ArgenX reports hints to efficacy of ARGX-113 in generalised myasthenia gravis

According to the company, 75% of patients (N=24) with confirmed generalised muscle weakness reported  a significant improvement in their MG-ADL scores over 6 weeks vs 25% who received placebo. Myasthenia Gravis Activity-of-Daily-Living  is an eight-item patient-reported scale developed to assess MG symptoms and their effects on daily activities.

Furthermore ARGX-113 demonstrated strong clinical improvement over placebo as measured by the surrogate clinical efficacy scales Quantitative Myasthenia Gravis (QMG), and Myasthenia Gravis Composite (MGC) disease severity scores as well as the Myasthenia Gravis Quality of Life (MGQoL) score.

"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," said James F. Howard Jr., principal investigator of the study.

Pharmacokinetic and pharmcodynamic data showed that patients in the treatment arm had a rapid and deep reduction of their total IgG levels and disease improvement was found to correlate with reduction in pathogenic IgG levels.

 "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 II studies in immune thrombocytopenia and pemphigus vulgaris," said ArgenX’s CMO Nicolas Leupin. The company, which recently licenced a cancer product, has already raised capital to finance Phase III development of ARG-113.

ARGX-113 was designed to exploit the natural interaction between IgG antibodies and the recycling receptor FcRn. It consists of the Fc-portion of an llama antibody that has been modified to block antibody recycling through FcRn binding and induces rapid depletion of the autoimmune disease-causing IgG autoantibodies.