Current Edition

argenx reports positive topline results from Phase 2 proof-of-concept trial of ARGX-113 (efgartigimod) in generalized myasthenia gravis

argenx (Euronext & Nasdaq: ARGX), a clinical-stage biotechnology company developing a deep pipeline of differentiated antibody-based therapies for the treatment of severe autoimmune diseases and cancer, today announced positive topline results from its Phase 2 proof-of-concept clinical trial of ARGX-113 (efgartigimod) in myasthenia gravis (MG) patients with confirmed generalized muscle weakness. The data showed a clinically meaningful and statistically significant benefit of ARGX-113 over placebo. In addition, ARGX-113 was found to have a favorable tolerability profile consistent with that observed in the Phase 1 study.
“There remains a clear unmet need for a safe and fast-acting treatment for patients with generalized MG, who continue to face serious, potentially life-threatening symptoms associated with their disease,” said Professor James F. Howard Jr., MD, Distinguished Professor of Neuromuscular Disease, professor of neurology, medicine and allied health, and chief of the Neuromuscular Disorders Section in the University of North Carolina School of Medicine, Chapel Hill, NC USA. “These data demonstrate a rapid and sustained benefit in disease score after treatment with ARGX-113, supporting further development of the drug as a potential new option to fill the current treatment gap for MG patients.
Phase 2 Trial Design
The Phase 2 double-blind, placebo-controlled, proof-of-concept trial enrolled 24 MG patients with generalized muscle weakness, and a total Myasthenia Gravis Activity-of-Daily-Living (MG-ADL) score >= 5 with more than 50% of the score consisting of non-ocular items. Patients were randomized to receive four weekly doses of either standard of care plus 10 mg/kg of ARGX-113, or standard of care plus placebo. Standard of care therapies included corticosteroids and/or immunomodulatory agents. The primary endpoints of the study were safety and tolerability. Secondary endpoints included efficacy as measured by the change from baseline of the MG-ADL, Quantitative Myasthenia Gravis (QMG), and Myasthenia Gravis Composite (MGC) disease severity scores; impact on quality of life as measured by the Myasthenia Gravis Quality of Life (MGQoL) score; and an assessment of pharmacokinetics (PK) and pharmacodynamic (PD) markers. All 24 patients were evaluable.
Top-line Results
Primary endpoint analysis revealed ARGX-113 to be well tolerated in all patients, with most adverse events (AEs) characterized as mild and deemed unrelated to the study drug. No serious or severe AEs were reported. The observed tolerability profile is consistent with the Phase 1 healthy volunteer study.
The secondary endpoint measures relating to efficacy showed ARGX-113 treatment resulted in rapid onset of action and strong clinical improvement over placebo during the entire duration of the study. 
Specifically, we observed that:
  • 75% of patients treated with ARGX-113 had a clinically meaningful and statistically significant improvement in MG-ADL scores (at least a 2-point reduction from baseline) for a period of at least 6 consecutive weeks versus 25% of patients on placebo (p = 0.0391). 
  • Clinical benefit in the ARGX-113 treatment group maximized as of 1 week after the administration of the last dose, achieving statistical significance over the placebo group (p = 0.0356) on the MG-ADL score. Increasing differentiation was observed between the
    ARGX-113 treatment group versus placebo with increasing MG-ADL thresholds.
  • Patients in the treatment arm showed rapid disease improvement, with clear separation from placebo 1 week after the first infusion.
  • All patients in the treatment arm showed a rapid and deep reduction of their total IgG levels and disease improvement was found to correlate with reduction in pathogenic IgG levels.
  • ARGX-113 demonstrated strong clinical improvement over placebo as measured by all four predefined clinical efficacy scales – MG-ADL, QMG, MGC and MG-QoL15.
“These results strengthen our conviction that reducing pathogenic autoantibodies may offer an innovative approach to treat myasthenia gravis and could give rise to potential therapeutic benefits in other neuromuscular conditions that are similarly mediated. Further, through our deeper understanding of the drug’s mechanism, we see promise of its potential across other disease categories as well, including autoimmune blood disorders or skin blistering diseases which we are evaluating in our two ongoing Phase 2 studies in immune thrombocytopenia and pemphigus vulgaris,” commented Nicolas Leupin, Chief Medical Officer of argenx. “We look forward to refining our plan forward and optimizing the broad potential of ARGX-113.”
argenx plans to present the full data from the trial at the American Academy of Neurology annual meeting (Los Angeles, April 21-27, 2018).
argenx is conducting two additional ongoing Phase 2 clinical trials of ARGX-113 in immune thrombocytopenia (ITP) and pemphigus vulgaris (PV). Topline data for the ITP trial and interim data from the PV trial are both expected in the second half of 2018.