Multicenter, phase III, randomized, blinded, controlled, parallel group with safety extension phase with crossover or continued treatment.

This is a 52-week, multicenter, phase III, randomized, blinded, controlled, parallel group with a 24-week treatment period followed by a safety extension phase with crossover or continued treatment 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
• Undergone at least 2 trials of medical treatments in the past
• Mean 3 cardinal symptom (3CS) score
• Bilateral ethmoid disease confirmed on CT
• Has been informed of the nature of the study and provided written informed consent
• Agrees to comply with all study requirements
• If on a waiting list for sinonasal surgery, willing to be removed from list or have surgery date cancelled for the duration of the study.

Exclusion Criteria:

• Inability to tolerate topical anesthesia or endoscopic procedure
• 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