AAV2 gene therapy readministration in three adults with congenital blindness

Abstract

Demonstration of safe and stable reversal of blindness after a single unilateral subretinal injection of a recombinant adeno-associated virus (AAV) carrying the RPE65 gene (AAV2-hRPE65v2) prompted us to determine whether it was possible to obtain additional benefit through a second administration of the AAV vector to the contralateral eye. Readministration of vector to the second eye was carried out in three adults with Leber congenital amaurosis due to mutations in the RPE65 gene 1.7 to 3.3 years after they had received their initial subretinal injection of AAV2-hRPE65v2. Results (through 6 months) including evaluations of immune response, retinal and visual function testing, and functional magnetic resonance imaging indicate that readministration is both safe and efficacious after previous exposure to AAV2-hRPE65v2.

Fig. 1

(A) Images of fundus photos compare the baseline (“Pre”) and d60 (“Post”) appearance and the predicted pre- and post-readministration visual field. There is extensive disease at baseline, with retinal pigment epithelial disturbance and geographical atrophy in the macula in patient CH12. Arrowheads indicate the lower border of the subretinal injection site, which was supratemporal and included the superior aspect of the macula in all three subjects. The lower border of the bleb was closer to the superior vascular arcade in CH12, whereas the lower borders for patients CH11 and NP01 were closer to the fovea. On the far right are the pre- and post-readministration visual fields. The predicted visual field changes based on the injection sites (and assuming a healthy retina) were similar for the three subjects (yellow shaded areas). Gray shaded areas denote scotomas (spots in the visual field in which vision is absent or decreased) that were altered in location at each different FO exam (only baseline scotomas are shown). (B) Full-field sensitivity threshold testing shows an increase in retinal light sensitivity (y axis shows sensitivity thresholds) in the left eyes of NP01 and CH11 by d30 persisting through the latest time point (d180), but no change in sensitivity of the previously injected eye for the three patients. There was no change in FST test results for either eye of patient CH12. (C) Improved PLR in the second eye to receive an injection of AAV2-hRPE65v2. Average pre-readministration PLR amplitudes of constriction are compared with those of post-readministration amplitudes (FOd30 to FOd180). PLR amplitudes were measured after illumination with light at 10 lux (CH12) or 0.4 lux (CH11 and NP01). *P = 0.08; **P = 0.009; ***P = 0.01.

Fig. 2

Subject CH12 fMRI results at baseline, FOd30, and FOd90. (A and B) Subject CH12 showed no cortical activation at baseline for high- and medium-contrast stimuli. (C and D) At FOd30, significant bilateral cortical activations were observed in response to the high-contrast stimulus (C), whereas no response was recorded for the medium-contrast stimulus (D). (E and F) At FOd90, CH12’s cortical responses to the same stimuli markedly increased especially for the high-contrast stimulus. Smaller clusters of activations are observed in response to medium-contrast stimulus at FOd90 (F).

Fig. 3

Subject CH11 fMRI results at baseline, FOd30, and FOd90. (A and B) Subject CH11 showed no baseline cortical activation to the high- or medium-contrast checkerboard stimuli. (C and D) Highly significant and widespread bilateral activation at FOd30 in response to both high- and medium-contrast stimuli, respectively. (E and F) A more marked increase in cortical activation was present at FOd90 for high-contrast (E) and medium-contrast (F) stimuli.

Fig. 4

Subject NP01 fMRI results at baseline, FOd45, and FOd90. (A and B) Subject NP01 showed no visual activation at baseline. (C and D) At FOd45, although significant cortical responses for the high-contrast stimulus were recorded (C), no response was observed for the medium-contrast stimulus (D). (E and F) At FOd90, NP01 showed significant activation for high-contrast (E) and medium-contrast (F) stimuli. Areas of activation at FOd90 were distributed in closer proximity to the primary visual cortex compared to FOd45 fMRI results [compare (E) and (C)].

Fig. 5

fMRI results for initially injected eyes in response to high- and medium-contrast stimuli at FO baseline, before injection of the contralateral eyes. (A and B) CH12’s fMRI results for the high- and medium-contrast stimuli showed bilateral activation. (C and D) CH11 showed activation to the high-contrast stimuli (C) but did not respond to medium-contrast stimuli (D). (E and F) Similar to CH11, NP01 responded to the high-contrast but not to the medium-contrast stimulus. The lower cortical activation for NP01 may be due to the fact that subject received the lowest dose of AAV2-hRPE65v2 for her initial subretinal injection and that subject is a chronic smoker (smoking is known to abate cortical blood flow and thus the fMRI signal).

Fig. 6

fMRI results for initially injected eyes 90 days after readministration of the contralateral eyes. (A and B) CH12’s fMRI results to high- and medium-contrast stimuli demonstrated significant bilateral cortical activation. (C and D) CH11 also showed widespread activation for high- and medium-contrast stimuli. (E and F) Although NP01 also showed activation in response to the high- and medium-contrast stimuli, they were at an uncorrected statistical threshold. Lower activation in NP01 may be due to a lower dose of AAV2-hRPE65v2 for the initial subretinal injection and the fact that this subject is a chronic smoker.