Discovery of : an Efficient Inhibitor of the HDM2-p53 Protein-Protein Interaction

An update patent review of MDM2-p53 interaction inhibitors (2019-2023)

INTRODUCTION

The activity of the major tumor suppressor protein p53 is disrupted in nearly all human cancer types, either by mutations in TP53 gene or by overexpression of its negative regulator, Mouse Double Minute 2 (MDM2). The release of p53 from MDM2 and its homolog MDM4 with inhibitors based on different chemistries opened up a prospect for a broad, non-genotoxic anticancer therapy.

AREAS COVERED

This article reviews the patents and patent applications between years 2019 and 2023 in the field of MDM2-p53 interaction inhibitors. The newly reported molecules searched in Espacenet, Google Patents, and PubMed were grouped into five general categories: compounds having single-ring, multi-ring, or spiro-oxindole scaffolds, peptide derivatives, and proteolysis-targeting chimeras (PROTACs). The article also presents the progress of MDM2 antagonists of various structures in recruiting or completed cancer clinical trials.

EXPERT OPINION

Despite 20 years of intensive studies after the discovery of the first-in-class small-molecule inhibitor, Nutlin-3, no drugs targeting MDM2-p53 interaction have reached the market. Nevertheless, more than 10 compounds are still being evaluated in clinics, both as standalone drugs and in combinations with other targeted therapies or standard chemotherapy agents, including two inhibitors in phase 3 studies and two compounds granted orphan-drug/fast-track designation by the FDA.

Rational design of small-sized peptidomimetic inhibitors disrupting protein-protein interaction

Protein-protein interactions are fundamental to nearly all biological processes. Due to their structural flexibility, peptides have emerged as promising candidates for developing inhibitors targeting large and planar PPI interfaces. However, their limited drug-like properties pose challenges. Hence, rational modifications based on peptide structures are anticipated to expedite the innovation of peptide-based therapeutics. This review comprehensively examines the design strategies for developing small-sized peptidomimetic inhibitors targeting PPI interfaces, which predominantly encompass two primary categories: peptidomimetics with abbreviated sequences and low molecular weights and peptidomimetics mimicking secondary structural conformations. We have also meticulously detailed several instances of designing and optimizing small-sized peptidomimetics targeting PPIs, including MLL1-WDR5, PD-1/PD-L1, and Bak/Bcl-xL, among others, to elucidate the potential application prospects of these design strategies. Hopefully, this review will provide valuable insights and inspiration for the future development of PPI small-sized peptidomimetic inhibitors in pharmaceutical research endeavors.

N-Oxide-to-Carbon Transmutations of Azaarene N-Oxides

Reactions that change the identity of an atom within a ring system are emerging as valuable tools for the site-selective editing of molecular structures. Herein, we describe the expansion of an underdeveloped transformation that directly converts azaarene-derived N-oxides to all-carbon arenes. This ring transmutation exhibits good functional group tolerance and replaces the N-oxide moiety with either unsubstituted, substituted, or isotopically labeled carbon atoms in a single laboratory operation.

MDM2 Inhibitors for Cancer Therapy: The Past, Present, and Future

Since its discovery over 35 years ago, MDM2 has emerged as an attractive target for the development of cancer therapy. MDM2's activities extend from carcinogenesis to immunity to the response to various cancer therapies. Since the report of the first MDM2 inhibitor more than 30 years ago, various approaches to inhibit MDM2 have been attempted, with hundreds of small-molecule inhibitors evaluated in preclinical studies and numerous molecules tested in clinical trials. Although many MDM2 inhibitors and degraders have been evaluated in clinical trials, there is currently no Food and Drug Administration (FDA)-approved MDM2 inhibitor on the market. Nevertheless, there are several current clinical trials of promising agents that may overcome the past failures, including agents granted FDA orphan drug or fast-track status. We herein summarize the research efforts to discover and develop MDM2 inhibitors, focusing on those that induce MDM2 degradation and exert anticancer activity, regardless of the p53 status of the cancer. We also describe how preclinical and clinical investigations have moved toward combining MDM2 inhibitors with other agents, including immune checkpoint inhibitors. Finally, we discuss the current challenges and future directions to accelerate the clinical application of MDM2 inhibitors. In conclusion, targeting MDM2 remains a promising treatment approach, and targeting MDM2 for protein degradation represents a novel strategy to downregulate MDM2 without the side effects of the existing agents blocking p53-MDM2 binding. Additional preclinical and clinical investigations are needed to finally realize the full potential of MDM2 inhibition in treating cancer and other chronic diseases where MDM2 has been implicated. SIGNIFICANCE STATEMENT: Overexpression/amplification of the MDM2 oncogene has been detected in various human cancers and is associated with disease progression, treatment resistance, and poor patient outcomes. This article reviews the previous, current, and emerging MDM2-targeted therapies and summarizes the preclinical and clinical studies combining MDM2 inhibitors with chemotherapy and immunotherapy regimens. The findings of these contemporary studies may lead to safer and more effective treatments for patients with cancers overexpressing MDM2.

Synthesis and biological evaluation of 4-imidazolidinone-containing compounds as potent inhibitors of the MDM2/p53 interaction

Inhibition of MDM2/p53 interaction with small-molecule inhibitors stabilizes p53 from MDM2 mediated degradation, which is a promising strategy for the treatment of cancer. In this report, a novel series of 4-imidazolidinone-containing compounds have been synthesized and tested in MDM2/p53 and MDM4/p53 FP binding assays. Upon SAR studies, compounds 2 (TB114) and 22 were identified as the most potent inhibitors of MDM2/p53 but not MDM4/p53 interactions. Both 2 and 22 exhibited strong antiproliferative activities in HCT-116 and MOLM-13 cell lines harboring wild type p53. Mechanistic studies show that 2 and 22 dose-dependently activated p53 and its target genes and induced apoptosis in cells based on the Western blot, qPCR, and flow cytometry assays. In addition, the antiproliferative activities of 2 and 22 were dependent on wild type p53, while they were not toxic to HEK-293 kidney cells. Furthermore, the on-target activities of 2 were general and applicable to other cancer cell lines with wild type p53. These attributes make 2 a good candidate for future optimization to discover a potential treatment of wild-type p53 cancer.

Design-rules for stapled peptides with in vivo activity and their application to Mdm2/X antagonists

Although stapled α-helical peptides can address challenging targets, their advancement is impeded by poor understandings for making them cell permeable while avoiding off-target toxicities. By synthesizing >350 molecules, we present workflows for identifying stapled peptides against Mdm2(X) with in vivo activity and no off-target effects. Key insights include a clear correlation between lipophilicity and permeability, removal of positive charge to avoid off-target toxicities, judicious anionic residue placement to enhance solubility/behavior, optimization of C-terminal length/helicity to enhance potency, and optimization of staple type/number to avoid polypharmacology. Workflow application gives peptides with >292x improved cell proliferation potencies and no off-target cell proliferation effects ( > 3800x on-target index). Application of these 'design rules' to a distinct Mdm2(X) peptide series improves ( > 150x) cellular potencies and removes off-target toxicities. The outlined workflow should facilitate therapeutic impacts, especially for those targets such as Mdm2(X) that have hydrophobic interfaces and are targetable with a helical motif.

Discovery of JN122, a Spiroindoline-Containing Molecule that Inhibits MDM2/p53 Protein-Protein Interaction and Exerts Robust In Vivo Antitumor Efficacy

MDM2 and MDM4 cooperatively and negatively regulate p53, while this pathway is often hijacked by cancer cells in favor of their survival. Blocking MDM2/p53 interaction with small-molecule inhibitors liberates p53 from MDM2 mediated degradation, which is an attractive strategy for drug discovery. We reported herein structure-based discovery of highly potent spiroindoline-containing MDM2 inhibitor (-)60 (JN122), which also exhibited moderate activities against MDM4/p53 interactions. In a panel of cancer cell lines harboring wild type p53, (-)60 efficiently promoted activation of p53 and its target genes, inhibited cell cycle progression, and induced cell apoptosis. Interestingly, (-)60 also promoted degradation of MDM4. More importantly, (-)60 exhibited good PK properties and exerted robust antitumor efficacies in a systemic mouse xenograft model of MOLM-13. Taken together, our study showcases a class of potent MDM2 inhibitors featuring a novel spiro-indoline scaffold, which is promising for future development targeting cancer cells with wild-type p53.

Molecular Docking and Molecular Dynamics Studies Reveal the Anticancer Potential of Medicinal-Plant-Derived Lignans as MDM2-P53 Interaction Inhibitors

The interaction between the tumor suppressor protein p53 and its negative regulator, the MDM2 oncogenic protein, has gained significant attention in cancer drug discovery. In this study, 120 lignans reported from Ferula sinkiangensis and Justicia procumbens were assessed for docking simulations on the active pocket of the MDM2 crystal structure bound to Nutlin-3a. The docking analysis identified nine compounds with higher docking scores than the co-crystallized reference. Subsequent AMDET profiling revealed satisfactory pharmacokinetic and safety parameters for these natural products. Three compounds, namely, justin A, 6-hydroxy justicidin A, and 6'-hydroxy justicidin B, were selected for further investigation due to their strong binding affinities of -7.526 kcal/mol, -7.438 kcal/mol, and -7.240 kcal/mol, respectively, which surpassed the binding affinity of the reference inhibitor Nutlin-3a (-6.830 kcal/mol). To assess the stability and reliability of the binding of the candidate hits, a molecular dynamics simulation was performed over a duration of 100 ns. Remarkably, the thorough analysis demonstrated that all the hits exhibited stable molecular dynamics profiles. Based on their effective binding to MDM2, favorable pharmacokinetic properties, and molecular dynamics behavior, these compounds represent a promising starting point for further refinement. Nevertheless, it is essential to synthesize the suggested compounds and evaluate their activity through in vitro and in vivo experiments.

Applications of palladium-catalyzed C-N cross-coupling reactions in pharmaceutical compounds

C-N cross-coupling bond formation reactions have become valuable approaches to synthesizing anilines and their derivatives, known as important chemical compounds. Recent developments in this field have focused on versatile catalysts, simple operation methods, and green reaction conditions. This review article presents an overview of C-N cross-coupling reactions in pharmaceutical compound synthesis reports. Selected examples of N-arylation reactions of various nitrogen-based compounds and aryl halides are defined for preparing pharmaceutical molecules.

An Analysis of Successful Hit-to-Clinical Candidate Pairs

An analysis of 156 published clinical candidates from the Journal of Medicinal Chemistry between 2018 and 2021 was conducted to identify lead generation strategies most frequently employed leading to drug candidates. As in a previous publication, the most frequent lead generation strategies resulting in clinical candidates were from known compounds (59%) followed by random screening approaches (21%). The remainder of the approaches included directed screening, fragment screening, DNA-encoded library screening (DEL), and virtual screening. An analysis of similarity was also conducted based on Tanimoto-MCS and revealed most clinical candidates were distant from their original hits; however, most shared a key pharmacophore that translated from hit-to-clinical candidate. An examination of frequency of oxygen, nitrogen, fluorine, chlorine, and sulfur incorporation in clinical candidates was also conducted. The three most similar and least similar hit-to-clinical pairs from random screening were examined to provide perspective on changes that occur that lead to successful clinical candidates.

Therapeutic Strategies to Activate p53

The p53 protein has appropriately been named the "guardian of the genome". In almost all human cancers, the powerful tumor suppressor function of p53 is compromised by a variety of mechanisms, including mutations with either loss of function or gain of function and inhibition by its negative regulators MDM2 and/or MDMX. We review herein the progress made on different therapeutic strategies for targeting p53.

fastDRH: a webserver to predict and analyze protein-ligand complexes based on molecular docking and MM/PB(GB)SA computation

Predicting the native or near-native binding pose of a small molecule within a protein binding pocket is an extremely important task in structure-based drug design, especially in the hit-to-lead and lead optimization phases. In this study, fastDRH, a free and open accessed web server, was developed to predict and analyze protein-ligand complex structures. In fastDRH server, AutoDock Vina and AutoDock-GPU docking engines, structure-truncated MM/PB(GB)SA free energy calculation procedures and multiple poses based per-residue energy decomposition analysis were well integrated into a user-friendly and multifunctional online platform. Benefit from the modular architecture, users can flexibly use one or more of three features, including molecular docking, docking pose rescoring and hotspot residue prediction, to obtain the key information clearly based on a result analysis panel supported by 3Dmol.js and Apache ECharts. In terms of protein-ligand binding mode prediction, the integrated structure-truncated MM/PB(GB)SA rescoring procedures exhibit a success rate of >80% in benchmark, which is much better than the AutoDock Vina (~70%). For hotspot residue identification, our multiple poses based per-residue energy decomposition analysis strategy is a more reliable solution than the one using only a single pose, and the performance of our solution has been experimentally validated in several drug discovery projects. To summarize, the fastDRH server is a useful tool for predicting the ligand binding mode and the hotspot residue of protein for ligand binding. The fastDRH server is accessible free of charge at http://cadd.zju.edu.cn/fastdrh/.

Structure-Based Discovery of MDM2/4 Dual Inhibitors that Exert Antitumor Activities against MDM4-Overexpressing Cancer Cells

Despite recent clinical progress in peptide-based dual inhibitors of MDM2/4, small-molecule ones with robust antitumor activities remain challenging. To tackle this issue, 31 (YL93) was structure-based designed and synthesized, which had MDM2/4 binding K_i values of 1.1 and 642 nM, respectively. In three MDM4-overexpressing cancer cell lines harboring wild-type p53, 31 shows improved cell growth inhibition activities compared to RG7388, an MDM2-selective inhibitor in late-stage clinical trials. Mechanistic studies show that 31 increased cellular protein levels of p53 and p21 and upregulated the expression of p53-targeted genes in RKO cells with MDM4 amplification. In addition, 31 induced cell-cycle arrest and apoptosis in western blot and flow cytometry assays. Taken together, dual inhibition of MDM2/4 by 31 elicited stronger antitumor activities in vitro compared to selective MDM2 inhibitors in wild-type p53 and MDM4-overexpressing cancer cells.

NMR Data-Driven Docking of HDM2-Inhibitor Complexes

We present an automated NMR-guided docking workflow that can be used to generate models of protein-ligand complexes based on data from NOE NMR experiments. The first step is to generate a number of intermolecular distance constraints from experimental NOE data. Then, the ligand is docked on an ensemble of receptor structures to account for protein flexibility, and multiple poses are generated. Finally, we use the NOE-based constraints to filter and score docking poses based on the percentage of NOE constraints that are consistent with protein-ligand interatomic distances. This workflow was successfully used during a Lead Optimization project to generate models of synthetic PPI inhibitors bound to the HDM2 protein.