ABSTRACT
The prosurvival BCL-2 proteins are attractive yet challenging targets for medicinal chemists. Their involvement in the initiation and progression of many, if not all, tumors makes them prime targets for developing new anticancer therapies. We present our approach based on de novo structure-based drug design. Using known structural information from complexes engaging opposing members of the BCL-2 family of proteins, we designed peptidomimetic compounds using a benzoylurea scaffold to reproduce key interactions between these proteins. A library stemming from the initial de novo designed scaffold led to the discovery of ligands with low micromolar potency (KD = 4 µM) and selectivity for BCL-XL. These compounds bind in the canonical BH3 binding groove in a binding mode distinct from previously known BCL-2 inhibitors. The results of our study provide insight into the design of a new class of antagonists targeting a challenging class of protein-protein interactions.
Subject(s)
Urea/analogs & derivatives , bcl-X Protein/antagonists & inhibitors , Crystallography, X-Ray , Drug Design , Magnetic Resonance Spectroscopy , Molecular Mimicry , Molecular Structure , Spectrometry, Mass, Electrospray Ionization , Structure-Activity Relationship , Urea/chemical synthesis , Urea/pharmacology , bcl-X Protein/chemistryABSTRACT
Developing potent molecules that inhibit Bcl-2 family mediated apoptosis affords opportunities to treat cancers via reactivation of the cell death machinery. We describe the hit-to-lead development of selective Bcl-XL inhibitors originating from a high-throughput screening campaign. Small structural changes to the hit compound increased binding affinity more than 300-fold (to IC50 < 20 nM). This molecular series exhibits drug-like characteristics, low molecular weights (Mw < 450), and unprecedented selectivity for Bcl-XL. Surface plasmon resonance experiments afford strong evidence of binding affinity within the hydrophobic groove of Bcl-XL. Biological experiments using engineered Mcl-1 deficient mouse embryonic fibroblasts (MEFs, reliant only on Bcl-XL for survival) and Bax/Bak deficient MEFs (insensitive to selective activation of Bcl-2-driven apoptosis) support a mechanism-based induction of apoptosis. This manuscript describes the first series of selective small-molecule inhibitors of Bcl-XL and provides promising leads for the development of efficacious therapeutics against solid tumors and chemoresistant cancer cell lines.
Subject(s)
Apoptosis/drug effects , Benzothiazoles/pharmacology , Hydrazones/pharmacology , bcl-X Protein/antagonists & inhibitors , Animals , Benzothiazoles/chemical synthesis , Benzothiazoles/metabolism , Binding, Competitive , Cell Line, Tumor , Cells, Cultured , Drug Discovery , Embryo, Mammalian/cytology , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/metabolism , Hydrazones/chemical synthesis , Hydrazones/metabolism , Kinetics , Mice , Mice, Knockout , Models, Chemical , Molecular Structure , Myeloid Cell Leukemia Sequence 1 Protein/deficiency , Myeloid Cell Leukemia Sequence 1 Protein/genetics , Surface Plasmon Resonance , bcl-2 Homologous Antagonist-Killer Protein/deficiency , bcl-2 Homologous Antagonist-Killer Protein/genetics , bcl-2-Associated X Protein/deficiency , bcl-2-Associated X Protein/genetics , bcl-X Protein/chemistry , bcl-X Protein/metabolismABSTRACT
The design of small molecules that mimic the BH3 domain and bind to Bcl-2 proteins has emerged as a promising approach to discovering novel anti-cancer therapeutics. We reveal the design and synthesis of conformationally constrained benzoylurea scaffolds as conformational probes. Central to helix mimicry, the intramolecular hydrogen bond in the benzoylurea plays a key role in the pre-organisation of the acyclic substrates for cyclisation via ring closing metathesis, providing efficient access to the constrained mimetics.
