A phase 2a, double-blind randomised placebo-controlled study to assess the safety, tolerance, efficacy, pharmacokinetics and immunogenicity of ARGX-119 in participants with Amyotrophic Lateral Sclerosis. The study will be followed by an extension study with active treatment.

This study is sponsored by ARGENX BV and aims to determine whether ARGX-119 can slow deterioration in ALS patients. ARGX-119 is a humanised, agonistic monoclonal antibody being developed as a novel treatment for patients with neuromuscular disorders. ARGX-119 binds to MUSK and stimulates its function. MUSK is an important protein that ensures the stability of neuromuscular junctions and ARGX-119 aims to counteract the loss of neuromuscular junctions in ALS.
The study will also assess the impact of ARGX-119 on muscle function. Furthermore, it will also assess the extent to which ARGX-119 is distributed in the body and eliminated from the body, how the immune system responds to ARGX-119 and whether being administered ARGX-119 affects participants’ quality of life.

This study lasts up to 100 weeks. The study consists of a screening period (up to 4 weeks), a double-blind treatment period (24 weeks), an extension of active treatment (48 weeks) and a safety follow-up period (24 weeks). At baseline, appropriate participants will be randomised in a 1:1:1:1 ratio to 1 of 3 ARGX-119 intravenous (IV) dose arms (3, 6 or 12 mg/kg) or placebo IV for the double-blind treatment period.

The study medication ARGX-119 will be administered intravenously over 60 minutes, initially every 2 weeks and every 4 weeks after 4 weeks.
Patients with ALS who are between 18 and 80 years of age, meet the TRICALS risk profile, may or may not be treated with a stable dose of riluzole (100mg/day), have a lung function (SVC) of ≥ 60% and meet criteria of muscle testing with nerve stimulation may be eligible to participate in this study. A total of 60 patients will be recruited internationally.