WAYNE, PA — Aclaris Therapeutics Inc. (Nasdaq: ACRS) has completed patient enrollment in its Phase 2 trial of bosakitug in patients with moderate-to-severe atopic dermatitis, marking a development milestone for the company’s experimental treatment as it prepares for top-line results expected in the fourth quarter of 2026.
The company said the randomized, double-blind, placebo-controlled study enrolled 109 patients and is designed to evaluate both the efficacy and safety of bosakitug, also known as ATI-045, in adults with moderate-to-severe disease.
Aclaris said the trial’s primary endpoint is the percent change from baseline in Eczema Area and Severity Index, or EASI, at week 24.
Secondary endpoints at week 24 include EASI-50, EASI-75 and EASI-90 response rates, validated Investigator Global Assessment response, body surface area response and Peak Pruritus Numerical Rating Scale scores relative to baseline.
The study will also evaluate safety, tolerability, pharmacodynamic biomarkers and the drug’s pharmacokinetic profile, according to the company.
“The strong interest in participating in this Phase 2 trial reflects the urgent need for innovative solutions in atopic dermatitis and the excitement surrounding bosakitug and the potential role of TSLP as a therapeutic target in this setting,” Dr. Jesse Hall, Aclaris’ chief medical officer, said in a statement.
Hall said the company believes bosakitug’s potency and 23-day half-life could support strong inhibition in the skin while allowing convenient dosing.
Bosakitug is an investigational humanized monoclonal antibody designed to target thymic stromal lymphopoietin, or TSLP, a cytokine involved in inflammatory signaling associated with allergic and skin diseases.
According to the company, bosakitug binds to human TSLP and blocks its interaction with the receptor complex, disrupting signal transduction and preventing immune cells targeted by TSLP from releasing pro-inflammatory cytokines.
Aclaris said TSLP is considered an upstream regulator of Type 2 immune response at the barrier surfaces of the skin and the respiratory and gastrointestinal tracts, and that it can activate downstream inflammatory targets including IL-4, IL-5, IL-13, IL-17 and molecules derived from T cells such as CCL17.
The company said expression of TSLP is elevated in people with respiratory and skin diseases, making it a relevant therapeutic target.
Aclaris also pointed to results from a previous single-arm Phase 2a trial in moderate-to-severe atopic dermatitis, in which bosakitug showed what the company described as a favorable safety profile and improvements across several efficacy measures at week 26.
In that earlier study, the company said 94% of participants achieved EASI-75, meaning at least a 75% improvement in disease severity, and 88% achieved clear or nearly clear skin as measured by Investigator Global Assessment scores of 0 or 1.
Aclaris said those responses were sustained beyond the last administered dose in that trial.
The company holds exclusive worldwide rights to bosakitug outside Greater China and said the drug may also have potential applications in other atopic, immunologic and respiratory diseases.
Atopic dermatitis is the most common form of eczema and affects about 10 million children and 17 million adults in the United States, according to the company.
Worldwide, the condition affects more than 200 million people, Aclaris said, adding that about 1 in 10 people will develop eczema during their lifetime.
Symptoms commonly include dry, cracked and itchy skin, along with raised bumps that may appear anywhere on the body.
With persistent scratching, affected skin can become inflamed, warm, thickened and damaged.
Aclaris cited data from the Asthma and Allergy Foundation of America indicating that about 40% of people with the disease have moderate or severe symptoms.
The company said moderate-to-severe atopic dermatitis can significantly affect quality of life and is associated with higher rates of social dysfunction and sleep impairment.
Aclaris, based in Wayne, is a clinical-stage biopharmaceutical company developing treatments for immuno-inflammatory diseases.
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