Voretigene Neparvovec for Treating Inherited Retinal Dystrophies Caused by RPE65 Gene Mutations: An Evidence Review Group Perspective of a NICE Highly Specialised Technology Appraisal

EQ-5D-5L health utility scores in Australian adults with inherited retinal diseases: A cross-sectional survey

PURPOSE

Economic evaluations of interventions for ocular disease require utility scores that accurately represent quality of life in the target population. This study aimed to describe the distribution of EQ-5D-5L utility values among Australian adults with symptomatic inherited retinal diseases (IRDs) and to assess the relationship between these scores and vision-related quality of life.

METHODS

A survey was administered predominantly online in 2021. Participants completed the EQ-5D-5L general health utility instrument, the EQ vertical visual analogue scale (EQ-VAS) and the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25). Self-reported IRD diagnoses were classified as being associated with central or widespread retinal involvement.

RESULTS

Responses from 647 participants aged 18-93 years were included, 50.1% were men and 77.6% had an IRD associated with widespread retinal involvement. The majority reported no problems with self-care and no pain/discomfort but did report anxiety/depression and problems with work, study, housework, or family/leisure activities. Most people with widespread involvement reported problems with mobility. Median EQ-5D-5L utility was 0.88 and 0.91 among people with widespread and central involvement, respectively (age and sex-adjusted p = 0.029); and median EQ-VAS was 75 and 80, respectively (adjusted p = 0.003). A moderate curvilinear correlation was observed between EQ-5D-5L and NEI-VFQ-25 composite score (Spearman's ρ 0.69), but not all people with poor vision-related quality of life had low EQ-5D-5L utility values.

CONCLUSIONS

EQ-5D-5L health utility values are correlated with vision-related quality of life among adults with IRDs. However, the EQ-5D-5L may not be sensitive to the full impact of vision impairment on quality of life.

[Inherited retinal diseases in Germany-Challenges in health care supply structure and diagnostics]

BACKGROUND

Inherited retinal diseases (IRD) are rare eye diseases and pose high diagnostic challenges. A care structure with few highly specialized centers in Germany, misdiagnosis due to the lack of molecular genetic testing, and a lack of a central registry lead to a lack of reliable information on the prevalence and distribution of IRDs in Germany.

METHODS

Based on clinical data from an ophthalmological center and molecular data from a genetic center as well as a nationwide health insurance data query, we estimated the prevalence of IRDs in Germany in addition to collecting information on their phenotypic and genotypic distribution.

RESULTS

The median travelling distance to the ophthalmological center was 60 km. The most frequent diagnoses were retinitis pigmentosa, macular dystrophy and general retinal dystrophy. Molecular genetic testing was performed in 87% of patients with clinical suspicion of IRD, with marked differences in frequencies among age cohorts. The molecular genetic detection rate in the genetic center was 51%. The prevalence of inherited retinal dystrophy in Germany determined by health insurance data retrieval was approximately 1:1150.

CONCLUSION

Many patients must travel long distances to visit specialized clinics for IRDs with access to genetic testing. To obtain more reliable numbers on the prevalence in Germany, routine molecular genetic testing, and a national registry for IRD detection are needed.

The blood-retina barrier in health and disease

The blood-retina barrier (BRB) is the term used to define the properties of the retinal capillaries and the retinal pigment epithelium (RPE), which separate the systemic circulation from the retina. More specifically, the inner blood-retina barrier (iBRB) is used to describe the properties of the endothelial cells that line the microvasculature of the inner retina, while the outer blood-retina barrier (oBRB) refers to the properties of the RPE cells that separate the fenestrated choriocapillaris from the retina. The BRB is not a fixed structure; rather, it is dynamic, with its components making unique contributions to its function and structural integrity, and therefore the retina. For example, while tight junction (TJ) proteins between retinal endothelial cells are the key molecular structures in the maintenance of the iBRB, other cell types surrounding endothelial cells are also important. In fact, this overall structure is termed the neurovascular unit (NVU). The integrity of the BRB is crucial in the maintenance of a 'dry', tightly regulated retinal microenvironment through the regulation of transcellular and paracellular transport. Specifically, breakdown of TJs can result in oedema formation, a hallmark feature of many retinal diseases. Here, we will describe the oBRB briefly, with a more in-depth focus on the structure and function of the iBRB in health and diseased states. Finally, the contribution of the BRB to the pathophysiology of age-related macular degeneration (AMD), diabetic retinopathy (DR) and other rarer retinal diseases will be discussed.

Economic Evidence on Potentially Curative Gene Therapy Products: A Systematic Literature Review

OBJECTIVE

The aim of this review was to summarize all available evidence on the cost effectiveness of potentially curative gene therapies and identify challenges that economic evaluations face in this area.

METHODS

We conducted a systematic review of four databases (PubMed/MEDLINE, Embase, CINAHL, EconLit) and grey literature sources. We conducted the search on August 23, 2019 and updated it on November 26, 2020. We included all English, French and Spanish language studies that addressed a gene therapy that had received regulatory approval or had entered a phase III trial, and also reported on costs related to the therapy. Critical appraisal was conducted to assess quality of reporting in included studies.

RESULTS

Fifty-six studies were identified. Of the 42 full economic evaluations, 71% (n = 30) evaluated chimeric antigen receptor T-cell therapies, most used either a Markov model (n = 17, 40%) and/or a partitioned survival model (n = 17, 40%), and 76% (n = 32) adopted a public or private payer perspective. The model characteristics with the greatest impact on cost effectiveness included assumptions about the efficacy of the treatment and the comparators used.

CONCLUSION

All gene therapies in this review were shown to be more effective than their comparators, although due to high costs not all were considered cost effective at standard cost-effectiveness thresholds. Despite their high cost, some gene therapies have the potential to dominate the alternatives in conditions with high mortality/disability. The choice of comparator and assumptions regarding long-term effectiveness had substantial impacts on cost-effectiveness estimates and need to be carefully considered. Both the quality of inputs and the quality of reporting were highly variable.

RPE65-associated inherited retinal diseases: consensus recommendations for eligibility to gene therapy

Background

This research aimed to establish recommendations on the clinical and genetic characteristics necessary to confirm patient eligibility for gene supplementation with voretigene neparvovec.

Methods

An expert steering committee comprising an interdisciplinary panel of Italian experts in the three fields of medical specialisation involved in the management of RPE65-associated inherited retinal disease (IRD) (medical retina, genetics, vitreoretinal surgery) proposed clinical questions necessary to determine the correct identification of patients with the disease, determine the fundamental clinical and genetics tests to reach the correct diagnosis and to evaluate the urgency to treat patients eligible to receive treatment with voretigene neparvovec. Supported by an extensive review of the literature, a series of statements were developed and refined to prepare precisely constructed questionnaires that were circulated among an external panel of experts comprising ophthalmologists (retina specialists, vitreoretinal surgeons) and geneticists with extensive experience in IRDs in Italy in a two-round Delphi process.

Results

The categories addressed in the questionnaires included clinical manifestations of RPE65-related IRD, IRD screening and diagnosis, gene testing and genotyping, ocular gene therapy for IRDs, patient eligibility and prioritisation and surgical issues. Response rates by the survey participants were over 90% for the majority of items in both Delphi rounds. The steering committee developed the key consensus recommendations on each category that came from the two Delphi rounds into a simple and linear diagnostic algorithm designed to illustrate the patient pathway leading from the patient’s referral centre to the retinal specialist centre.

Conclusions

Consensus guidelines were developed to guide paediatricians and general ophthalmologists to arrive at the correct diagnosis of RPE65-associated IRD and make informed clinical decisions regarding eligibility for a gene therapy approach to RPE65-associated IRD. The guidelines aim to ensure the best outcome for the patient, based on expert opinion, the published literature, and practical experience in the field of IRDs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01868-4.

Methodological Challenges in the Economic Evaluation of a Gene Therapy for RPE65-Mediated Inherited Retinal Disease: The Value of Vision

The emergence of gene therapies challenge health economists to evaluate interventions that are often provided to a small patient population with a specific gene mutation in a single dose with high upfront costs and uncertain long-term benefits. The objective of this study was to illustrate the methodological challenges of evaluating gene therapies and their implications by discussing four economic evaluations of voretigene neparvovec (VN) for the treatment of RPE65-mediated inherited retinal disease. The checklist for economic evaluations of gene therapies of Drummond et al. was applied to the economic evaluations of VN performed by US Institute for Clinical and Economic Review, two country adaptations of the company model in the UK and the Netherlands, and another US publication. The main differences in methodological choices and their impact on cost-effectiveness results were assessed and further explored with sensitivity analyses using the Dutch model. To enable comparison between the economic evaluations, costs were converted to US dollars. Different methodological choices were made in the economic evaluations of VN resulting in large differences in the incremental cost-effectiveness ratio varying from US$79,618 to US$643,813 per QALY. The chosen duration of treatment effect, source of utility values, discount rate and model structure had the largest impact on the cost-effectiveness. This study underlines the findings from Drummond et al. that standard methods can be used to evaluate gene therapies. However, given uncertainty about (particularly long-term) outcomes of gene therapies, guidance is required on the acceptable extrapolation of treatment effect of gene therapies and on how to handle the uncertainty around this extrapolation in scenario and sensitivity analyses to aid health technology assessment research and align submissions of future gene therapies.