A Study Testing Safety and Efficacy of Transtympanic Paliroden for the Treatment of Cochlear Synaptopathy in Participants With Chronic, Constant Tinnitus

The goal of this clinical trial is to investigate if paliroden (CIL001) is safe and can help treat cochlear synaptopathy in adult participants 18-75 years of age with normal hearing thresholds and normal cognition who exhibit chronic, constant tinnitus in both ears and have difficulty understanding speech in noisy environments. The main questions it aims to answer are: * Is the study drug safe and tolerable over 6 months after injection into the middle ear? * How much of the study drug is in the bloodstream at different time points after injection? * How effective is a single dose of the study drug at treating cochlear synaptopathy in participants with chronic, constant tinnitus, as measured by hearing and listening tests? Injection of the study drug will be compared to injection of a placebo (a substance with no study drug in it) to see if there is a difference. Participants will be screened for eligibility and potentially receive a one-time injection into the middle ear of paliroden or placebo. The study lasts approximately 6 to 7 months if completing the whole study. Based on the visit windows, this could be between 190 and 218 days including a maximum of 42 days for Screening \& Run-in and 175 days post-treatment. Participants will: * Visit the clinic for checkups and tests multiple times over the course of the study * Complete a large battery of hearing and listening tests, answer questionnaires about their experiences, and provide blood samples for various tests * Receive an injection of either the study drug or placebo (a substance that has no active drug in it), if eligible