Design, Synthesis, and Characterization of a Potent, Nonpeptide, Cell-Permeable, Bivalent Smac Mimetic That Concurrently Targets Both the BIR2 and BIR3 Domains in XIAP

Abstract

XIAP is a central apoptosis regulator that inhibits apoptosis by binding to and inhibiting the effectors caspase-3/-7 and an initiator caspase-9 through its BIR2 and BIR3 domains, respectively. Smac protein in its dimeric form effectively antagonizes XIAP by concurrently targeting both its BIR2 and BIR3 domains. We report the design, synthesis and characterization of a non-peptide, cell-permeable, bivalent small-molecule (SM-164) which mimics Smac protein for targeting XIAP. Our study shows that SM-164 binds to XIAP containing both BIR domains with an IC 50 value of 1.39 nM, being 300 and 7000-times more potent than its monovalent counterparts and the natural Smac AVPI peptide, respectively. SM-164 concurrently interacts with both BIR domains in XIAP and functions as an ultra-potent antagonist of XIAP in both cell-free functional and cell-based assays. SM-164 targets cellular XIAP and effectively induces apoptosis at concentrations as low as 1 nM in leukemia cancer cells, while having a minimal toxicity to normal human primary cells at 10,000 nM. The potency of bivalent SM-164 in binding, functional and cellular assays is 2-3 orders of magnitude higher than its corresponding monovalent Smac mimetics.

Smac Mimetic Compounds Potentiate Interleukin-1β-mediated Cell Death

“…Reagents-Smac mimetic compound SM-164 was synthesized as described previously (24). Smac mimetic compound AEG40730, as described previously (11) Viability Assay-Tumor cells were plated onto 96-well flat bottom plates at various cell densities depending on the cell type.…”

Simultaneous activation of p53 and inhibition of XIAP enhance the activation of apoptosis signaling pathways in AML

“…Development of SMAC mimetics as a strategy to neutralize XIAP and induce cell death is under active investigation. 20,21 ABT-10 is one such compound. 22 p53 is a potent apoptosis inducer.…”

Peptides Mimicking the Unique ARTS-XIAP Binding Site Promote Apoptotic Cell Death in Cultured Cancer Cells

“…These approaches include antisense oligonucleotides or RNAibased technologies selectively inhibiting expression of XIAP (34,35). In addition, small molecules mimicking IBM domain were designed and tested in clinical trials (36,37,39,(45)(46)(47).…”