Efgartigimod falls short in pemphigus trial, missing its primary endpoint

A large phase 3 trial (ADDRESS) has found that adding subcutaneous efgartigimod to standard prednisone therapy did not meaningfully improve remission rates in adults with moderate-to-severe pemphigus. The randomized, double-blind trial enrolled 222 patients across 82 sites in 20 countries, comparing efgartigimod plus prednisone against placebo plus prednisone over 30 weeks.

Despite the drug producing notable reductions in immunoglobulin G and disease-specific antibody levels early in treatment, these biological changes didn't translate into better clinical outcomes. Remission rates, time to disease control, and total prednisone use were all similar between the two groups — a disappointing result for a therapy that had shown promise in other autoimmune conditions.

Key Takeaways:

• Only 35.5% of efgartigimod-treated patients with pemphigus vulgaris achieved complete remission vs. 30.3% on placebo — a non-significant difference
• Anti-desmoglein antibody levels dropped by over 60%, yet Pemphigus Disease Area Index scores didn't improve accordingly
• Adverse events were slightly more common with efgartigimod (89.1% vs. 76%), though most were mild to moderate and no deaths occurred

Why it matters: Pemphigus is a rare, potentially life-threatening autoimmune blistering disease with limited treatment options. While efgartigimod's failure here is a setback, its acceptable safety profile keeps the door open for further investigation in autoimmune conditions.