CLINICAL TRIAL / NCT05295459

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