**Study Summary** This clinical study evaluates the safety and effectiveness of a new nasal spray, XJN010, for people with Parkinson's disease who experience "off" episodes. **Parkinson's disease** is a brain disorder that affects movement, often causing stiffness and shaking. An "off" episode is when the usual medication stops working well and symptoms get worse. The study is **double-blind** (neither doctors nor participants know who gets the real treatment or placebo) and **placebo-controlled** (some participants get a non-active substance to compare with the real treatment). Participants will be in the study from Day 1 to Day 14. A total of 84 patients will be randomly assigned to receive either the nasal spray or a placebo. **Key Points:** - The study lasts for two weeks. - Participants are randomly assigned to treatment or placebo groups. - The study requires no new medications to be started during the trial and stable doses of existing medications. Before joining, potential participants will undergo screening to ensure they meet the criteria, such as age (30-85 years), Parkinson's diagnosis, and no recent major surgeries or other medical conditions that could affect the study. Participants need to agree to follow all study instructions and use effective birth control methods if applicable.