HSP90AA1 and retinal degeneration: In addition, some preclinical studies have reported that severe retinal degeneration occurred in rats and beagle dogs after treatment with Hsp90 inhibitors [46,58,59].The oral administration of the Hsp90 scaffold N-terminal inhibitor CH5164840 led to a loss of pupillary light reflex, abnormal electroretinographic (ERG) responses, and histological changes in the photoreceptor outer nuclear layer, including photoreceptor degeneration, in beagle dogs [58].