国立保健医療科学院 保健医療経済評価研究センター
Center for Outcomes Research and Economic
Evaluation for Health (C2H), National Institute of
Public Health (NIPH) | URL:https://c2h.niph.go.jp

November 24, 2023

[C2H2204] Summary of cost-effectiveness evaluationof Efgartigimod Alfa (Vyvgart)
1. Purpose of use
Generalized myasthenia gravis (gMG) patients who are not sufficiently
responsive to steroids or an immunosuppressive drug)
2. Price of the device
Efgartigimod alfa has been reimbursed since April 2023, and the drug price is
JPY 421,455 for Vyvgart® for intravenous infusion 400 mg as of September 2023.
The price is determined based on the Cost Calculation Method with a 5%
usefulness premium and a 10% market premium (no premium coefficient). Theproduct is designated as an item for the Cost-effectiveness Evaluation with H1classification.
3. Scope of Cost-effectiveness Evaluation
Efgartigimod alfa is used to improve symptoms of gMG. The scope ofCost-effectiveness Evaluation determined at the first session of the Expert
Committee of Cost-Effectiveness Evaluation (ECCEE) is described below.
As it is expected that the efficacy of efgartigimod alfa could differ between
acetylcholine receptor antibody–positive and antibody–negative patients, those
populations were determined as the target populations. The comparators wereprednisolone ± immunosuppressive drug ± acetylcholinesterase inhibitor.

Generalized myasthenia gravis (not sufficiently responsive toTarget

steroids or an immunosuppressive drug)

population(a) Acetylcholine receptor antibody–positive patients(b) Acetylcholine receptor antibody–negative patients

Comparator

Prednisolone ± immunosuppressive drug ± acetylcholinesterase
inhibitor

4. Evaluation of additional benefits
The manufacturer did not conduct a systematic review in the base case analysis
and evaluated the additional benefits of efgartigimod alfa for patients with gMG
as a whole without complying with the scope determined at ECCEE. Based on theresults of the Quantitative Myasthenia Gravis (QMG) responder rate (defined asa score improvement rate of ≥ 3) and the Myasthenia Gravis-Activities of Daily
Living (MG-ADL) responder rates (defined as a score improvement rate of ≥ 2)
in the ADAPT trial, a randomized controlled trial for efgartigimod alfa, themanufacturer concluded that efgartigimod alfa had additional benefits in the gMG
population as a whole.
The academic group considered that the evaluation should be conductedaccording to the scope, and therefore evaluated the additional benefits for each
population based on the ADAPT trial.
For population (a), acetylcholine receptor antibody–positive patients, the QMG
responder rates were significantly higher for efgartigimod alfa (efgartigimod alfa
41/65 [63%], placebo 9/64 [14%], odds ratio 10.84 [95% confidence interval{CI} 4.18–31.20]), and MG-ADL responder rates were also significantly higher
for efgartigimod alfa (efgartigimod alfa 44/65 [68%], placebo 19/64 [30%], odds
ratio 4.95 [95% CI: 2.21–11.53]).
Based on the results, the academic group concluded that efgartigimod alfa had
additional benefits for population (a).
For population (b), acetylcholine receptor antibody–negative patients, the QMG
responder rates were 10/19 (53%) for efgartigimod alfa and 7/19 (36.8%) for
placebo, and the MG-ADL responder rates were 13/19 (68.4%) for efgartigimodalfa and 12/19 (63.2%) for placebo.
As the sample of antibody-negative patients was not sufficiently large and theresults had large uncertainty, the academic group concluded that it could not be
judged from the currently available evidence that efgartigimod alfa had additional
benefits for population (b).

5. Results of the cost-effectiveness analysis
The manufacturer conducted cost-utility analysis using a Markov model, which
had states of efgartigimod alfa or the comparator as first-line treatments,
intravenous immunoglobulin or plasma exchange as second-line treatments,eculizumab as third-line treatment (only for population [a]), and the best
supportive care.
In the academic analysis, cost-minimization analysis was performed for
population (b). For population (a), the model structure and transition probabilities
were revised as it was considered that the rates of patients receiving eculizumab
were overestimated; the drug cost of and costs related to efgartigimod alfa wererevised and productivity loss was excluded.
The ECCEE accepted the following:
Population

ComparatorICER(JPY/QALY)(a) Acetylcholine receptor
antibody–positive patients(b) Acetylcholine receptor
antibody–negative patients

Prednisolone ±immunosuppressive drug ±111,660,260

acetylcholinesterase inhibitor
Prednisolone ±immunosuppressive drug ±acetylcholinesterase inhibitor

Cost increase