Argenx's Vyvgart Hytrulo comes up short again, this time in the rare disease pemphigus

Less than one month after reporting a trial fail for Vyvgart Hytrulo in a rare bleeding disorder, argenx has swung and missed in a group of chronic blistering diseases.

This time, a phase 3 trial flop in two subgroups of patients with pemphigus has prompted argenx to abandon its ambitions in the disease area altogether. Investors were surprised and disappointed and sent the company's shares down by around 25% mid-morning Wednesday.

In the study, the proportion of patients with pemphigus vulgaris or pemphigus foliaceus who experienced complete remission on Vyvgart Hytrulo and a minimal dose of steroids was not “significantly different” than the percentage who achieved the same results on placebo and steroids, the company said in a press release.

Vyvgart Hytrulo is the brand name of the subcutaneous form of Vyvgart, which is FDA-approved to treat myasthenia gravis.

Around 35% (or 44 out of 124) of patients treated with the subcutaneous drug met the primary endpoint of complete remission, while 30.3% of patients on placebo could say the same. The study also missed its secondary endpoints, which included time to disease control and complete remission.

Argenx is “disappointed” by the results, “particularly for pemphigus patients who have seen little innovation in this treatment space,” chief medical officer Luc Truyen, M.D., Ph.D., said in the release.

The company has decided against any further development in this disease area. Instead, argenx will opt to “prioritize” Vyvgart development in a host of severe autoimmune indications.

Vyvgart Hytrulo saw similar results in the rare bleeding disorder primary immune thrombocytopenia just last month, missing both primary and secondary endpoints in a phase 3 study. That flop marked the first setback for the company and its commercial product.

Still, argenx stuck to its broad ambitions for the med after the miss. At the time, CEO Tim Van Hauwermeiren projected Vyvgart would be active in 15 different immunoglobin G-mediated autoimmune indications by 2025.

The company reported third-quarter sales of $329 million for the med, bringing its total haul for the first nine months of the year to $816 million due to its speedy success in generalized myasthenia gravis (gMG) after two years on the market.