This study will evaluate the effect and safety of 611 in patients with Chronic Rhinosinusitis with Nasal Polyps (CRSwNP).

The main purpose is to evaluate the effect of 611 on a background of mometasone furoate nasal spray (MFNS) in reducing endoscopic nasal polyp score (NPS) and nasal congestion/obstruction score (NCS) severity in eligible patients with CRSwNP whose disease remains inadequately controlled despite daily treatment with intranasal corticosteroid (INCS) therapy in comparison to placebo.

Inclusion Criteria:

1. Female and male patients aged ≥18 and ≤ 75 years at the time of screening.
2. Bilateral CRSwNP.
3. Bilateral NPS of ≥5 with a minimum score of 2 in each nasal cavity
4. Nasal Congestion Score of > 2 at screening and a weekly average severity of > 1 at time of randomization.
5. Patients whose bilateral sino-nasal polyposis remains inadequately controlled despite prior treatment with SCS anytime within the past 2 years; and/or had a medical contraindication/intolerance to SCS; and/or received nasal polyp surgery 6 months before signing the ICF.

Exclusion Criteria:

1. Patients with other nasal diseases or symptoms.
2. Patients who are taking or have taken the following prohibited therapies as specified, e.g., systemic steroids within 4 weeks prior to screening, less than 3 months or 5 half-lives for biologic therapy prior to screening.
3. Patients who have active Hepatitis B, Hepatitis C or HIV infections as determined by positive results at Screening.
4. History of cancer.
5. Known or suspected history of immunosuppression.
6. Known with allergic or intolerant to mometasone furoate spray or 611/placebo.