Phase 2 Trial in Acetylcholine Receptor Antibody-Positive Myasthenia Gravis of Transition from Intravenous to Subcutaneous Immunoglobulin: the MGSCIg Study.

Background and purpose: Data on maintenance therapy with subcutaneous immuno- globulin (SCIg) in myasthenia gravis (MG) are limited. We report on transitioning ace- tylcholine receptor (AChR) antibody-positive (Ab+) MG patients on stable intravenous immunoglobulin (IVIg) regimens as part of routine clinical care to SCIg 1:1.2.Methods: This multicenter North American open -label prospective investigator-initiated study had two components: the IVIg Stabilization Period (ISP) enrolling patients already on IVIg as part of routine clinical care (Weeks -10 to -1), followed by transition of stable MG subjects to SCIg in the Experimental Treatment Period (ETP; Weeks 0 to 12). We hypothesized that > 65% of patients entering the ETP would have a stable Quantitative Myasthenia Gravis (QMG) score from Week 0 to Week 12. Secondary outcome meas- ures included other efficacy measures, safety, tolerability, IgG levels, and treatment satisfaction.Results: We recruited 23 patients in the ISP, and 22 entered the ETP. A total of 12 sub- jects (54.5%) were female, and 18 (81.8%) were White, with mean age 51.4 +/- 17 years. We obtained Week 12 ETP QMG data on 19 of 22; one subject withdrew from ETP owing to clinical deterioration, and two subjects withdrew due to dislike of needles. On primary analysis, 19 of 22 participants (86.4%, 95% confidence interval = 0.72- 1.00) were treat- ment successes using last observation carried forward (p = 0.018). Secondary efficacy measures supported MG stability. SCIg was safe and well tolerated, and IgG levels were stable. Treatment satisfaction was comparable between ISP and ETP.Conclusions: MG patients on IVIg as part of their routine clinical care remained stable on monthly IVIg dosage, and most maintained similar disease stability on SCIg.