This study will consist of a dose escalation (single ascending dose - SAD and multiple ascending dose- MAD) and dose expansion (single dose expansion and/or multiple dose expansion). Dose escalation will consist of up to 4 cohorts for single ascending dose (SAD) and up to 2 cohorts for multiple ascending dose (MAD) with different dose levels. For SAD, after randomization on Day 1, participants will receive ASP0598 Otic Solution or placebo administration into the affected ear. Participants will return to the site on days 2, 3, 8, 15, 29, and 57 [end of study (EOS)]. Day 3 evaluations will only be performed for cohorts 1, 2 and 3. For MAD, after randomization on Day 1, participants will receive ASP0598 Otic Solution or placebo administration into the affected ear and will receive additional treatments into the same ear on Days 15 and 29. Participants will return to the investigative site on Days 8, 15, 22, 29, 36, 57, and 85 (EOS). Dose expansion will be based on the safety and efficacy results from an interim analysis. An interim analysis will be conducted after completion of SAD and again after completion of MAD. If dose expansion is opened, 2 or 3 treatment groups will be selected. If 3 groups are selected, participants will be randomized in a 1:1:1 ratio of high dose ASP0598 Otic Solution, low dose ASP0598 Otic Solution, and Placebo. If 2 groups are selected, participants will be randomized in a 1:1 ratio of high dose ASP0598 Otic Solution and Placebo. For single dose expansion, after randomization on Day 1, participants will receive ASP0598 otic solution or placebo administration into the affected ear. Participants will return to the investigative site on days 15, 29, 57, and 85 (EOS). For multiple dose expansion, after randomization on Day 1, participants will receive ASP0598 Otic Solution or placebo administration into the affected ear. Participants will receive additional treatment in the same ear on Days 15 and 29. In cases where complete closure is confirmed on either Day 15 or Day 29, no additional treatment is required at those visit(s). Participants will return to the investigative site on Days 15, 29, 43, 57, 85 and 113 (EOS).
The primary purpose of this study is to evaluate the safety and tolerability of ASP0598 Otic Solution. This study will also evaluate the efficacy of ASP0598 otic solution.