This is a multicenter, randomized, double-blind, placebo-controlled, parallel-group Phase II clinical trial. Its primary objective is to explore and preliminarily evaluate the efficacy and safety of LP-003 Injection in the treatment of participants with chronic rhinosinusitis with nasal polyps (CRSwNP), as well as to investigate its pharmacokinetic (PK), pharmacodynamic (PD) profiles, and immunogenicity.

Inclusion Criteria:

1. Capable of understanding the study and voluntarily signing the Informed Consent Form (ICF);

2. Aged 18 to 75 years (inclusive) at the time of signing the ICF, regardless of gender;

3. Diagnosis of bilateral chronic rhinosinusitis with nasal polyps (CRSwNP);

4. Persistence of the following symptoms for ≥ 4 weeks prior to the screening/run-in period:

   • Nasal congestion;
   • Any one of the other symptoms: mucoid or mucopurulent nasal discharge, head and facial distension/pain, hyposmia or anosmia;

5. Nasal Polyp Score (NPS) ≥ 5 points, with each nasal cavity scoring at least ≥ 2 points during the screening/run-in period and prior to randomization;

6. Participants report moderate to severe nasal congestion during the screening/run-in period and prior to randomization:

   • Nasal Congestion Score (NCS) of 2 or 3 points at the screening/run-in period (Visit 1, V1);
   • Mean weekly NCS ≥ 2 points prior to randomization;

7. With bilateral CRSwNP despite prior treatment with systemic corticosteroids (SCS) such as oral corticosteroids (OCS) within 2 years prior to screening; and/or has contraindications to SCS treatment or is intolerant to SCS; and/or has undergone nasal polypectomy within 6 months prior to screening, with persistent bilateral CRSwNP.

8. Has been on a stable dosage of intranasal corticosteroids (INCS) for at least 4 weeks prior to screening;

9. Demonstrates ≥80% adherence to mometasone furoate nasal spray (MFNS) administration during the run-in period (with a minimum of 14 days of use).

Exclusion Criteria:

1. Concurrent other nasal diseases or nasal symptoms;

2. Acute upper respiratory tract infection at screening, which the investigator assesses may affect nasal symptom scoring;

3. Severe infection requiring intravenous antibiotics and/or hospitalization within 4 weeks prior to randomization that has not yet resolved, or active infection requiring oral antibiotics within 2 weeks prior to randomization that has not yet resolved; the investigator assesses that enrollment of the participant may pose uncontrollable risks;

4. Concurrent active parasitic infection (e.g., helminths) or suspected parasitic infection;

5. Known or suspected history of immunosuppression, including a history of invasive opportunistic infections (e.g., histoplasmosis, listeriosis, coccidioidomycosis, pneumocystosis, aspergillosis); or participants with a history of such infections that have resolved but are assessed by the investigator as likely to recur frequently;

6. Any severe or unstable disease that the investigator believes may affect the participant's safety during the study and/or hinder the participant from completing the study;

7. Has any severe or unstable disease that, in the investigator's judgment, may affect the safety of the trial participant during the study and/or preclude the participant from completing the study, including but not limited to cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious, endocrine, metabolic, autoimmune, hematological, or psychiatric disorders.

8. Current or prior receipt of the following treatments:

   • Use of traditional Chinese medicine (TCM) or proprietary Chinese medicines for chronic rhinosinusitis within 1 week prior to screening;
   • Use of medium- or short-acting systemic corticosteroids (SCS) within 4 weeks prior to randomization, or long-acting SCS within 6 weeks prior to randomization;
   • Receipt of any systemic monoclonal antibody therapy [e.g., Stapokibart, Dupilumab, Mepolizumab, Omalizumab, Tezepelumab, etc.] within 10 weeks prior to randomization or within 5 half-lives (whichever is longer);
   • Use of systemic immunosuppressants within 4 weeks prior to randomization or within 5 half-lives (whichever is longer);
   • Initiation of leukotriene receptor antagonist (LTRA) therapy within 4 weeks prior to randomization (participants who have been receiving stable-dose LTRA therapy for at least 4 weeks prior to randomization are eligible for enrollment);

9. For participants with concurrent asthma, the forced expiratory volume in 1 second (FEV1) as a percentage of predicted value ≤ 50% during the screening/run-in period;

10. Known allergy or intolerance to any component of the investigational product and/or mometasone furoate nasal spray;

11. Pregnant or lactating females;

12. Any other conditions that the investigator deems inappropriate for the participant to participate in the study.