Argenx (ARGX) said Monday that a phase 3 study of its drug Vyvgart met its primary endpoint in treating patients with AChR-Ab seronegative generalized myasthenia gravis, an autoimmune disease.

The company said patients treated with Vyvgart in the study generally showed "statistically significant and clinically meaningful" improvement over those given a placebo.

Argenx said it plans to use the results of the 119-patient study to submit a supplemental biologics license application to the US Food and Drug Administration seeking to expand Vyvgart indications label to include adults with all subtypes of the rare, neuromuscular autoimmune disease that causes potentially life-threatening muscle weakness and chronic fatigue.