Fenfluramine posted the highest efficacy in class, a 62.3% greater reduction in convulsive seizures than placebo, but its REMS cardiac-monitoring burden and a roughly 3x list-price premium over cannabidiol define the competitive contest.
Dravet syndrome is a paediatric-onset developmental and epileptic encephalopathy, and its US market is defined by three FDA-approved, syndrome-specific agents layered on a generic valproate and clobazam backbone. Cannabidiol (Epidiolex, Jazz Pharmaceuticals, acquired with GW Pharma) was approved in June 2018 as the first cannabis-derived FDA drug on the GWPCARE programme. Fenfluramine (Fintepla, UCB, acquired with Zogenix) followed in June 2020 with a REMS cardiac-monitoring requirement. Stiripentol (Diacomit, Biocodex) was approved in August 2018 for adjunctive use with valproate and clobazam.
The competitive story turns on an efficacy-versus-cost tension. In its pivotal Study 1, fenfluramine 0.7 mg/kg/day produced a 62.3% greater reduction in monthly convulsive seizure frequency than placebo (median reduction 74.9%), the strongest published result in the class, but carries a REMS echocardiography burden and a weight-based list price averaging near $96,000/year. Cannabidiol's GWPCARE1 trial showed a 38.9% median convulsive-seizure reduction versus 13.3% on placebo at a lower list price (~$32,000/year), and no generic has yet entered the US market (ANDA litigation settled to the late 2030s). Stiripentol remains adjunct-only, reimbursed within the valproate/clobazam regimen.
FDA-approved Dravet syndrome therapies — United States, 2026
| Drug (Brand / INN) | Mechanism | Company | US Approval | Key Trial Result |
|---|---|---|---|---|
| Epidiolex (cannabidiol) | Plant-derived cannabidiol (oral) | Jazz Pharmaceuticals | Jun 2018 | GWPCARE1: convulsive-seizure frequency −38.9% vs −13.3% placebo |
| Fintepla (fenfluramine) | Serotonin-releasing agent, low-dose (oral); REMS | UCB (Zogenix) | Jun 2020 | Study 1: 62.3% greater reduction in monthly convulsive seizures vs placebo |
| Diacomit (stiripentol) | GABA-A modulator + CYP inhibitor (oral, adjunct) | Biocodex | Aug 2018 | STICLO: 71% responder rate vs 5% placebo (adjunct to valproate + clobazam) |
| Valproate / clobazam | GABAergic AED backbone (generic) | Multiple generics | — | Backbone standard of care; inadequate seizure control in most Dravet patients |
Sources: FDA Drugs@FDA (approval status and dates); GWPCARE1, NEJM 2017 (PMID 28538134); fenfluramine Study 1, Lancet 2019 (PMID 31862249); STICLO, Lancet 2000 (PMID 11089822).
What this brief answers
Every section answers a named commercial question your team is asking, scoped to your asset.
Delivers
- Cannabidiol, fenfluramine and stiripentol compared across GWPCARE1, Study 1 and STICLO
- oral dosing and the Fintepla REMS cardiac-monitoring requirement
- positioning on the valproate/clobazam backbone
Delivers
- Lower-cost cannabidiol as a step-edit gate before fenfluramine
- the outlook for eventual generic cannabidiol (ANDA litigation settled to the late 2030s)
- the efficacy-versus-cost argument fenfluramine must make to hold access
Delivers
- Study 1 efficacy positioning
- the roughly 3x list-price premium over cannabidiol
- prescriber and payer decision drivers in a small, severe paediatric population
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Commission This BriefWhat's inside
- How three FDA-approved syndrome-specific agents (cannabidiol, fenfluramine, stiripentol) layer onto the generic valproate-clobazam backbone.
- Why the valproate-clobazam AED backbone provides inadequate seizure control in most Dravet patients despite being standard of care.
- How Jazz's Epidiolex (June 2018), UCB's Fintepla (June 2020), and Biocodex's Diacomit (August 2018) entered the US market.
- Why Fintepla's REMS cardiac-monitoring requirement distinguishes fenfluramine's safety profile from cannabidiol and adjunct-only stiripentol.
- Why fenfluramine's Study 1 result (62.3% greater seizure reduction than placebo) is the strongest published figure in the class.
- How GWPCARE1's 38.9% cannabidiol seizure reduction and STICLO's 71% stiripentol responder rate compare to placebo.
- How cannabidiol's roughly $32,000 annual list price versus fenfluramine's ~$96,000 creates a natural step-edit gate.
- Why payers can use lower-cost cannabidiol as a first-line gate before fenfluramine despite its smaller efficacy edge.
- Why no generic cannabidiol will reach the US market before the late 2030s under settled ANDA litigation.
- How fenfluramine's roughly 3x price premium over cannabidiol forces prescribers to justify its efficacy advantage to payers.
- How ANDA litigation settling generic cannabidiol entry to the late 2030s preserves Epidiolex's branded position for over a decade.
- Why any next-generation Dravet agent must still be measured against the generic valproate-clobazam backbone standard of care.
Included with every brief
How AXLRx builds this brief
Prepared by MoatRx analysts.
Every AXLRx brief is built from primary regulatory sources (FDA Drugs@FDA, ClinicalTrials.gov), peer-reviewed literature, and live payer and HTA documentation — not secondary summaries, market-research reports, or unverified estimates. Findings are independently verified before inclusion; if a figure cannot be sourced to a live record, it does not ship.
US Dravet Syndrome Competitive Intelligence sources: FDA Drugs@FDA (approval status and dates); the GWPCARE1 cannabidiol trial (Devinsky et al., NEJM 2017, PMID 28538134); the pivotal fenfluramine Study 1 (Lagae et al., Lancet 2019, PMID 31862249); and the STICLO stiripentol trial (Chiron et al., Lancet 2000, PMID 11089822).
- Cannabidiol GWPCARE1 efficacy verified against Devinsky et al., NEJM 2017 (PMID 28538134)
- Fenfluramine 62.3% reduction verified against the pivotal Study 1, Lagae et al., Lancet 2019 (PMID 31862249)
- Stiripentol responder rate verified against the STICLO trial, Chiron et al., Lancet 2000 (PMID 11089822)
- Approval status and indications verified against FDA Drugs@FDA
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