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Introduction/Aims: Individuals with refractory generalized myasthenia gravis (gMG) who have a history of rituximab use and experience persistent symptoms represent a population with unmet treatment needs. The aim of this analysis was to evaluate the efficacy and safety of eculizumab in patients with refractory anti-acetylcholine receptor antibody-positive (AChR+) gMG previously treated with rituximab. Methods: This post hoc subgroup analysis of the phase 3 REGAIN study (NCT01997229) and its open-label extension (OLE; NCT02301624) compared baseline characteristics, safety, and response to eculizumab in participants who had previously received rituximab with those who had not. Rituximab use was not permitted within the 6 months before screening or during REGAIN/OLE. Results: Of 125 REGAIN participants, 14 had received rituximab previously (7 received placebo and 7 received eculizumab). In the previous-rituximab group, 57% had used at least four other immunosuppressants compared with 16% in the no-previous-rituximab group. Myasthenia Gravis Activities of Daily Living total scores from eculizumab baseline to week 130 of eculizumab treatment improved in both the previous-rituximab and no-previous-rituximab groups (least-squares mean −4.4, standard error of the mean [SEM] 1.0 [n = 9] and least-squares mean −4.6, SEM 0.3 [n = 67], respectively; difference = 0.2, 95% confidence interval −1.88 to 2.22). In addition, in both groups, most patients who were treated with eculizumab for 130 weeks achieved a Myasthenia Gravis Foundation of America post-intervention status of minimal manifestations (66.7% and 65.0%, respectively). The eculizumab safety profile was similar between groups and consistent with its established profile. Discussion: Eculizumab is an effective therapy for patients with refractory AChR+ gMG, irrespective of whether they had received rituximab treatment previously.

Background: The efficacy and tolerability of eculizumab were assessed in REGAIN, a 26-week, phase 3, randomized, double-blind, placebo-controlled study in anti-acetylcholine receptor antibody-positive (AChR+) refractory generalized myasthenia gravis (gMG), and its open-label extension. Methods: Attainment of ‘minimal symptom expression’ was evaluated using patient-reported outcome measures of gMG symptoms [MG activities of daily living scale (MG-ADL), 15-item MG quality of life questionnaire (MG-QOL15)] at the completion of REGAIN and during the open-label extension. ‘Minimal symptom expression’ was defined as MG-ADL total score of 0–1 or MG-QOL15 total score of 0–3. Results: At REGAIN week 26, more eculizumab-treated patients achieved ‘minimal symptom expression’ versus placebo [MG-ADL: 21.4% vs 1.7%; difference 19.8%; 95% confidence interval (CI) 8.5, 31.0; p = 0.0007; MG-QOL15: 16.1% vs 1.7%; difference 14.4%; 95% CI 4.3, 24.6; p = 0.0069]. During the open-label extension, the proportion of patients in the placebo/eculizumab group who achieved ‘minimal symptom expression’ increased after initiating eculizumab treatment and was sustained through 130 weeks of open-label eculizumab (MG-ADL: 1.7 to 27.8%; MG-QOL15: 1.7 to 19.4%). At extension study week 130, similar proportions of patients in the eculizumab/eculizumab and placebo/eculizumab groups achieved ‘minimal symptom expression’ (MG-ADL: 22.9% and 27.8%, respectively, p = 0.7861; MG-QOL15: 14.3% and 19.4%, respectively, p = 0.7531). The long-term tolerability of eculizumab was consistent with previous reports. Conclusions: Patients with AChR+ refractory gMG who receive eculizumab can achieve sustained ‘minimal symptom expression’ based on patient-reported outcomes. ‘Minimal symptom expression’ may be a useful tool in measuring therapy effectiveness in gMG. Trial registration: ClinicalTrials.gov NCT01997229, NCT02301624.