100,000 diagnosed US patients narrow to a 55,000-65,000-patient pool with no adequate novel therapy, and gene-therapy uptake is running well below its own pre-launch projection.
The funnel starts at roughly 100,000 Americans living with sickle cell disease, occurring in about 1 in 365 Black or African American births. Within that population, an estimated 20,000-30,000 patients have severe, recurrent vaso-occlusive disease, defined as two or more severe crises a year, the subset for whom one-time gene therapy is clinically relevant. But clinical relevance and actual eligibility are not the same thing: age, HSCT-candidacy, comorbidity, and state-by-state Medicaid contracting under CMS's Cell and Gene Therapy Access Model narrow that subset further, to an estimated 5-10% of the total SCD population who can realistically access Casgevy or Lyfgenia today.
The larger and commercially more consequential number sits outside the gene-therapy funnel entirely. Hydroxyurea-inadequate or -intolerant patients, those with three or more crises a year despite six-plus months at maximum tolerated dose, number an estimated 15,000-20,000. Gene-therapy-ineligible patients, whether by age, comorbidity, non-HSCT candidacy, or residence in a state without a Medicaid CGTA agreement, number more than 40,000. Combined, that is 55,000-65,000 US patients with no adequate novel therapy option, a white space that exists precisely because crizanlizumab and voxelotor were both withdrawn from the market and nothing has replaced them. Even within the smaller eligible pool, uptake has lagged: an estimated 50-100 patients were treated with Casgevy or Lyfgenia in the first 12 months post-launch, against pre-launch projections of 200-300, held back by HSCT-centre qualification and slow Medicaid negotiation.
US sickle cell disease funnel — from diagnosed population to the no-adequate-therapy pool
| Funnel Stage | Population | Source |
|---|---|---|
| Diagnosed US SCD population | ~100,000 | Hassell, Am J Prev Med 2010 (PMID 20331952) |
| Severe, gene-therapy-relevant subset (≥2 severe VOCs/yr) | 20,000-30,000 | US SCD disease landscape assessment |
| Hydroxyurea-inadequate or -intolerant patients | 15,000-20,000 | IQVIA SCD treatment claims data 2024 |
| Gene-therapy-ineligible patients (age, comorbidity, no state Medicaid CGTA) | 40,000+ | Medicaid CGTA state adoption tracker |
| Combined no-adequate-therapy pool | 55,000-65,000 | IQVIA SCD treatment claims data 2024 |
| Gene-therapy patients actually treated, first 12 months | 50-100 (vs 200-300 projected) | Vertex/bluebird bio commercial updates |
Sources: Hassell KL, Am J Prev Med 2010 (PMID 20331952); CDC Sickle Cell Disease surveillance data; ASH 2020 SCD guidelines; CMS Cell and Gene Therapy Access Model (2024); IQVIA SCD treatment claims data 2024; Medicaid CGTA state adoption tracker; Vertex and bluebird bio commercial updates.
What this model answers
Every section answers a named commercial question your team is asking, scoped to your asset.
Delivers
- The 15,000-20,000 hydroxyurea-inadequate/intolerant pool
- the 40,000-plus gene-therapy-ineligible pool
- why the combined 55,000-65,000 white space exists and how it was built after two withdrawals
Delivers
- The 5-10% eligibility narrowing from HSCT-candidacy and Medicaid CGTA state adoption
- the qualified-treatment-centre bottleneck
- where the gap between projected and actual uptake actually sits
Delivers
- 8-sheet structure (Strategic Context, Inputs, Model, Projections, Sensitivity, References, Market Context, QC)
- 112 formulas, zero hardcoded cells
- CDC/ASH/CMS source citation per conversion step
Custom model delivered in 72 hours.
Commission This ModelWhat's inside
- Why the no-adequate-therapy pool, not gene-therapy eligibility alone, sets the true addressable market
- Pressure-tested against the post-withdrawal treatment landscape before the rest of the model is built out
- ~100,000 diagnosed US SCD patients (Hassell, Am J Prev Med 2010)
- Genotype spectrum: HbSS ~60-65%, HbSC ~25%, HbS/β-thalassemia ~8-10%
- 20,000-30,000 patients with severe, recurrent vaso-occlusive disease
- Distinguishing clinical relevance from actual gene-therapy eligibility
- 15,000-20,000 hydroxyurea-inadequate or -intolerant patients
- 40,000+ gene-therapy-ineligible patients and how the two pools combine to 55,000-65,000
- 50-100 patients treated in year one against 200-300 projected
- HSCT-centre qualification and state Medicaid CGTA adoption as the binding constraints
- Which assumptions move the addressable pool most
- Scenario ranges across the hydroxyurea-inadequate and gene-therapy-ineligible pathways
- Patient volume by horizon under conservative, base, and aggressive scenarios
- Revenue translation inputs for the 55,000-65,000-patient white space
- The open questions your forecasting team must close before the model is finalised
- Structured for an internal forecast-review session
Included with every brief
How AXLRx builds this model
Prepared by MoatRx analysts.
Every AXLRx patient flow model is built on a five-layer funnel: population, disease burden (E1), severity and diagnosis capture (E2), treatment and eligibility (E3), market access (E4), then Year 1-3-5 projections across three scenarios. Delivered as a live Excel workbook, not a static table: 112 formulas across 8 sheets, zero hardcoded cells.
US Sickle Cell Disease sources: Hassell, Am J Prev Med 2010 (PMID 20331952), CDC SCD surveillance data, ASH 2020 guidelines, CMS Cell and Gene Therapy Access Model program documentation, and IQVIA treatment claims data 2024.
- Diagnosed US SCD population estimate verified against Hassell KL, Am J Prev Med 2010 (PMID 20331952)
- Severe subset and hydroxyurea utilisation cross-checked against CDC surveillance data and ASH 2020 guidelines
- Hydroxyurea-inadequate and gene-therapy-ineligible pool sizing verified against IQVIA SCD treatment claims data 2024 and the Medicaid CGTA state adoption tracker
- Gene-therapy year-one uptake versus projection verified against Vertex and bluebird bio commercial updates
Frequently asked questions
Commission this model
AXLRx delivers rare disease patient flow models built for forecasting and launch teams sizing the US sickle cell disease no-adequate-therapy population. Custom model in 72 hours.
Specify your indication, market, and cohort definition.
AXLRx analyst confirms funnel scope and comparator set before building.
Research-verified patient flow model in 72 hours with optional analyst readout.