ATI-052

ATI-052 is an investigational **humanized anti-TSLP and anti-IL-4Rα bispecific antibody** being developed by Aclaris for Th2-driven immuno-inflammatory diseases. It was originally discovered by Biosion as **BSI-502** and was licensed by Aclaris in November 2024 for territories outside Greater China. Mechanistically, ATI-052 is designed to simultaneously block **thymic stromal lymphopoietin** signaling upstream and **interleukin-4 receptor alpha** signaling downstream, thereby suppressing IL-4 and IL-13 biology and broader type 2 inflammatory cascades relevant to diseases such as **atopic dermatitis** and **asthma**. Company disclosures describe ATI-052 as using the same TSLP-binding Fab region as bosakitug while being engineered for tighter FcRn binding to extend half-life. Public Aclaris updates in 2026 reported positive first-in-human Phase 1a SAD/MAD healthy volunteer results with favorable tolerability, robust pharmacodynamic inhibition of TSLP- and IL-4-induced CCL17/TARC, and a profile supporting potential dosing up to every three months; the program then advanced into Phase 1b proof-of-concept studies in atopic dermatitis and asthma.

Other names

ATI-052ATI052ATI 052