Narcolepsy and Idiopathic Hypersomnia (IH) are sleep disorders. Narcolepsy makes people very sleepy during the day, while IH causes long, often unrefreshing sleep. This study looks at the long-term effects of a medicine called ORX750 for people who have these conditions. It is a continuation of an earlier study (called the parent study), which means participants must have finished that study first. In this study, everyone will know they are getting ORX750 (it's open-label, meaning no placebo or fake medicine).

• Participants must have completed the previous study and be willing to follow new rules.
• New illnesses that could interfere may exclude you from the study.
• No medications for narcolepsy or IH can be used outside the study treatment.

This study will help understand if ORX750 is safe and effective for a longer time. Participants will need to visit the study site regularly and follow the study guidelines closely.