Eligible subjects will be randomized in a 3:1 ratio to receive investigational medicinal product (IMP) N91115 (daily [QD] or every 12 hours [Q12H]) or matching placebo (QD or Q12H) for 7 days and will be followed for safety while housed in the clinical research unit (CRU) until discharge on Day 8. Pharmacokinetics will be followed from Study Day 1 through the morning of Study Day 8. The subjects will be discharged from the CRU and complete the post treatment withdrawal phase, including a follow-up phone call on Day 15.