Localised remyelination therapy for hearing-in-noise disorders: a first-in-class approach to protecting cognitive and mental health

Background

Hearing-in-noise disorders affect roughly one third of adults over 40 and one half over 65, yet no approved treatment exists. The downstream cost is not merely auditory. Longitudinal cohort studies have repeatedly identified untreated hearing impairment as the single largest modifiable risk factor for late-life dementia, and it is independently associated with depression, social withdrawal, and accelerated cognitive decline. The condition is sometimes described as the “cocktail party problem”; clinicians variously label it hidden hearing loss or central auditory processing disorder. Competing schools of thought invoke cochlear synaptopathy, cortical dysfunction, or outer hair cell pathology. None fully reconcile the clinical phenotype. None has yielded a tractable therapy.

Aims

We tested the hypothesis that auditory brain stem dysfunction contributes to this problem. Specifically, that demyelination of the heavily myelinated medial nucleus of the trapezoid body (MNTB) afferents disrupts the microsecond-scale temporal coding required for sound localization and spatial unmasking of speech. Our objectives were threefold. First, establish causality between MNTB demyelination and the cocktail-party deficit. Second, determine whether a pharmacological remyelination strategy paired with activity-dependent stimulation could reverse the phenotype in aged animals. Third, translate the approach into a regulated human trial.

Methods

Computational modelling was used to simulate the impact of focal demyelination on MNTB temporal precision. Stereotaxic injections of lysolecithin into young Mongolian gerbils were used to experimentally demyelinate MNTB fibers; demyelination was confirmed with coherent anti-Stokes Raman scattering microscopy and electron microscopy. Behavioural deficits were quantified with prepulse inhibition; brainstem function with auditory brainstem response (ABR) wave III amplitude. Naturally aged (two-year-old) gerbils exhibiting documented cocktail-party deficits then received a 30-day combination of clemastine fumarate (10 mg/kg/day, oral) and one hour of daily engineered sound stimulation. Within-subject pre–post comparisons and between-group analyses evaluated efficacy. The clinical study is a single-centre, double-blind, placebo-controlled, four-arm factorial trial (n = 344) testing clemastine fumarate and engineered sound therapy against matched placebos, with adaptive conditional-power termination of futile monotherapy arms. The primary endpoint is speech-in-noise performance at 15° and 30° spatial separations; the secondary endpoint is ABR wave III amplitude as a remyelination biomarker.

Results

Lysolecithin lesions faithfully recapitulated the age-related pathology, electrophysiology, and behavioural phenotype, suggesting that age-related demyelination of MNTB afferent fibers plays a significant role in the cocktail party problem – effectively making “young animals old”. The 30-day combination therapy reversed over 90% of behavioural deficits in aged gerbils, restored ABR wave III amplitude, and produced microscopic evidence of remyelination – effectively making “old animals young”. Monotherapies were largely inert. By contrast, combining oligodendrocyte-maturation pharmacology with activity-dependent stimulation was highly effective. The Phase I/IIa trial received FDA IND clearance in September 2025 and the first participants were enrolled in April of 2026.

Conclusions

MNTB demyelination is a tractable, mechanistically coherent target for the auditory deficit most strongly linked to cocktail party problems in older adults, which affects up to 800 million patients worldwide. Restoring central auditory myelination may protect not only hearing in noise, but also the cognitive and mental-health trajectories of these patients.

References

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