Abstract
Purpose :
Gene therapy is currently the only FDA-approved treatment for an inherited retinal degeneration and has shown promise in clinical trials for the treatment for several other genetic retinal diseases. As more gene therapies receive market approval, healthcare systems may struggle to cover such expensive medicines regardless of their clinical efficacy. We have applied the published Phase I/II data from choroideremia gene therapy AAV.REP1 as a case study to model the cost-effectiveness of gene therapy in which visual function is close to normal in early life but then progresses to blindness.
Methods :
We built a lifetime clinically-informed Markov model of choroideremia-associated progressive visual field and acuity loss, quantified using quality-adjusted life years (QALYs). Cost-effectiveness was calculated across varying product costs from $100,000 to $1 million. Incremental net monetary benefit (iNMB) was calculated to determine the incremental cost-effectiveness of AAV.REP1 over the lifetime of the patient. The model was applied to patients at three different stages of the disease – early, mid, and late as defined by their combined remaining retinal area, visual acuity, and age – to replicate how the treatment is likely to be applied.
Results :
Since untreated eyes invariably continue to progress, the QALY can be modeled at whichever stage the intervention occurs. AAV.REP1 delivered 8.65 QALYs in early-stage patients, 4.46 QALYs for mid-stage patients, and 1.14 QALYs for late-stage patients over their lifetime. Over shorter time horizons, AAV.REP1 delivered up to 2 QALYs. At the lowest price-point of $100,000, AAV.REP1 was cost-effective for all subgroups; at $1 million, AAV.REP1 was cost-effective for early and mid-stage patients. The iNMB analyses showed the benefit of AAV.REP1 was greatest later in life. AAV.REP1 was not found to be cost-effective over shorter time horizons at all but the lowest price points, likely because of the slow progression of choroideremia even without treatment over short horizons.
Conclusions :
When evaluated across the lifetime of the patient, AAV.REP1 delivers significant QALY benefit and is generally cost-effective. Over shorter time horizons, gene therapy with AAV.REP1 was generally found to be less cost-effective, due to the slow disease progression. The long-term benefit of AAV.REP1 should therefore be considered when assessing QALY values for gene therapy interventions at early stages.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.