Multicomponent reactions (MCRs) are one-pot reactions employing more than two starting materials, e.g. 3, 4, … 7, where most of the atoms of the starting materials are incorporated in the final product.1 Several descriptive tags are regularly attached to MCRs (Fig. 1): they are atom economic, e.g. the majority if not all of the atoms of the starting materials are incorporated in the product; they are efficient, e.g. they efficiently yield the product since the product is formed in one-step instead of multiple sequential steps; they are convergent, e.g. several starting materials combine in one reaction to form the product; they exhibit a very high bond-forming-index (BFI), e.g. several non-hydrogen atom bonds are formed in one synthetic transformation.2 Therefore MCRs are often a useful alternative to sequential multistep synthesis.






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Figure 1


Above: multistep syntheses can be divergent (sequential) or convergent; below: in analogy MCR reactions are convergent and one or two component reactions are divergent or less convergent.

Chemistry and Biology Of Multicomponent Reactions

The MDM2 and MDMX (also known as HDMX and MDM4) proteins are deregulated in many human cancers and exert their oncogenic activity predominantly by inhibiting the p53 tumour suppressor. However, the MDM proteins modulate and respond to many other signalling networks in which they are embedded. Recent mechanistic studies and animal models have demonstrated how functional interactions in these networks are crucial for maintaining normal tissue homeostasis, and for determining responses to oncogenic and therapeutic challenges. This Review highlights the progress made and pitfalls encountered as the field continues to search for MDM-targeted antitumour agents.

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MDM2, MDMX and p53 in oncogenesis and cancer therapy.

Currently, around 11 million people are living with a tumour that contains an inactivating mutation of TP53 (the human gene that encodes p53) and another 11 million have tumours in which the p53 pathway is partially abrogated through the inactivation of other signalling or effector components. The p53 pathway is therefore a prime target for new cancer drug development, and several original approaches to drug discovery that could have wide applications to drug development are being used. In one approach, molecules that activate p53 by blocking protein-protein interactions with MDM2 are in early clinical development. Remarkable progress has also been made in the development of p53-binding molecules that can rescue the function of certain p53 mutants. Finally, cell-based assays are being used to discover compounds that exploit the p53 pathway by either seeking targets and compounds that show synthetic lethality with TP53 mutations or by looking for non-genotoxic activators of the p53 response.

Awakening guardian angels: drugging the p53 pathway

The tumour suppressor p53 is the most frequently mutated gene in human cancer, with more than half of all human tumours carrying mutations in this particular gene. Intense efforts to develop drugs that could activate or restore the p53 pathway have now reached clinical trials. The first clinical results with inhibitors of MDM2, a negative regulator of p53, have shown efficacy but hint at on-target toxicities. Here, we describe the current state of the development of p53 pathway modulators and new pathway targets that have emerged. The challenge of targeting protein-protein interactions and a fragile mutant transcription factor has stimulated many exciting new approaches to drug discovery.

Drugging the p53 pathway: understanding the route to clinical efficacy

Indoles in multicomponent processes (MCPs).

Intensive anticancer drug discovery efforts have been made to develop small molecule inhibitors of the p53-MDM2 and p53-MDMX interactions. We present here the structures of the most potent inhibitors bound to MDM2 and MDMX that are based on the new imidazo-indole scaffold. In addition, the structure of the recently reported spiro-oxindole inhibitor bound to MDM2 is described. The structures indicate how the substituents of a small molecule that bind to the three subpockets of the MDM2/X-p53 interaction should be optimized for effective binding to MDM2 and/or MDMX. While the spiro-oxindole inhibitor triggers significant ligand-induced changes in MDM2, the imidazo-indoles share similar binding modes for MDMX and MDM2, but cause only minimal induced-fit changes in the structures of both proteins. Our study includes the first structure of the complex between MDMX and a small molecule and should aid in developing efficient scaffolds for binding to MDMX and/or MDM2.

Structures of low molecular weight inhibitors bound to MDMX and MDM2 reveal new approaches for p53-MDMX/MDM2 antagonist drug discovery

/pdf/robust-generation-of-lead-compounds-for-protein-protein-1tp1r1ewgw.pdf

Robust Generation of Lead Compounds for Protein-Protein Interactions by Computational and MCR Chemistry: p53/Hdm2 Antagonists

The Mdm2 and Mdmx proteins are the principal negative regulators of the p53 tumor suppressor. Reactivation of p53 activity by disrupting the Mdm2/Mdmx-p53 interactions offers new possibilities for anticancer therapeutics. Here, we present crystal structures of two complexes, a p53-like mutant peptide with the N-terminal domains of Mdm2 and Mdmx, respectively. The structures reveal that the p53 mutant peptide (amino acid sequence: LTFEHYWAQLTS) assumes virtually identical conformations in both complexes despite the different shapes of the p53-binding pockets in these two proteins, has a more extended helical nature compared to the Mdm2-bound wild-type p53 peptide, and does not disturb the native folds of Mdm2 or Mdmx. The extension of the helical structure in the mutant p53 peptide greatly improves its binding to Mdm2 and Mdmx. The fluorescence polarization assay that we have developed using this peptide indicates the affinities towards Mdm2 of 3.6 nM and for Mdmx of 6.1 nM, compared to the low micromolar binding of a similar length wild-type p53 peptide to Mdm2/Mdmx. Our assay does not require expensive non-native amino acids, and allows measurements of the interaction with both Mdm2 and Mdmx in identical conditions-without modification of experimental conditions or setups between the two proteins. The structural information presented here, coupled with the robust fluorescence polarization assay, should enable development of a simple pharmacophore model of cross-selective Mdm2-Mdmx/p53 inhibitors.

High affinity interaction of the p53 peptide-analogue with human Mdm2 and Mdmx

Although there is no shortage of potential drug targets, there are only a handful known low-molecular-weight inhibitors of protein-protein interactions (PPIs). One problem is that current efforts are dominated by low-yield high-throughput screening, whose rigid framework is not suitable for the diverse chemotypes present in PPIs. Here, we developed a novel pharmacophore-based interactive screening technology that builds on the role anchor residues, or deeply buried hot spots, have in PPIs, and redesigns these entry points with anchor-biased virtual multicomponent reactions, delivering tens of millions of readily synthesizable novel compounds. Application of this approach to the MDM2/p53 cancer target led to high hit rates, resulting in a large and diverse set of confirmed inhibitors, and co-crystal structures validate the designed compounds. Our unique open-access technology promises to expand chemical space and the exploration of the human interactome by leveraging in-house small-scale assays and user-friendly chemistry to rationally design ligands for PPIs with known structure.

/pdf/enabling-large-scale-design-synthesis-and-validation-of-1d4itqte83.pdf

Enabling Large-Scale Design, Synthesis and Validation of Small Molecule Protein-Protein Antagonists

1,4-Thienodiazepine-2,5-diones have been synthesized via the Ugi-Deprotection-Cyclization (UDC) approach starting from Gewald 2-aminothiophenes in a convergent and versatile manner. The resulting scaffold is unprecedented, cyclic, and peptidomimetic with four points of diversity introduced from readily available starting materials. In addition to eighteen synthesized and characterized compounds, a virtual compound library was generated and evaluated for chemical space distribution and drug-like properties. A small focused compound library of 1,4-thienodiazepine-2,5-diones has been screened for the activity against p53-Mdm2 interaction. Biological evaluations demonstrated that some compounds exhibited promising antagonistic activity.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1747-0285.2010.00989.x

Siglinde Wolf

Papers

Structures of low molecular weight inhibitors bound to MDMX and MDM2 reveal new approaches for p53-MDMX/MDM2 antagonist drug discovery

Robust Generation of Lead Compounds for Protein-Protein Interactions by Computational and MCR Chemistry: p53/Hdm2 Antagonists

High affinity interaction of the p53 peptide-analogue with human Mdm2 and Mdmx

Enabling Large-Scale Design, Synthesis and Validation of Small Molecule Protein-Protein Antagonists

1,4-Thienodiazepine-2,5-diones via MCR (I): Synthesis, Virtual Space and p53-Mdm2 Activity