The purpose of this Phase 2 clinical trial is to evaluate the safety, tolerability and efficacy of AC102 administered as single intratympanic injection compared to oral steroid treatment in patients with Idiopathic Sudden Sensorineural Hearing Loss (ISSNHL).

Inclusion Criteria:

• Male or female patients aged between 18 and 85 years
• Unilateral ISSNHL
• Onset of unilateral ISSNHL between 24 to 120 hours prior to randomization
• An absolute air conduction hearing threshold of at least 65 dB,
• Patients with a relative hearing loss of at least 30 dB compared to the current audiogram of the non-affected ear

Exclusion Criteria:

• Insufficient handling of the language used in the speech audiometry tests
• Bilateral hearing loss
• Acute hearing loss from noise trauma, barotrauma or head trauma in either ear at any time
• Congenital hearing loss
• Conductive hearing loss or combined hearing loss determined by a 4PTA > 10 dB
• History of ISSNHL in the past 1 years in the affected ear