title: Pharmacology of smac mimetics; chemotype differentiation based on physical association with caspase regulators and cellular transport.
abstract: Cellular levels of inhibitor of apoptosis (IAP) proteins are elevated in multiple human cancers and their activities often play a part in promoting cancer cell survival by blocking apoptotic pathways, controlling signal transduction pathways and contributing to resistance. These proteins function through interactions of their BIR (baculoviral IAP repeat) protein domains with pathway components and these interactions are endogenously antagonized by Smac/Diablo (second mitochondrial activator of caspases/direct IAP binding protein with low isoelectric point). This report describes development of synthetic smac mimetics (SM) and compares their binding, antiproliferative and anti-tumor activities. All dimeric antagonists inhibit in vitro smac tetrapeptide binding to recombinant IAP proteins, rescue IAP-bound caspase-3 activity and show anti-proliferative activity against human A875 melanoma cells. One heterodimeric SM, SM3, binds tightly to IAP proteins in vitro and slowly dissociates (greater than two hours) from these protein complexes compared to the other antagonists. In addition, in vitro SM anti-proliferation potency is influenced by ABCB1 transporter (ATP-binding cassette, sub-family B; MDR1, P-gp) activities and one antagonist, SM5, does not appear to be an ABCB1 efflux pump substrate. All dimeric smac mimetics inhibit the growth of human melanoma A875 tumors implanted in athymic mice at well-tolerated doses. One antagonist, SM4, shows broad spectrum in vivo anti-tumor activity and modulates known pharmacodynamic markers of IAP antagonism. These data taken together demonstrate the range of diverse dimeric IAP antagonist activities and supports their potential as anticancer agents.
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA. Electronic address: Randy.Talbott@BMS.Com.
authors: Randy L
authors: RL
authors: Talbott
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Robert M
authors: RM
authors: Borzilleri
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Charu
authors: C
authors: Chaudhry
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Joseph
authors: J
authors: Fargnoli
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Henry
authors: H
authors: Shen
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Craig
authors: C
authors: Fairchild
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Bryan
authors: B
authors: Barnhart
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Marie
authors: M
authors: Ortega
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Thomas E
authors: TE
authors: McDonagh
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Ragini
authors: R
authors: Vuppugalla
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Gregory D
authors: GD
authors: Vite
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: John T
authors: JT
authors: Hunt
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Marco
authors: M
authors: Gottardis
authors: Bristol-Myers Squibb Research, PO Box 4000, Princeton, NJ 08543-4000, USA.
authors: Joseph G
authors: JG
authors: Naglich
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D001692:Biological Transport / Q000187:drug effects*; D032701:Biomimetics / Q000379:methods; D053148:Caspase 3 / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D045325:HCT116 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors*; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors*; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D053148:Caspase 3
keywords: ABCB1; Apoptosis; Caspase-3; MDR; Smac; XIAP