9x05

IL-33 and Itepekimab fab and Tozorakimab fab ternary complex structure

spinqualitylabelsall models 9x05, resolution 3.64Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9x05 is a 5 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.64Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function IL33_HUMAN Cytokine that binds to and signals through IL1RL1/ST2 and its stimulation recruits MYD88, IRAK1, IRAK4, and TRAF6, followed by phosphorylation of MAPK3/ERK1 and/or MAPK1/ERK2, MAPK14, and MAPK8. Induces T-helper type 2-associated cytokines. Acts as a chemoattractant tor Th2 cells, and may function as an "alarmin", that amplifies immune responses during tissue injury. In quiescent endothelia the uncleaved form is constitutively and abundantly expressed, and acts as a chromatin-associated nuclear factor with transcriptional repressor properties, it may sequester nuclear NF-kappaB/RELA, lowering expression of its targets. This form is rapidely lost upon angiogenic or proinflammatory activation. Publication Abstract from PubMed Interleukin-33 (IL-33), an alarmin cytokine of the IL-1 family, drives type 2 inflammation through signaling via the ST2 and IL-1RAcP receptors, making it a critical therapeutic target for inflammatory diseases such as asthma and chronic obstructive pulmonary disease. Current therapeutic strategies have primarily focused on antibodies that target IL-33 or ST2 to disrupt their specific interaction. However, the structural mechanisms underlying antibody-mediated neutralization of IL-33 remain poorly understood. Here, we report the structures of three antibodies in clinical trial - etokimab, itepekimab, and tozorakimab - complexed with IL-33, determined by X-ray crystallography and cryo-electron microscopy. Structural analysis reveals two distinct neutralizing epitopes on IL-33, termed Epitope 1 at IL-33/ST2 binding Site 1 and Epitope 2 at IL-33/ST2 binding Site 2. Tozorakimab, which targets Epitope 1, completely blocks ST2 engagement by sterically occluding the ST2 D1-D2 domain-binding interface. In contrast, etokimab and itepekimab, which recognize Epitope 2, interfere with IL-33 recognition of the ST2 D3 domain and thereby only partially inhibit ST2 binding. These structural and biochemical findings provide a molecular explanation for the differential efficacy of the three antibodies in inhibiting IL-33 signaling in cellular assays. Collectively, our results provide valuable insights into the molecular determinants of efficacy for existing IL-33 therapeutics and offer a structural framework for the rational design of next-generation IL-33 targeted inhibitors. Structures of clinical antibodies bound to IL-33 uncover two distinct epitopes underlying differential efficacy.,Chen J, Wang Y, Wang X MAbs. 2026 Dec;18(1):2639673. doi: 10.1080/19420862.2026.2639673. Epub 2026 Mar , 1. PMID:41765683 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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