Discovery of 1,5-Dihydro-4H-imidazol-4-one Derivatives as Potent, Selective Antagonists of CXC Chemokine Receptor 2.

CXC chemokine receptors 1 (CXCR1) and 2 (CXCR2) have been demonstrated to have critical roles in cancer metastasis. Because they share high homology sequences, it is still unclear how to design selective CXCR1 or CXCR2 antagonists. Based on a pharmacophore model we built, compound 2 bearing a 1,5-dihydro-4H-imidazol-4-one scaffold was identified as a selective CXCR2 antagonist with a low CXCR1 antagonism preference. Further optimization and structure-activity relationship studies led to compound C5 that overcame the disadvantages of compound 2 and performed with higher selectivity. It showed excellent oral bioavailability and in vitro anticancer metastasis activity. Further dynamic simulation of the molecular protein complex showed that the amino acid residue K320 of CXCR2 contributed most to the selectivity of C5. This study provides important clues for the design of new CXCR2 selective antagonists, and C5 can be a molecular tool for investigating the difference in the biological function of CXCR1 and CXCR2.

Identification of new IDH2R140Q inhibitors by discriminatory analysis-based molecular docking and biological evaluation.

Isocitrate dehydrogenase 2 (IDH2) is a key enzyme in the regulation of cell metabolism. Its mutated type can lead to the accumulation of 2-hydroxyglutarate, which is often related to malignancies such as acute myeloid leukemia. Therefore, it is necessary to find new inhibitors targeting mutant IDH2. Discriminatory analysis-based molecular docking was employed to screen the ChemDiv compound library, which resulted in the identification of three new IDH2R140Q inhibitors with moderate-to-good IC50 values. Among them, compounds 1 and 3 displayed good selectivity against other mutant or wild-type IDH proteins. The most potent compound 1, bearing the [1,2,4]triazolo[1,5-a]pyrimidin scaffold, was subjected to dynamic simulations to provide more information on the binding mode with IDH2R140Q , providing structural clues to further optimize compound 1 as a new mutant IDH2 inhibitor.

Structure-based design, synthesis and bioactivity evaluation of macrocyclic inhibitors of mutant isocitrate dehydrogenase 2 (IDH2) displaying activity in acute myeloid leukemia cells.

The enzymes involved in the metabolic pathways in cancer cells have been demonstrated as important therapeutic targets such as the isocitrate dehydrogenase 2 (IDH2). A series of macrocyclic derivatives was designed based on the marketed IDH2 inhibitor AG-221 by using the conformational restriction strategy. The resulted compounds showed moderate to good inhibitory potential against different IDH2-mutant enzymes. Amongst, compound C6 exhibited better IDH2R140Q inhibitory potency than AG-221, and showed excellent activity of 2-hydroxyglutarate (2-HG) suppression in vitro and its mesylate displayed good pharmacokinetic profiles. Moreover, C6 performed strong binding mode to IDH2R140Q after computational docking and dynamic simulation, which may serve as a good starting point for further development.

Bis-reaction-trigger as a strategy to improve the selectivity of fluorescent probes.

By the strategy of equipping a fluorophore with two reaction triggers that are tailored to the specific chemistry of peroxynitrite, we have developed a highly selective probe for detecting peroxynitrite in live cells. Sequential response by the two triggers enabled the probe to reveal various degrees of nitrosative stress in live cells via a sensitive emission colour change.

Design, synthesis, and molecular docking study of 3H-imidazole[4,5-c]pyridine derivatives as CDK2 inhibitors.

A novel series of imidazo[4,5-c]pyridine-based CDK2 inhibitors were designed from the structure of CYC202 via scaffold hopping strategy. These compounds were synthesized and biologically evaluated for their CDK2 inhibitory and in vitro anti-proliferation potential against cancer cell lines. Several compounds exhibited potent CDK2 inhibition with IC50 values of less than 1 µM. The most potent compound 5b showed excellent CDK2 inhibitory (IC50 = 21 nM) and in vitro anti-proliferation activity against three different cell lines (HL60, A549, and HCT116). The molecular docking and dynamic studies portrayed the potential binding mechanism between 5b and CDK2, and several key interactions between them were observed, which would be the reason for its potent CDK2 inhibitory and anti-proliferation activities. Therefore, the pyridin-3-ylmethyl moiety would serve as an excellent pharmacophore for the development of novel CDK2 inhibitors for targeted anti-cancer therapy.

Discovery and optimization of phthalazinone derivatives as a new class of potent dengue virus inhibitors.

Using a dengue replicon cell line-based screening, we identified 3-(dimethylamino)propyl(3-((4-(4-fluorophenyl)-1-oxophthalazin-2(1H)-yl)methyl)phenyl)carbamate (10a) as a potent DENV-2 inhibitor, with an IC50 value of 0.64 µM. A series of novel phthalazinone derivatives based on hit 10a were synthesized and evaluated for their in vitro anti-DENV activity and cytotoxicity. The subsequent SAR study and optimization led to the discovery of the most promising compound 14l, which displayed potent anti-DENV-2 activity, with low IC50 value against DENV-2 RNA replication of 0.13 µM and high selectivity (SI = 89.2) with acceptable pharmacokinetics profiles.

Discovery of Novel Succinate Dehydrogenase Inhibitors by the Integration of in Silico Library Design and Pharmacophore Mapping.

Succinate dehydrogenase (SDH) has been demonstrated as a promising target for fungicide discovery. Crystal structure data have indicated that the carboxyl "core" of current SDH inhibitors contributed largely to their binding affinity. Thus, identifying novel carboxyl "core" SDH inhibitors would remarkably improve the biological potency of current SDHI fungicides. Herein, we report the discovery and optimization of novel carboxyl scaffold SDH inhibitor via the integration of in silico library design and a highly specific amide feature-based pharmacophore model. To our delight, a promising SDH inhibitor, A16c (IC50 = 1.07 µM), with a novel pyrazol-benzoic scaffold was identified, which displayed excellent activity against Rhizoctonia solani (EC50 = 11.0 µM) and improved potency against Sclerotinia sclerotiorum (EC50 = 5.5 µM) and Phyricularia grisea (EC50 = 12.0 µM) in comparison with the positive control thifluzamide, with EC50 values of 0.09, 33.2, and 33.4 µM, respectively. The results showed that our virtual screening strategy could serve as a powerful tool to accelerate the discovery of novel SDH inhibitors.

Integrating docking scores and key interaction profiles to improve the accuracy of molecular docking: towards novel B-RafV600E inhibitors.

A set of ninety-eight B-RafV600E inhibitors was used for the development of a molecular docking based QSAR model using linear and non-linear regression models. The integration of docking scores and key interaction profiles significantly improved the accuracy of the QSAR models, providing reasonable statistical parameters (Rtrain2 = 0.935, Rtest2 = 0.728 and QCV2 = 0.905). The established MD-SVR (molecular docking based SMV regression) model as well as model screening of a natural product database was carried out and two natural products (quercetin and myricetin) with good prediction activities were biologically evaluated. Both compounds exhibited promising B-RafV600E inhibitory activities (ICQuercetin50 = 7.59 µM and ICMyricetin50 = 1.56 µM), suggesting a high reliability and good applicability of the established MD-SVR model in the future development of B-RafV600E inhibitors with high efficacy.

Design, Synthesis and Evaluation of Indene Derivatives as Retinoic Acid Receptor α Agonists.

A series of novel indene-derived retinoic acid receptor α (RARα) agonists have been designed and synthesized. The use of receptor binding, cell proliferation and cell differentiation assays demonstrated that most of these compounds exhibited moderate RARα binding activity and potent antiproliferative activity. In particular, 4-((3-isopropoxy-2,3-dihydro-1H-inden-5-yl)-carbamoyl)benzoic acid (36d), which showed a moderate binding affinity, exhibited a great potential to induce the differentiation of NB4 cells (68.88% at 5 µM). Importantly, our work established indene as a promising skeleton for the development of novel RARα agonists.

Design, synthesis and biological evaluation of novel 4-alkynyl-quinoline derivatives as PI3K/mTOR dual inhibitors.

A novel series of 4-alkynyl-quinoline derivatives were designed, synthesized and biologically evaluated for their PI3Kα inhibitory activities and anti-proliferative effects against two cancer cell lines PC-3 and HCT-116. Most of them showed potent PI3Kα inhibitory activities with IC50 values at low nanomolar level and good to excellent anti-proliferative effects against both cell lines. Among them, compound 15d, the most potent one, was selected for further biological evaluation. As a result, 15d displayed strong inhibitory activity against other class I PI3K isoforms (PI3Kß, PI3Kγ and PI3Kδ) and mTOR with an acceptable kinase selectivity profile. Moreover, the western blot assay indicated that the phosphorylation of Akt, another downstream effector of PI3K, can be remarkably suppressed by 15d at cellular level. All these experimental results suggested that 15d is a potent PI3K/mTOR dual inhibitor and could serve as a promising lead compound for the development of anticancer agents.

MSFTZ, a flavanone derivative, induces human hepatoma cell apoptosis via a reactive oxygen species- and caspase-dependent mitochondrial pathway.

Hepatocellular carcinoma (HCC) is the most common malignancy of the liver. It is unfortunate that HCCs are highly refractory to conventional chemotherapy, radiation therapy, and even immunotherapy. Thus, novel therapeutic targets need to be sought for the successful treatment of HCCs. We now report that (+/-)-(3aRS,4SR)-2-(2-chloro-4-methylsulfonylphenyl)-4'-chloro-3alpha,4-diethoxy-flavane[4,3-d]-D1,9b-1,2,3-thiadiazoline (MSFTZ), a synthesized flavanone derivative, induced growth arrest and apoptosis of HCCs both in vitro and in vivo. MSFTZ induced a time- and dose-dependent increase in HCC apoptosis through caspase-3 activation and poly(ADP-ribose) polymerase-1 cleavage. Activation of caspase-9 induced by MSFTZ suggested that MSFTZ-induced signaling was mediated through a mitochondrial death pathway. In addition, we observed an elevation of reactive oxygen species (ROS) and a consequent loss of mitochondrial membrane potential, further suggesting that MSFTZ-induced death signaling was mediated through a mitochondrial oxygen stress pathway. These events were associated with a decrease and increase in Bcl-2 and Bax expression, respectively, as well as phosphorylation of mitogen-activated protein kinase (MAPK) and activation of p53-MDM2 pathway. However, the antioxidant N-acetylcysteine opposed MSFTZ-mediated mitochondrial dysfunction, caspase activation, Bcl-2/Bax modulation, and apoptosis, supporting the role of ROS in the apoptotic process. We were surprised that we failed to observe the protective effect of N-acetylcysteine against MSFTZ-induced MAPK activation. Furthermore, MSFTZ had an antitumor effect in vivo by 34.8 to 78.7% reduction of tumor size in SMMC-7721-xenografted nude mice. We conclude that MSFTZ induces HCC cell apoptosis both in vivo and in vitro via caspase- and ROS-dependent mitochondrial pathway. In addition, MSFTZ has potential as a novel therapeutic agent for the treatment of HCC.

Synthesis and anticancer activity of a novel class of flavonoids: 2,4-diarylchromane[4,3-d]-delta(1,9b)-1,2,3-thiadiazolines.

A series of 2,4-diarylchromane[4,3-d]-Delta(1,9b)-1,2,3-thiadiazolines have been synthesized by cyclization of corresponding 2-arylchroman-4-one-arylhydrazones with SOCl(2) then treated with alcohol. All the compounds have been tested for their antiproliferative activity in vitro against six human tumor cell lines, and the highly potent derivative 11a exhibited in vivo inhibitory effect on tumor growth. Mechanism research indicated that it is due to 11a that induces DNA fragmentation.

Antileukemia activity of MSFTZ-a novel flavanone analog.

A newly synthesized flavanone derivative, (+/-)-(3aRS,4SR)-2-(2-chloro-4-methyl- sulfonylphenyl)-4'-chloro-3a,4-diethoxy-flavane[4,3-d]-Delta-1,2,3-thiadiazoline (MSFTZ), was investigated for its antileukemia activity and molecular mechanisms. Cytotoxicity assay confirmed the high antiproliferative efficiency of MSFTZ in six leukemia cell lines (including two drug-resistant cell lines), with 50% inhibition of cell viability values ranging from 1.0 to 9.2 micromol/l. The results of flow cytometry assay showed that the percentage of apoptotic HL-60 cells was 68.3% after 48 h treatment with MSFTZ, suggesting that the activation of the apoptosis pathway was an anticancer property of MSFTZ. Furthermore, the protein changes related to apoptosis were investigated. Exposure of HL-60 cells to MSFTZ induced pro-caspase-9 and pro-caspase-3 cleavage, X-linked inhibitor of apoptosis protein and Bcl-X(L) downregulation, and poly(ADP-ribose) polymerase degradation. Treatment of cells with MSFTZ resulted in a time-dependent reduction in phosphorylation (activation) of extracellular signal-regulated kinase 1/2 and an increase in phosphorylation (activation) of Jun N-terminal kinase. Taken together, our results demonstrated that activation of mitogen-activated protein kinase and apoptotic cascade is involved in MSFTZ-induced antileukemia activity. All data suggest that MSFTZ is a promising chemotherapy drug.