BACKGROUND: In the Phase 3 MycarinG study (NCT03971422), six once-weekly subcutaneous infusions of rozanolixizumab significantly improved myasthenia gravis (MG)-specific outcomes versus placebo in patients with acetylcholine receptor or muscle-specific tyrosine kinase autoantibody-positive generalized MG (gMG). Following completion of MycarinG, patients could enroll in the open-label extension MG0004 study (NCT04124965) to receive chronic weekly rozanolixizumab. METHODS: Patients were re-randomized 1:1 to once-weekly rozanolixizumab 7 or 10 mg/kg for up to 52 infusions. The primary endpoints were the occurrence of treatment-emergent adverse events (TEAEs) and TEAEs leading to rozanolixizumab discontinuation. After ≥6 visits/infusions patients could switch to the MG0007 study (NCT04650854) to receive cyclic rozanolixizumab treatment. RESULTS: In MG0004, 70 patients received rozanolixizumab 7 mg/kg (n = 35) or 10 mg/kg (n = 35). Mean treatment duration was 22.9 and 23.7 weeks, respectively, due to rollover into MG0007. TEAEs were reported in 60/70 (85.7%) patients
most were mild/moderate. The most frequently reported TEAEs were headache (25/70 [35.7%]), diarrhea (13/70 [18.6%]) and decreased blood immunoglobulin G (11/70 [15.7%]). There were no opportunistic, serious or severe infections, serious or severe hypersensitivity or injection-site reactions, any anaphylactic reactions or albumin or lipid abnormalities. Maximum mean reduction from baseline in MG Activities of Daily Living score was 3.1 in the 7 mg/kg group and 4.1 in the 10 mg/kg group. CONCLUSION: Chronic weekly rozanolixizumab for up to 52 infusions was generally well tolerated, and clinically relevant improvements across MG-specific outcomes were maintained, supporting the long-term use of rozanolixizumab in patients with gMG. TRIAL REGISTRATION: NCT04124965 (registered October 11, 2019).