This interim analysis reports changes in concomitant immunosuppressive therapy (IST) use during a phase 3 open-label extension (OLE) study of eculizumab in adults (aged ≥ 18 years) with anti-acetylcholine receptor antibody-positive refractory generalized myasthenia gravis (gMG) (NCT02301624).

IST use is associated with side effects and compromised quality of life in some people with MG.

The OLE enrolled 117 adults who had completed REGAIN, a 6-month randomized, double-blind, placebo-controlled study of eculizumab. During REGAIN, changes in concomitant MG therapies were not permitted. During the OLE, participants received eculizumab 1200 mg every 2 weeks following a 4-week blinded induction phase. Adjustments to concomitant MG therapies, including ISTs, were at the investigator’s discretion but were not a protocol requirement. Concomitant medication use was recorded at all scheduled visits, and at unscheduled visits for an MG crisis/clinical deterioration. The data cut-off for this interim analysis was 31 December 2017.

Median eculizumab treatment duration from OLE baseline was 22.7 months (range, 1 day to 37.3 months; 227 patient-years’ exposure). At OLE baseline, 98.3% (115/117) of participants were receiving at least one IST. Thereafter, 67.5% (79/117) stopped or decreased the dose of an IST on 439 occasions in total, most commonly because of MG symptom improvement (46.2% [54/117] of participants on 256/439 occasions), and 53.8% (63/117) started or increased the dose of an IST on 189 occasions, most commonly because of MG symptom worsening (32.5% [38/117] of participants on 89/189 occasions).

In eculizumab-treated adults with gMG, a numerically larger proportion stopped or decreased the dose of a concomitant IST than started or increased the dose. MG symptom improvement and MG symptom worsening were the most common reasons for stopping/decreasing and starting/increasing IST, respectively.