Horizon Therapeutics plc announced the first patient has enrolled in a Phase 2, randomized, placebo-controlled trial to evaluate its development-stage medicine daxdilimab, a potentially first-in-class, fully human monoclonal antibody targeting anti-ILT7 depletes certain dendritic cells to treat people with moderate-to-severe primary discoid lupus erythematosus (DLE). DLE is a rare, chronic, inflammatory skin condition characterized by lesions that result in scarring, irreversible hair loss and skin discoloration with no approved therapies. The localized form of primary DLE is characterized by limited cutaneous involvement of the head and scalp and usually accounts for 70% of primary DLE.

The generalized form is characterized beyond this and includes the head-body area and usually accounts for about 30% of primary DLE. In the United States, approximately 30,000 patients with DLE are appropriate for treatment with novel therapies, including biologics. Primary DLE incidence rates are approximately four times higher among women compared with men and the disease has a higher prevalence among non-Latino Black and Latino populations.

Horizon expects to enroll approximately 100 participants in the trial. The primary endpoint is the mean change in Cutaneous Lupus Erythematosus Disease Area and Severity Index-Activity (CLASI-A) score from baseline to Week 24. This endpoint is used to measure activity in inflammatory lupus skin disease and ranges from 0 to 70 with higher scores indicating more active and skin damaging disease.

Key inclusion criteria include a diagnosis of moderate-to-severe DLE for more than six months prior to screening supported by a biopsy and/or a clinical feature score of = 7 on the DLE Classification Criteria (DLECC) scale. This score is used to specifically validate and classify DLE across several clinical variables including atrophic scarring, disease location on the body and dyspigmentation.