Gene Editing for CEP290-Associated Retinal Degeneration

BACKGROUND

CEP290-associated inherited retinal degeneration causes severe early-onset vision loss due to pathogenic variants in CEP290. EDIT-101 is a clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) gene-editing complex designed to treat inherited retinal degeneration caused by a specific damaging variant in intron 26 of CEP290 (IVS26 variant).

METHODS

We performed a phase 1-2, open-label, single-ascending-dose study in which persons 3 years of age or older with CEP290-associated inherited retinal degeneration caused by a homozygous or compound heterozygous IVS26 variant received a subretinal injection of EDIT-101 in the worse (study) eye. The primary outcome was safety, which included adverse events and dose-limiting toxic effects. Key secondary efficacy outcomes were the change from baseline in the best corrected visual acuity, the retinal sensitivity detected with the use of full-field stimulus testing (FST), the score on the Ora-Visual Navigation Challenge mobility test, and the vision-related quality-of-life score on the National Eye Institute Visual Function Questionnaire-25 (in adults) or the Children's Visual Function Questionnaire (in children).

RESULTS

EDIT-101 was injected in 12 adults 17 to 63 years of age (median, 37 years) at a low dose (in 2 participants), an intermediate dose (in 5), or a high dose (in 5) and in 2 children 9 and 14 years of age at the intermediate dose. At baseline, the median best corrected visual acuity in the study eye was 2.4 log10 of the minimum angle of resolution (range, 3.9 to 0.6). No serious adverse events related to the treatment or procedure and no dose-limiting toxic effects were recorded. Six participants had a meaningful improvement from baseline in cone-mediated vision as assessed with the use of FST, of whom 5 had improvement in at least one other key secondary outcome. Nine participants (64%) had a meaningful improvement from baseline in the best corrected visual acuity, the sensitivity to red light as measured with FST, or the score on the mobility test. Six participants had a meaningful improvement from baseline in the vision-related quality-of-life score.

CONCLUSIONS

The safety profile and improvements in photoreceptor function after EDIT-101 treatment in this small phase 1-2 study support further research of in vivo CRISPR-Cas9 gene editing to treat inherited retinal degenerations due to the IVS26 variant of CEP290 and other genetic causes. (Funded by Editas Medicine and others; BRILLIANCE ClinicalTrials.gov number, NCT03872479.).

EFFICACY OF MARIBAVIR IN VALGANCICLOVIR-RESISTANT CYTOMEGALOVIRUS RETINITIS

PURPOSE

To determine whether maribavir is effective at treating ganciclovir-resistant cytomegalovirus retinitis.

METHODS

Retrospective case report of a lung-transplant patient with bilateral cytomegalovirus retinitis documented with serum and aqueous humor studies and color fundus photographs.

RESULTS

A 72-year-old lung-transplant patient with active ganciclovir-resistant cytomegalovirus was treated with intravitreal foscarnet therapy in one eye. Retinitis developed in the contralateral eye and was managed with systemic maribavir alone. Active retinitis regressed in both the eye treated with intravitreal foscarnet and the uninjected eye.

CONCLUSION

This patient's results suggest that systemic maribavir is an effective treatment for treatment-resistant cytomegalovirus retinitis.

Motion-selective areas V5/MT and MST appear resistant to deterioration in choroideremia

Choroideremia (CHM) is an X-linked recessive form of hereditary retinal degeneration, which preserves only small islands of central retinal tissue. Previously, we demonstrated the relationship between central vision and structure and population receptive fields (pRF) using functional magnetic resonance imaging (fMRI) in untreated CHM subjects. Here, we replicate and extend this work, providing a more in-depth analysis of the visual responses in a cohort of CHM subjects who participated in a retinal gene therapy clinical trial. fMRI was conducted in six CHM subjects and six age-matched healthy controls (HC's) while they viewed drifting contrast pattern stimuli monocularly. A single ∼3-minute fMRI run was collected for each eye. Participants also underwent ophthalmic evaluations of visual acuity and static automatic perimetry (SAP). Consistent with our previous report, a single ∼ 3 min fMRI run accurately characterized ophthalmic evaluations of visual function in most CHM subjects. In-depth analyses of the cortical distribution of pRF responses revealed that the motion-selective regions V5/MT and MST appear resistant to progressive retinal degenerations in CHM subjects. This effect was restricted to V5/MT and MST and was not present in either primary visual cortex (V1), motion-selective V3A or regions within the ventral visual pathway. Motion-selective areas V5/MT and MST appear to be resistant to the continuous detrimental impact of CHM. Such resilience appears selective to these areas and may be mediated by independent retina-V5/MT anatomical connections that bypass V1. We did not observe any significant impact of gene therapy.

Vitreoretinal lymphoma presenting as frosted branch angiitis in a patient with diffuse large B-cell lymphoma

Purpose

To describe the evaluation, diagnosis, and treatment of vitreoretinal lymphoma presenting as frosted branch angiitis in a patient with diffuse large B-cell lymphoma (DLBCL).

Observations

A 57-year-old woman with a history of non-Hodgkin lymphoma and recent DLBCL relapse presented with frosted branch angiitis that raised suspicion for an infectious retinitis but was found to be vitreoretinal lymphoma.

Conclusions and Importance

This case primarily highlights the importance of considering vitreoretinal lymphoma on the differential diagnosis of etiologies of frosted branch angiitis. Despite suspicion for vitreoretinal lymphoma, it is also important to treat empirically for infectious etiologies of retinitis in cases of frosted branch angiitis. In this case where the diagnosis was ultimately vitreoretinal lymphoma, weekly alternating intravitreal injections of methotrexate and rituximab led to improvement in visual acuity and retinal infiltration.

Optimization and Validation of a Virtual Reality Orientation and Mobility Test for Inherited Retinal Degenerations

Purpose

To optimize a virtual reality (VR) orientation and mobility (O&M) test of functional vision in patients with inherited retinal degenerations (IRDs).

Methods

We developed an O&M test using commercially available VR hardware and custom-generated software. Normally sighted subjects (n = 20, ages = 14-67 years) and patients with IRDs (n = 29, ages = 15-63 years) participated. Individuals followed a dim red arrow path to a "course exit," while trying to identify nine obstacles adjacent to, or directly in their path. Dark-adapted subjects completed 35 randomly selected VR courses at increasing luminances, twice per luminance step, binocularly, and uni-ocularly. Performance was graded automatically by the software. Patients with IRD completed a modified Visual Function Questionnaire (VFQ).

Results

Normally sighted subjects identified approximately 50% of the obstacles at the dimmest course luminance. Except for two patients with IRD with poor vision, all patients were able to complete the test, although they required brighter (by >2 log units) luminances to identify 50% of the obstacles. In a single-luminance screening test in which normal subjects detected at least eight of nine objects, most patients with IRD underperformed; their performance related to disease severity, as measured by visual acuity, kinetic visual field extent, and VFQ scores. Test-retest differences in object detection were similar to the differences between the two eyes (±2 SD = ±2 objects).

Conclusions

This VR-O&M test was able to distinguish subjects with IRDs from normal subjects reliably and reproducibly.

Translational Relevance

This easily implemented, flexible, and objectively scored VR-O&M test promises to become a useful tool to assess the impact that IRDs and their treatments have on functional vision.

Lessons Learned from the Development of the First FDA-Approved Gene Therapy Drug, Voretigene Neparvovec-rzyl

In the 5 years following U.S. Food and Drug Administration (FDA) approval of the first gene therapy reagent approved to treat a genetic disease, voretigene neparvovec-rzyl (Luxturna), retinal disease clinics, hospital pharmacies, operating rooms, and even health insurance entities around the world have incorporated gene therapy as a standard procedure. The success of Luxturna has helped pave the way to establish a template for developing other gene therapy reagents that promise to restore sight or halt the progression of photoreceptor cell loss in both inherited and acquired retinal diseases. Here we review lessons learned from development of a gene therapy drug for RPE65 disease and how these lessons may expedite the development of additional treatments for previously untreatable blinding conditions.

Restoration of Vision and Retinal Responses After Adeno-Associated Virus-Mediated Optogenetic Therapy in Blind Dogs

Purpose

Optogenetic gene therapy to render remaining retinal cells light-sensitive in end-stage retinal degeneration is a promising strategy for treatment of individuals blind because of a variety of different inherited retinal degenerations. The clinical trials currently in progress focus on delivery of optogenetic genes to ganglion cells. Delivery of optogenetic molecules to cells in the outer neural retina is predicted to be even more advantageous because it harnesses more of the retinal circuitry. However, this approach has not yet been tested in large animal models. For this reason, we evaluated the safety and efficacy of optogenetic therapy targeting remaining diseased cone photoreceptors in the Rcd1 dog model of retinitis pigmentosa.

Methods

Imaging and measures of retinal function and functional vision were carried out, as well as terminal studies evaluating multi-electrode array recordings and histology.

Results

Animals remained healthy and active throughout the study and showed improved retinal and visual function as assessed by electroretinography and visual-evoked potentials, improved navigational vision, and improved function of cone photoreceptors and the downstream retinal circuitry.

Conclusions

The findings demonstrate that an optogenetic approach targeting the outer retina in a blind large animal model can partially restore vision.

Translational Relevance

This work has translational relevance because the approach could potentially be extrapolated to treat humans who are totally blind because of retinal degenerative disease.

Short-term Assessment of Subfoveal Injection of Adeno-Associated Virus-Mediated hCHM Gene Augmentation in Choroideremia Using Adaptive Optics Ophthalmoscopy

Importance

Subretinal injection for gene augmentation in retinal degenerations forcefully detaches the neural retina from the retinal pigment epithelium, potentially damaging photoreceptors and/or retinal pigment epithelium cells.

Objective

To use adaptive optics scanning light ophthalmoscopy (AOSLO) to assess the short-term integrity of the cone mosaic following subretinal injections of adeno-associated virus vector designed to deliver a functional version of the CHM gene (AAV2-hCHM) in patients with choroideremia.

Design, Setting, and Participants

This longitudinal case series study enrolled adult patients with choroideremia from February 2015 to January 2016 in the US. To be included in the study, study participants must have received uniocular subfoveal injections of low-dose (5 × 1010 vector genome per eye) or high-dose (1 × 1011 vector genome per eye) AAV2-hCHM. Analysis began February 2015.

Main Outcomes and Measures

The macular regions of both eyes were imaged before and 1 month after injection using a custom-built multimodal AOSLO. Postinjection cone inner segment mosaics were compared with preinjection mosaics at multiple regions of interest. Colocalized spectral-domain optical coherence tomography and dark-adapted cone sensitivity was also acquired at each time point.

Results

Nine study participants ranged in age from 26 to 50 years at the time of enrollment, and all were White men. Postinjection AOSLO images showed preservation of the cone mosaic in all 9 AAV2-hCHM-injected eyes. Mosaics appeared intact and contiguous 1 month postinjection, with the exception of foveal disruption in 1 patient. Optical coherence tomography showed foveal cone outer segment shortening postinjection. Cone-mediated sensitivities were unchanged in 8 of 9 injected and 9 of 9 uninjected eyes. One participant showed acute loss of foveal optical coherence tomography cone outer segment-related signals along with cone sensitivity loss that colocalized with disruption of the mosaic on AOSLO.

Conclusions and Relevance

Integrity of the cone mosaic is maintained following subretinal delivery of AAV2-hCHM, providing strong evidence in support of the safety of the injections. Minor foveal thinning observed following surgery corresponds with short-term cone outer segment shortening rather than cone cell loss. Foveal cone loss in 1 participant raises the possibility of individual vulnerability to the subretinal injection.

Growth and Nutritional Outcomes in Children Post-Haematopoietic Stem Cell Transplant without Exposure to Total Body Irradiation

AIMS

Poor growth in childhood cancer survivors who undergo haematopoietic stem cell transplant (HSCT) without exposure to radiation is reported anecdotally, although literature to support this is limited. The aims of this study were to assess the change in height standard deviation score (SDS) and the final adult height (FAH) in children who underwent chemotherapy-only conditioned HSCT and to identify predictors of poor growth.

MATERIALS AND METHODS

We conducted a retrospective hospital medical record review (1984-2010) of children (1-10 years) who underwent chemotherapy-only conditioned HSCT, noting anthropology measurements at cancer diagnosis, HSCT, 10 years old and FAH.

RESULTS

The median age at HSCT of the 53 patients was 4.5 years, 75% had a haematological malignancy and 25% a solid tumour. Half of the cohort underwent allogenic HSCT and most (89%) conditioned with busulphan. The mean change in height SDS from primary cancer diagnosis to FAH was -1.21 (±1.18 SD), equivalent to 7-8.5 cm loss, with a mean FAH of -0.91 SDS (±1.10 SD). The greatest height loss occurred between diagnosis and HSCT (-0.77 SDS, 95% confidence interval -1.42, -0.12, P = 0.01), with no catch-up growth seen by FAH. Patients with solid tumours had the greatest height loss. Overall body mass index SDS did not change significantly over time, or by cancer type.

CONCLUSIONS

Chemotherapy-only conditioned HSCT during childhood can impact FAH, with the greatest height loss occurring prior to HSCT and no catch-up growth after treatment finishes. Children transplanted for a solid tumour malignancy seem to be more at risk, possibly due to intensive treatment regimens, both pre-transplant and during conditioning.

Proliferative retinopathy and retinal detachment in pediatric atypical hemolytic uremic syndrome

We report the case of a 14-year-old boy with history of microangiopathic hemolytic crises secondary to atypical hemolytic uremic syndrome presenting with new-onset decreased vision, flashes, and floaters in his left eye. The patient had a history of chronic retinal detachment in the right eye and retinal neovascularization in the left eye treated with panretinal photocoagulation at age 5. He was now found to have a new combined tractional-rhegmatogenous retinal detachment in the left eye. Despite surgical reattachment of the retina, he had progressive retinal and optic nerve ischemia, with resultant left eye visual acuity of light perception. To our knowledge, this is the first reported case of proliferative retinopathy and tractional and rhegmatogenous retinal detachments in a pediatric patient with atypical hemolytic uremic syndrome.

Utility of In Vitro Mutagenesis of RPE65 Protein for Verification of Mutational Pathogenicity Before Gene Therapy

Importance

Next-generation sequencing can detect variants of uncertain significance (VUSs), for some of which gene therapy would not be advantageous. Therefore, the pathogenicity of compound heterozygous or homozygous variants should be confirmed before bilateral vitrectomy and administration of voretigene neparvovec-rzyl.

Objective

To describe an in vitro mutagenesis assay for assessing the pathogenicity of variants in the RPE65 gene.

Design, Setting, and Participants

This case series was conducted at 2 tertiary referral centers. Clinical history, imaging, and electrophysiologic testing results were reviewed from September 5, 2008, to December 31, 2019. Participants were 4 pediatric patients with Leber congenital amaurosis who were evaluated for or met the inclusion criteria for phase 1 to 3 clinical trials or were referred for voretigene neparvovec-rzyl treatment.

Main Outcomes and Measures

A functional assay was used to confirm the pathogenicity of novel RPE65 VUSs in 4 patients with Leber congenital amaurosis.

Results

Four patients with Leber congenital amaurosis had VUSs in RPE65. Patients 1 and 2 were siblings with the homozygous VUS c.311G>T p.(G104V). Patient 3 was a compound heterozygote with 1 known pathogenic allele, c.1202_1203insCTGG p.(Glu404AlafsTer4), and 1 VUS, c.311G>T p.(G104V), which segregated to separate alleles. Patient 4 was also a compound heterozygote with 1 pathogenic variant, c.11 + 5G>A, and 1 variant in trans, c.1399C>T p.(P467S). In vitro mutagenesis revealed that the G104V and P467S RPE65 proteins were catalytically inactive (0% isomerase activity). Patients 1 and 2 were excluded from participation in a phase 1 trial owing to high Adeno-associated virus 2 capsid-neutralizing antibodies. Patients 3 (G104V) and 4 (P467S) underwent successful surgical gene therapy with voretigene neparvovec-rzyl, and their response to lower white light intensity and visual field increased in fewer than 30 days after gene therapy intervention.

Conclusions and Relevance

Findings from this study suggest that, in patients with missense mutations in RPE65, functional assays of protein function can be performed to assess the pathogenicity of variants in both compound heterozygous and homozygous cases. Given the potential risks of gene therapy operations, in vitro RPE65 activity testing should be considered to avoid the possibility of treating a false genotype.

Durability of Voretigene Neparvovec for Biallelic RPE65-Mediated Inherited Retinal Disease: Phase 3 Results at 3 and 4 Years

PURPOSE

To determine whether functional vision and visual function improvements after voretigene neparvovec (VN; Luxturna [Spark Therapeutics, Inc]) administration in patients with biallelic RPE65 mutation-associated inherited retinal disease are maintained at 3 to 4 years and to review safety outcomes.

DESIGN

Open-label, randomized, controlled phase 3 trial.

PARTICIPANTS

Thirty-one individuals were enrolled and randomized 2:1 to intervention (n = 21) or control (n = 10). One participant from each group withdrew before, or at, randomization.

METHODS

Patients in the original intervention (OI) group received bilateral subretinal VN injections. Delayed intervention (DI) patients served as control participants for 1 year then received VN.

MAIN OUTCOME MEASURES

Change from injection baseline in bilateral performance on the multiluminance mobility test (MLMT), a measure of ambulatory navigation, and change from injection baseline in full-field light sensitivity threshold white light, visual field (VF), and visual acuity (VA).

RESULTS

Mean bilateral MLMT change scores at year 4 for OI patients and year 3 for DI patients were 1.7 and 2.4, respectively, with 71% of patients with a year 3 visit able to pass MLMT at the lowest light level. Mean change in full-field light sensitivity threshold white light, averaged over both eyes at year 4 for OI patients and year 3 for DI patients, was -1.90 log₁₀(cd.s/m²) and -2.91 log₁₀(cd.s/m²), respectively. Mean change in Goldmann kinetic VF III4e sum total degrees, averaged across both eyes, was 197.7 at year 4 for OI patients and 157.9 at year 3 for DI patients. Mean change in VA (Holladay scale), averaged across both eyes, was -0.003 logarithm of the minimum angle of resolution (logMAR) at year 4 for OI patients and -0.06 logMAR at year 3 for DI patients. One OI patient experienced retinal detachment at approximately year 4 that impacted VA for the OI group. No product-related serious adverse events (AEs) occurred, nor did any deleterious immune responses.

CONCLUSIONS

Improvements in ambulatory navigation, light sensitivity, and VF were consistent in both intervention groups. Overall, improvements were maintained up to 3 to 4 years, with ongoing observation. The safety profile of VN was consistent with vitrectomy and the subretinal injection procedure and was similar between intervention groups, with no product-related serious AEs reported.

A Virtual Reality Orientation and Mobility Test for Inherited Retinal Degenerations: Testing a Proof-of-Concept After Gene Therapy

Purpose

To test the ability of a virtual reality (VR) orientation and mobility (O&M) protocol to serve a measure of functional vision for patients with inherited retinal degenerations (IRDs).

Methods

A VR-O&M protocol designed using a commercially available VR hardware was tested in normally sighted control subjects (n=7; ages 10–35yo; Average 22.5yo) and patients with RPE65-associated Leber Congenital Amaurosis (n=3; ages 7–18yo; Average 12.7yo), in two of them before and after gene therapy. Patients underwent perimetry and full-field sensitivity testing. VR-O&M parameters correlated with the visual dysfunction.

Results

Visual acuities in RPE65 patients were on average worse than 20/200, dark-adapted sensitivity losses >5 log units, and fields constricted between 20° and 40°. Before treatment, patients required ~1000-fold brighter environment to navigate, had at least x4 more collisions, and were slower both to orient and navigate compared to control subjects. Improvements in cone- (by 1–2 L.u.) and rod-mediated (by >4 L.u.) sensitivities post-treatment led to fewer collisions (at least by half) at ~100-fold dimmer luminances, and to x4 times faster navigation times.

Conclusion

This study provides proof-of-concept data in support for the use of VR-O&M systems to quantify the impact that the visual dysfunction and improvement of vision following treatments has on functional vision in IRDs. The VR-O&M was useful in potentially challenging scenarios such as in pediatric patients with severe IRDs.

Translational Relevance

A VR-O&M test will provide much needed flexibility, both in its deployment as well as in the possibility to test various attributes of vision that may be impacted by gene therapy in the setting of translational studies.

Precis

This study provides proof-of-concept data in support for the use of a virtual reality orientation and mobility test to quantify the impact of the disease and of treatments thereof on functional vision in inherited retinal degenerations.

Clinical Perspective: Treating RPE65-Associated Retinal Dystrophy

Until recently, there was no approved treatment for a retinal degenerative disease. Subretinal injection of a recombinant adeno-associated virus (AAV) delivering the normal copy of the human RPE65 cDNA led to reversal of blindness first in animal models and then in humans. This led to the first US Food and Drug Administration (FDA)-approved gene therapy product for a genetic disease, voretigene neparvovec-rzyl (Luxturna). Luxturna was then approved by the European Medicines Association and is now available in the US through Spark Therapeutics and worldwide through Novartis. Not only has treatment with Luxturna changed the lives of people previously destined to live a life of blindness, but it has fueled interest in developing additional gene therapy reagents targeting numerous other genetic forms of inherited retinal disease. This review describes many of the considerations for administration of Luxturna and describes how lessons from experience with Luxturna could lead to additional gene-based treatments of blindness.

Compensatory Cross-Modal Plasticity Persists After Sight Restoration

Sensory deprivation prompts extensive structural and functional reorganizations of the cortex resulting in the occupation of space for the lost sense by the intact sensory systems. This process, known as cross-modal plasticity, has been widely studied in individuals with vision or hearing loss. However, little is known on the neuroplastic changes in restoring the deprived sense. Some reports consider the cross-modal functionality maladaptive to the return of the original sense, and others view this as a critical process in maintaining the neurons of the deprived sense active and operational. These controversial views have been challenged in both auditory and vision restoration reports for decades. Recently with the approval of Luxturna as the first retinal gene therapy (GT) drug to reverse blindness, there is a renewed interest for the crucial role of cross-modal plasticity on sight restoration. Employing a battery of task and resting state functional magnetic resonance imaging (rsfMRI), in comparison to a group of sighted controls, we tracked the functional changes in response to auditory and visual stimuli and at rest, in a group of patients with biallelic mutations in the RPE65 gene (“RPE65 patients”) before and 3 years after GT. While the sighted controls did not present any evidence for auditory cross-modal plasticity, robust responses to the auditory stimuli were found in occipital cortex of the RPE65 patients overlapping visual responses and significantly elevated 3 years after GT. The rsfMRI results showed significant connectivity between the auditory and visual areas for both groups albeit attenuated in patients at baseline but enhanced 3 years after GT. Taken together, these findings demonstrate that (1) RPE65 patients present with an auditory cross-modal component; (2) visual and non-visual responses of the visual cortex are considerably enhanced after vision restoration; and (3) auditory cross-modal functions did not adversely affect the success of vision restitution. We hypothesize that following GT, to meet the demand for the newly established retinal signals, remaining or dormant visual neurons are revived or unmasked for greater participation. These neurons or a subset of these neurons respond to both the visual and non-visual demands and further strengthen connectivity between the auditory and visual cortices.

Cytomegalovirus retinitis in an immunocompetent host after complicated cataract surgery

Purpose

To report a case of an immunocompetent patient who developed cytomegalovirus (CMV) retinitis after complicated cataract surgery resulting in aphakia.

Observations

A 67-year-old man with type 2 diabetes developed retinitis six months after cataract surgery that resulted in aphakia. Anterior chamber DNA testing was positive for CMV. Comprehensive systemic work-up revealed no immune insufficiency. The retinitis was successfully treated with intravitreal foscarnet and extended oral valgancyclovir treatment, however, he subsequently developed rhegmatogenous retinal detachment.

Conclusion and importance

CMV retinitis may occur in immunocompetent patients in the setting of aphakia and prolonged topical steroid use.

Safety of Same-Eye Subretinal Sequential Readministration of AAV2-hRPE65v2 in Non-human Primates

We have demonstrated safe and effective subretinal readministration of recombinant adeno-associated virus serotype (rAAV) to the contralateral eye in large animals and humans even in the setting of preexisting neutralizing antibodies (NAbs). Readministration of AAV to the same retina may be desirable in order to treat additional areas of the retina not targeted initially or to boost transgene expression levels at a later time point. To better understand the immune and structural consequences of subretinal rAAV readministration to the same eye, we administered bilateral subretinal injections of rAAV2-hRPE65v2 to three unaffected non-human primates (NHPs) and repeated the injections in those same eyes 2 months later. Ophthalmic exams and retinal imaging were performed after the first and second injections. Peripheral blood monocytes, serum, and intraocular fluids were collected at baseline and post-injection time points to characterize the cellular and humoral immune responses. Histopathologic and immunohistochemical studies were carried out on the treated retinas. Ipsilateral readministration of AAV2-hRPE65v2 in NHPs did not threaten the ocular or systemic health through the time span of the study. The repeat injections were immunologically and structurally well tolerated, even in the setting of preexisting serum NAbs. Localized structural abnormalities confined to the outer retina and retinal pigmented epithelium (RPE) after readministration of the treatment do not differ from those observed after single or contralateral administration of an AAV carrying a non-therapeutic transgene in NHPs and were not observed in a patient treated with the nearly identical, FDA-approved, AAV2-hRPE65v2 vector (voretigene neparvovec-rzyl), suggesting NHP-specific abnormalities.

Visual Function at the Atrophic Border in Choroideremia Assessed with Adaptive Optics Microperimetry

PURPOSE

Recent advances in retinal imaging allow visualization of structural abnormalities in retinal disease at the cellular level. This study used adaptive optics (AO) microperimetry to assess visual sensitivity with high spatial precision and to examine how function varies across 2 phenotypic features observed in choroideremia: atrophic lesion borders and outer retinal tubulations (ORTs).

DESIGN

Cross-sectional study.

PARTICIPANTS

Twelve choroideremia patients.

METHODS

A custom AO scanning light ophthalmoscope (AOSLO) equipped with both confocal and nonconfocal split-detection imaging methods was used to image the photoreceptor inner and outer segment mosaics. For AO microperimetry, circular 550-nm stimuli were presented through the AOSLO system; stimuli were either 9.6 or 38.3 arcmin² (approximately 60 or 15 times smaller than a Goldman III stimulus). Test locations were identified in structural images and stimuli were targeted to these locations using real-time retinal tracking combined with measurements of transverse chromatic aberration. Psychophysical detection thresholds were measured at the atrophic border in 12 patients. Additionally, visual sensitivity was probed along ORTs in 4 patients.

MAIN OUTCOME MEASURE

Visual sensitivity thresholds measured with AO microperimetry at retinal locations corresponding to structural phenotypes observed on AOSLO retinal images.

RESULTS

In choroideremia, sharp borders between intact central islands of the photoreceptor mosaic and complete atrophy of the outer retina and retinal pigment epithelium were observed in both split-detection and confocal structural images. Adaptive optics microperimetry at locations spanning these borders showed a commensurately sharp decrease in function, with readily measurable visual sensitivity on one side and dense scotoma on the other. These functional transitions often occurred over a distance smaller than the diameter of the Goldman III stimulus. Thresholds measured along ORTs showed dense scotoma over the tubule in all 4 participants, despite the visibility of remnant cone inner segments on the AO images.

CONCLUSIONS

Choroideremia patients exhibited sharp functional transitions that collocated with structural transitions from intact to severely degenerated retina. We found no evidence of visual sensitivity over ORTs. Measuring cone function with high resolution offered insight into disease mechanisms and may enable precise assessment of whether experimental therapies, such as gene therapy, provide a functional benefit.

RDH12 Mutations Cause a Severe Retinal Degeneration With Relatively Spared Rod Function

Purpose

To describe the retinal phenotype of pediatric patients with mutations in the retinol dehydrogenase 12 (RDH12) gene.

Methods

Twenty-one patients from 14 families (ages 2-17 years) with RDH12-associated inherited retinal degeneration (RDH12-IRD) underwent a complete ophthalmic exam and imaging with spectral domain optical coherence tomography (SD-OCT) and near infrared and short-wavelength fundus autofluorescence. Visual field extent was measured with Goldmann kinetic perimetry, visual thresholds with dark-adapted static perimetry or with dark-adapted chromatic full-field stimulus testing (FST) and transient pupillometry.

Results

Visual acuity ranged from 20/40 to light perception. There was parafoveal depigmentation or atrophic maculopathies accompanied by midperipheral intraretinal pigment migration. SD-OCT revealed foveal thinning in all patients and detectable but thinned outer nuclear layer (ONL) at greater eccentricities from the fovea. Photoreceptor outer segment (POS) signals were only detectable in small pockets within the central retina. Measurable kinetic visual fields were limited to small (<5-10°) central islands of vision. Electroretinograms were reported as undetectable or severely reduced in amplitude. FST sensitivities to a 467 nm stimulus were rod-mediated and reduced on average by ∼2.5 log units. A thinned central ONL colocalized with severely reduced to nondetectable cone-mediated sensitivities. Pupillometry confirmed the psychophysically measured abnormalities.

Conclusions

RDH12-IRD causes an early-onset, retina-wide disease with particularly severe central retinal abnormalities associated with relatively less severe rod photoreceptor dysfunction, a pattern consistent with an early-onset cone-rod dystrophy. Severely abnormal POS but detectable ONL in the pericentral and peripapillary retina suggest these regions may become targets for gene therapy.

Comparing Clinical Perimetry and Population Receptive Field Measures in Patients with Choroideremia

Purpose

Choroideremia (CHM) is an X-linked recessive form of hereditary retinal degeneration, which, at advanced stages, leaves only small central islands of preserved retinal tissue. Unlike many other retinal diseases, the spared tissue in CHM supports excellent central vision and stable fixation. Such spared topography in CHM presents an ideal platform to explore the relationship between preserved central retinal structure and the retinotopic organization of visual cortex by using functional magnetic resonance imaging (fMRI).

Methods

fMRI was conducted in four participants with CHM and four healthy control participants while they viewed drifting contrast pattern stimuli monocularly. A single ∼3-minute fMRI run was collected for each eye separately. fMRI data were analyzed using the population receptive field (pRF) modeling approach. Participants also underwent ophthalmic evaluations of visual acuity and static automatic perimetry.

Results

The spatial distribution and strength of pRF estimates correlated positively and significantly with clinical outcome measures in most participants with CHM. Importantly, the positive relationship between clinical and pRF measurements increased with increasing disease progression. A less consistent relationship was observed for control participants.

Conclusions

Although reflecting only a small sample size, clinical evaluations of visual function in participants with CHM were well characterized by the spatial distribution and strength of pRF estimates by using a single ∼3-minute fMRI experiment. fMRI data analyzed with pRF modeling may be an efficient and objective outcome measure to complement current ophthalmic evaluations. Specifically, pRF modeling may be a feasible approach for evaluating the impact of interventions to restore visual function.

Identification of a novel pathogenic missense mutation in PRPF31 using whole exome sequencing: a case report

BACKGROUND

Variants in PRPF31, which encodes pre-mRNA processing factor 31 homolog, are known to cause autosomal-dominant retinitis pigmentosa (adRP) with incomplete penetrance. However, the majority of mutations cause null alleles, with only two proven pathogenic missense mutations. We identified a novel missense mutation in PRPF31 in a family with adRP.

METHODS

We performed whole exome sequencing to identify possible pathogenic mutations in the proband of a family with adRP. Available affected family members had a full ophthalmological evaluation including kinetic and two-colour dark adapted static perimetry, electroretinography and multimodal imaging of the retina. Two patients had evaluations covering nearly 20 years. We carried out segregation analysis of the probable mutation, PRPF31 c.590T>C. We evaluated the cellular localisation of the PRPF31 variant (p.Leu197Pro) compared with the wildtype PRPF31 protein.

RESULTS

PRPF31 c.590T>C segregated with the disease in this four-generation autosomal dominant pedigree. There was intrafamilial variability in disease severity. Nyctalopia and mid-peripheral scotomas presented from the second to the fourth decade of life. There was severe rod >cone dysfunction. Visual acuity (VA) was relatively intact and was maintained until later in life, although with marked interocular asymmetries. Laboratory studies showed that the mutant PRPF31 protein (p.Leu197Pro) does not localise to the nucleus, unlike the wildtype PRPF31 protein. Instead, mutant protein resulted in punctate localisation to the cytoplasm.

CONCLUSIONS

c.590T>C is a novel pathogenic variant in PRPF31 causing adRP with incomplete penetrance. Disease may be due to protein misfolding and associated abnormal protein trafficking to the nucleus.

Amelioration of Neurosensory Structure and Function in Animal and Cellular Models of a Congenital Blindness

Most genetically distinct inherited retinal degenerations are primary photoreceptor degenerations. We selected a severe early onset form of Leber congenital amaurosis (LCA), caused by mutations in the gene LCA5, in order to test the efficacy of gene augmentation therapy for a ciliopathy. The LCA5-encoded protein, Lebercilin, is essential for the trafficking of proteins and vesicles to the photoreceptor outer segment. Using the AAV serotype AAV7m8 to deliver a human LCA5 cDNA into an Lca5 null mouse model of LCA5, we show partial rescue of retinal structure and visual function. Specifically, we observed restoration of rod-and-cone-driven electroretinograms in about 25% of injected eyes, restoration of pupillary light responses in the majority of treated eyes, an ∼20-fold decrease in target luminance necessary for visually guided behavior, and improved retinal architecture following gene transfer. Using LCA5 patient-derived iPSC-RPEs, we show that delivery of the LCA5 cDNA restores lebercilin protein and rescues cilia quantity. The results presented in this study support a path forward aiming to develop safety and efficacy trials for gene augmentation therapy in human subjects with LCA5 mutations. They also provide the framework for measuring the effects of intervention in ciliopathies and other severe, early-onset blinding conditions.

Prescreening whole exome sequencing results from patients with retinal degeneration for variants in genes associated with retinal degeneration

Background

Accurate clinical diagnosis and prognosis of retinal degeneration can be aided by the identification of the disease-causing genetic variant. It can confirm the clinical diagnosis as well as inform the clinician of the risk for potential involvement of other organs such as kidneys. It also aids in genetic counseling for affected individuals who want to have a child. Finally, knowledge of disease-causing variants informs laboratory investigators involved in translational research. With the advent of next-generation sequencing, identifying pathogenic mutations is becoming easier, especially the identification of novel pathogenic variants.

Methods

We used whole exome sequencing on a cohort of 69 patients with various forms of retinal degeneration and in whom screens for previously identified disease-causing variants had been inconclusive. All potential pathogenic variants were verified by Sanger sequencing and, when possible, segregation analysis of immediate relatives. Potential variants were identified by using a semi-masked approach in which rare variants in candidate genes were identified without knowledge of the clinical diagnosis (beyond "retinal degeneration") or inheritance pattern. After the initial list of genes was prioritized, genetic diagnosis and inheritance pattern were taken into account.

Results

We identified the likely pathogenic variants in 64% of the subjects. Seven percent had a single heterozygous mutation identified that would cause recessive disease and 13% had no obviously pathogenic variants and no family members available to perform segregation analysis. Eleven subjects are good candidates for novel gene discovery. Two de novo mutations were identified that resulted in dominant retinal degeneration.

Conclusion

Whole exome sequencing allows for thorough genetic analysis of candidate genes as well as novel gene discovery. It allows for an unbiased analysis of genetic variants to reduce the chance that the pathogenic mutation will be missed due to incomplete or inaccurate family history or analysis at the early stage of a syndromic form of retinal degeneration.

Efficacy and safety of voretigene neparvovec (AAV2-hRPE65v2) in patients with RPE65-mediated inherited retinal dystrophy: a randomised, controlled, open-label, phase 3 trial

BACKGROUND

Phase 1 studies have shown potential benefit of gene replacement in RPE65-mediated inherited retinal dystrophy. This phase 3 study assessed the efficacy and safety of voretigene neparvovec in participants whose inherited retinal dystrophy would otherwise progress to complete blindness.

METHODS

In this open-label, randomised, controlled phase 3 trial done at two sites in the USA, individuals aged 3 years or older with, in each eye, best corrected visual acuity of 20/60 or worse, or visual field less than 20 degrees in any meridian, or both, with confirmed genetic diagnosis of biallelic RPE65 mutations, sufficient viable retina, and ability to perform standardised multi-luminance mobility testing (MLMT) within the luminance range evaluated, were eligible. Participants were randomly assigned (2:1) to intervention or control using a permuted block design, stratified by age (<10 years and ≥10 years) and baseline mobility testing passing level (pass at ≥125 lux vs <125 lux). Graders assessing primary outcome were masked to treatment group. Intervention was bilateral, subretinal injection of 1·5 × 10¹¹ vector genomes of voretigene neparvovec in 0·3 mL total volume. The primary efficacy endpoint was 1-year change in MLMT performance, measuring functional vision at specified light levels. The intention-to-treat (ITT) and modified ITT populations were included in primary and safety analyses. This trial is registered with ClinicalTrials.gov, number NCT00999609, and enrolment is complete.

FINDINGS

Between Nov 15, 2012, and Nov 21, 2013, 31 individuals were enrolled and randomly assigned to intervention (n=21) or control (n=10). One participant from each group withdrew after consent, before intervention, leaving an mITT population of 20 intervention and nine control participants. At 1 year, mean bilateral MLMT change score was 1·8 (SD 1·1) light levels in the intervention group versus 0·2 (1·0) in the control group (difference of 1·6, 95% CI 0·72-2·41, p=0·0013). 13 (65%) of 20 intervention participants, but no control participants, passed MLMT at the lowest luminance level tested (1 lux), demonstrating maximum possible improvement. No product-related serious adverse events or deleterious immune responses occurred. Two intervention participants, one with a pre-existing complex seizure disorder and another who experienced oral surgery complications, had serious adverse events unrelated to study participation. Most ocular events were mild in severity.

INTERPRETATION

Voretigene neparvovec gene replacement improved functional vision in RPE65-mediated inherited retinal dystrophy previously medically untreatable.

FUNDING

Spark Therapeutics.

On variants and disease-causing mutations: Case studies of a SEMA4A variant identified in inherited blindness

The p.R713Q variant of the semaphorin-4a-encoding gene, SEMA4a, has been reported to cause autosomal dominant retinitis pigmentosa. Here we show three families with retinal degeneration in which unaffected family members are either homozygous or heterozygous for the variant. The p.R713Q variant in SEMA4A is insufficient to cause either autosomal recessive or autosomal dominant retinitis pigmentosa and is unlikely to be pathogenic.

Management of Presumed Endogenous Fungal Endophthalmitis in a Child With Acute Lymphoblastic Leukemia

The authors describe a case of presumed endogenous fungal endophthalmitis in an immunocompetent pediatric patient with acute lymphoblastic leukemia. A 15-year-old boy with a history of high-risk B-cell acute lymphoblastic leukemia status post-chemotherapy presented with acute changes in vision in his left eye. Fundus examination revealed a white bi-lobed chorioretinal lesion with overlying vitritis and associated subretinal fluid. Magnetic resonance imaging of the brain revealed small ring-enhancing lesions in the right parietal and left occipital lobes. Blood, cerebrospinal fluid, aqueous, and vitreous cultures were all negative. Bone marrow and vitreous cytology were negative for malignant cells. The patient was treated for presumed fungal endophthalmitis with systemic and intravitreal voriconazole, followed by pars plana vitrectomy with intravitreal voriconazole and amphotericin B injections. The chorioretinal lesion resolved and visual acuity recovered to 20/20. Chorioretinal infiltrates in a patient with leukemia may require treatment even in the absence of a definitive diagnostic test result. Intervention should be guided by risk analysis and clinical judgment. [J Pediatr Ophthalmol Strabismus. 2017;54:e42-e46.].

Intravitreal Bevacizumab for the Treatment of Vitreous Hemorrhage Due to Proliferative Diabetic Retinopathy

PURPOSE

To evaluate the outcomes of intravitreal bevacizumab (IVB) use in patients with a vitreous hemorrhage (VH) secondary to proliferative diabetic retinopathy (PDR).

DESIGN

Retrospective, interventional case series.

METHODS

Patients who presented to Scheie Eye Institute between January 2008 and January 2015 with a new VH secondary to PDR and treated with IVB were included. Exclusion criteria consisted of IVB treatment prior to the study, a history of pars plana vitrectomy (PPV), and less than 1 year of follow-up. Outcomes of interest were additional treatments including PPV, injections, and panretinal photocoagulation (PRP), as well as visual acuity at baseline and at 1 year.

RESULTS

Of the 111 eligible eyes, 55 (49.5%) had PRP, 35 (31.6%) were managed with injections alone, and 21 (18.9%) had PPV after 1 year. The overall average number of injections during this time was 2 (range, 1-9), and 13 (11.7%) eyes were managed with a single injection alone. Of the 69 eyes with 2 years of follow-up, 43 (62.3%) had PRP, 16 (23.2%) were treated with injections alone, and 10 (14.5%) had PPV.

CONCLUSIONS

This study underscores the potentially important role that IVB injections have in the management of patients with VH secondary to PDR. The results indicate that a proportion of patients may be treated with a minimal amount of intervention requiring 1 or 2 anti-vascular endothelial growth factor injections only. Also, the rate of PPV at 2 years (27.9%, n = 31) suggests that most patients may be managed nonsurgically.

Evaluation of Dose and Safety of AAV7m8 and AAV8BP2 in the Non-Human Primate Retina

Within the next decade, we will see many gene therapy clinical trials for eye diseases, which may lead to treatments for thousands of visually impaired people around the world. To target retinal diseases that affect specific cell types, several recombinant adeno-associated virus (AAV) serotypes have been generated and used successfully in preclinical mouse studies. Because there are numerous anatomic and physiologic differences between the eyes of mice and "men" and because surgical delivery approaches and immunologic responses also differ between these species, this study evaluated the transduction characteristics of two promising new serotypes, AAV7m8 and AAV8BP2, in the retinas of animals that are most similar to those of humans: non-human primates (NHPs). We report that while AAV7m8 efficiently targets a variety of cell types by subretinal injection in NHPs, transduction after intravitreal delivery was mostly restricted to the inner retina at lower doses that did not induce an immune response. AAV8BP2 targets the cone photoreceptors efficiently but bipolar cells inefficiently by subretinal injection. Additionally, transduction by both serotypes in the anterior chamber of the eye and the optic pathway of the brain was observed post-intravitreal delivery. Finally, we assessed immunogenicity, keeping in mind that these AAV capsids may be used in future clinical trials. We found that AAV8BP2 had a better safety profile compared with AAV7m8, even at the highest doses administered. These studies underscore the differences in AAV transduction between mice and primates, highlighting the importance of careful evaluation of therapeutic vectors in NHPs prior to moving to clinical trials.

Safety and durability of effect of contralateral-eye administration of AAV2 gene therapy in patients with childhood-onset blindness caused by RPE65 mutations: a follow-on phase 1 trial

BACKGROUND

Safety and efficacy have been shown in a phase 1 dose-escalation study involving a unilateral subretinal injection of a recombinant adeno-associated virus (AAV) vector containing the RPE65 gene (AAV2-hRPE65v2) in individuals with inherited retinal dystrophy caused by RPE65 mutations. This finding, along with the bilateral nature of the disease and intended use in treatment, prompted us to determine the safety of administration of AAV2-hRPE65v2 to the contralateral eye in patients enrolled in the phase 1 study.

METHODS

In this follow-on phase 1 trial, one dose of AAV2-hRPE65v2 (1.5 × 10(11) vector genomes) in a total volume of 300 μL was subretinally injected into the contralateral, previously uninjected, eyes of 11 children and adults (aged 11-46 years at second administration) with inherited retinal dystrophy caused by RPE65 mutations, 1.71-4.58 years after the initial subretinal injection. We assessed safety, immune response, retinal and visual function, functional vision, and activation of the visual cortex from baseline until 3 year follow-up, with observations ongoing. This study is registered with ClinicalTrials.gov, number NCT01208389.

FINDINGS

No adverse events related to the AAV were reported, and those related to the procedure were mostly mild (dellen formation in three patients and cataracts in two). One patient developed bacterial endophthalmitis and was excluded from analyses. We noted improvements in efficacy outcomes in most patients without significant immunogenicity. Compared with baseline, pooled analysis of ten participants showed improvements in mean mobility and full-field light sensitivity in the injected eye by day 30 that persisted to year 3 (mobility p=0.0003, white light full-field sensitivity p<0.0001), but no significant change was seen in the previously injected eyes over the same time period (mobility p=0.7398, white light full-field sensitivity p=0.6709). Changes in visual acuity from baseline to year 3 were not significant in pooled analysis in the second eyes or the previously injected eyes (p>0.49 for all time-points compared with baseline).

INTERPRETATION

To our knowledge, AAV2-hRPE65v2 is the first successful gene therapy administered to the contralateral eye. The results highlight the use of several outcome measures and help to delineate the variables that contribute to maximal benefit from gene augmentation therapy in this disease.

FUNDING

Center for Cellular and Molecular Therapeutics at The Children's Hospital of Philadelphia, Spark Therapeutics, US National Institutes of Health, Foundation Fighting Blindness, Institute for Translational Medicine and Therapeutics, Research to Prevent Blindness, Center for Advanced Retinal and Ocular Therapeutics, Mackall Foundation Trust, F M Kirby Foundation, and The Research Foundation-Flanders.

Plasticity of the human visual system after retinal gene therapy in patients with Leber's congenital amaurosis

Much of our knowledge of the mechanisms underlying plasticity in the visual cortex in response to visual impairment, vision restoration, and environmental interactions comes from animal studies. We evaluated human brain plasticity in a group of patients with Leber's congenital amaurosis (LCA), who regained vision through gene therapy. Using non-invasive multimodal neuroimaging methods, we demonstrated that reversing blindness with gene therapy promoted long-term structural plasticity in the visual pathways emanating from the treated retina of LCA patients. The data revealed improvements and normalization along the visual fibers corresponding to the site of retinal injection of the gene therapy vector carrying the therapeutic gene in the treated eye compared to the visual pathway for the untreated eye of LCA patients. After gene therapy, the primary visual pathways (for example, geniculostriate fibers) in the treated retina were similar to those of sighted control subjects, whereas the primary visual pathways of the untreated retina continued to deteriorate. Our results suggest that visual experience, enhanced by gene therapy, may be responsible for the reorganization and maturation of synaptic connectivity in the visual pathways of the treated eye in LCA patients. The interactions between the eye and the brain enabled improved and sustained long-term visual function in patients with LCA after gene therapy.

Dissociations of the Fluocinolone Acetonide Implant: The Multicenter Uveitis Steroid Treatment (MUST) Trial and Follow-up Study

PURPOSE

To describe fluocinolone acetonide implant dissociations in the Multicenter Uveitis Steroid Treatment (MUST) Trial.

DESIGN

Randomized clinical trial with extended follow-up.

METHODS

Review of data collected on the first implant in the eye(s) of participants. Dissociation was defined as the drug pellet no longer being affixed to the strut and categorized as spontaneous or surgically related.

RESULTS

A total of 250 eyes (146 patients) had at least 1 implant placed. Median follow-up time after implant placement was 6 years (range 0.5-9.2 years). Thirty-four dissociations were reported in 30 participants. There were 22 spontaneous events in 22 participants; 6-year cumulative risk of a spontaneous dissociation was 4.8% (95% confidence interval [CI]: 2.4%-9.1%). The earliest event occurred 4.8 years after placement. Nine of 22 eyes with data had a decline in visual acuity ≥5 letters temporally related to the dissociation. Thirty-nine implant removal surgeries were performed, 33 with replacement. Twelve dissociations were noted during implant removal surgeries in 10 participants (26%, 95% CI 15%-48%); 5 of these eyes had a decline in visual acuity ≥5 letters after surgery. The time from implant placement to removal surgery was longer for the surgeries at which dissociated implants were identified than for those without one (5.7 vs 3.7 years, P < .001). Overall, visual acuity declined 15 or more letters from pre-implant values in 22% of affected eyes; declines were frequently associated with complications of uveitis or its treatment.

CONCLUSION

There is an increasing risk of dissociation of Retisert implants during follow-up; the risk is greater with removal/exchange surgeries, but the risk of both spontaneous and surgically related events increases with longevity of the implants. In 22% of affected eyes visual acuity declined by 15 letters. In the context of eyes with moderate to severe uveitis for years, this rate is not unexpected.

Cobalamin C Deficiency Shows a Rapidly Progressing Maculopathy With Severe Photoreceptor and Ganglion Cell Loss

PURPOSE

To describe in detail the retinal structure and function of a group of patients with cobalamin C (cblC) disease.

METHODS

Patients (n = 11, age 4 months to 15 years) with cblC disease (9/11, early onset) diagnosed by newborn screening underwent complete ophthalmic examinations, fundus photography, near-infrared reflectance imaging, and spectral-domain optical coherence tomography (SD-OCT). Electroretinograms (ERGs) were performed in a subset of patients.

RESULTS

Patients carried homozygous or compound heterozygote mutations in the methylmalonic aciduria and homocystinuria type C (MMACHC) gene. Late-onset patients had a normal exam. All early-onset patients showed a maculopathy; older subjects had a retina-wide degeneration (n = 4; >7 years of age). In general, retinal changes were first observed before 1 year of age and progressed within months to a well-established maculopathy. Pseudocolobomas were documented in three patients. Measurable visual acuities ranged from 20/200 to 20/540. Nystagmus was present in 8/11 patients; 5/6 patients had normal ERGs; 1/6 had reduced rod-mediated responses. Spectral-domain OCT showed macular thinning, with severe ganglion cell layer (GCL) and outer nuclear layer (ONL) loss. Inner retinal thickening was observed in areas of total GCL/ONL loss. A normal lamination pattern in the peripapillary nasal retina was often seen despite severe central and/or retina-wide disease.

CONCLUSIONS

Patients with early-onset cblC and MMACHC mutations showed an early-onset, unusually fast-progressing maculopathy with severe central ONL and GCL loss. An abnormally thickened inner retina supports a remodeling response to both photoreceptor and ganglion cell degeneration and/or an interference with normal development in early-onset cblC.

Detailed functional and structural phenotype of Bietti crystalline dystrophy associated with mutations in CYP4V2 complicated by choroidal neovascularization

PURPOSE

To describe in detail the phenotype of a patient with Bietti crystalline dystrophy (BCD) complicated by choroidal neovascularization (CNV) and the response to intravitreal Bevacizumab (Avastin^®; Genentech/Roche).

METHODS

A 34-year-old woman with BCD and mutations in CYP4V2 (c.802-8_806del13/p.H331P:c992A>C) underwent a complete ophthalmic examination, full-field flash electroretinography (ERG), kinetic and two-color dark-adapted perimetry, and dark-adaptometry. Imaging was performed with spectral domain optical coherence tomography (SD-OCT), near infrared (NIR) and short wavelength (SW) fundus autofluorescence (FAF), and fluorescein angiography (FA).

RESULTS

Best-corrected visual acuity (BCVA) was 20/20 and 20/60 for the right and left eye, respectively. There were corneal paralimbal crystal-like deposits. Kinetic fields were normal in the peripheral extent. Retinal crystals were most obvious on NIR-reflectance and corresponded with hyperreflectivities within the RPE on SD-OCT. There was parafoveal/perifoveal hypofluorescence on SW-FAF and NIR-FAF. Rod > cone sensitivity loss surrounded fixation and extended to ~10° of eccentricity corresponding to regions of photoreceptor outer segment-retinal pigmented epithelium (RPE) interdigitation abnormalities. The outer nuclear layer was normal in thickness. Recovery of sensitivity following a ~76% rhodopsin bleach was normal. ERGs were normal. A subretinal hemorrhage in the left eye co-localized with elevation of the RPE on SD-OCT and leakage on FA, suggestive of CNV. Three monthly intravitreal injections of Bevacizumab led to restoration of BCVA to baseline (20/25).

CONCLUSION

crystals in BCD were predominantly located within the RPE. Photoreceptor outer segment and apical RPE abnormalities underlie the relatively extensive retinal dysfunction observed in relatively early-stage BCD. Intravitreal Bevacizumab was effective in treating CNV in this setting.

Adeno-associated virus 8-mediated gene therapy for choroideremia: preclinical studies in in vitro and in vivo models

BACKGROUND

Choroideremia (CHM) is a slowly progressive X-linked retinal degeneration that results in a loss of photoreceptors, retinal pigment epithelium and choroid. CHM, the gene implicated in choroideremia, encodes Rab escort protein-1 (REP-1), which is involved in the post-translational activation via prenylation of Rab proteins.

METHODS

We evaluated AAV8.CBA.hCHM, a recombinant adeno-associated virus serotype 8 (rAAV8) vector, which targets retinal cells efficiently, for both therapeutic effect and safety in vitro and in vivo in a murine model. In vitro studies included western blot analyses and prenylation assays. In vivo studies included ophthalmoscopy, pupillometry, histology and immunofluorescence analysis.

RESULTS

Infection with AAV8.CBA.hCHM induced the expression of REP-1 protein in a dose-responsive fashion. Transduction with AAV8.CBA.hCHM reverses the biochemical and pathogenetic defects in CHM both in vitro and in vivo and showed no safety concerns in the in vivo investigations performed in the present study.

CONCLUSIONS

AAV8 is a promising vector for human clinical gene therapy trials for choroideremia.

High-resolution adaptive optics retinal imaging of cellular structure in choroideremia

PURPOSE

We characterized retinal structure in patients and carriers of choroideremia using adaptive optics and other high resolution modalities.

METHODS

A total of 57 patients and 18 carriers of choroideremia were imaged using adaptive optics scanning light ophthalmoscopy (AOSLO), optical coherence tomography (OCT), autofluorescence (AF), and scanning light ophthalmoscopy (SLO). Cone density was measured in 59 eyes of 34 patients where the full cone mosaic was observed.

RESULTS

The SLO imaging revealed scalloped edges of RPE atrophy and large choroidal vessels. The AF imaging showed hypo-AF in areas of degeneration, while central AF remained present. OCT images showed outer retinal tubulations and thinned RPE/interdigitation layers. The AOSLO imaging revealed the cone mosaic in central relatively intact retina, and cone density was either reduced or normal at 0.5 mm eccentricity. The border of RPE atrophy showed abrupt loss of the cone mosaic at the same location. The AF imaging in comparison with AOSLO showed RPE health may be compromised before cone degeneration. Other disease features, including visualization of choroidal vessels, hyper-reflective clumps of cones, and unique retinal findings, were tabulated to show the frequency of occurrence and model disease progression.

CONCLUSIONS

The data support the RPE being one primary site of degeneration in patients with choroideremia. Photoreceptors also may degenerate independently. High resolution imaging, particularly AOSLO in combination with OCT, allows single cell analysis of disease in choroideremia. These modalities promise to be useful in monitoring disease progression, and in documenting the efficacy of gene and cell-based therapies for choroideremia and other diseases as these therapies emerge. (ClinicalTrials.gov number, NCT01866371.).

Late recurrence of retinopathy of prematurity after treatment with both intravitreal bevacizumab and laser

An infant of 36 weeks' postmenstrual age (PMA) and 25 weeks' gestation received bilateral intravitreal bevacizumab injections for type 1 retinopathy of prematurity. He underwent laser photocoagulation in both eyes 5 days later, confluent except for 1 clock hour obscured by hemorrhage in the left eye. Despite initial regression, neovascularization in both vascularized and lasered retina with plus disease recurred, requiring repeat laser bilaterally at 51 weeks' PMA and vitrectomy in the left eye at 54 weeks' PMA. Whereas late recurrence is thought to occur rarely after laser treatment, infants who have received both bevacizumab injections and laser may still require long-term surveillance for recurrence. In this case, fundus photography proved valuable for appreciating recurrent plus disease because the initial treatments had resulted in marked retinal vessel attenuation.

Retinal Structure in Cobalamin C Disease: Mechanistic and Therapeutic Implications

PURPOSE

To describe the retinal structure in a patient with cobalamin C (cblC) disease.

METHODS

A 13-year-old male patient diagnosed with cblC disease during a perinatal metabolic screening prompted by jaundice and hypotony underwent ophthalmic examinations, electroretinography (ERG) and spectral domain optical coherence tomography (SD-OCT).

RESULTS

The patient carried a homozygous (c.271dupA) mutation in the methylmalonic aciduria and homocystinuria type C (MMACHC) gene. At age 3 months he had a normal eye exam. A pigmentary maculopathy progressed to chorioretinal atrophy from 5-10 months. ERG at 7 months was normal. A nystagmus remained stable since the age of 2 years. At age 13, visual acuity was 20/250 (right eye) and 20/400 (left eye), with a +5.00 D correction, a level of vision maintained since first measurable at age 5 years. SD-OCT showed bilateral macular coloboma-like lesions; there was also a thickened surface layer with ganglion cell layer thinning. Photoreceptor outer segment loss and thinning of the outer nuclear layer (ONL) transitioned to regions with no discernible ONL with a delaminated, thickened, inner retina.

CONCLUSIONS

A thick surface layer near the optic nerve resembling an immature retina and an initially normal macula that rapidly developed coloboma-like lesions suggest there may be an interference with retinal/foveal development in cblC, a mechanism of maculopathy that may be shared by other early onset retinal degenerations. Photoreceptor loss and inner retinal remodeling confirm associated photoreceptor degeneration.

AAV-mediated gene therapy for choroideremia: preclinical studies in personalized models

Choroideremia (CHM) is an X- linked retinal degeneration that is symptomatic in the 1^st or 2^nd decade of life causing nyctalopia and loss of peripheral vision. The disease progresses through mid-life, when most patients become blind. CHM is a favorable target for gene augmentation therapy, as the disease is due to loss of function of a protein necessary for retinal cell health, Rab Escort Protein 1 (REP1).The CHM cDNA can be packaged in recombinant adeno-associated virus (rAAV), which has an established track record in human gene therapy studies, and, in addition, there are sensitive and quantitative assays to document REP1 activity. An animal model that accurately reflects the human condition is not available. In this study, we tested the ability to restore REP1 function in personalized in vitro models of CHM: lymphoblasts and induced pluripotent stems cells (iPSCs) from human patients. The initial step of evaluating safety of the treatment was carried out by evaluating for acute retinal histopathologic effects in normal-sighted mice and no obvious toxicity was identified. Delivery of the CHM cDNA to affected cells restores REP1 enzymatic activity and also restores proper protein trafficking. The gene transfer is efficient and the preliminary safety data are encouraging. These studies pave the way for a human clinical trial of gene therapy for CHM.