IL-25

Class

First-in-class anti-IL-25 monoclonal antibody

IL-25, also called IL-17E, is a signaling protein released by epithelial cells that line the airways, skin, and gut when they are irritated by allergens, viruses, or other environmental insults. It belongs to the IL-17 cytokine family but plays a distinct role: rather than driving classic inflammatory defense against bacteria, it acts as an early trigger, or "alarmin," that switches on type 2 immune responses. It does this by activating innate lymphoid cells, mast cells, and helper T cells that then release downstream messengers such as IL-4, IL-5, and IL-13, which produce mucus overproduction, tissue eosinophilia, and heightened airway or skin reactivity. Because IL-25 acts near the top of this signaling cascade, blocking it is intended to dampen the entire downstream type 2 response rather than neutralizing a single effector cytokine. This strategy is relevant to diseases characterized by allergic or eosinophilic inflammation, including asthma, atopic dermatitis, and chronic sinus disease with nasal polyps. A monoclonal antibody directed against IL-25 works by binding the free cytokine before it can engage its receptor, preventing the initiating signal that would otherwise set off the broader inflammatory cascade.