This study looks at how well a nasal spray medicine, OPN-375, works and how safe it is for teens with nasal polyps, which are small growths inside the nose. The study lasts for 16 weeks, with an additional 12-week open-label phase where everyone gets the actual medicine. Randomized means participants are chosen by chance to get either the medicine or a placebo (a fake treatment). Double-blind means neither the doctors nor the participants know who gets which treatment at first. The study will include around 120 adolescents aged 12-17. To join, you need to have nasal polyps and some nose congestion, be able to stop other nasal medicines, and be able to use the study equipment correctly. You will need to keep a daily diary about your symptoms. If you have certain health conditions, have had many nasal surgeries, or are pregnant, you cannot join. The study involves regular doctor visits and tests. It's important to talk to your doctor and parents before deciding to join.

• Study lasts 28 weeks total, with regular visits.
• Random chance of receiving real or fake treatment initially.
• Must stop other nasal medicines during the study.