2,5-Diketopiperazines (DKPs): Promising Scaffolds for Anticancer Agents.

2,5-Diketopiperazine (2,5-DKP) derivatives represent a family of secondary metabolites widely produced by bacteria, fungi, plants, animals, and marine organisms. Many natural products with DKP scaffolds exhibited various pharmacological activities such as antiviral, antifungal, antibacterial, and antitumor. 2,5-DKPs are recognized as privileged structures in medicinal chemistry, and compounds that incorporate the 2,5-DKP scaffold have been extensively investigated for their anticancer properties. This review is a thorough update on the anti-cancer activity of natural and synthesized 2,5-DKPs from 1997 to 2022. We have explored various aspects of 2,5-DKPs modifications and summarized their structure-activity relationships (SARs) to gain insight into their anticancer activities. We have also highlighted the novel approaches to enhance the specificity and pharmacokinetics of 2,5-DKP-based anticancer agents.

A Synthetic ERR Agonist Alleviates Metabolic Syndrome.

Physical exercise induces physiologic adaptations and is effective at reducing the risk of premature death from all causes. Pharmacological exercise mimetics may be effective in the treatment of a range of diseases including obesity and metabolic syndrome. Previously, we described the development of SLU-PP-332, an agonist for the estrogen-related receptor (ERR)α, ß, and γ nuclear receptors that activates an acute aerobic exercise program. Here we examine the effects of this exercise mimetic in mouse models of obesity and metabolic syndrome. Diet-induced obese or ob/ob mice were administered SLU-PP-332, and the effects on a range of metabolic parameters were assessed. SLU-PP-332 administration mimics exercise-induced benefits on whole-body metabolism in mice including increased energy expenditure and fatty acid oxidation. These effects were accompanied by decreased fat mass accumulation. Additionally, the ERR agonist effectively reduced obesity and improved insulin sensitivity in models of metabolic syndrome. Pharmacological activation of ERR may be an effective method to treat metabolic syndrome and obesity. SIGNIFICANCE STATEMENT: An estrogen receptor-related orphan receptor agonist, SLU-PP-332, with exercise mimetic activity, holds promise as a therapeutic to treat metabolic diseases by decreasing fat mass in mouse models of obesity.

Estrogen-Related Receptor Agonism Reverses Mitochondrial Dysfunction and Inflammation in the Aging Kidney.

A gradual decline in renal function occurs even in healthy aging individuals. In addition to aging, per se, concurrent metabolic syndrome and hypertension, which are common in the aging population, can induce mitochondrial dysfunction and inflammation, which collectively contribute to age-related kidney dysfunction and disease. This study examined the role of the nuclear hormone receptors, the estrogen-related receptors (ERRs), in regulation of age-related mitochondrial dysfunction and inflammation. The ERRs were decreased in both aging human and mouse kidneys and were preserved in aging mice with lifelong caloric restriction (CR). A pan-ERR agonist, SLU-PP-332, was used to treat 21-month-old mice for 8 weeks. In addition, 21-month-old mice were treated with a stimulator of interferon genes (STING) inhibitor, C-176, for 3 weeks. Remarkably, similar to CR, an 8-week treatment with a pan-ERR agonist reversed the age-related increases in albuminuria, podocyte loss, mitochondrial dysfunction, and inflammatory cytokines, via the cyclic GMP-AMP synthase-STING and STAT3 signaling pathways. A 3-week treatment of 21-month-old mice with a STING inhibitor reversed the increases in inflammatory cytokines and the senescence marker, p21/cyclin dependent kinase inhibitor 1A (Cdkn1a), but also unexpectedly reversed the age-related decreases in PPARG coactivator (PGC)-1α, ERRα, mitochondrial complexes, and medium chain acyl coenzyme A dehydrogenase (MCAD) expression. These studies identified ERRs as CR mimetics and as important modulators of age-related mitochondrial dysfunction and inflammation. These findings highlight novel druggable pathways that can be further evaluated to prevent progression of age-related kidney disease.

Synthetic ERRα/ß/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity.

Repetitive physical exercise induces physiological adaptations in skeletal muscle that improves exercise performance and is effective for the prevention and treatment of several diseases. Genetic evidence indicates that the orphan nuclear receptors estrogen receptor-related receptors (ERRs) play an important role in skeletal muscle exercise capacity. Three ERR subtypes exist (ERRα, ß, and γ), and although ERRß/γ agonists have been designed, there have been significant difficulties in designing compounds with ERRα agonist activity. Additionally, there are limited synthetic agonists that can be used to target ERRs in vivo. Here, we report the identification of a synthetic ERR pan agonist, SLU-PP-332, that targets all three ERRs but has the highest potency for ERRα. Additionally, SLU-PP-332 has sufficient pharmacokinetic properties to be used as an in vivo chemical tool. SLU-PP-332 increases mitochondrial function and cellular respiration in a skeletal muscle cell line. When administered to mice, SLU-PP-332 increased the type IIa oxidative skeletal muscle fibers and enhanced exercise endurance. We also observed that SLU-PP-332 induced an ERRα-specific acute aerobic exercise genetic program, and the ERRα activation was critical for enhancing exercise endurance in mice. These data indicate the feasibility of targeting ERRα for the development of compounds that act as exercise mimetics that may be effective in the treatment of numerous metabolic disorders and to improve muscle function in the aging.

Ligand-based design, synthesis, computational insights, and in vitro studies of novel N-(5-Nitrothiazol-2-yl)-carboxamido derivatives as potent inhibitors of SARS-CoV-2 main protease.

The global outbreak of the COVID-19 pandemic provokes scientists to make a prompt development of new effective therapeutic interventions for the battle against SARS-CoV-2. A new series of N-(5-nitrothiazol-2-yl)-carboxamido derivatives were designed and synthesised based on the structural optimisation principle of the SARS-CoV Mpro co-crystallized WR1 inhibitor. Notably, compound 3b achieved the most promising anti-SARS-CoV-2 activity with an IC50 value of 174.7 µg/mL. On the other hand, compounds 3a, 3b, and 3c showed very promising SARS-CoV-2 Mpro inhibitory effects with IC50 values of 4.67, 5.12, and 11.90 µg/mL, respectively. Compound 3b docking score was very promising (-6.94 kcal/mol) and its binding mode was nearly similar to that of WR1. Besides, the molecular dynamics (MD) simulations of compound 3b showed its great stability inside the binding pocket until around 40 ns. Finally, a very promising SAR was concluded to help to design more powerful SARS-CoV-2 Mpro inhibitors shortly.

Design, Synthesis and Antitumor Activity of Novel Dispiro[oxindole-cyclohexanone]- pyrrolidines.

BACKGROUND: Spirooxindoles are privileged scaffolds in medicinal chemistry, which were identified through Wang's pioneering work as inhibitors of MDM2-p53 interactions. OBJECTIVE: To design and synthesize 2,6-diarylidenecyclohexanones and dispiro[oxindole-cyclohexanone]- pyrrolidines having potential antitumor effect. METHODS: Dispiro[oxindole-cyclohexanone]-pyrrolidines 6a-h were synthesized in a regioselective manner via 1,3-dipolar cycloaddition reaction of 2,6-diarylidenecyclohexanones 3a-h, isatin, and sarcocine. Compounds 6a-h were alkylated to give (7-10)a,b. All compounds were evaluated in vitro for their antitumor activity and cytotoxic selectivity against breast cancer cell lines (MCF-7 and MDA-MB-231), breast fibrosis cell line (MCF10a), and placental cancer cell line (JEG-3). Molecular modeling inside the MDM2 binding site was performed using AutoDock4.2. RESULTS: Synthesized compounds showed antitumor activity comparable to tamoxifen and compounds 3a,b,f,g and 9a,b showed selective cytotoxicity against tumor cells but reduced toxicity toward MCF-10a cells. Molecular modelling shows that both classes of synthesized compounds are predicted to fit the deep hydrophobic cleft on the surface of MDM2 and mimic the interactions between p53 and MDM2. CONCLUSION: The synthesized compounds have antitumor activity against MCF-7, MDA-MB-231, and JEG-3. Few compounds showed a selective cytotoxic effect and may have the potential to inhibit MDM2 and stimulate p53. In the future, studies regarding the optimization of medicinal chemistry as well as mechanistic studies will be conducted to enhance the inhibition effect of identified compounds and elucidate their mechanism of action.

Synthesis and structure activity relationship of the first class of LXR inverse agonists.

Liver X Receptors (LXRs) are members of the nuclear receptor family, and they play significant role in lipid and cholesterol metabolism. Moreover, they are key regulators of several inflammatory pathways. Pharmacological modulation of LXRs holds great potential in treatment of metabolic diseases, neurodegenerative diseases, and cancer. We were the first group to identify LXR inverse agonists SR9238 (6) and SR9243 (7) and demonstrate their potential utility in treating liver diseases and cancer. Here, we present the results of structure-activity relationship (SAR) studies, based around SR9238 (6) and SR9243 (7). This study led to identification of 16, 17, 19, and 38, which were more potent inverse agonists than SR9238 (6) and SR9243 (7) and inhibited expression of the fatty acid synthase gene in DU145 cells. We previously demonstrated that inhibition of FASN is correlated to the anticancer activity of SR9243 (7) and this suggests that new inverse agonists have great potential as anticancer agents. We identified compounds with distinct selectivity toward both LXR isoforms, which can be excellent tools to study the pharmacology of both isoforms. We employed molecular dynamic (MD) simulations to better understand the molecular mechanism underlying inverse agonist activity and to guide our future design.

Structure-based design and synthesis of conformationally constrained derivatives of methyl-piperidinopyrazole (MPP) with estrogen receptor (ER) antagonist activity.

Nuclear Estrogen receptors (ER) are cytoplasmic proteins; translocated to the nucleus to induce transcriptional signals after getting bound to the estrogen hormone. ER activation implicated in cancer cell proliferation of female reproductive organs. Thus, the discovery of ER antagonists is a reliable strategy to combat estrogen-dependent breast cancer. Endometrial carcinoma is one of the complications encountered upon long-term therapy by selective estrogen receptor modulators (SERMs) like Tamoxifen (TMX) and methyl piperidinopyrazole (MPP). Thus, the ER-full antagonist is a solution to improve the safety of this class of therapeutics during the treatment of breast cancer. We selected MPP as a lead structure to design conformationally constrained analogs. Structural rigidification is a proven strategy to transform the SERMs into full antagonists. Accordingly, we synthesized 7-methoxy-3-(4-methoxyphenyl)-4,5-dihydro-2H-benzo[g]indazoles (4), (6a-c),(8-12) along with the biphenolic counterparts(13-19)that are the anticipated active metabolites. The 4-nitrophenyl derivative(4)is with the most balanced profile regardingthe in vivoanti-uterotrophic potential (EC50 = 4.160 µM); and the cytotoxicity assay of the corresponding active metabolite(13)against ER+ breast cancer cell lines (MCF-7 IC50 = 7.200 µM, T-47D IC50 = 11.710 µM). The inconsiderable uterotrophic activities of the elaborated ER-antagonists and weak antiproliferative activity of the compound(13)against ovarian cancer (SKOV-3 IC50 = 29.800 µM) highlighted it as a good start point to elaborate potential ER-full antagonists devoid of endometrial carcinoma. Extending the pendant chain that protrudes from the 2-(4-(substituted)-phenyl) ring of the new benzo-indazoles is recommended for enhancing the potency based on the binding mode of compound(13)in the ligand-binding domain (LBD) of ER.

Design and synthesis of novel pyrazolo[3,4-d]pyrimidin-4-one bearing quinoline scaffold as potent dual PDE5 inhibitors and apoptotic inducers for cancer therapy.

PDE5 targeting represents a new and promising strategy for apoptosis induction and inhibition of tumor cell growth due to its over-expression in diverse types of human carcinomas. Accordingly, we report the synthesis of series of pyrazolo[3,4-d]pyrimidin-4-one carrying quinoline moiety (11a-r) with potential dual PDE5 inhibition and apoptotic induction for cancer treatment. These hybrids were structurally elucidated and characterized with variant spectroscopic techniques as 1H NMR, 13C NMR and elemental analysis. The assessment of their anticancer activities has been declared. All the rationalized compounds 11a-r have been selected for their cytotoxic activity screening by NCI against 60 cell lines. Compounds 11a, 11b, 11j and 11k were the most active hybrids. Among all, compound 11j was further selected for five dose tesing and it displayed outstanding activity with strong antitumor activity against the nine tumor subpanels tested with selectivity ratios ranging from 0.019 to 8.3 at the GI50 level. Further, the most active targets 11a, b, j and k were screened for their PDE5 inhibitory activity, compound 11j (with IC50 1.57 nM) exhibited the most potent PDE5 inhibitory activity. Moreover, compound 11j is also showed moderate EGFR inhibition with IC50 of 5.827 ± 0.46 µM, but significantly inhibited the Wnt/ß-catenin pathway with IC501286.96 ± 12.37 ng/mL. In addition, compound 11j induced the intrinsic apoptotic mitochondrial pathway in HepG2 cells as evidenced by the lower expression levels of the anti-apoptotic Bcl-2 protein, and the higher expression of the pro-apoptotic protein Bax, p53, cytochrome c and the up-regulated active caspase-9 and caspase-3 levels. All results confirmed by western blotting assay. Compound 11j exhibit pre G1 apoptosis and cell cycle arrest at G2/M phase. In conclusion, hybridization of quinoline moiety with the privileged pyrazolo[3,4-d]pyrimidinon-4-one structure resulted in highly potent anticancer agent, 11j, which deserves more study, in particular, in vivo and clinical investiagtions, and it is expected that these results would be applied for more drug discovery process.

Modulation of estrogen-related receptors subtype selectivity: Conversion of an ERRß/γ selective agonist to ERRα/ß/γ pan agonists.

Estrogen Related Receptors (ERRs) are key regulators of energy homeostasis and play important role in the etiology of metabolic disorders, skeletal muscle related disorders, and neurodegenerative diseases. Among the three ERR isoforms, ERRα emerged as a potential drug target for metabolic and neurodegenerative diseases. Although ERRß/γ selective agonist chemical tools have been identified, there are no chemical tools that effectively target ERRα agonism. We successfully engineered high affinity ERRα agonism into a chemical scaffold that displays selective ERRß/γ agonist activity (GSK4716), providing novel ERRα/ß/γ pan agonists that can be used as tools to probe the physiological roles of these nuclear receptors. We identified the structural requirements to enhance selectivity toward ERRα. Molecular modeling shows that our novel modulators have favorable binding modes in the LBP of ERRα and can induce conformational changes where Phe328 that originally occupies the pocket is dislocated to accommodate the ligands in a rather small cavity. The best agonists up-regulated the expression of target genes PGC-1α and PGC-1ß, which are necessary to achieve maximal mitochondrial biogenesis. Moreover, they increased the mRNA levels of PDK4, which play an important role in energy homeostasis.

Synthesis and Evaluation of Troponoids as a New Class of Antibiotics.

Novel antibiotics are urgently needed. The troponoids [tropones, tropolones, and α-hydroxytropolones (α-HT)] can have anti-bacterial activity. We synthesized or purchased 92 troponoids and evaluated their antibacterial activities against Staphylococcus aureus, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa. Preliminary hits were assessed for minimum inhibitory concentrations (MIC80) and cytotoxicity (CC50) against human hepatoma cells. Sixteen troponoids inhibited S. aureus/E. coli/A. baumannii growth by ≥80% growth at <30 µM with CC50 values >50 µM. Two selected tropolones (63 and 285) inhibited 18 methicillin-resistant S. aureus (MRSA) strains with similar MIC80 values as against a reference strain. Two selected thiotropolones (284 and 363) inhibited multidrug-resistant (MDR) E. coli with MIC80 ≤30 µM. One α-HT (261) inhibited MDR-A. baumannii with MIC80 ≤30 µM. This study opens new avenues for development of novel troponoid antibiotics to address the critical need to combat MDR bacterial infections.