Multicenter, phase III, randomized, blinded, controlled, parallel group.

This is a 24-week, multicenter, phase III, randomized, blinded, controlled, parallel group with a 24-week treatment period to evaluate the efficacy and safety of LYR-210 compared with sham control for treatment in adults with CRS.

Inclusion Criteria:

• Age ≥18
• Diagnosed as having CRS
• Bilateral ethmoid disease confirmed on CT
• Mean 3 cardinal symptom (3CS) score
• Undergone at least 2 trials of medical treatments in the past
• Has been informed of the nature of the study and provided written informed consent
• Agrees to comply with all study requirements
• If currently on a waiting list for sinonasal surgery, willing to be removed from the waiting list or have preplanned surgery date cancelled for the duration of the study. [Note: this does not preclude a participant from receiving or being recommended for sinonasal surgery as rescue treatment during the study].

Exclusion Criteria:

• Inability to tolerate topical anesthesia
• Previous nasal surgery
• Presence of nasal polyp grade 2 or higher
• Seasonal allergic rhinitis
• Perennial rhinitis with symptoms that are well controlled by regular use of intranasal corticosteroids
• Severe asthma
• History or clinical evidence or suspicion of invasive fungal sinusitis, allergic fungal rhinosinusitis, atrophic rhinitis, or odontogenic sinusitis
• Obstruction preventing proper placement and retention of LYR-210 as seen on endoscopy
• Anatomic variation that, in the opinion of the investigator, would adversely impact placement of LYR-210 as seen on CT
• Known history of hypersensitivity or intolerance to corticosteroids
• Known history of hypothalamic pituitary adrenal axial dysfunction
• Previous pituitary or adrenal surgery
• Dental procedure/implant on maxillary dentition within 4 weeks of the Screening visit.
• Past or present acute or chronic intracranial or orbital complications of CRS
• History or diagnosis (in either eye) of glaucoma or ocular hypertension
• Past or present functional vision in only 1 eye
• Past, present, or planned organ transplant or chemotherapy with immunosuppression
• Currently positive for COVID-19 or residual sinonasal symptoms from a previous COVID-19 infection
• Pregnant or breast feeding. Females of child-bearing potential must test negative for pregnancy at the time of screening
• Evidence of disease or condition expected to compromise survival or ability to complete follow-up assessments
• Currently participating in an investigational drug or device study
• Determined by the investigator as not suitable to be enrolled

Except as approved by Sponsor, single center data will not be published before multicenter data, unless >1 year has elapsed since completion of the Study. PI may publish single center data provided that PI shall: i) provide a copy of the publication to Sponsor at least 60 days in advance of submission for publication; ii) delete Sponsor Confidential Information and make other reasonable changes; and iii) delay submission by up to 90 additional days to permit intellectual property filings.