The study, “Economic Evaluation of Stiripentol for Dravet Syndrome: A Cost-Utility Analysis,” was published in PharmacoEconomics.
Combination therapy, or the use of more than one treatment, is required to treat Dravet syndrome because the condition is typically resistant to anti-epileptic therapies. Stiripentol is often used in combination with clobazam and valproate in Dravet patients who show resistance to those therapies alone.
Although stiripentol has been approved for use in Canada to treat Dravet patients, its associated long-term costs and benefits have not been well-studied and its cost effectiveness is unclear.
While the manufacturer reports one figure in its cost analysis, a common drug review by the Canadian Agency for Drugs and Technologies in Health, an independent, nonprofit organization, noted several limitations with the analysis both in terms of methodology and in data assumptions, and questions the methods used to calculate the figure.
To conduct a cost-effectiveness analysis of the use of stiripentol as an add-on treatment to clobazam and valproate in Dravet patients, researchers used data from published studies to perform a model-based cost-utility analysis from the perspective of the Canadian healthcare system.
The outcomes associated with stiripentol treatment were measured based on computer-simulated replications. Their results yielded several outputs including an estimation of costs and quality-adjusted life-years (QALYs) in patients receiving stiripentol with clobazam and valproate over a 10-year period.
QALYs is a measure used to assess disease and determine value for money of treatments. In general, one unit of QALY is considered to be equivalent to one year in perfect health.
Researchers estimated that patients using stiripentol would gain 0.6 QALYs over a 10-year period compared with those using just clobazam and valproate.
Another measure used by the researchers to assess the benefits and costs of using stiripentol was the so-called incremental cost-effectiveness ratio (ICER) which, simply put, measures the financial cost of each QALY gained.
Although the manufacturer claims that the ICER of stiripentol is CA$50,122 per QALY gained over five years, the current study found that the use of stiripentol was associated with an ICER of CA$151,310.
At a willingness-to-pay threshold of CA$50,000, stiripentol was the optimal treatment in 5.2% of replications, while at a willingness-to-pay threshold of CA$100,000, stiripentol would be the optimal treatment in 20.7% of replications.
Results suggest that, from the perspective of the Canadian public healthcare payer, stiripentol is not a cost-effective Dravet treatment, and its “price would need to be reduced by at least 60% to ensure that funding of stiripentol would not lead to a reduction in overall population health,” the researchers said.