A 4,000-patient moderate-severe subgroup and a 12,000-15,000-patient total prevalence estimate are not competing numbers, they measure different scopes, and both are needed to size the UK gMG opportunity correctly.
The narrower figure comes from MGA UK survey and registry data layered onto NHS neuromuscular network coordination: an estimated 4,000 UK patients have moderate-to-severe generalised myasthenia gravis and are not on any NICE-recommended novel therapy, managed instead on the pyridostigmine plus corticosteroid, azathioprine, or mycophenolate backbone, with IVIg or plasma exchange reserved for crises. This is a clinically-defined subgroup: patients whose disease severity and treatment gap are specifically what a novel-agent launch would need to address, and it deliberately excludes mild or well-controlled gMG that does not currently represent an addressable commercial population.
The broader figure, 12,000-15,000 total UK gMG patients, comes from a launch-readiness population estimate that counts the full diagnosed prevalence, including patients whose disease is mild or already adequately controlled on standard therapy and who are not part of the near-term addressable pool the narrower figure describes. The two numbers are not in tension; the 4,000-patient figure is a clinically-defined subset of the 12,000-15,000-patient total, and the gap between them, roughly 8,000-11,000 patients, is mild or well-controlled disease outside the immediate commercial opportunity. Inside the narrower, addressable population, an estimated 2,000-3,000 patients are refractory to immunosuppressant therapy (MGFA Class II-IV), the population that would benefit most acutely from a novel agent clearing NICE's cost-effectiveness bar, a bar that has already rejected two consecutive biologics (eculizumab's terminated TA636 appraisal and efgartigimod's TA1069 rejection).
UK gMG sizing — a nested subgroup, not a contradiction, between two scope-different estimates
| Sizing Estimate | Population | Scope | Source |
|---|---|---|---|
| Moderate-severe subgroup (narrower) | ~4,000 patients | Not on any NICE-recommended novel agent; excludes mild/well-controlled disease | MGA UK survey and registry data |
| Total prevalence (broader) | 12,000-15,000 patients | All diagnosed gMG, including mild and well-controlled cases | UK gMG launch-readiness population estimate |
| Refractory subgroup (nested within both) | 2,000-3,000 patients | Immunosuppressant-inadequate, MGFA Class II-IV | MGA UK survey; NICE TA636/TA1069 documentation |
Sources: MGA UK annual survey and membership data 2023; NICE eculizumab gMG termination decision document (TA636); NICE efgartigimod appraisal GID-TA10986 and final guidance TA1069.
What this model answers
Every section answers a named commercial question your team is asking, scoped to your asset.
Delivers
- The MGA UK survey's 4,000-patient moderate-severe subgroup versus the 12,000-15,000-patient total prevalence estimate
- the scope difference between them explained explicitly
- guidance on which anchor fits a near-term addressable-population forecast
Delivers
- 2,000-3,000-patient refractory (MGFA Class II-IV) subgroup sizing
- the NICE TA636/TA1069 access-rejection precedent
- the pricing-adjacent sizing implication of a population NICE has twice declined to fund access for
Delivers
- The 8,000-11,000-patient gap between the narrower and broader estimates
- why this population is not part of the near-term commercial pool
- the sizing-model discipline of stating scope rather than picking one number silently
Custom model delivered in 72 hours.
Commission This ModelWhat's inside
- Why scope, not measurement error, explains the gap between the 4,000 and 12,000-15,000 estimates
- Pressure-tested against NICE's rejection of two consecutive gMG biologics
- 4,000-patient MGA UK survey population definition
- Why this subgroup excludes mild and well-controlled disease
- 12,000-15,000-patient total UK gMG prevalence
- The 8,000-11,000-patient gap and what it represents
- Why the two figures are nested, not competing
- The refractory subgroup (2,000-3,000) inside both estimates
- Which scope assumption moves the addressable population most
- NICE access-precedent scenarios (TA636, TA1069) and their sizing implications
- The full triangulated model, re-runnable with your own scope assumptions
- The open sizing questions your team must close before the number is used in planning
Included with every brief
How AXLRx builds this model
Prepared by MoatRx analysts.
Every AXLRx market sizing model triangulates at least two independent methods before accepting a patient count. Where two figures differ because they measure different scopes rather than because one is wrong, the model states the scope difference explicitly and presents both figures rather than silently selecting one.
UK myasthenia gravis sizing sources: MGA UK annual survey and membership data 2023, NICE TA636 (eculizumab, terminated 2020), and NICE TA1069 (efgartigimod, not recommended, June 2025).
- Moderate-severe subgroup and refractory population figures verified against MGA UK annual survey data 2023
- Total UK gMG prevalence estimate verified against the UK gMG launch-readiness population assessment
- NICE access precedent (TA636 termination; TA1069 rejection) verified against the published NICE decision documents
- The scope difference between the narrower and broader estimates is stated explicitly rather than reconciled into a single unexplained figure
Frequently asked questions
Commission this model
AXLRx delivers rare disease market sizing models built for forecasting and strategy teams sizing the UK gMG opportunity. Custom model in 72 hours.
Specify your indication, target market, and cohort definition.
AXLRx analyst confirms triangulation methods and scope definitions before building.
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