Positive topline data was announced from the phase 3 ADAPT trial of efgartigimod (ARG-113; argenx) in adult patients with generalized myasthenia gravis (gMG).

The multicenter, randomized, double-blind, placebo-controlled trial assessed the efficacy and safety of efgartigimod in 167 adults with gMG. Patients were randomized to receive either efgartigimod via intravenous infusion or placebo for 26 weeks. The primary end point was the percentage of responders on the Myasthenia Gravis Activities of Daily Living (MG-ADL) score among acetylcholine receptor-antibody positive (AChR-Ab+) generalized myasthenia gravis (gMG) patients. Responders were defined as having at least a 2-point improvement on the MG-ADL score for at least 4 consecutive weeks.

Findings from the trial demonstrated that a significantly greater proportion of AChR-Ab+ patients treated with efgartigimod met the primary end point compared with placebo (67.7% vs 29.7%, respectively; P <.0001). Additionally, a greater proportion of efgartigimod-treated AChR-Ab+ patients responded on the Quantitative Myasthenia Gravis (QMG) score compared with placebo (63.1% vs 14.1%, respectively; P <.0001); a responder was defined as having at least a 3-point improvement for at least 4 consecutive weeks. Forty percent of efgartigimod-treated AChR-Ab+ patients also achieved minimal symptom expression, defined as a MG-ADL scores of 0 (symptom free) or 1, compared with 11.1% for placebo.

Moreover, efgartigimod achieved statistically significant results for additional secondary end points and prespecified analyses, including MG-ADL responders for both AChR-Ab+ and AChR-antibody negative patients, clinically meaningful improvement of at least 2-points in total MG-ADL score, and fast onset of response on MG-ADL score. With regard to safety, efgartigimod was well tolerated and comparable to placebo.

Full detailed results will be submitted for presentation at a future medical meeting. Patients who completed the 26-week ADAPT trial were eligible to enroll into the open-label extension trial (ADAPT+). The Company plans to submit a Biologics License Application (BLA) by the end of 2020.

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“The data showed that efgartigimod drove fast and deep responses, including in a proportion of patients who achieved minimal or no symptoms after treatment,”  said Wim Parys, MD, Chief Medical Officer of argenx. “In addition, we saw responses that lasted beyond 8 or 12 weeks, supporting our plans to offer individualized dosing schedules that are purpose-fit to the variability in disease course that gMG patients experience.”

For more information visit argenx.com.