Intravitreal Delivery of rAAV2tYF-CB-hRS1 Vector for Gene Augmentation Therapy in Patients with X-Linked Retinoschisis: 1-Year Clinical Results

PURPOSE

To evaluate the safety and efficacy of rAAV2tYF-CB-hRS1, a recombinant adeno-associated virus vector expressing retinoschisin (RS1), in individuals with retinal disease caused by mutations in the RS1 gene.

DESIGN

Open-label, phase I/II dose-escalation clinical trial.

SUBJECTS

Twenty-two adults and 5 children with X-linked retinoschisis (XLRS), aged 10 to 79 years, were enrolled.

METHODS

The participants received an intravitreal (IVT) injection of rAAV2tYF-CB-hRS1, at 1 of 3 dose levels, in the poorer-seeing eye and were followed up for a minimum of 1 year after treatment.

MAIN OUTCOME MEASURES

The primary safety measures were local (ocular) or systemic (nonocular) adverse events (AEs) during the 12-month period after study agent administration. Efficacy was assessed based on measures of best-corrected visual acuity (BCVA), schisis cavity volume, static perimetry visual field testing, and electroretinography (ERG).

RESULTS

The IVT administration of rAAV2tYF-CB-hRS1 was generally safe at each of the dose levels. There were no AEs resulting in early termination, and no dose-limiting toxicities were reported. The most common ocular AEs observed were related to ocular inflammation (blurred vision, visual impairment, and the presence of vitreous cells, keratic precipitates, vitreous floaters, anterior chamber cells, and vitreous haze). Ocular inflammation was generally either mild or moderate in severity and responsive to standard immunosuppressive therapy, except in 3 participants (all in the highest-dose group) who developed chronic uveitis, which required prolonged therapy. Two patients experienced retinal detachments. There was no overall improvement in BCVA, visual fields, or ERG in the study eye compared with that in the fellow eye for any dose group. Variable changes in the cystic cavity volume over time were similar in the study and fellow eyes.

CONCLUSIONS

Gene augmentation therapy with rAAV2tYF-CB-hRS1 for XLRS was generally safe and well tolerated but failed to demonstrate a measurable treatment effect. The clinical trial is ongoing through 5 years of follow-up to assess its long-term safety.

Macular spatial distribution of preserved autofluorescence in patients with choroideremia

BACKGROUND/AIMS

To better understand the pattern of degeneration progression in cases with choroideremia.

METHODS

A cohort of genotypically confirmed choroideremia cases who underwent optical coherence tomography (OCT) and fundus autofluorescence (FAF) imaging was studied. Using HEYEX review software, the foveal centre was marked on FAF images under guidance of corresponding OCT images, followed by application of an ETDRS grid. The boundaries of preserved autofluorescence (AF) were manually segmented in each individual ETDRS subfield. The regional distribution of preserved AF was assessed by comparing its area among the various subfields.

RESULTS

A total of 168 eyes from 84 choroideremia cases were enrolled. There was a statistically significant difference in the amount of preserved AF area between inner subfields as determined by one-way analysis of variance (F (3,668)=9.997, p<0.001) and also between outer subfields (F (3,668)=8.348, p<0.001). A Tukey posthoc test revealed that the preserved AF area in the nasal subfields in both the inner and outer subfields was significantly smaller compared with analogue subfields.

CONCLUSION

The asymmetric spatial distribution of preserved AF in choroideremia (corresponding to the stellate shaped nature of these regions) suggests that the progression of degeneration has directional preference.

UV- and midwave-sensitive cone-driven retinal responses of the mouse: a possible phenotype for coexpression of cone photopigments

Molecular biological, histological and flicker electroretinographic results have established that mice have two cone photopigments, one peaking near 350 nm (UV-cone pigment) and a second near 510 nm [midwave (M)-cone pigment]. The goal of this investigation was to measure the action spectra and absolute sensitivities of the UV-cone- and M-cone-driven b-wave responses of C57BL/6 mice. To achieve this goal, we suppressed rod-driven signals with steady or flashed backgrounds and obtained intensity-response relations for cone-driven b-waves elicited by narrowband flashes between 340 and 600 nm. The derived cone action spectra can be described as retinal1 pigments with peaks at 355 and 508 nm. The UV peak had an absolute sensitivity of approximately 8 nV/(photon microm2) at the cornea, approximately fourfold higher than the M peak. In an attempt to isolate UV-cone-driven responses, it was discovered that an orange conditioning flash (lambda > 530 nm) completely suppressed ERG signals driven by both M pigment- and UV pigment-containing cones. Analysis showed that the orange flash could not have produced a detectable response in the UV-cone pathway were their no linkage between M pigment- and UV pigment-generated signals. Because cones containing predominantly the UV and M pigments have been shown to be located largely in separate parts of the mouse retina (), the most probable linkage is coexpression of M pigment in cones primarily expressing UV pigment. New histological evidence supports this interpretation (). Our data are consistent with an upper bound of approximately 3% coexpression of M pigment in the cones that express mostly the UV pigment.

Extreme responsiveness of the pupil of the dark-adapted mouse to steady retinal illumination

PURPOSE

To measure the dependence of the size of the pupils of mice on steady retinal illumination.

METHODS

Anesthetized C57BL/6 mice aged 7 to 8 weeks were placed in a ganzfeld chamber in darkness, and in monochromatic (510 nm) and white light whose intensity was varied more than 6 log units. The pupils of the mice were photographed with an infrared video camera and recorded on videotape and the pupil areas determined by digital image analysis of the video recordings.

RESULTS

Fully dark-adapted murine pupils had an area of 2.29 +/- 0.35 mm2. The minimum pupil size at saturating intensity was 0.10 +/- 0.05 mm2. The steady state pupil area declined to half its dark-adapted maximum when ganzfeld luminance was 10(-5) scotopic candela (scot. cd) per meter squared. Pupil area declined to 20% of the dark-adapted magnitude at approximately 10(-3) scot. cd/m2.

CONCLUSIONS

The mouse pupil can regulate retinal illumination by a factor exceeding 20. The neural circuitry that determines steady state murine pupil size is extremely sensitive to retinal illumination and under these experimental conditions is controlled almost exclusively by rod signals. This follows, because the ganzfeld illuminance (10(-5) scot. cd/m2) that causes the pupil to constrict to half its dark-adapted value corresponds to only approximately 0.01 photoisomerization per rod per second, whereas 80% reduction in pupil area occurs at approximately 1 photoisomerization per rod per sec. Based on this extreme responsiveness to steady illumination, the hypothesis is proposed that the murine pupil functions to protect a retinal circuit that can become saturated at extremely low photon capture rates. General principles of dark-adapted retinal circuitry support the identification of the first three neurons in the circuit as the rod, the rod bipolar, and the AII-amacrine. The rod and rod bipolar neurons do not approach saturation at the intensities at which the pupil constricts, however, and it seems unlikely that the AII-amacrine does. Thus the retinal neurons protected from saturation by the mouse pupil constrictions are probably ganglion cells with large receptive fields that have sustained responses.