Criteria for Inclusion: 1. Presence of unilateral, progressive vestibular schwannoma. 2. Vestibular schwannoma larger than 2 mm. 3. Profound hearing loss, defined by pure-tone audiometry thresholds or word recognition score, in the affected ear. 4. Able and willing to comply with all trial requirements, including willingness to participate in a separate long term follow-up study after completion of this trial. Criteria for Exclusion: 1. Prior diagnosis of NF2 and/or bilateral vestibular schwannoma. 2. Prior surgery or radiation therapy for vestibular schwannoma. 3. Clinical history consistent with endolymphatic hydrops (documented fluctuating sensorineural hearing loss and/or episodic vertigo) in the affected ear. 4. Profound hearing loss, defined by pure-tone audiometry thresholds or word recognition score, in the unaffected ear. 5. Prior participation in a clinical trial with an investigational drug within six months prior to administration (Day 0), or any prior participation in a gene therapy clinical trial.