Argenx: Another Vyvgart Trial Failure Brings Our Fair Value Estimate to $466/EUR 425

Argenx’s autoimmune drug Vyvgart Hytrulo has failed to improve responses over low-dose steroids in two related dermatology indications—pemphigus vulgaris and pemphigus foliaceus—and we’ve lowered our fair value estimates to $466/EUR 425 from $539/EUR 490. This disappointing news comes on the heels of the drug’s November 2023 failure in a key trial in a hematology indication (idiopathic thrombocytopenic purpura). The failure also adds to our confusion over the potential breadth of indications for Vyvgart, which had positive data this year in the poorly understood neurology indication of CIDP, where we had assigned a lower probability of approval, but was seen as much more likely to offer improvement over existing treatments in ITP and pemphigus, due to the role of IgG autoantibodies (and Vyvgart’s ability to lower IgG) in these diseases. We think this failure could also hint at potential failure for another dermatological indication currently in a pivotal trial: bullous pemphigoid. Following the pemphigus failure on Dec. 20, Argenx management has decided not to take an interim look at the potentially registrational trial in this indication, opting to complete the full trial and also likely implementing some trial design changes.