Argenx dealt another blow as Vyvgart Hytrulo fails again

Shares in Argenx have been taking a bashing this morning after the company announced its new subcutaneous formulation of Vyvgart had missed the mark in another phase 3 trial.

The Netherlands-based biopharma said that Vyvgart Hytrulo (efgartigimod alfa) was unable to hit its efficacy objectives in the 222-subject ADDRESS trial involving adult patients with pemphigus vulgaris and pemphigus foliaceus, rare autoimmune blistering diseases affecting the skin and mucous membranes.

The failure – which the company said may have been caused by an unexpectedly high response with background corticosteroid therapy – means that Argenx is also taking a long hard look at the phase 2/3 BALLAD trial of the drug in bullous pemphigoid. Although, it will allow the study to continue for now, before deciding on its future.

All told, 35.5% of subjects on subcutaneous Vyvgart achieved the trial’s primary objective of sustained complete remission on a minimal dose of steroids within 30 weeks, compared to just over 30% of the placebo arm, which was not a statistically significant difference.

The negative result in pemphigus comes just a few weeks after the subcutaneous version of Vyvgart failed to show efficacy in the ADVANCED-SC study in rare bleeding disorder primary immune thrombocytopenia (ITP).

Argenx has been selling an intravenous formulation of Vyvgart for muscle-wasting disease generalised myasthenia gravis (gMG) since 2021, and that was joined by Vyvgart Hytrulo after the latter was approved for the same indication in the US and EU earlier this year.

Combined, the two drugs made $816 million in sales in the first nine months of the year, putting the Vyvgart franchise well on course to top the $1 billion sales threshold for 2023.

Future blockbuster growth forecasts have, however, relied heavily on anticipated growth for Vyvgart Hytrulo, which allows for a once-weekly injection administered by a healthcare professional that takes around a minute, rather than a weekly, hour-long IV infusion delivered at a clinic with the original version. In its gMG trials, Vyvgart Hytrulo was found to be as effective as the original Vyvgart.

“We are disappointed by today’s results, particularly for pemphigus patients, who have seen little innovation in this treatment space,” said Luc Truyen, Argenx’s chief medical officer.

“While we will not move forwards into pemphigus, our job today is the same as yesterday – continue to be execution-focused and data-driven, apply learnings across our ongoing development programmes, and pursue optimal development of efgartigimod,” he added.

“2023 was a remarkable year of growth for Argenx across the business and we are poised to build on our success in 2024.”

Shares in the company were down 28% at the time of writing.