A Study of the Efficacy and Safety of JZP-258 in Subjects With Narcolepsy With Cataplexy

This is a double-blind, placebo-controlled, randomized-withdrawal, multicenter study of the efficacy and safety of JZP-258.

Subjects will be transitioned to JZP-258 based on their treatment status at study entry. All subjects will begin JZP-258 treatment at the beginning of this period and continue through Week 12. They will be treated with JZP-258 alone for the final two weeks of this 12-week period. Once the JZP-258 dose has been optimized per the Investigator's judgment, these subjects may enter the 2-week Stable-Dose Period with that dose. Subjects are eligible to enter the Double-Blind Randomized-Withdrawal Period if the dose of JZP-258 remains unchanged during the Stable-Dose Period and, in the judgment of the Investigator, no clinically significant worsening in narcolepsy symptoms or clinically significant adverse events due to JZP-258 treatment have occurred. Subjects will return for a Safety Follow-up visit 2 weeks after the Double-Blind Randomized-Withdrawal Period. Subjects who complete the double-blind treatment period during the Main Study are eligible to enter a 24-week Open-Label Extension. During this period subjects will receive open label JZP-258. Subjects will return for a Safety Follow-up visit 2 weeks after the Open-Label Extension Period.