Horizon Therapeutics’ Daxdilimab Phase 2 trial fails to reach primary endpoint in SLE

Horizon Therapeutics plc (Nasdaq: HZNP) announced that its Phase 2 clinical trial studying the efficacy of daxdilimab in the treatment of systemic lupus erythematosus (SLE) did not achieve a statistically significant difference between daxdilimab and a placebo in reaching the primary endpoint.

The primary measure was the proportion of patients achieving a British Isles Lupus Assessment Group (BILAG) 2004 Index-based Combined Lupus Assessment (BICLA) response and an oral glucocorticoid (OGC) dose of ≤7.5 mg/day (prednisone equivalent) from the baseline OGC dose at 48 weeks. However, numerical differences were noted in other endpoints, and no safety concerns were reported.

Elizabeth H.Z. Thompson, executive vice president, research and development at Horizon Therapeutics, stated, “While we are disappointed that the trial did not meet its primary endpoint, we will continue to work with investigators to assess these data to determine next steps for our SLE clinical program.”

The Phase 2 clinical trial for systemic lupus erythematosus registered 214 patients with moderate-to-severe symptoms. These patients were divided into three arms, where they received either daxdilimab at 200 mg every four weeks, 200 mg every 12 weeks, or a placebo every four weeks. The additional trial endpoints included the Systemic Lupus Erythematosus Responder Index of 4 (SRI-4), other measures of lupus disease activity, and reduction in OGC.

Daxdilimab is an anti-ILT7 human monoclonal antibody that depletes certain dendritic cells, possibly disrupting the inflammation cycle that leads to tissue damage in various autoimmune conditions. Horizon Therapeutics is also studying daxdilimab’s effectiveness in treating alopecia areata, discoid lupus erythematosus, lupus nephritis, and plans to study its potential in treating dermatomyositis or anti-synthetase inflammatory myositis.