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Gene therapy success reported in blindness cases

April 28, 2008
World Science staff

A gene ther­a­py was used to par­tially cure blind­ness due to an in­her­it­ed con­di­tion, doc­tors said this week, in clin­i­cal tri­al re­sults hailed as one of the first clear suc­cesses for gene ther­a­py.

Re­search­ers used the treat­ment for a type of in­her­it­ed blind­ness and said they found it to cause no side ef­fects, and slight im­prove­ments in vi­sion in four out of six pa­tients stud­ied.

A patient navi­gates an obs­ta­cle course as his vi­sion is test­ed during a cli­n­i­cal tri­al for the gene ther­apy treat­ment. (Cour­tesy A.M. Ma­guire et al.)
The tri­als in­volved young pa­tients with a con­di­tion called Leber’s con­gen­i­tal am­au­ro­sis, a rare in­her­it­ed dis­ease caused by an ab­nor­mal­ity in a gene called RPE65. The con­di­tion ap­pears at birth or in the first few months of life and causes pro­gres­sive de­te­riora­t­ion and loss of vi­sion. 

Gene ther­a­py is a relatively new class of ex­pe­ri­men­tal treat­ments aimed at re­plac­ing or fix­ing de­fec­tive genes. Past gene ther­a­py clin­i­cal tri­als have met with lim­it­ed suc­cess de­spite high hopes.

The new find­ings were pub­lished Sun­day in a pair of stud­ies in the New Eng­land Jour­nal of Med­i­cine.

“Show­ing for the first time that gene ther­a­py can work in pa­tients with eye dis­ease is a very sig­nif­i­cant mile­stone,” said Uni­ver­s­ity Col­lege Lon­don opthal­molo­g­ist Rob­in Ali, a re­search­er in one of the stud­ies. “This tri­al es­tab­lishes proof of prin­ci­ple of gene ther­a­py for in­her­it­ed reti­nal dis­ease and paves the way for the de­vel­op­ment of gene ther­a­py ap­proaches for a broad range of eye dis­or­ders.”

The re­search­ers in both stud­ies used harm­less vi­rus­es to de­liv­er cor­rected ver­sions of a de­fec­tive gene in­to the eyes of the pa­tients. “We de­vel­oped sur­gi­cal tech­niques to en­a­ble ac­cess to the cells be­neath the ret­i­nas of pa­tients, us­ing a very fi­ne nee­dle to de­liv­er the mod­i­fied virus,” said the uni­ver­s­ity’s James Bain­bridge, who led the sur­gi­cal team in the Ali stu­dy. “It is tre­men­dously ex­cit­ing to see that this tech­nique is safe in an ex­tremely frag­ile tis­sue and can im­prove vi­sion in a con­di­tion pre­vi­ously con­sid­ered wholly un­treat­able.”

Oth­er in­sti­tu­tions in­volved in the re­search in­clud­ed Mich­i­gan State Uni­ver­s­ity, the Uni­ver­s­ity of Penn­syl­va­nia, How­ard Hughes Med­i­cal In­sti­tute in Chevy Chase, Md. and the Sec­ond Uni­ver­s­ity of Stud­ies in Na­ples, It­a­ly.

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A gene therapy was used to partially reverse blindness due to an inherited condition, doctors said this week, in clinical trial results hailed as one of the first clear successes for gene therapy. Researchers used the treatment for a type of inherited blindness and said they found it to cause no side effects, and slight improvements in vision in four out of six patients studied. The trials involved young patients with a condition called Leber’s congenital amaurosis, a rare inherited disease caused by an abnormality in a gene called RPE65. The condition appears at birth or in the first few months of life and causes progressive deterioration and loss of vision. Gene therapy is a class of experimental treatments aimed at replacing or fixing defective genes, but past gene therapy clinical trials have met with limited success despite great hopes. The findings were published yesterday in a pair of studies in the New England Journal of Medicine. “Showing for the first time that gene therapy can work in patients with eye disease is a very significant milestone,” said University College London opthalmologist Robin Ali, a researcher in one of the studies. “This trial establishes proof of principle of gene therapy for inherited retinal disease and paves the way for the development of gene therapy approaches for a broad range of eye disorders.” The researchers in both studies used harmless viruses to deliver corrected versions of a defective gene into the eyes of the patients. “We developed surgical techniques to enable access to the cells beneath the retinas of patients, using a very fine needle to deliver the modified virus,” said the university’s James Bainbridge, who led the surgical team in the Ali study. “It is tremendously exciting to see that this technique is safe in an extremely fragile tissue and can improve vision in a condition previously considered wholly untreatable.” Other institutions involved in the research included Michigan State University, the University of Pennsylvania, Howard Hughes Medical Institute in Chevy Chase, Md. and the Second University of Studies in Naples, Italy.