, male or female.
• History of allergic diseases (self-reported is acceptable), including, but not limited to, food allergies, allergic rhinitis, allergic asthma, urticaria, and atopic dermatitis.
• Agreement to use effective contraception during the study and for 6 months after the end of the study.
• Subject and parent or legal guardian able to understand and voluntarily sign the informed consent form, and comply with study visits and related procedures.

Exclusion Criteria:

• Allergic to LP-003 or its excipients.
• Any serious or uncontrolled chronic disease (e.g., severe arrhythmia, ischemic heart disease, NYHA Class III/IV heart failure, severe pulmonary disease, inadequately controlled asthma, hypertension, diabetes, hypo- or hyperthyroidism) that may affect subject safety as determined by the Investigator.
• History of severe allergic reactions.
• Abnormal venous access, venipuncture or subcutaneous injection intolerance, history of needle or blood phobia.
• Estimated glomerular filtration rate (eGFR) <30 mL/min/1.73m² at screening.
• ALT or AST > ULN and considered clinically significant by the Investigator.
• Any other abnormal screening test result that, in the Investigator's opinion, could affect subject safety or study assessments.
• Systemic corticosteroid therapy (intravenous, intramuscular, or oral) within 4 weeks prior to study drug administration.
• Use of medications known to interact with epinephrine (e.g., β-blockers, ACE inhibitors, tricyclic antidepressants) within 4 weeks prior to administration.
• Use of biologic products (e.g., omalizumab) within 6 months prior to administration.
• Receipt vaccines within 14 days before administration or planning vaccination during the study.
• Participation in other clinical trials within 3 months prior to screening or within 5 half-lives of investigational product discontinuation (whichever is longer).
• Any other conditions that the Investigator considers subjects unsuitable for participation in the study.