phenotypic optimization of urea-thiophene carboxamides to yield potent, well tolerated, and orally active protective agents against aminoglycoside-induced hearing loss

Hearing loss is a major public health concern with no pharmaceutical intervention for hearing protection or restoration. using zebrafish neuromast hair cells, a robust model for mammalian auditory and vestibular hair cells, we identified a urea-thiophene carboxamide, 1 (orc-001), as protective against aminoglycoside antibiotic (aga)-induced hair cell death. the 50% protection (hc 50 ) concentration conferred by 1 is 3.2 μm with protection against 200 μm neomycin approaching 100%. compound 1 was sufficiently safe and drug-like to validate otoprotection in an in vivo rat hearing loss model. we explored the structure-activity relationship (sar) of this compound series to improve otoprotective potency, improve pharmacokinetic properties and eliminate off-target activity. we present the optimization of 1 to yield 90 (orc-13661). compound 90 protects mechanosensory hair cells with hc 50 of 120 nm and demonstrates 100% protection in the zebrafish assay and superior physiochemical, pharmacokinetic, and toxicologic properties, as well as complete in vivo protection in rats.