Subcutaneous (SC) administration of efgartigimod (Enhanze®) appears to treat generalized myasthenia gravis (MG) effectively, according to a press release by Argenx.

The phase 3 ADAPT-SC study results consisted of a multicenter, randomized, open-label, parallel-group clinical trial that included 110 adults previously diagnosed with MG with an MG Activities of Daily Living (MG-ADL) score above 4. All individuals were equally divided into either a group that received SC efgartigimod or intravenous (IV) efgartigimod for 5 weeks.

Patients with SC administration achieved similar immunoglobulin G (IgG) reduction compared to the IV administration group after 29 days, with a decrease of 66.4% and 62.2%, respectively. Furthermore, SC efgartigimod users reported a 2-point or more improvement in the MG-ADL score and a 3-point or more increase on the Quantitative MG score for at least 1 month.

“Our goal is to redefine and deliver targeted treatment options for people living with [generalized MG] globally,” Tim Van Hauwermeiren, chief executive officer of Argenx said. “The ADAPT-SC results mark another important step toward achieving this, and further support our vision of delivering a broad array of treatment options for [generalized MG].”

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Although mostly well-tolerated among patients, some presented with transient mild to moderate injection site reactions, which suggests this may be another possible advantage over the IV presentation since the latter has been associated with more severe hypersensitivity reactions that include skin rash, swelling, and even shortness of breath.

Regardless of this encouraging result, more studies need to confirm the safety of this drug to assess whether the SC administration also increases the risk of infections as the IV does, mostly urinary tract and respiratory infections. Even though efgartigimod is not new in the treatment for MG, in a chronic disease such as this, a medication that the patient can easily administer is of utmost importance for treatment adherence and hence, mortality reduction.

The SC formulation combines efgartigimod with a recombinant human hyaluronidase to aid in the drug administration in the SC tissue. Both presentations still share the same pharmacodynamics as a human IgG1 antibody fragment that binds to the neonatal FC receptor, downregulating the production of IgG autoantibodies and diminishing the recycling process.

Reference

Argenx announces positive topline phase 3 data from adapt-sc study evaluating subcutaneous efgartigimod for generalized myasthenia gravis. News release. Argenx; March 22, 2022.