Two FcRn antagonists and a subcutaneous C5 inhibitor entered US gMG inside 24 months — and the AChR-antibody line decides which patients the complement class can reach.
Generalised myasthenia gravis (gMG) is now a multi-mechanism market. The FcRn antagonists lower pathogenic IgG and carry broad generalised-MG labels with no complement-restricting serology requirement: efgartigimod (Vyvgart / Vyvgart Hytrulo, argenx; IV approved December 2021, subcutaneous June 2023) and rozanolixizumab (Rystiggo, UCB; June 2023). The complement class splits by route: the IV C5 inhibitors eculizumab (Soliris, October 2017) and ravulizumab (Ultomiris, April 2022) from AstraZeneca/Alexion, and UCB's subcutaneous macrocyclic-peptide C5 inhibitor zilucoplan (Zilbrysq, October 2023). Efgartigimod anchored the FcRn entry with a 68% MG-ADL responder rate versus 30% on placebo in the ADAPT trial.
The competitive story turns on two forces. First, antibody segmentation: roughly 85% of gMG patients are AChR-antibody positive, and the C5 inhibitors are approved only in that subgroup — so MuSK-positive and seronegative patients, about 15% of the market, are reachable by the FcRn class but not by complement inhibition. Second, UCB's dual-asset position: it holds both an FcRn antagonist (rozanolixizumab) and a C5 inhibitor (zilucoplan), so it participates on whichever side of the FcRn-versus-complement sequence a payer imposes. A network meta-analysis of the innovative-therapy trials placed efgartigimod as the treatment with the highest probability of being best on MG-ADL, with the FcRn class showing a greater short-term QMG effect than the complement class.
FDA-approved generalised myasthenia gravis therapies — United States, 2026
| Drug (Brand / INN) | Mechanism / Route | Company | Indication / Serology | US Approval | Key Trial Result |
|---|---|---|---|---|---|
| Vyvgart / Vyvgart Hytrulo (efgartigimod) | FcRn antagonist (IV / SC) | argenx | Generalised MG; broad label (no serology restriction) | IV Dec 2021; SC Jun 2023 | ADAPT: MG-ADL responder 68% vs 30% placebo (PMID 34146511) |
| Rystiggo (rozanolixizumab) | FcRn antagonist (SC) | UCB | Generalised MG; AChR+ or MuSK+ | Jun 2023 | MycarinG: MG-ADL −3.37 vs −0.78 placebo (PMID 37059507) |
| Zilbrysq (zilucoplan) | C5 complement inhibitor (SC peptide) | UCB | Generalised MG; AChR-Ab+ only | Oct 2023 | RAISE: MG-ADL −4.39 vs −2.30 placebo (per FDA label) |
| Soliris (eculizumab) | C5 complement inhibitor (IV) | AstraZeneca / Alexion | AChR+ refractory gMG | Oct 2017 | REGAIN: QMG −4.2 vs −1.5 placebo (per FDA label) |
| Ultomiris (ravulizumab) | C5 complement inhibitor, long-acting (IV) | AstraZeneca / Alexion | AChR+ gMG | Apr 2022 | CHAMPION-MG: MG-ADL −3.1 vs −1.4 placebo (per FDA label) |
Sources: FDA Drugs@FDA (approval status, dates, and serology restrictions); ADAPT, Lancet Neurol 2021 (PMID 34146511); MycarinG, Lancet Neurol 2023 (PMID 37059507); RAISE, REGAIN and CHAMPION-MG results per FDA labels; comparative context per Saccà F et al. network meta-analysis, Eur J Neurol 2023 (PMID 37204031).
What this brief answers
Every section answers a named commercial question your team is asking, scoped to your asset.
Delivers
- • FcRn (IgG lowering) vs C5 (complement) mechanism and the AChR+-only restriction on the complement class • Efficacy across ADAPT, MycarinG, RAISE, REGAIN and CHAMPION-MG • IV vs subcutaneous administration and dosing burden by agent • Where the broad-label FcRn class captures MuSK+ and seronegative patients
Delivers
- • How UCB participates on both the FcRn and C5 sides of the access sequence • Rozanolixizumab vs efgartigimod head-to-head positioning considerations • Zilucoplan's AChR+ restriction and subcutaneous self-injection advantage vs IV C5 • Prescriber switching dynamics across the two UCB assets
Delivers
- • Antibody subtype distribution and the addressable population per mechanism • Complement-eligible (AChR+ refractory) vs FcRn-eligible (all generalised MG) sizing • Targeting implications for the ~15% of patients the C5 class cannot reach • Comparative-effectiveness evidence gaps between FcRn, C5 and traditional immunosuppression
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Commission This BriefWhat's inside
- Why efgartigimod and rozanolixizumab lower pathogenic IgG while eculizumab, ravulizumab and zilucoplan block complement instead.
- How three novel mechanisms reached US approval within 24 months, the fastest class expansion in rare neurology.
- How ADAPT's 68% MG-ADL responder rate versus 30% on placebo anchored efgartigimod's FcRn entry in December 2021.
- Why REGAIN, CHAMPION-MG and RAISE trial results still frame Soliris, Ultomiris and Zilbrysq against the newer FcRn class.
- Why the C5 inhibitors are approved only in the roughly 85% of gMG patients who are AChR-antibody positive.
- How the broad-label FcRn class reaches the remaining 15% of MuSK-positive and seronegative patients C5 cannot.
- How UCB's dual FcRn-plus-C5 asset position lets it compete on either side of the payer sequence.
- Why zilucoplan's subcutaneous self-injection differentiates Zilbrysq from IV-dosed Soliris and Ultomiris.
- How payers can impose either an FcRn-first or C5-first step-edit sequence given UCB's presence on both sides.
- Why AChR+ serology confirmation is the gate that determines complement-inhibitor eligibility before any step-edit applies.
- How the network meta-analysis ranked efgartigimod highest on probability of being best on MG-ADL among innovative therapies.
- Why the FcRn class's greater short-term QMG effect versus complement inhibitors shapes next-generation positioning.
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 Myasthenia Gravis Competitive Intelligence sources: FDA Drugs@FDA (approval status, dates, and serology restrictions), primary trial publications in The Lancet Neurology (ADAPT, MycarinG), the RAISE, REGAIN and CHAMPION-MG results as reflected in FDA labelling, and the Saccà F et al. network meta-analysis in the European Journal of Neurology comparing FcRn and complement mechanisms.
- Efgartigimod ADAPT MG-ADL responder result verified against Howard JF et al. Lancet Neurol 2021 (PMID 34146511)
- Rozanolixizumab MycarinG MG-ADL result verified against Bril V et al. Lancet Neurol 2023 (PMID 37059507)
- Comparative FcRn vs complement efficacy verified against Saccà F et al. network meta-analysis, Eur J Neurol 2023 (PMID 37204031)
- Approval status, indications, and AChR+ serology restrictions verified against FDA Drugs@FDA
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