Narcolepsy is a sleep disorder that makes people very sleepy during the day. JZP441 is a new medicine being tested for people with Narcolepsy Type 1 (NT1). This study will help find out if JZP441 is safe and works well for these patients. The study is called Phase 1b, meaning it's in the early stages of testing. It will compare JZP441 to a placebo (a fake pill with no medicine) to see if it really helps.

Participants should be adults aged 18-64 with NT1. They have to meet certain health conditions, like having a body weight of at least 50 kg for men and 45 kg for women. They must also agree to not become pregnant or father a child during the study.

• The study involves multiple visits and follows a double-blind format, meaning neither you nor the study staff will know if you're getting JZP441 or placebo.
• Participants will be asked to take several forms of tests for sleepiness.
• Some health conditions or medications might make you ineligible for the study.