Key takeaways
- 1 in 15,700 US Dravet syndrome birth incidence, Kaiser Permanente Northern California cohort
- 6,000-8,000 Dravet Syndrome Foundation US prevalence estimate, consistent with the incidence-based method
- ~75% of clinical Dravet cases with a confirmed de novo SCN1A mutation
- 1,400-2,000 US patients inadequately controlled on cannabidiol plus fenfluramine, the addressable refractory cohort at 35-40% of prevalence
Incidence-based epidemiology and the Dravet Syndrome Foundation's registry-based prevalence estimate agree on a 6,000-8,000 patient US population, and the commercially addressable segment sits inside it: 1,400-2,000 patients remain inadequately controlled on the two approved branded agents.
Two independent methods size the US Dravet syndrome population, and they converge rather than diverge. The epidemiology method starts from a population-based incidence study: a Kaiser Permanente Northern California cohort put incidence at 1 per 15,700 births, roughly twice the earlier 1-in-40,000 estimate, with a likely-pathogenic de novo SCN1A mutation confirmed in approximately 75% of clinical cases. Applied against US birth cohorts and adjusted for a paediatric-onset, lifelong condition, that incidence rate is consistent with the Dravet Syndrome Foundation's registry-based prevalence estimate of 6,000 to 8,000 patients, the figure this model treats as the total addressable population.
The commercially relevant question is not total prevalence but treatment status within it. Of the estimated 6,000 to 8,000 US patients, 55 to 60% are managed on cannabidiol (Epidiolex) as first-line branded therapy, and 25 to 30% have stepped up to fenfluramine (Fintepla) after an inadequate cannabidiol response. That still leaves 35 to 40%, an estimated 1,400 to 2,000 patients, inadequately controlled, less than 50% seizure reduction, even on the combination of both branded agents. This refractory cohort, not the total prevalence figure, is the addressable population for any new Dravet-specific therapy, and it is the number a launch forecast should be built on.
US Dravet sizing — incidence-based estimate versus registry-based prevalence
| Sizing Method | Population Estimate | Source |
|---|---|---|
| Epidemiology-based (incidence) | 1 in 15,700 births; ~75% de novo SCN1A-confirmed | Kaiser Permanente Northern California cohort, Pediatrics 2015 |
| Registry-based (prevalence) | 6,000-8,000 patients | Dravet Syndrome Foundation |
| Treatment-status segmentation | 55-60% on cannabidiol; 25-30% on fenfluramine | Dravet Syndrome Foundation census 2023 |
| Refractory cohort (addressable) | 1,400-2,000 patients, 35-40% of prevalence | Derived from treatment-status segmentation |
Sources: Wu et al., Incidence of Dravet Syndrome in a US Population, Pediatrics 2015 (PMID 26438699); Dravet Syndrome Foundation census 2023 and prevalence estimate; UCB Fintepla REMS programme data 2024.
What this model answers
Every section answers a named commercial question your team is asking, scoped to your asset.
- How does the Kaiser Permanente incidence-based estimate of 1 in 15,700 reconcile with the Dravet Syndrome Foundation's registry-based prevalence of 6,000-8,000 patients? • Incidence-to-prevalence methodology • the de novo SCN1A confirmation rate • the triangulation confidence range between the two methods
- Within the 6,000-8,000 patient population, how many are already adequately controlled on cannabidiol and fenfluramine, and how many remain the addressable refractory cohort? • Treatment-status breakdown at 55-60% on cannabidiol and 25-30% on fenfluramine • the 1,400-2,000 patient refractory-cohort sizing • sensitivity ranking of the inputs that move this total
- Is total prevalence or the refractory-cohort size the right number to build a launch forecast on? • Why the addressable population is the refractory cohort, not total prevalence • scenario ranges tied to treatment-response assumptions • a confidence rating per input
What's inside
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1 · The Binding Constraint 2 pp
- Why the refractory cohort, not total prevalence, is the number that determines addressable market size
- Pressure-tested against the incidence-vs-registry triangulation before the rest of the model is built out
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2 · Epidemiology-Based Sizing 3 pp
- Kaiser Permanente Northern California incidence study, 1 in 15,700 births
- De novo SCN1A confirmation rate and what it implies for a genetically-defined prevalence
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3 · Registry-Based Sizing 3 pp
- Dravet Syndrome Foundation prevalence estimate, 6,000-8,000 patients
- Cross-check against the epidemiology-based estimate
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4 · Treatment-Status Segmentation 3 pp
- Cannabidiol and fenfluramine treated-population shares (55-60%, 25-30%)
- Sizing the refractory, inadequately-controlled cohort
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5 · Triangulation & Confidence Range 3 pp
- Where the two prevalence methods agree
- The treatment-response segmentation as the binding commercial variable
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6 · Sensitivity Analysis 3 pp
- Refractory-share assumption ranked against the prevalence-rate assumption
- Scenario ranges tied to treatment-response definitions
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7 · Client Alignment Questions 2 pp
- The open sizing questions your team must close before the number is used in planning
Appendix and source ledger included · 45-minute analyst readout included with delivery
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Commission this model
AXLRx delivers rare disease market sizing models built for forecasting and strategy teams sizing the US Dravet syndrome opportunity. Custom model in 72 hours.
- 1. Submit your requestSpecify your indication, market, and cohort definition.
- 2. Scoping callAXLRx analyst confirms triangulation methods and comparator set before building.
- 3. DeliveryResearch-verified sizing model in 72 hours with optional analyst readout.
How AXLRx builds this model
Prepared by MoatRx analysts on the AXLRx commercial consulting engine.
Every AXLRx market sizing model triangulates at least two independent methods, epidemiology-based and registry-based, before accepting a patient count. This is explicitly a sizing model, a static patient count, distinct from a Patient Flow or forecasting model that models dynamic revenue and uptake.
US Dravet syndrome sizing sources: Wu et al. (Pediatrics 2015, PMID 26438699), the Dravet Syndrome Foundation census 2023 and prevalence estimate, and UCB Fintepla REMS programme data 2024.
- US incidence (1 in 15,700) and de novo SCN1A fraction verified against Wu et al., Pediatrics 2015 (PMID 26438699)
- Registry-based prevalence estimate (6,000-8,000) verified against Dravet Syndrome Foundation data
- Treatment-status shares (55-60% cannabidiol, 25-30% fenfluramine) and the refractory-cohort estimate verified against Dravet Syndrome Foundation census 2023 and UCB Fintepla REMS programme data 2024
Frequently asked questions
Deliverables What formats are included with every model?
Every commissioned Market Sizing Model includes an editable 5-sheet Excel model (Cover, Model, Research Validation, QC, Sensitivity) and a PDF methodology brief, with no PowerPoint deck, since a sizing model is built to be worked in directly, not presented from. An optional 45-minute analyst readout call is included.
Sources How is the patient count verified?
AXLRx triangulates every sizing estimate across at least two independent methods, epidemiology-based and registry-based; no single-source number ships unverified.
Customisation Can I size a specific subpopulation or treatment-status segment?
Yes. The intake form captures your indication, target market, and cohort definition. A scoping call confirms scope before research starts. Commission via the intake form to start.