ABSTRACT
The design and synthesis of a series of novel tricyclic IAP inhibitors is reported. Rapid assembly of the core tricycle involved two key steps: Rh-catalyzed hydrogenation of an unsaturated bicyclic ring system and a Ru-catalyzed ring closing alkene metathesis reaction. The final Smac mimetics bind to cIAP1 and XIAP BIR3 domains and elicit the desired phenotype in cellular proliferation assays. Dimeric IAP inhibitors were found to possess nanomolar potency in a cellular proliferation assay and favourable in vitro drug-like properties.
Subject(s)
Drug Design , Heterocyclic Compounds, 3-Ring/pharmacology , Inhibitor of Apoptosis Proteins/metabolism , Cell Line , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Heterocyclic Compounds, 3-Ring/chemical synthesis , Heterocyclic Compounds, 3-Ring/chemistry , Humans , Inhibitor of Apoptosis Proteins/chemical synthesis , Inhibitor of Apoptosis Proteins/chemistry , Molecular Structure , Structure-Activity RelationshipABSTRACT
We previously reported octahydropyrrolo[1,2-a]pyrazine derivative 2 (T-3256336) as a potent antagonist for inhibitors of apoptosis (IAP) proteins. Because compound 2 was susceptible to MDR1 mediated efflux, we developed another scaffold, hexahydropyrazino[1,2-a]indole, using structure-based drug design. The fused benzene ring of this scaffold was aimed at increasing the lipophilicity and decreasing the basicity of the scaffold to improve the membrane permeability across MDR1 expressing cells. We established a chiral pool synthetic route to yield the desired tricyclic chiral isomers. Chemical modification of the core scaffold led to a representative compound 50, which showed strong inhibition of IAP binding (X chromosome-linked IAP [XIAP]: IC50 23 nM and cellular IAP [cIAP]: IC50 1.1 nM) and cell growth inhibition (MDA-MB-231 cells: GI50 2.8 nM) with high permeability and low potential of MDR1 substrate.
Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Cell Membrane Permeability/drug effects , Drug Design , Indoles/pharmacology , Inhibitor of Apoptosis Proteins/pharmacology , Pyrazines/pharmacology , ATP Binding Cassette Transporter, Subfamily B , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Survival/drug effects , Crystallography, X-Ray , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Humans , Indoles/chemical synthesis , Indoles/chemistry , Inhibitor of Apoptosis Proteins/chemical synthesis , Inhibitor of Apoptosis Proteins/chemistry , Models, Molecular , Molecular Structure , Pyrazines/chemical synthesis , Pyrazines/chemistry , Structure-Activity RelationshipABSTRACT
Apoptotic induction mechanisms are of crucial importance for the general homeostasis of multicellular organisms. In cancer the apoptotic pathways are downregulated, which, at least partly, is due to an abundance of inhibitors of apoptosis proteins (IAPs) that block the apoptotic cascade by deactivating proteolytic caspases. The Smac protein has an antagonistic effect on IAPs, thus providing structural clues for the synthesis of new pro-apoptotic compounds. Herein, we report a solid-phase approach for the synthesis of Smac-derived tetrapeptide libraries. On the basis of a common (N-Me)AVPF sequence, peptides incorporating triazoloprolines and biarylalanines were synthesized by means of Cu(I)-catalyzed azide-alkyne cycloaddition and Pd-catalyzed Suzuki cross-coupling reactions. Solid-phase procedures were optimized to high efficiency, thus accessing all products in excellent crude purities and yields (both typically above 90%). The peptides were subjected to biological evaluation in a live/dead cellular assay which revealed that structural decorations on the AVPF sequence indeed are highly important for cytotoxicity toward HeLa cells.
Subject(s)
Alanine/chemistry , Inhibitor of Apoptosis Proteins/chemical synthesis , Oligopeptides/chemical synthesis , Peptidomimetics/chemical synthesis , Proline/chemistry , Solid-Phase Synthesis Techniques/methods , Alanine/analogs & derivatives , Alkynes/chemistry , Azides/chemistry , Catalysis , Copper/chemistry , Hydrocarbons, Aromatic/chemistry , Inhibitor of Apoptosis Proteins/chemistry , Inhibitor of Apoptosis Proteins/pharmacology , Models, Chemical , Oligopeptides/chemistry , Oligopeptides/pharmacology , Palladium/chemistry , Peptidomimetics/chemistry , Peptidomimetics/pharmacology , Proline/analogs & derivatives , Triazoles/chemistryABSTRACT
A series of new Smac mimetics have been designed, synthesized, and evaluated. The most potent compound 10 binds to XIAP, cIAP-1, and cIAP-2 BIR3 proteins with K(i) of 3.9, 0.37, and 0.25 nM, respectively. Compound 10 antagonizes XIAP in a cell-free functional assay and induces rapid cIAP-1 degradation in cancer cells. Compound 10 inhibits cell growth in the MDA-MB-231 cancer cell line with an IC(50) of 8.9 nM.
