Chiesi Group’s idebenone faced a regulatory setback last month after the U.S. FDA issued a complete response letter (CRL) to the company’s NDA for Leber hereditary optic neuropathy (LHON), a rare inherited disorder that causes sudden vision loss.But a chance missed for Chiesi may be an opportunity for gene therapies, including Gensight Biologics SA’s lenadogene nolparvovec (Lumevoq; GS-010).