Pirazolopiridazinas y métodos para tratar las enfermedades degenerativas de la retina y la pérdida de audición asociada con el síndrome de Usher

Un compuesto de fórmula I:**Fórmula** o una sal farmacéuticamente aceptable del mismo, en la que R1 es:**Fórmula** R2 es:**Fórmula** y a es 0, 1, o 2. Compounds, compositions and methods for the treatment of retinal degenerative diseases, such as retinitis pigmentosa, Leber's congenital Amaurosis, Syndromic retinal degenerations, age-related macular degeneration and Usher Syndrome, and hearing loss associated with Usher Syndrome are described herein. Usher Syndrome, a rare genetic disorder and a leading cause of deafness and blindness, is associated with a mutation in any one of ten genes.