Gene therapy for inherited deafness may soon reach human trials, but researchers have lacked adequate animal models to test safety and efficacy in primates. This limitation could delay potentially life-changing treatments for children born with genetic hearing loss affecting inner ear hair cells. Scientists have now engineered marmoset monkeys with complete knockouts of the OTOF gene, creating the first non-human primate model that precisely mimics a major form of human congenital deafness. The team used CRISPR gene editing to disrupt OTOF in fertilized marmoset eggs, producing offspring with the same auditory synaptopathy seen in deaf children lacking functional otoferlin protein. These genetically modified marmosets showed profound hearing loss while maintaining normal cochlear structure, exactly matching the human condition where sound detection fails at the critical synaptic junction between inner hair cells and auditory nerve fibers. The breakthrough addresses a critical gap in translational hearing research. Previous gene therapy studies relied primarily on mouse models, which differ significantly from human ear anatomy and immune responses. With clinical trials for OTOF gene therapy already targeting pediatric patients, this primate model provides essential validation capabilities for testing dosing strategies, delivery methods, and long-term safety profiles before human implementation. The marmoset model represents a significant advancement in precision medicine approaches to inherited deafness. However, the ethical considerations of creating deaf primates for research purposes highlight the complex balance between advancing human therapeutics and animal welfare in biomedical research.