Netherlands-based pharmaceutical company Argenx has reported negative topline results from the Phase III ADDRESS study investigating efgartigimod to treat adults with pemphigus vulgaris (PV) and pemphigus foliaceous (PF).  

The study showed no significant difference in complete remission on minimal steroids between efgartigimod and placebo in PV patients. The study did not meet its primary endpoint, with 35.5% of subjects achieving complete remission in the efgartigimod arm versus 30.3% in the placebo cohort. The drug maintained a favourable safety profile in the study.  

The randomised, double-blind, placebo-controlled ADDRESS trial (NCT04598451) evaluated the safety and efficacy of efgartigimod in 222 adult patients with PV or PF.  

The primary endpoint measured the proportion of PV patients achieving sustained complete remission on minimal corticosteroids within 30 weeks. Key secondary endpoints included cumulative corticosteroid and time to disease control. 

Efgartigimod showed a consistent pharmacodynamic effect, reducing immunoglobulin G and desmoglein antibodies up to 75%. However, corticosteroids also led to significant autoantibody reduction in both groups. 

Pemphigus is a group of rare autoimmune disorders that cause blistering of the skin and mucous membranes. PF primarily causes superficial skin blisters, particularly on the face, whereas PV is typically more severe, impacting deeper layers such as mucous membranes in the mouth. 

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By GlobalData

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

This marks the second setback for argenx in a month with the company’s stock price plummeting by 30% following the news. 

At the end of last month, argenx announced that its subcutaneous formulation of Vyvgart Hytrulo (efgartigimod alfa) had come up short of placebo in a Phase III study in primary immune thrombocytopenia, a rare bleeding disorder.  

Vyvgart is a neonatal Fc receptor (FcRn) inhibitor monoclonal antibody. Its intravenous form is marketed in Europe, the US and the UK for generalised myasthenia gravis. Vyvgart generated global revenues of $400.7m last year, according to argenx’s 2022 annual report. 

In April 2023, Genmab teamed up with argenx for the development of oncology and autoimmune disease therapies through their engineering platforms.