OTOS (otospiralin) is a small protein expressed by fibrocytes in the inner ear cochlea and vestibule 1. These non-sensory cochlear cells are critical for maintaining ionic and hydric homeostasis in the endolymph 2. OTOS appears essential for normal auditory function; Otos-deficient mice exhibit moderate deafness with degeneration of type II and IV fibrocytes, while hair cells and stria vascularis remain intact 2. This suggests OTOS dysfunction impairs fibrocyte-dependent cochlear physiology and may predispose to age-related hearing loss 2. OTOS has significant clinical relevance in cisplatin-induced ototoxicity. Genetic variants in OTOS associate with cisplatin-induced tinnitus in cancer survivors, with a genome-wide significant SNP near OTOS (rs7606353, P = 2 × 10⁻⁶) 3. G alleles of OTOS SNPs rs77124181 and rs2291767 are over-represented in ototoxicity-free patients, suggesting a protective role 4. OTOS overexpression in auditory cell lines confers resistance to cisplatin-induced cytotoxicity 3. These findings position OTOS as a potential otoprotective therapeutic target for chemotherapy-induced hearing loss, with pathway analysis implicating potassium ion transport mechanisms 3.