ADAPT Trial of Efgartigimod and its Potential in gMG: James F. Howard, MD

“The other thing that was very gratifying was the safety profile. It was very nominal and much like those who were in the placebo arm of the study… The infusion reactions were the same—in fact, more in the placebo arm than in the drug arm, so that was very gratifying as well. What we’re seeing is a very rapidly acting drug with, albeit variable, but fairly prolonged, duration of action with a very nominal [adverse] effect profile.”

New data from the phase 3 ADAPT trial (NCT03669588) of efgartigimod (Argenx) suggest that the first-in-class investigational antibody fragment to target the neonatal Fc receptor (FcRn) is well-tolerated and efficacious in treating patients with generalized myasthenia gravis (gMG). The full analysis showed that the drug met the primary end point by improving gMG activities of daily living (MG-ADL) scores for patients with acetylcholine receptor-antibody positive (AChR-Ab+) gMG compared with those in the placebo group (67.7% vs. 29.7%; P <.0001).

Additionally, 40.0% of efgartigimod-treated AChR-Ab+ patients achieved minimal or no symptoms compared to 11.1% treated with placebo. All told, 167 patients were randomized, 84 in the efgartigimod group and 83 in the placebo group. Of the full population, 77% (n = 129) were AChR-Ab+.

Of those in the treatment group 77% (n = 65) experienced treatment-emergent adverse events (AEs), while and 84% (n = 70) of the placebo group did. The most frequent AEs reported were headache (efgartigimod: 29% [n = 24]; placebo: 28% [n = 23]) and nasopharyngitis (efgartigimod: 12% [n = 10]; placebo: 18% [n = 15]). Five percent (n = 4) of efgartigimod-treated patients and 8% (n = 7) patients in the placebo group had a serious AE, and each group had 3 patients (4%) discontinue treatment during the study.

An open-label extension trial is ongoing, called ADAPT+ (NCT03770403), and there are plans to explore a potential subcutaneous administration of the agent in addition to its current intravenous infusion formulation. As well, the FDA is currently reviewing a biologics license application submitted by Argenx for efgartigimod for the treatment of gMG, with a PDUFA date of December 17, 2021.

Lead author James F. Howard, MD, Distinguished Professor of Neuromuscular Disease, and professor of neurology and medicine, University of North Carolina School of Medicine, spoke with NeurologyLive to share his perspectives on the data. He discussed some of the unique findings of the analysis, the potential of this agent, and his experience with the drug in its clinical development.

REFERENCE
Howard JF, Bril V, Vu T, et al. Safety, efficacy, and tolerability of efgartigimod in patients with generalised myasthenia gravis (ADAPT): a multicentre, randomised, placebo-controlled, phase 3 trial. Lancet Neurol. 2021. 20:526-536.