LAUSR

This letter is to comment on the review article ‘Emerging gene therapy products on RPGR-associated retinitis pigmentosa’ by Martinez-Fernandez de la Camara and colleagues published in this issue of Expert Opinion On Emerging Drugs [1]. We would like to bring to the Editor’s notice our concerns regarding what we perceive as an unbalanced review of the existing scientific literature around RPGR biology and its relation to retinal gene therapy development, as well as the speculative, and in parts factually wrong conclusions that are drawn during the manuscript’s discussion of four clinical-stage experimental gene therapies. We hereby provide clarifications on the structure and function of the RPGR gene, as well as the design and efficacy data of one of the gene therapy vectors discussed in the aforementioned manuscript. In addition, since the acceptance of the aforementioned manuscript for publication, the development program for the codon optimized RPGR vector developed by the University of Oxford/Nightstar Therapeutics Ltd. (sponsored by Biogen Inc.) has been suspended after Biogen announced in May 2021 that the primary endpoint was not met in its Phase 2/3 XIRIUS clinical trial.