title: Design, synthesis, and biological activity of a potent Smac mimetic that sensitizes cancer cells to apoptosis by antagonizing IAPs.
abstract: Designed second mitochondrial activator of caspases (Smac) mimetics based on an accessible [7,5]-bicyclic scaffold bind to and antagonize protein interactions involving the inhibitor of apoptosis (IAP) proteins, X-chromosome-linked IAP (XIAP), melanoma IAP (ML-IAP), and c-IAPs 1 and 2 (cIAP1 and cIAP2). The design rationale is based on a combination of phage-panning data, peptide binding studies, and a survey of potential isosteres. The synthesis of two scaffolds is described. These compounds bind the XIAP-baculoviral IAP repeat 3 (BIR3), cIAP1-BIR3, cIAP2-BIR3, and ML-IAP-BIR domains with submicromolar affinities. The most potent Smac mimetic binds the cIAP1-BIR3 and ML-IAP-BIR domains with a K i of 50 nM. The X-ray crystal structure of this compound bound to an ML-IAP/XIAP chimeric BIR domain protein is compared with that of a complex with a phage-derived tetrapeptide, AVPW. The structures show that these compounds bind to the Smac-binding site on ML-IAP with identical hydrogen-bonding patterns and similar hydrophobic interactions. Consistent with the structural data, coimmunoprecipitation experiments demonstrate that the compounds can effectively block Smac interactions with ML-IAP. The compounds are further demonstrated to activate caspase-3 and -7, to reduce cell viability in assays using MDA-MB-231 breast cancer cells and A2058 melanoma cells, and to enhance doxorubicin-induced apoptosis in MDA-MB-231 cells.
authors.affiliation: Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080, USA.
authors.forename: Kerry
authors.initials: K
authors.lastname: Zobel
authors.forename: Lan
authors.initials: L
authors.lastname: Wang
authors.forename: Eugene
authors.initials: E
authors.lastname: Varfolomeev
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Franklin
authors.forename: Linda O
authors.initials: LO
authors.lastname: Elliott
authors.forename: Heidi J A
authors.initials: HJ
authors.lastname: Wallweber
authors.forename: David C
authors.initials: DC
authors.lastname: Okawa
authors.forename: John A
authors.initials: JA
authors.lastname: Flygare
authors.forename: Domagoj
authors.initials: D
authors.lastname: Vucic
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Fairbrother
authors.forename: Kurt
authors.initials: K
authors.lastname: Deshayes
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001665:Binding Sites; D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D018360:Crystallography, X-Ray; D015195:Drug Design; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020169:Caspases