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Celine-Lea Halioua-Haubold, Jasleen Jolly, Rafael Pinedo Villanueva, David Brindley, Robert E MacLaren; A dual variable Markov model to assess the potential benefits of choroideremia gene therapy on quality adjusted life years (QALYs). Invest. Ophthalmol. Vis. Sci. 2018;59(9):3897.
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© ARVO (1962-2015); The Authors (2016-present)
Gene therapy is currently the only therapeutic option for inherited retinal degenerations. Although the significant reimbursement costs of gene therapies may pose challenges for patient access, it needs to be balanced against the impact of sight loss. To investigate the benefit of retinal gene therapy, we estimated the potential quality of life impact of choroideremia (CHM) associated visual degeneration. CHM is an appropriate model of a gene therapy disease target: it has a young patient population, has no treatment, and invariably causes blindness, thereby having a severe impact on quality of life.
We built a lifetime Markov model of CHM-associated progressive visual degeneration. The impact of visual impairment on the patient was measured in quality-adjusted life-years (QALYs). In the hypothetical scenario, patients received either no treatment or the curative gene therapy, which was assumed to be 98% effective in halting degeneration in either one or both eyes when both eyes are treated. Three case studies were modeled: 20-year-old patients with preserved retinal area and visual acuity (P1); 45-year-olds who had significantly deteriorated retinal area but preserved visual acuity (P2); and 60-year-old patients who had both significantly deteriorated retinal area and reduced visual acuity (P3). The data were modelled on published natural history data of the disease. Patients who received successful gene therapy were assumed still to be at risk of visual impairment due to non-CHM disease or injury at population-wide rates.
On the assumption that CHM patients receiving gene therapy showed significant retention of visual functionality over non-treated patients, subgroup P1 patients were estimated to gain a mean of 19.96 QALYs; for P2 the expected increase in quality of life was 6.68 QALYs, whereas for P3, gene therapy was associated with an expected gain of 4.43 QALYs.
In young adults in the earlier stages of the disease, successful gene therapy provides a significant increase in health-related quality of life that can be quantified. In pediatric patients, the impact may be higher. Even for older patients with very advanced degeneration, the gains are smaller but still present.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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