Horizon Therapeutics plc announced the first patient has enrolled in a Phase 2, open-label, proof-of-concept trial to evaluate its development-stage medicine daxdilimab (HZN-7734), a potentially first-in-class, fully human monoclonal antibody targeting immunoglobulin-like transcript 7 (ILT7), to treat people with moderate-to-severe alopecia areata. Alopecia areata is a common, acute onset autoimmune disorder characterized by transient, non-scarring hair loss. It is the second most common form of alopecia and is associated with comorbidities including depression, anxiety and autoimmune diseases such as lupus erythematosus and vitiligo.

More than 600,000 people live with alopecia areata in the United States, of which approximately 40,000 are appropriate for treatment with novel therapies, including biologics. Approximately 30 participants who meet trial eligibility will be enrolled. The primary endpoint is the percent change from baseline in Severity of Alopecia Tool (SALT) score at Week 24.

This endpoint is a well-validated metric and widely utilized tool for determining the degree of hair loss and regrowth4. SALT scores are measured on a scale from 1 to 100, with 1 representing “no hair loss” and 100 representing “total hair loss.” Secondary endpoints include the percent change from baseline in SALT scores and the proportion of participants who achieve =50%improvement in SALT over time through Week 48. Key inclusion criteria include =50% and =95% total scalp hair loss as defined by the SALT score at screening and day one of the trial.

Participants must be experiencing a current episode of hair loss lasting >3 months but <7 years. An investigator's assessment will be conducted to ensure that hair regrowth is possible and there is no evidence of active regrowth present at the baseline, with no known history of significant regrowth in the previous six months.