Efgartigimod Effective for Myasthenia Gravis Treatment
A phase 3 clinical trial (NCT03669588) showed efficacy and safety of efgartigimod (Argenx, Boston, MA) for treatment of generalized myasthenia gravis (MG). Both individuals who were positive (n=129) and negative for antibodies (n=38) to the acetylcholine receptor (antiAChR+/-) were included in the trial.
In those who were antiAChR+, treatment with efgartidimod improved Myasthenia Gravis Activities of Daily Living (MG-ADL) scores by at least 2 points for 4 consecutive weeks compared with 29.7% of those who received placebo (P<.001). Similarly, a 3-point or more improvement on the Quantitative Myasthenia Gravis scale (QMG) occurred in 63.1% of individuals who were antiAChR+ and treated with efgartigimod vs 14.1% with placebo (P<.001). In those who were antiAChR-, 47.4% of those treated with efgartigimod had these improvements on both MG-ADL and QMG compared with those treated with placebo.
Subsequent infusions were given every 4 weeks depending on individual participant's response. The percentage who had improvements on MG-ADL and QMG increased with subsequent infusions. Of the participants with antiAChR+, 40% achieved minimal symptom expression for at least 1 week of a 4-week treatment cycle compared with 11.1% who were treated with placebo. A second infusion was not needed by 27% of participants. Of those who needed more than 1 infusion, duration of effect lasted 16% needed retreatment within 4 to 6 weeks, 75% after 6 to 12 weeks, and 9% after 12 weeks. Of those who did not respond in the first 4 weeks of treatment, 37% did respond after a second treatment cycle.
Adverse events included infections, infusion reactions, headache, nasopharyngitis, and nausea; the incidence of adverse effects was similar in those treated with efgartigimod and placebo. Upper respiratory and urinary infections were more common with efgartigimod and were mostly mild.
Participants in this study had MG-ADL scores of 5 or more with more than 50% of their symptoms being nonocular who were randomly assigned 1:1 to receive an initial treatment cycle of 4 weekly infusions of efgartigimod (10 mg/kg) or placebo.
Efgartigimod is a human IgG1 antibody Fc-fragment that blocks the FcR; thereby decreasing IgG recycling and reducing IgG autoantibody levels.