Background

Inherited retinal diseases (IRDs) are a group of rare genetic disorders that result in progressive vision loss. Among the most severe IRDs is X-linked Retinitis Pigmentosa (XLRP) which primarily affects males due to its X-linked recessive inheritance, with symptoms typically beginning in childhood. Patients initially experience night blindness, followed by tunnel vision and eventual central vision loss, leading to blindness by the fourth decade of life. Severity of visual impairment can be measured using a variety of tools - visual field, visual acuity, ellipsoid zone width, ellipsoid zone area, and vision-guided mobility assessment - but no universally agreed-on metric exists for measuring disease progression. 

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Challenge

The client's primary challenge was defining XLRP health states in order to model disease progression and quantify the benefits offered by an innovative therapy, as definitions of degrees of visual loss varied in literature, guidelines and previous clinical trials. In addition, the use of a novel XLRP-specific tool for modelling of utilities needed to be validated by experts, as EQ-5D and other generic and disease-specific tools were not sensitive enough to capture the impact of XLRP on patients' quality of life.  

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Approach

A panel of 10 globally renowned experts was convened for a two-day virtual advisory board. To ensure alignment and provide comprehensive context, participants attended a pre-advisory board webinar. This session outlined the client’s clinical development programme, detailed the objectives of the advisory board, and introduced key discussion topics. A Q&A session at the end allowed participants to address any preliminary questions.

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Outcomes

• ​The panel recommended using a combination of standard tools for measuring short- and long-term vision impairment, while highlighting the utility of emerging technologies to model disease progression. Clear benefits and drawbacks were outlined for modelling progression based on both eyes, the best eye, and the worst eye.   

• Experts reviewed the client's proposed novel approach for modelling XLRP utilities and made practical recommendations for addressing potential questions from HTA bodies.  Market-specific recommendations were also made for strengthening the evidence base by using supplementary tools and conducting additional studies.  

• These recommendations enabled the client to refine their modelling strategy and align it with HTA requirements, and to be better positioned to demonstrate the value of the novel therapy effectively.