Cost Effectiveness of Adding Fenfluramine to Standard of Care for Patients with Dravet Syndrome in Sweden

Objective This study evaluated, in a Swedish setting, the cost effectiveness of fenfluramine (FFA) as an add-on to standard of care (SoC) for reducing seizure frequency in Dravet syndrome, a severe developmental epileptic encephalopathy. Methods Cost effectiveness of FFA+SoC compared with SoC only was evaluated using a patient-level simulation model with a lifetime horizon. Patient characteristics and treatment effects, including convulsive seizures, seizure-free days and mortality, were derived from FFA clinical trials. Resource use and costs included cost of drug acquisition, routine care and monitoring, as well as ongoing and emergency resources. Quality of life (QoL) estimates for patients and their caregivers were derived from clinical trial data. Robustness was evaluated by one-way sensitivity analysis, probabilistic sensitivity analysis and scenario analyses. Results Lifetime cost of FFA+SoC was ~3 million SEK per patient compared with ~1.5 million SEK for SoC only. FFA+SoC generated 15% more QALYs than SoC only (21.2 vs 18.5 over a lifetime), resulting in an incremental cost-effectiveness ratio (ICER) of ~540,000 SEK. Moreover, FFA+SoC had a higher probability of being cost effective than SoC only from a willingness-to-pay threshold of 710,000 SEK. Results remained generally consistent across scenario analyses, with only few exceptions (exclusions of carer utility or FFA effect on sudden unexpected death in epilepsy). Conclusion Due to better seizure control, FFA is a clinically meaningful add-on therapy and was estimated to be a cost-effective addition to current SoC for patients with this rare disease in Sweden at a willingness-to-pay threshold of 1,000,000 SEK.