Efficacy and Safety of 186 mcg of OPN-375 Nasal Spray Twice a Day (BID) in Adolescents With Chronic Rhinosinusitis Without Nasal Polyps

Change from baseline to the end of Week 4 in the average instantaneous CSS (evaluation of symptom severity immediately preceding the time of scoring).

The CSS consists of the sum of the scores (0-3) assigned to each of the following symptoms of CRS: nasal congestion, nasal discharge (anterior and/or posterior), facial pain/pressure sensation, where 0 = no symptoms, 1 = mild symptoms, 2 = moderate symptoms, and 3 = severe symptoms. The total CSS for each day can range from 0 to 9. Participants will report symptom severity immediately preceding the time of scoring every morning (AM). The baseline CSS is the average of the CSS's over the last 7 days of the single-blind run-in period. The end of Week 4 CSS is the average of the CSS's over the 7 days before Week 4.

Frequency of acute exacerbations of CRS over the 12-week treatment period

Acute exacerbations of CRS (AECRS) are defined as a worsening of symptoms that requires an escalation of treatment. The number of AECRS experienced by each participant will be recorded.

Change from baseline to the end of Week 4 on CSS score in subjects using an intranasal steroid treatment for CRS within 30 days of Visit 1/Screening

The CSS consists of the sum of the scores (0-3) assigned to each of the following symptoms of CRS: nasal congestion, nasal discharge (anterior and/or posterior), facial pain/pressure sensation, where 0 = no symptoms, 1 = mild symptoms, 2 = moderate symptoms, and 3 = severe symptoms. The total CSS for each day can range from 0 to 9. Participants will report symptom severity immediately preceding the time of scoring every morning (AM). The baseline CSS is the average of the CSS's over the last 7 days of the single-blind run-in period. The end of Week 4 CSS is the average of the CSS's over the 7 days before Week 4. This outcome will assess this change in CSS specifically in the subgroup of participants who were symptomatic at trial entry despite reported use of an intranasal steroid for treatment of CRS within 30 days of Visit 1/Screening.

Change from baseline to the end of Weeks 8 and 12 in CSS

The CSS consists of the sum of the scores (0-3) assigned to each of the following symptoms of CRS: nasal congestion, nasal discharge (anterior and/or posterior), facial pain/pressure sensation, where 0 = no symptoms, 1 = mild symptoms, 2 = moderate symptoms, and 3 = severe symptoms. The total CSS for each day can range from 0 to 9. Participants will report symptom severity immediately preceding the time of scoring every morning (AM). The baseline CSS is the average of the CSS's over the last 7 days of the single-blind run-in period. The CSS for the end of Week 8 and Week 12 is the average of the CSS's over the 7 days before Week 8 and Week 12, respectively.

Change from baseline to the end of Weeks 4, 8 and 12 in four separate cardinal CRS symptoms

Participants will rate each of the following four cardinal symptoms of CRS every morning based on symptom severity immediately before reporting: nasal congestion, facial pain or pressure sensation, nasal discharge (anterior and/or posterior), and sense of smell. Participants will rate each symptom on a scale of 0 to 3, where 0 = no symptoms, 1 = mild symptoms, 2 = moderate symptoms, and 3 = severe symptoms. Scores from the 7 days immediately preceding each timepoint will be averaged. The change in 7-day average score from baseline to Week 4, Week 8, and Week 12 for each symptom will be assessed individually.

Assessment of safety through Adverse Events (AEs)

Safety will be assessed by reporting frequency and severity (mild, moderate, or severe) of AEs experienced by participants during the trial. AEs will be collected beginning at time of signing of the Informed Consent Form (ICF) through end of participation (Week 12 or early termination).

Assessment of safety by nasal examination

Nasal examinations will be completed on all participants via nasoendoscopy at screening and end of study (Week 12 or early termination). Physicians performing the nasoendoscopies will record the presence of epistaxis, septal erosion/perforation, and details related to ulceration/erosion of any area other than the septum. The frequency and severity of findings from these exams will be reported.

Assessment of safety by ocular examination visual acuity

Ocular examinations will be performed during screening period and end of participation (Week 12 or early termination), and will include an assessment of visual acuity. Visual acuity will be assessed using an eye chart (EVA, EDTRS or Snellen) and will be recorded for each eye in the form of a fraction: 20/x.

Assessment of safety by ocular examination intraocular pressure (IOP)

Ocular examinations will be performed during screening period and end of participation (Week 12 or early termination), and will include an assessment of intraocular pressure. Intraocular pressure will be assessed using a Goldmann applanation tonometer mounted on a slit lamp, a hand-held applanation Goldmann-type tonometer, or a Tono-Pen. Two measurements will be performed for each eye. If the first 2 measurements differ by more than 3 mm Hg, a third measurement will be performed. The average value of the 2 or 3 measurements will be calculated. Subjects in whom IOP is elevated above 21 mm Hg will not be enrolled. Any new occurrence of intraocular pressure elevation above 21 mm Hg will require subject withdrawal.