This is a multi-center, randomized, double blind, placebo-controlled study to evaluate the efficacy, safety, PK, PD and immumogenicity of CM310 in comparison to placebo in addition to a background treatment of mometasone furcate nasal spray (MFNS) in patients with chronic rhinosinusitis with nasal polyposis (CRSwNP).

The study consists of a Screening/run-in Period (up to 4 weeks), a Randomized, Double Blind Treatment Period (16 weeks, till End-of-Treatment Visit) and a Safety Follow-up Period (8 weeks, till End-of-Study Visit).

56 patients who meet eligibility criteria will be randomized 1:1 to receive either CM310 300mg or matched placebo subcutaneously every two weeks (Q2W) for a total of 8 times. All patients will receive MFNS on a daily basis as a background treatment throughout the study. MFNS is required to use no less than 14 days during Screening/run-in Period.

Central reading will be implemented to nasal endoscopic nasal polyp score (NPS) , CT scans to Lund-Mackay score and volume of the involved area of nasosinusitis on 3D-construction images, and nasal polyp biopsy tissue analysis to eosinophil counts & percentage.

Inclusion Criteria:

• Bilateral CRSwNP.
• Prior treatment with systemic corticosteroids (SCS), and/or contraindicate to or intolerance to SCS, and/or with prior surgery to nasal polyps.
• Stable dose of intranasal corticosteroids for at least 4 weeks before screening.
• Ongoing symptoms for at least 4 weeks before screening：1)Nasal congestion/obstruction; 2)Othe symptom, e.g., loss of smell or rhinorrhea.
• Bilateral NPS of ≥5 with a minimum score of 2 in each nasal cavity at screening and at baseline.
• NCS score of 2 or 3 at screening and at baseline.
• Eosinophilic level meets the one of the following criteria: 1) serum eosinophil count ≥6.9% (without concomitant asthma) or ≥3.7% (with concomitant asthma) at screening; 2) absolute count of ≥55 per high power field or percentage of ≥27% in eosinophil level from nasal polyps biospy tissue.
• Contraception.

Exclusion Criteria:

• Not enough washingout period for previous therapy, e.g., less than 10 weeks or 5 half-lives (whichever is longer) for IL-4Rα antagonists, less than 8 weeks or 5 half-lives for biologic therapy/systemic immunosuppressant, less than 6 months for sinus surgery (including polypectomy).
• concurrent disease, e.g., ongoing rhinitis medicamentosa, acute sinusitis, nasal infection or upper respiratory infection, allergic fungal rhinosinusitis, malignancy, uncontrolled chronic disease such as cardivascular diseases, tuberculosis, diabetes etc.
• Allergic or intolerant to mometasone furoate spray or CM310/placebo.
• Significant liver or renal dysfunction.
• Other.