OBJECTIVES: The FDA anticipate that 10-20 cell and gene therapies will be approved per year by 2025. Prevalence of target diseases has a big impact on payers, as well as manufacturers. Here, we analyse the prevalence of disease areas being targeted in gene therapy clinical trials, and consider what the implications of prevalence are for both industry and healthcare systems.

METHODS: A list of gene therapies in Phase I - III development was extracted from clinicaltrials.gov. Prevalence was categorised as follows: prevalent (>50/100,000), rare (≤50 - ≥2/100,000), and ultra-rare (<2/100,000). Prevalence of the disease areas assessed was based on Orphanet data.

RESULTS: The 98 gene therapy assets analysed, 50% were targeting rare diseases. 35% of disease areas were classed as ultra-rare, whilst 15% were classed as prevalent conditions. The prevalent conditions almost exclusively fell under the therapy areas of neurology and ophthalmology, with Parkinson’s disease and AMD accounting for over half of the prevalent category. Ultra-rare conditions were most typically metabolic or neurologic, a number of the lysosomal storage disorders fitting into this category.

CONCLUSIONS: Rare diseases account for 50% of the gene therapy pipeline and are a potentially attractive compromise of a reasonably large addressable population for manufacturers that will not create an overly large budget impact for payers and allow manufacturers to obtain a competitive price. Over a third of disease areas being targeted by gene therapies are ultra-rare. Previous examples demonstrate the challenge of launching in ultra-rare diseases, where the number of eligible patients can at times be prohibitively low. Finally, it is worth noting that 15% of gene therapies are being tested in prevalent conditions. Should any of these prevalent disease-targeted gene therapies launch, it will provide an interesting challenge for payers and manufacturers alike, given currently approved gene therapies are targeted against either rare or ultra-rare conditions.