4p59 | pdb_00004p59
HER3 extracellular domain in complex with Fab fragment of MOR09825
Structural highlights
Disease[ERBB3_HUMAN] Defects in ERBB3 are the cause of lethal congenital contracture syndrome type 2 (LCCS2) [MIM:607598]; also called Israeli Bedouin multiple contracture syndrome type A. LCCS2 is an autosomal recessive neurogenic form of a neonatally lethal arthrogryposis that is associated with atrophy of the anterior horn of the spinal cord. The LCCS2 syndrome is characterized by multiple joint contractures, anterior horn atrophy in the spinal cord, and a unique feature of a markedly distended urinary bladder. The phenotype suggests a spinal cord neuropathic etiology.[1] Function[ERBB3_HUMAN] Binds and is activated by neuregulins and NTAK.[2] Publication Abstract from PubMedHER2/HER3 dimerization resulting from overexpression of HER2 or neuregulin (NRG1) in cancer leads to HER3-mediated oncogenic activation of phosphoinositide 3-kinase (PI3K) signaling. Although ligand-blocking HER3 antibodies inhibit NRG1-driven tumor growth, they are ineffective against HER2-driven tumor growth because HER2 activates HER3 in a ligand-independent manner. In this study, we describe a novel HER3 monoclonal antibody (LJM716) that can neutralize multiple modes of HER3 activation, making it a superior candidate for clinical translation as a therapeutic candidate. LJM716 was a potent inhibitor of HER3/AKT phosphorylation and proliferation in HER2-amplified and NRG1-expressing cancer cells, and it displayed single-agent efficacy in tumor xenograft models. Combining LJM716 with agents that target HER2 or EGFR produced synergistic antitumor activity in vitro and in vivo. In particular, combining LJM716 with trastuzumab produced a more potent inhibition of signaling and cell proliferation than trastuzumab/pertuzumab combinations with similar activity in vivo. To elucidate its mechanism of action, we solved the structure of LJM716 bound to HER3, finding that LJM716 bound to an epitope, within domains 2 and 4, that traps HER3 in an inactive conformation. Taken together, our findings establish that LJM716 possesses a novel mechanism of action that, in combination with HER2- or EGFR-targeted agents, may leverage their clinical efficacy in ErbB-driven cancers. An antibody that locks HER3 in the inactive conformation inhibits tumor growth driven by HER2 or neuregulin.,Garner AP, Bialucha CU, Sprague ER, Garrett JT, Sheng Q, Li S, Sineshchekova O, Saxena P, Sutton CR, Chen D, Chen Y, Wang H, Liang J, Das R, Mosher R, Gu J, Huang A, Haubst N, Zehetmeier C, Haberl M, Elis W, Kunz C, Heidt AB, Herlihy K, Murtie J, Schuller A, Arteaga CL, Sellers WR, Ettenberg SA Cancer Res. 2013 Oct 1;73(19):6024-35. doi: 10.1158/0008-5472.CAN-13-1198. Epub, 2013 Aug 8. PMID:23928993[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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