An adeno-associated virus vector improved visual function in two of six patients treated for choroideremia, according to a letter published in the New England Journal of Medicine.
The letter summarized results of a study conducted at the University of Oxford, U.K.
“Best corrected visual acuity is a reliable marker of visual function. In contrast to Leber’s congenital amaurosis, in which visual acuity is generally profoundly affected early in life, choroideremia and most types of retinitis pigmentosa are characterized by progressive loss of the visual field, with visual acuity remaining close to normal levels until the very late stages of disease. Therefore, in some patients, the effect of preserving visual acuity with the use of retinal gene therapy may take several years to become apparent,” the authors wrote.
Choroideremia is caused by mutations in the gene CHM.
Investigators injected AAV.REP1, a non-mutated form of CHM in an adeno-associated virus (AAV) vector, into the vicinity of the retinal pigment epithelium and photoreceptor cells.
Injected volumes of AAV.REP1 were 0.1 mL and 0.06 mL.
Results showed that early visual improvement in two of the six patients was sustained at 3.5 years after treatment, despite progressive degeneration in non-treated control eyes.
At 3.5 years, ETDRS visual acuity increased by 21 letters, or more than four lines, from baseline in one patient and by 18 letters, more than three lines, in the other patient.
VA in the respective patients’ control eyes decreased by 18 letters and six letters.
The other four patients had good baseline VA and had limited potential improvement.
One patient developed cataract at 2 years; the patient’s VA at 3.5 years was similar to the value reported at 12 months after treatment, before the cataract was visually significant, the authors wrote. – by Matt Hasson
Disclosure: See the letter for a full list of all authors’ relevant financial disclosures.