ARGX-113, developed by Dutch pharmaceutical firm Argenx, is an investigational therapy to treat autoimmune diseases. It works by decreasing the number of circulating autoimmune antibodies in diseases such as myasthenia gravis (MG), multiple sclerosis and systemic lupus erythematosus.

How ARGX-113 works

Antibodies are proteins produced in response to foreign molecules invading the body. Also known as immunoglobulins, they fall into five classes: IgG, IgA, IgM, IgD and IgE. Most antibodies in the blood and fluid that surround tissues and cells belong to the IgG class. In autoimmune diseases such as MG, the body produces dangerously high levels of IgG.

Antibodies are divided into two Fab regions and one Fc region. The Fc region provides the binding site for receptors on the surface of B-cells and is also where secondary antibodies bind. ARGX-113 is the Fc portion of an antibody that has been modified by Argenx scientists to increase its affinity for IgGs beyond that of normal antibodies. As a result, ARGX-113 blocks the formation of disease-causing IgG.

ARGX-113 in clinical trials

A Phase 2 study (NCT02965573) to assess the safety, efficacy and pharmacokinetics of ARGX-113 in MG patients with generalized muscle weakness has already recruited half of the 24 participants required for the trial. ARGX-113 will be given on top of current treatment, which includes cholinesterase inhibitorscorticosteroids or immunosuppressants.

Researchers will assess ARGX-113 by measuring changes in the incidence and severity of adverse events and changes in vital signs, electrocardiogram and blood markers. Secondary objectives include efficacy and pharmacokinetics and pharmacodynamics assessment, using different quality-of-life-scales and blood markers.

In former Phase 1 studies, ARGX-113 had demonstrated favorable safety and tolerability with different doses and dosing regimens, with promising reductions in disease-causing IgG.

Other details

Argenx expects to present data from its Phase 2 study in the first quarter of 2018. The company is also studying ARGX-113 for the treatment of primary immune thrombocytopenia, an autoimmune disease that affects platelets.

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