Discovery of novel indolin-2-one compounds as potent inhibitors of HsClpP for cancer treatment.

Human caseinolytic protease proteolytic subunit (HsClpP) is a highly conserved serine protease that plays an essential role in cell homeostasis through removal of the damaged and/or misfolded proteins. Recently, due to its critical role in cancer proliferation and metastasis, HsClpP has been considered as a promising target for the cancer treatment. In this paper, through a random screening toward a library of 2086 bioactive chemicals, a novel compound I, 3-(3,5-dibromo-4-hydroxybenzylidene) -5-iodoindolin-2-one, was identified as a potent suppressor of HsClpP. Herein, a series of compound I derivatives were synthesized, and evaluated for their anti-cancer activities on a variety of cancers cells. Through the preliminary biological assay in vitro, including MTT assay and proteolytic activity assay, compound I was identified as the most potent inhibitor. Treatment with compound I impaired the migration of Hela cells. In addition, compound I disrupted the mitochondrial function, and reduced the level of the SDHB and induced the production of the ATF4. In general, compound I is a promising probe of HsClpP for cancer treatment, and is a good lead compound for the development of novel anti-cancer agent.

Discovery of 5-(Piperidin-4-yl)-1,2,4-oxadiazole Derivatives as a New Class of Human Caseinolytic Protease P Agonists for the Treatment of Hepatocellular Carcinoma.

Chemical agonism of human caseinolytic protease P (HsClpP) is increasingly being recognized as a potential anticancer strategy due to its critical role in maintaining mitochondrial homeostasis. We unveil the discovery of 5-(piperidin-4-yl)-1,2,4-oxadiazole derivatives as a novel class of HsClpP agonists and demonstrate for the first time the application of HsClpP agonists in the treatment of hepatocellular carcinoma (HCC) (Pace, A.; Pierro, P. The new era of 1,2,4-oxadiazoles. Org. Biomol. Chem. 2009, 7 (21), 4337-4348). Compound SL44 exhibited potent HsClpP agonistic activity in the α-casein hydrolysis assay (EC50 = 1.30 µM) and inhibited the proliferation of HCCLM3 cells (IC50 = 3.1 µM, 21.4-fold higher than hit ADX-47273). Mechanistically, SL44 induces degradation of respiratory chain complex subunits and leads to apoptosis in HCC cells. In vivo results demonstrated that SL44 has potent tumor growth inhibitory activity and has a superior safety profile compared to the kinase inhibitor sorafenib. Overall, we developed a novel class of HsClpP agonists that can potentially be used for the treatment of HCC.

Exploration of novel isoxazole-fused quinone derivatives as anti-colorectal cancer agents through inhibiting STAT3 and elevating ROS level.

Colorectal cancer (CRC) is trending to be a major health problem throughout the world. Therapeutics with dual modes of action have shown latent capacity to create ideal anti-tumor activity. Signal transducer and activator of transcription 3 (STAT3) has been proved to be a potential target for the development of anti-colon cancer drug. In addition, modulation of tumor redox homeostasis through deploying exogenous reactive oxygen species (ROS)-enhancing agents has been widely applied as anti-tumor strategy. Thus, simultaneously targeting STAT3 and modulation ROS balance would offer a fresh avenue to combat CRC. In this work, we designed and synthesized a novel series of isoxazole-fused quinones, which were evaluated for their preliminary anti-proliferative activity against HCT116 cells. Among these quinones, compound 41 exerted excellent in vitro anti-tumor effect against HCT116 cell line with an IC50 value of 10.18 ± 0.4 nM. Compound 41 was proved to bind to STAT3 by using Bio-Layer Interferometry (BLI) assay, and can significantly inhibit phosphorylation of STAT3. It also elevated ROS of HCT116 cells by acting as a substrate of NQO1. Mitochondrial dysfunction, apoptosis, and cell cycle arrest, which was caused by compound 41, might be partially due to the inhibition of STAT3 phosphorylation and ROS production induced by 41. Moreover, it exhibited ideal anti-tumor activity in human colorectal cancer xenograft model and good safety profiles in vivo. Overall, this study provided a novel quinone derivative 41 with excellent anti-tumor activity by inhibiting STAT3 and elevating ROS level, and gave insights into designing novel anti-tumor therapeutics by simultaneously modulation of STAT3 and ROS.

Discovery of a Novel Series of Homo sapiens Caseinolytic Protease P Agonists for Colorectal Adenocarcinoma Treatment via ATF3-Dependent Integrated Stress Response.

Homo sapiens caseinolytic protease P (HsClpP) activation is a promising strategy for colon cancer treatment. In this study, CCG1423 was identified as a selective activator of HsClpP. After optimization, NCA029 emerged as the most potent compound, with an EC50 of 0.2 µM against HsClpP. Molecular dynamics revealed that the affinity of NCA029 for the YYW aromatic network is crucial for its selectivity toward HsClpP. Furthermore, NCA029 displayed favorable pharmacokinetics and safety profiles and significantly inhibited tumor growth in HCT116 xenografts, resulting in 83.6% tumor inhibition. Mechanistically, NCA029 targeted HsClpP, inducing mitochondrial dysfunction and activating the ATF3-dependent integrated stress response, ultimately causing cell death in colorectal adenocarcinoma. These findings highlight NCA029 as an effective HsClpP activator with potential for colon cancer therapy.

Rational Design of a Novel Class of Human ClpP Agonists through a Ring-Opening Strategy with Enhanced Antileukemia Activity.

The activation of Homo sapiens Casein lysing protease P (HsClpP) by a chemical or genetic strategy has been proved to be a new potential therapy in acute myeloid leukemia (AML). However, limited efficacy has been achieved with classic agonist imipridone ONC201. Here, a novel class of HsClpP agonists is designed and synthesized using a ring-opening strategy based on the lead compound 1 reported in our previous study. Among these novel scaffold agonists, compound 7k exhibited remarkably enhanced proteolytic activity of HsClpP (EC50 = 0.79 ± 0.03 µM) and antitumor activity in vitro (IC50 = 0.038 ± 0.003 µM). Moreover, the intraperitoneal administration of compound 7k markedly suppressed tumor growth in Mv4-11 xenograft models, achieving a tumor growth inhibition rate of 88%. Concurrently, 7k displayed advantageous pharmacokinetic properties in vivo. This study underscores the promise of compound 7k as a significant HsClpP agonist and an antileukemia drug candidate, warranting further exploration for AML treatment.

Discovery and Optimization of Novel SaFabI Inhibitors as Specific Therapeutic Agents for MRSA Infection.

As the rate-limiting enzyme in fatty acid biosynthesis, Staphylococcus aureus enoyl-acyl carrier protein reductase (SaFabI) emerges as a compelling target for combating methicillin-resistant S. aureus (MRSA) infections. Herein, compound 1, featuring a 4-(1H-benzo[d]imidazol-2-yl)pyrrolidin-2-one scaffold, was identified as a potent SaFabI inhibitor (IC50 = 976.8 nM) from an in-house library. Subsequent optimization yielded compound n31, with improved inhibitory efficacy on enzymatic activity (IC50 = 174.2 nM) and selective potency against S. aureus (MIC = 1-2 µg/mL). Mechanistically, n31 directly inhibited SaFabI in cellular contexts. Moreover, n31 exhibited favorable safety and pharmacokinetic profiles, and dose-dependently treated MRSA-induced skin infections, outperforming the approved drug, linezolid. The chiral separation of n31 resulted in (S)-n31, with superior activities (IC50 = 94.0 nM, MIC = 0.25-1 µg/mL) and in vivo therapeutic efficacy. In brief, our research proposes (S)-n31 as a promising candidate for SaFabI-targeted therapy, offering specific anti-S. aureus efficacy and potential for further development.

Discovery and Mechanistic Study of Novel Mycobacterium tuberculosis ClpP1P2 Inhibitors.

Caseinolytic protease P (ClpP) responsible for the proteolysis of damaged or misfolded proteins plays a critical role in proteome homeostasis. MtbClpP1P2, a ClpP enzyme complex, is required for survival in Mycobacterium tuberculosis, and it is therefore considered as a promising target for the development of antituberculosis drugs. Here, we discovered that cediranib and some of its derivatives are potent MtbClpP1P2 inhibitors and suppress M. tuberculosis growth. Protein pull-down and loss-of-function assays validated the in situ targeting of MtbClpP1P2 by cediranib and its active derivatives. Structural and mutational studies revealed that cediranib binds to MtbClpP1P2 by binding to an allosteric pocket at the equatorial handle domain of the MtbClpP1 subunit, which represents a unique binding mode compared to other known ClpP modulators. These findings provide us insights for rational drug design of antituberculosis therapies and implications for our understanding of the biological activity of MtbClpP1P2.

IMP075 targeting ClpP for colon cancer therapy in vivo and in vitro.

ONC201 is a well-known caseinolytic protease (ClpP)activator with established benefits against multiple tumors, including colorectal cancer (CRC). In this study, we investigated the anticancer effects and associated mechanisms of the ClpP agonist IMP075, derived from ONC201. Acute toxicity and CCK-8 assayswere employed to determine the safety of IMP075. The effectiveness of IMP075 was investigated in HCT116 cells and a mouse xenograft tumor model. Additionally, the properties of IMP075 were evaluated by pharmacokinetic,CYP inhibition, and hERG inhibition assays. Finally, isothermal titration calorimetry (ITC), differential scanning fluorimetry (DSF), cellular thermal shift assay (CETSA), molecular dynamics simulations, point mutations, and shRNA experiments were employed to elucidate the potential mechanism of IMP075. Compared with ONC201, IMP075 exhibited similar toxicity and improved antitumor effects in vitro and in vivo. Interestingly, the affinity and agonistic effects of IMP075 on ClpP were superior to ONC201, which allowed IMP075 to disrupt respiratory chain integrity at lower doses in HCT116 cells, leading to mitochondrial dysfunction. Furthermore, molecular dynamics simulations demonstrate that IMP075 forms two pairs of hydrogen bonds with ClpP, maintaining ClpP in an agonistic state. Importantly, the antiproliferative activity of IMP075 significantly decreased following ClpP knockdown. Our findings substantiate that IMP075 exerts excellent antitumor effects against CRC by activating ClpP-mediated impairment of mitochondrial function. Due to its superior properties, IMP075 appears to be have huge prospects for application.

Discovery of a Novel Series of Imipridone Compounds as Homo sapiens Caseinolytic Protease P Agonists with Potent Antitumor Activities In Vitro and In Vivo.

Homo sapiens caseinolytic protease P (HsClpP) plays an important role in maintaining mitochondrial proteostasis. Activating HsClpP has been proved to be a potential strategy for cancer therapy. In this paper, a novel class of HsClpP agonists is designed and synthesized using a position shift strategy based on the imipridone ONC201. Among these newly synthesized imipridone derivatives, compound 16z exhibits remarkably enhanced antitumor activity (IC50 = 0.04 µM against HCT116 cells). It can improve HsClpP thermal stability and induce mitochondrial dysfunction, reactive oxygen species production, cell cycle arrest in the G0/G1 phase, and apoptosis of HCT116 cells. Moreover, compound 16z possesses excellent pharmacokinetic profiles and significantly inhibits tumor growth in HCT116 cell-inoculated xenograft nude mouse models. Our study demonstrates that 16z has potential to be an antitumor drug candidate for further development and provides insights for the design of the next generation of HsClpP agonists for cancer treatment.

Human ClpP protease, a promising therapy target for diseases of mitochondrial dysfunction.

Human caseinolytic protease P (HsClpP), an ATP-dependent unfolding peptidase protein in the mitochondrial matrix, controls protein quality, regulates mitochondrial metabolism, and maintains the integrity and enzyme activity of the mitochondrial respiratory chain (RC). Studies show that abnormalities in HsClpP lead to mitochondrial dysfunction and various human diseases. In this review, we provide a comprehensive overview of the structure and biological function of HsClpP, and the involvement of its dysexpression or mutation in mitochondria for a panel of important human diseases. We also summarize the structural types and binding modes of known HsClpP modulators. Finally, we discuss the challenges and future directions of HsClpP targeting as promising approach for the treatment of human diseases of mitochondrial origin.

Rapid Immobilization of Simulated Radioactive Soil Waste Using Self-Propagating Synthesized Gd2Ti2O7 Pyrochlore Matrix.

A rapid and effective method is necessary in the disposal of severely radioactive contaminated soil waste. Simulated Ce-bearing radioactive soil waste was immobilized by self-propagating high-temperature synthesis (SHS) within 5 min in this study. The main work includes the rapid synthesis of soil waste forms, the analysis of phase composition, microstructure and chemical durability. These results show that the simulated nuclide Ce was successfully immobilized into the pyrochlore-rich waste matrice, whose main phases are SiO2, pyrochlore (Gd2Ti2O7) and Cu. The normalized leaching rates of Si and Na on the 42nd day are 1.86 × 10-3 and 1.63 × 10-2 g·m-2·d-1, respectively. And the normalized leaching rate of Ce also remains at low level (10-5-10-6 g·m-2·d-1) within 42 days.