Post-Hoc Analysis of ADAPT Reveals Several Subgroup Responders to Efgartigimod

When grouping patients by clinical characteristics such as time from diagnosis, thymectomy status, and concomitant medications, new findings from the phase 3 ADAPT study (NCT03669588) showed that efgartigimod (Vyvgart; Argenx) is consistently effective across subgroups of individuals with generalized myasthenia gravis (gMG).

The study featured 129 patients with acetylcholine receptor autoantibody positive (AChR-Ab+) gMG who received intravenous efgatigimod 10 mg/kg or placebo in cycles of 4 weekly infusions, with subsequent cycles based on clinical evaluation. In those who had less than 3 years since diagnosis, 76.8% (11 of 14) of efgartigimod-treated patients demonstrated at least a 2-point improvement for at least 4 consecutive weeks on Myasthenia Gravis Activities of Daily Living (MG-ADL) vs 23.5% of those on placebo (difference, 55.0%; 95% CI, 25.6-84.5).

These data were presented at the 2023 Muscular Dystrophy Association (MDA) Clinical and Scientific Conference, held March 19-22, in Dallas, Texas, by senior investigator James Howard, MD, FAAN, Distinguished Professor of Neuromuscular Disease, and chief, Neuromuscular Disorders Section, University of North Carolina School of Medicine. In the analysis, responder status was defined as at least 2-point improvement on MG-ADL or at least 3-point improvement on Quantitative Myasthenia Gravis (QMG) scores.

In non-thymectomized patients, 85.0% (17 of 20) on efgartigimod achieved responder status vs 32.4% (11 of 34) of those on placebo. An even greater between-group difference was seen for concomitant medications, as 84.6% (11 of 13) of those on efgartigimod while only receiving concomitant acetylcholinesterase inhibitors achieved responder status vs 16.7% of those on placebo (difference, 67.9%; 95% CI, 32.3-100.0). For those who received any corticosteroid, 63.0% (29 of 46) of patients on efgartigimod were responders compared with 29.4% (15 of 51) on placebo (difference, 33.6; 95% CI, 14.9-52.4). Results for other subgroups, along with the proportion of QMG responders, also favored efgartigimod.

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Efgartigimod was originally approved in December 2021 based on findings from ADAPT. In the original analysis, the agent was shown to be well-tolerated and efficacious, meeting the primary end point of improvement in MG-ADL scores relative to placebo (67.7% vs 29.7%; P <.0001). Additionally, 40.0% of efgartigimod-treated AChR-Ab+ patients achieved minimal or no symptoms compared with 11.1% treated with placebo.²

Recently published ancillary data from ADAPT has also indicated significant positive effects from efgartigimod on patients’ health-related quality of life (HRQoL). Comparing the 2 arms, significantly greater improvements in HRQoL scores were seen in those on efgartigimod, even among patients who had poor HRQoL at baseline. Relative to placebo, there was a greater reduction in Myasthenia Gravis-Quality of Life 15-item revised scores for AChR-Ab+ participants on efgartigimod (P <.0001), with statistically significant differences maintained for up to 8 weeks in treatment cycle 1 and treatment cycle 2. Throughout the study, there was an observed trend in mean change in MG-QOL15r that was similar to that in total IgG level, by week.³

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REFERENCES
1. Ritt E, Bril V, Vu T, et al. Efgartigimod demonstrates consistent improvements in generalized myasthenia gravis across patient subgroups, including early in diagnosis. Presented at: MDA 2023; March 19-22; Dallas, TX. Abstract 134
2. Howard JF, Bril V, Vu T, et al. Safety, efficacy, and tolerability of efgartigimod in patients with generalised myasthenia gravis (ADAPT): a multicentre, randomised, placebo-controlled, phase 3 trial. Lancet Neurol. 2021;20(7):526-536. doi:10.1016/S1474-4422(21)00159-9
3. Sacca F, Barnett C, Vu T, et al. Efgartigimod improved health-related quality of life in generalized myasthenia gravis: results from a randomized, double-blind, placebo-controlled, phase 3 study (ADAPT). Journal of Neurol. Published online January 4, 2023. doi:10.1007/s00415-022-11517.