The purpose of this study is to measure decreases in daytime sleepiness, and disease symptoms in participants with Narcolepsy Type 2 (NT2) when taking ALKS 2680 tablets compared with placebo tablets.

Inclusion Criteria:

• Is willing and able, in the opinion of the Investigator, to understand and comply with protocol requirements, including the following: lifestyle considerations and restrictions, adherence to contraception guidance, adherence to actigraphy and diary requirements, if receiving treatment for OSA, adherence to primary OSA therapy over the 30 days prior to Visit 1, and throughout the study, including during overnight visits.
• Meets the diagnostic criteria of NT2 according to ICSD-3-TR guidelines, confirmed by diagnostic evaluations (either PSG/MSLT).

Exclusion Criteria:

• Has another comorbid sleep disorder or condition that may influence the sleep-wake cycle.
• Has a history or presence of other clinically significant (treated or untreated) illness, disease, abnormality, or surgical procedure that, in the opinion of the Investigator, might compromise participant safety, interfere with any study assessment, or affect the participant's ability to complete the study.
• Is currently enrolled in another interventional clinical trial or has received any investigational drug or used any interventional investigational device within 30 days prior to Visit 1. Participants previously enrolled in Study ALKS 2680-202 are not eligible for enrollment.
• Is currently pregnant, breastfeeding, or is planning to become pregnant during the study