Inclusion Criteria:
* Age 18-75 years old, gender is not limited;
* Bilateral chronic sinusitis (with or without nasal polyps) that meets the diagnostic criteria of The Chinese Guidelines for the Diagnosis and Treatment of Chronic Sinusitis (2018);
* Systemic corticosteroids (at least 1 course of prednisone 0.5 to 1 mg/kg/day or equivalent for at least 5 days) within 2 years prior to the screening, but bilateral chronic sinusitis still exist; and/or patients with drug contraindications/intolerance to systemic glucocorticoids, and (or) patients who have undergone sinus surgery within 6 months before the screening;
* Before the screening, subjects must have used a stable dose of intranasal corticosteroids (INCS) for more than 4 weeks; For participants who used INCS alternatives rather than Mometasone furoate nasal spray (MFNS) prior to screening, participants should be willing to switch to MFNS in the duration of the study;
* Subjects with asthma started inhaled glucocorticoids at a stable dose at least 4 weeks before the screening and could remain inhaled glucocorticoid doses unchanged throughout the study;
* Patients in the Run-in period should be willing to conduct diary, daily symptom assessment and maintain a stable dose of MFNS with at least 70% adherence;
* Be able to read and understand, and be willing to sign informed consent;
* Participants and their partners agreed to use effective contraception throughout the study period (from the beginning of the screening/run-in period to 3 months after the last dose).
* Part A only：Bilateral nasal polyp score (NPS) assessed by nasal endoscopy ≥5 at both screening and randomization, with a score of ≥2 in each nostril;
* Part A only：Nasal congestion score (NCS) ≥2 at screening (daily score) and at randomization (weekly average score);
* Part A only：The following symptoms have been present continuously for at least 8 weeks prior to screening: ① nasal congestion; ② any other symptom, such as hyposmia/anosmia or rhinorrhea.
* Part B only：Prior to randomization, participants must have bilateral sinus inflammation on CT scan with a total bilateral LMK score ≥8, and bilateral ethmoid sinus opacification.
* Part B only： No nasal polyps confirmed by nasal endoscopy at Visit 1 and at randomization.
* Part B only：Subjects must have had persistent hyposmia for at least 4 consecutive weeks prior to Visit 1.
* Part B only：At screening, subjects have moderate or severe smell loss (smell loss score ≥2), and the weekly average severity ≥2 at randomization.
* Part B only：Subjects must have a sTSS (nasal congestion \[NC\], rhinorrhea, facial pain/pressure) ≥2 at screening (daily score) and at randomization (weekly average score).
* Part B only：Participants who have had at least one blood routine test within 2 years prior to screening, or at screening, showing blood eosinophils meeting any of the following criteria:
1. Blood eosinophil count ≥0.25×10⁹/L;
2. Blood eosinophil percentage ≥6.9% and the subject does not have asthma;
3. Blood eosinophil percentage ≥3.7% and the subject has asthma.
Exclusion Criteria:
* Any of the following laboratory abnormalities present at screening or randomization:
1. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \>2.5 × upper limit of normal (ULN);
2. Total bilirubin \>2 × ULN (except for indirect bilirubin elevation secondary to Gilbert's syndrome);
3. Creatinine \>1.5 × ULN;
* Any disease that the investigator considers unstable and may affect the patient's safety throughout the study period, or affect or interpretation with the results, or interfere with the patient's ability to complete the entire research process, including but not limited to cardiovascular, gastrointestinal, liver, kidney, neurological, musculoskeletal, infectious, endocrine, metabolic, hematologic diseases, psychiatric disorders, or major limb disorders. For example, but not limited to: ischemic heart disease, left ventricular failure, arrhythmia, uncontrolled hypertension, uncontrolled hyperglycemia, cerebrovascular disease, etc.;
* Patients with active autoimmune disease（including, but not limited to, Hashimoto's thyroiditis, Graves' disease, inflammatory bowel disease, primary biliary cholangitis, systemic lupus erythematosus, multiple sclerosis and other neuroinflammatory diseases, psoriasis vulgaris, and rheumatoid arthritis）;
* Known or suspected immunosuppression, including but not limited to a history of invasive opportunistic infections (such as histoplasmosis, listeriosis, coccidioidomycosis, pneumocystosis, aspergillosis), even if the infection has resolved;
* Subjects with active malignant tumors or a history of malignant tumors; Patients with basal cell carcinoma, localized squamous cell carcinoma of the skin, or carcinoma in situ of the cervix may be enrolled in this study if at least 12 months have elapsed since the completion of curative treatment prior to Visit 1; patients with other malignant tumors may be enrolled in this study if at least 5 years have elapsed since the completion of curative treatment prior to Visit 1;
* History of active pulmonary tuberculosis within the 12 months before screening;
* Active hepatitis during the screening period, or positive hepatitis B surface antigen (HBsAg), or positive hepatitis B core antibody (HBcAb) and positive hepatitis B virus (HBV) DNA, or positive hepatitis C virus (HCV) antibody and positive HCV-RNA; or positive for antibodies to human immunodeficiency virus (Anti-HIV) or positive for treponemal antibodies (Anti-TP);
* Diagnosed with helminth parasitic infection within 6 months before the screening period, did not receive standard treatment or the standard treatment was ineffective;
* Subjects who have received any of the following treatments:
1. Sinus surgery or sinonasal surgery within 6 months prior to screening (Visit 1);
2. Treatment with monoclonal antibodies within 8 weeks or 5 half-lives prior to screening, whichever is longer, including but not limited to benralizumab, mepolizumab, omalizumab, reslizumab, dupilumab, and other drugs of the same class (IL-4R inhibitors), etc;
3. Treatment with immunosuppressive agents within 8 weeks or 5 half-lives prior to screening, whichever is longer, including but not limited to cyclophosphamide, cyclosporine, interferon-γ, azathioprine, methotrexate, mycophenolate mofetil, and tacrolimus, etc;
4. Use of other non-biologic investigational drugs within 8 weeks or 5 half-lives prior to screening, whichever is longer;
5. Intravenous immunoglobulin (IVIG) therapy and/or plasmapheresis within 30 days prior to the screening visit (Visit 1);
6. Subjects who received leukotriene antagonists/modifiers within 4 weeks prior to randomization (subjects on a stable dose of leukotriene modifiers for ≥30 consecutive days prior to randomization may be enrolled);
7. Initiated allergen immunotherapy within 3 months prior to screening, or planned to initiate such treatment during the study period or to change the treatment dose during the study;
8. Receipt of live attenuated vaccines within 4 weeks prior to screening, or planned receipt of live attenuated vaccines during the study period;
9. Use of systemic corticosteroids within 4 weeks prior to screening;
10. Within 2 weeks prior to screening or during the screening/run-in period, had a chronic active or acute infection requiring systemic treatment with antibiotics, antiviral, antiparasitic, antiprotozoal, or antifungal agents;
* Patients with combined asthma should be excluded if they have:
1. Forced expiratory volume in the first second (FEV1) ≤ 50% of normal estimates;
2. Acute exacerbation of asthma within 90 days prior to screening, requiring hospitalization (\>24 hours);
3. used daily doses higher than 1000 mcg of fluticasone or equivalent inhaled corticosteroids (ICS);
* The subject had concomitant diseases that prevented him/her from completing the screening period assessment or from evaluating the primary efficacy endpoint:
1. Deviation of the nasal septum causing complete obstruction of at least one nostril;
2. Acute sinusitis, nasal infection, or upper respiratory tract infection at screening or within 2 weeks prior to screening;
3. Persistent rhinitis medicamentosa;
4. Diagnosed with eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome), granulomatosis with polyangiitis (Wegener's granulomatosis), Young's syndrome, Kartagener's syndrome or other ciliary dyskinesia syndromes, or cystic fibrosis;
5. Radiologically suspected or confirmed fungal rhinosinusitis;
* Subjects with nasal malignancies and benign tumors (e.g., papillomas, hemangiomas, etc.);
* Subjects who are unable to use MFNS or who are allergic or intolerant to mometasone furoate nasal spray;
* Subjects with a history of anaphylaxis to any biological agent (other than local injection site reactions);
* Pregnant or lactating women;
* Alcoholism, drug addiction and known drug dependence;
* Have participated in clinical trials of other medical devices within 12 weeks before screening;
* The subject had poor compliance in the research and could not complete the study as judged by the investigator;
* In the judgment of the investigator or sponsoring medical reviewer, it is believed that there are any medical or psychiatric symptoms that put the subject at risk, interfere with participation in the study, or interfere with the interpretation of the results of the study.
