OBJECTIVES: To assess the number needed to treat (NNT) and costs required to achieve improvements in symptoms and functional activities with targeted therapies for myasthenia gravis (MG).

METHODS: Relative to conventional therapy (CT), NNTs and annual costs for achieving one point improvement in Quantitative Myasthenia Gravis score (QMG), one additional patient with minimal clinically important difference (MCID) in QMG (≥ 3 point improvement), and one additional patient achieving minimal symptom expression (MSE; Myasthenia Gravis-Activities of Daily Living score of 0 or 1) were estimated for efgartigimod (EFG), intravenous immunoglobulin (IVIg), and eculizumab (ECU). All treatments were used in conjunction with CT. Costs per improved outcome (CPR) were compared between EFG, IVIg, and ECU. Efficacy was evaluated at week 4 of respective phase 3 randomized trials (ADAPT [NCT03669588], NCT02473952, REGAIN [NCT01997229]). Annual drug acquisition and administration costs (2021 USD) were considered.

RESULTS: Compared with CT, mean NNTs to achieve one point improvement and MCID in QMG were 0.19 and 2.31 for EFG, 0.52 and 7.14 for IVIg, and 0.56 and 6.25 for ECU. NNTs to achieve an additional patient with MSE was 3.46 for EFG and 8.13 for ECU. Compared to EFG, the mean annual CPR to achieve one point improvement and MCID in QMG were higher for IVIg (Difference [95% confidence interval] = $36,130 [$14,024, $58,237] per point improvement in QMG; $583,669 [$0, $1,473,027] per one patient with MCID in QMG) and ECU ($340,659 [$158,038, $523,280]; $3,760,825 [$1,391,543, $6,130,107]). Cost to achieve one additional patient with MSE was $4,761,649 ($2,859,671, $6,663,626) higher for ECU compared with EFG.

CONCLUSIONS: NNT and cost per improved efficacy help inform comparative clinical efficacy and cost-effectiveness across MG treatments. Evidence indicates more favorable treatment benefit and economic value for EFG with fewer NNT and lower cost required to achieve improved outcomes compared to other treatments.