This is a phase 1 safety study performed in male or female adult participants with an established diagnosis of severe to profound sensorineural hearing loss that meets the criteria for cochlear implantation and the participant has already chosen to undergo cochlear implant surgery.

Approximately 12 participants will be enrolled in the study. Assessed will be safety and tolerability of FX-322 administered by intratympanic injection. Also assessed will be the FX-322 concentration in cochlear fluid (perilymph), the pharmacokinetic (PK) profile of FX-322 to determine the systemic exposure to FX-322.

Inclusion Criteria:

1. Male or female adult subjects with an established diagnosis of severe to profound sensorineural hearing loss audiometric threshold of 80 dB HL or poorer at 500 Hz that meets the criteria for cochlear implantation and the subject has already chosen to undergo cochlear implant surgery.
2. Willingness and ability to comply with scheduled visits, ear examination, drug administration plan, auditory and laboratory tests, study restrictions, and all study procedures.

Other protocol-defined inclusion criteria may apply

Exclusion Criteria:

1. Persistent perforation of tympanic membrane or other tympanic membrane disorder that would interfere with the delivery and safety assessment of an intra -tympanic medication or reasonably be suspected to affect tympanic membrane healing after injection.
2. Any conductive component defined as air-bone gaps >10 dB at two or more frequencies.

Other protocol-defined exclusion criteria may apply