Melrilimab is a human IgG2-kappa (IgG2κ) monoclonal antibody that specifically targets the interleukin-33 receptor (IL-33R), also known as IL1RL1, ST2, DER4, or FIT-1. The IgG2 isotype is selected to minimize effector functions such as antibody-dependent cellular cytotoxicity (ADCC). By binding to IL-33R with high affinity, it blocks the interaction between the receptor and its cytokine ligand IL-33, thereby inhibiting downstream signaling through the MYD88/NF-κB pathway. This blockade aims to suppress the type 2 inflammatory responses driven by IL-33. It is being developed for the treatment of allergic and inflammatory diseases in which the IL-33/ST2 axis plays a central role, such as asthma, atopic dermatitis, and chronic obstructive pulmonary disease (COPD).