Efgartigimod Meets Primary End Point in Myasthenia Gravis

Wim Parys, MD

Argenx announced that efgartigimod, its first-in-class antibody fragment designed to reduce disease-causing immunoglobulin G (IgG) antibodies, met its primary end point—the percentage of responders on the Myasthenia Gravis Activities of Daily Living (MG-ADL) score—among patients with acetylcholine receptor-antibody positive (AChR-Ab+) generalized myasthenia gravis (gMG).

Results from the ADAPT trial showed that 67.7% of AChR-Ab+ patients treated with efgartigimod achieved the primary end point compared with 29.7% on placebo (P <.0001). Also, responders defined as having at least a 3-point improvement on the Quantitative Myasthenia Gravis (QMG) score were found in 63.1% of AChR-Ab+ patients on efgartigimod, compared with 14.1% on placebo (P <.0001).

Achievement of minimal symptom expression, defined as MG-ADL scores of 0 or 1, or otherwise symptom free, was observed in 40.0% and 11.1% of efgartigimod-treated AChR-Ab+ patients and placebo patients, respectively.

“With the ADAPT trial, we set out to evaluate efgartigimod’s ability to redefine the treatment paradigm for people living with gMG. The data showed that efgartigimod drove fast and deep responses, including in a proportion of patients who achieved minimal or no symptoms after treatment,” Wim Parys, MD, chief medical officer, Argenx, said in a statement.

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A list of secondary end points that demonstrated significant differences in the efgartigimod arm for AChR-Ab&shy;+ patients compared with placebo include MG-ADL responders in the overall population, as well as both AChR-Ab+ and AChR-antibody negative patients (P <.0001), and time on trial in clinically meaningful improvement, defined as an MG-ADL improvement >2 (P = .0001). Additional significant differences from efgartigimod group for AChR-Ab+ patients compared with placebo were fast onset of response on MG-ADL score, defined as onset observed in first 2 weeks (P = .0004).

A sustained response was seen in 88.6% AChR-Ab+ patients who met the primary end point for at least 6 weeks, 56.8% for at least 8 weeks, and 34.1% for at least 12 weeks. Furthermore, 70.6% of AChR-Ab+ patients received a second treatment cycle, compared to only 25.6% of placebo patients.

ADAPT was a phase 3, randomized, double-blind, placebo-controlled, global trial that evaluated the safety and efficacy of efgartigimod in patients with gMG. A total of 167 patients who had a confirmed gMG diagnosis and an MG-ADL score of 5 or greater were included in the trial. Patients were on a stable dose of at least 1 gMG treatment prior to randomization, including acetylcholinesterase inhibitors, corticosteroids or nonsteroidal immunosuppressive drugs, and were required to remain on that stable dose throughout the primary trial.

As part of the primary trial, patients were randomized 1:1 to efgartigimod or placebo over a 26-week stretch. To ensure individualized treatment, each patient underwent a treatment cycle followed by a variable number of subsequent treatment cycles. Those treatment cycles contained 4 infusions of intravenous (IV) efgartigimod 10 mg/kg or placebo at weekly intervals. Patients who completed the 26 weeks were eligible to roll-over into ADAPT Plus, the open-label extension of ADAPT.

Parys went on to say, “Based on these data, we intend to submit a BLA for efgartigimod to the FDA before the end of the year, taking us one step closer to potentially making efgartigimod available to patients in 2021.”

REFERENCE

Argenx announces positive topline results from phase 3 ADAPT trial of efgartigimod in patients with generalized myasthenia gravis [news release]. Breda, Netherlands: Argenx. Published May 26, 2020. Accessed May 29, 2020. globenewswire.com/news-release/2020/05/26/2038308/0/en/argenx-Announces-Positive-Topline-Results-from-Phase-3-ADAPT-Trial-of-Efgartigimod-in-Patients-with-Generalized-Myasthenia-Gravis.html