Privileged Scaffolds Targeting Bromodomain-containing Protein 4.

In recent years, bromodomain-containing protein 4 (BRD4), a member of the bromodomain and extra terminal domain (BET) family, has been one of the most widely studied targets. BRD4 is a transcriptional regulation factor, which regulates cell transcription, marks mammalian biological mitosis, regulates cell cycle, and plays an important role in the biological process of cancer occurrence and development. It has been demonstrated that the imbalance or dysfunction of BRD4 expression leads to various types of cancers, including testicular gene nuclear protein melanoma, acute myeloid leukemia, colon cancer, breast cancer, liver cancer, and midline cancer. Therefore, inhibition of BRD4 has become a valuable approach in the treatment of these cancers. To date, there are numerous BRD4 inhibitors in preclinical development, some of which have entered human clinical trials. In this review, current progress in the development of privileged scaffolds designed as BRD4 inhibitors will be discussed by focusing on structure-activity relationship, selectivity, and mechanisms of action.

Design, synthesis and mechanism studies of novel dual PARP1/BRD4 inhibitors against pancreatic cancer.

Inducing the deficiency of homologous recombination (HR) repair is an effective strategy to broaden the indication of PARP inhibitors in pancreatic cancer treatment. Repression of BRD4 has been reported to significantly elevate HR deficiency and sensitize cancer cells to PARP1/2 inhibitors. Inspired by the concept of synthetic lethality, we designed, synthetized and optimized a dual PARP1/BRD4 inhibitor III-7, with a completely new structure and high selectivity against both targets. III-7 repressed the expression and activity of PARP1 and BRD4 to synergistically inhibit the malignant growth of pancreatic cancer cells in vitro and in vivo. Based on the results of bioinformatic analysis, we found that Olaparib induced the acceleration of mitosis and recovery of DNA repair to cause the generation of drug resistance. III-7 reversed Olaparib-induced adaptive resistance and induced cell cycle arrest and DNA damage by perturbing PARP1 and BRD4-involved signaling pathways. We believe that the PARP1/BRD4 dual inhibitors are novel and promising antitumor agents, which provide an efficient strategy for pancreatic cancer treatment.

FDI-6 and olaparib synergistically inhibit the growth of pancreatic cancer by repressing BUB1, BRCA1 and CDC25A signaling pathways.

Inducing homologous recombination (HR) deficiency is a promising strategy to broaden the indication of PARP1/2 inhibitors in pancreatic cancer treatment. In addition to inhibition kinases, repression of the transcriptional function of FOXM1 has been reported to inhibit HR-mediated DNA repair. We found that FOXM1 inhibitor FDI-6 and PARP1/2 inhibitor Olaparib synergistically inhibited the malignant growth of pancreatic cancer cells in vitro and in vivo. The results of bioinformatic analysis and mechanistic study showed that FOXM1 directly interacted with PARP1. Olaparib induced the feedback overexpression of PARP1/2, FOXM1, CDC25A, CCND1, CDK1, CCNA2, CCNB1, CDC25B, BRCA1/2 and Rad51 to promote the acceleration of cell mitosis and recovery of DNA repair, which caused the generation of adaptive resistance. FDI-6 reversed Olaparib-induced adaptive resistance and inhibited cell cycle progression and DNA damage repair by repressing the expression of FOXM1, PARP1/2, BUB1, CDC25A, BRCA1 and other genes-involved in cell cycle control and DNA damage repair. We believe that targeting FOXM1 and PARP1/2 is a promising combination therapy for pancreatic cancer without HR deficiency.

FDI-6 inhibits the expression and function of FOXM1 to sensitize BRCA-proficient triple-negative breast cancer cells to Olaparib by regulating cell cycle progression and DNA damage repair.

Inducing homologous-recombination (HR) deficiency is an effective strategy to broaden the indications of PARP inhibitors in the treatment of triple-negative breast cancer (TNBC). Herein, we find that repression of the oncogenic transcription factor FOXM1 using FOXM1 shRNA or FOXM1 inhibitor FDI-6 can sensitize BRCA-proficient TNBC to PARP inhibitor Olaparib in vitro and in vivo. Mechanistic studies show that Olaparib causes adaptive resistance by arresting the cell cycle at S and G2/M phases for HR repair, increasing the expression of CDK6, CCND1, CDK1, CCNA1, CCNB1, and CDC25B to promote cell cycle progression, and inducing the overexpression of FOXM1, PARP1/2, BRCA1/2, and Rad51 to activate precise repair of damaged DNA. FDI-6 inhibits the expression of FOXM1, PARP1/2, and genes involved in cell cycle control and DNA damage repair to sensitize TNBC cells to Olaparib by blocking cell cycle progression and DNA damage repair. Simultaneously targeting FOXM1 and PARP1/2 is an innovative therapy for more patients with TNBC.

Discovery of Potent and Novel Dual PARP/BRD4 Inhibitors for Efficient Treatment of Pancreatic Cancer.

Targeting poly(ADP-ribose) polymerase1/2 (PARP1/2) is a promising strategy for the treatment of pancreatic cancer with breast cancer susceptibility gene (BRCA) mutation. Inducing the deficiency of homologous recombination (HR) repair is an effective way to broaden the indication of PARP1/2 inhibitor for more patients with pancreatic cancer. Bromodomain-containing protein 4 (BRD4) repression has been reported to elevate HR deficiency. Therefore, we designed, synthetized, and optimized a dual PARP/BRD4 inhibitor III-16, with a completely new structure and high selectivity against PARP1/2 and BRD4. III-16 showed favorable synergistic antitumor efficacy in pancreatic cancer cells and xenografts by arresting cell cycle progression, inhibiting DNA damage repair, and promoting autophagy-associated cell death. Moreover, III-16 reversed Olaparib-induced acceleration of cell cycle progression and recovery of DNA repair. The advantages of III-16 over Olaparib suggest that dual PARP/BRD4 inhibitors are novel and promising agents for the treatment of advanced pancreatic cancer.

Discovery of novel VEGFR-2 inhibitors embedding 6,7-dimethoxyquinazoline and diarylamide fragments.

VEGF/VEGFR-2 signaling plays a critical part in tumor angiogenesis. Inhibition of this pathway has been considered as a promising approach for cancer treatment. In this work, a series of 6,7-dimethoxy-4-anilinoquinazoline derivatives bearing diarylamide moiety were designed, synthesized and evaluated as potent inhibitors of VEGFR-2 kinase. Their in vitro antiproliferation activities against two human cancer cell lines Hep-G2 and MCF-7 have also been determined. Among them, compound 14b exhibited the most potent inhibitory activity against VEGFR-2 with IC50 value of 0.016 ± 0.002 µM and it showed the most potent antiproliferative effect against Hep-G2 and MCF-7 with IC50 values at low-micromolar range. Molecular docking studies revealed that these compounds represented by the most potent compound 14b could bind well to the ATP-binding site of VEGFR-2, which suggested that compound 14b could be a potential anticancer agent targeting VEGFR-2.

Discovery of novel limonin derivatives as potent anti-inflammatory and analgesic agents.

Novel series of limonin derivatives (V-A-1-V-A-8, V-B-1-V-B-8) were synthesized by adding various tertiary amines onto the C (7)-position of limonin. The synthesized compounds possessed favorable physicochemical property, and the intrinsic solubility of the novel compounds were significantly improved, compared with limonin. Different pharmacological models were used to evaluate the analgesic and anti-inflammatory activities of the target compounds. Compound V-A-8 exhibited the strongest in vivo activity among the novel limonin analogs; its analgesic activity was more potent than aspirin and its anti-inflammatory activity was stronger than naproxen under our testing conditions.

Dual inhibition of HY023016 based on binding properties of platelet membrane receptor subunit glycoprotein Ibα and thrombin exosites.

Thrombin has long been suggested as a desirable antithrombotic target, but anti-thrombin therapy without anti-platelet thereby has never achieved the ideal effect. HY023016 is a novel compound, in our previous study, it exerted better anti-thrombotic than dabigatran etexilate. The present study aims to illustrate the excess anti-thrombotic molecular mechanisms of HY023016 through thrombin anion exosites and the platelet membrane receptor subunit glycoprotein Ibα (GPIbα). HY023016 strongly inhibited the conversion of fibrinogen to fibrous may via blocking thrombin exosite I. We also discovered that HY023016 remarkably inhibited exosite II by a loss of affinity for the γ'-peptide of fibrinogen and for heparin. Furthermore, a solid phase binding assay revealed that HY023016 inhibited ristocetin-induced washed platelets bind to von Willebrand factor (vWF). In GST pull-down assay, HY023016 decreased the binding of recombinant vWF-A1 to GPIbα N-terminal. Thus, HY023016 provides an innovative idea for designing multi-targeted anti-thrombotic drugs and laying a scientific foundation for reducing "total thrombosis risk" in a clinical drug treatment.

VEGFR-2 inhibitors and the therapeutic applications thereof: a patent review (2012-2016).

INTRODUCTION: Angiogenesis is an important component of certain normal physiological processes, but aberrant angiogenesis contributes to some pathological disorders and in particular to tumor growth. Activation of vascular endothelial growth factor receptor-2 (VEGFR-2) by vascular endothelial growth factor (VEGF) is a critical step in the signal transduction pathway that initiates tumor angiogenesis. Inhibition of angiogenesis via blocking VEGF/VEGFR-2 signaling pathway has emerged as a potential approach to anticancer therapy. Indeed, this approach has recently been clinically validated with the approvals of VEGFR-2 inhibitors. Areas covered: This review accounts for small-molecule inhibitors and antibodies of VEGFR-2 reported in the patent literature covering between January 2012 and June 2016, and their potential use as therapeutics for cancers, angiogenesis-related disorders and inflammatory diseases. Expert opinion: Despite the attractiveness of anti-angiogenic therapy by VEGF inhibition alone, several issues may limit this approach. VEGF expression levels can be elevated by numerous diverse stimuli such as the activation of other RTK signaling transduction pathway. Therefore, the development of multi-targeted tyrosine kinase inhibitors and the strategy of using these agents in conjunction with other anti-cancer agents are recent interesting therapeutic approaches that could give promising results.

Design and discovery of 4-anilinoquinazoline-urea derivatives as dual TK inhibitors of EGFR and VEGFR-2.

EGFR and VEGFR-2 are involved in pathological disorders and the progression of different kinds of tumors, the combined blockade of EGFR and VEGFR signaling pathways appears to be an attractive approach to cancer therapy. In this work, a series of 4-anilinoquinazoline derivatives containing substituted diaryl urea or glycine methyl ester moiety were designed and identified as EGFR and VEGFR-2 dual inhibitors. Compounds 19i, 19j and 19l exhibited the most potent inhibitory activities against EGFR (IC50 = 1 nM, 78 nM and 51 nM, respectively) and VEGFR-2 (IC50 = 79 nM, 14 nM and 14 nM, respectively), they showed good antiproliferative activities as well. Molecular docking established the interaction of 19i with the DFG-out conformation of VEGFR-2, suggesting that they might be type II kinase inhibitors.

Evaluating antithrombotic activity of HY023016 on rat hypercoagulable model.

The generation of thrombus is not considered as an isolated progression without other pathologic processes, which may also enhance procoagulant state. The purpose of this study was to assess whether HY023016, a novel dabigatran prodrug and an oral direct thrombin inhibitor, or dabigatran etexilate, another thrombin inhibitor can improve the state of whole blood hypercoagulability in vitro/vivo. By using whole blood flow cytometry we explored the effects of HY023016 and dabigatran etexilate on thrombin and ADP-induced human platelet-leukocyte aggregation generated in vitro. With the method of continuous infusion of thrombin intravenous, we successfully established a rat hypercoagulable model and evaluated the effect of HY023016 or dabigatran etexilate in vivo. HY023016 was able to inhibit thrombin- or ADP-induced platelet P-selectin or CD40L expression, leukocyte CD11b expression and formation of platelet-leukocyte aggregates in dose-dependent manner. Dabigatran etexilate was unable to affect ADP-induced platelet P-selectin or CD40L expression, leukocyte CD11b expression and formation of platelet-leukocyte aggregates. Based on rat hypercoagulable model, dabigatran etexilate could reverse thrombin-induced circulatory system hypercoagulable state in a concentration-dependent manner. Dabigatran etexilate also inhibited electrical stimulation induced formation of arterial thrombus in rat under hypercoagulable state, and extracorporal circulation-induced formation of thrombus in dose-dependent manner. Compared with dabigatran etexilate, HY023016 showed nearly equal or even better antithrombotic activity, regardless of reversing the cycle of rat hypercoagulable state or inhibiting platelet-leukocyte aggregation. In surrmary, HY023016 could effectively improve hypercoagulable state of circulatory system.

Design and discovery of 4-anilinoquinazoline-acylamino derivatives as EGFR and VEGFR-2 dual TK inhibitors.

Both EGFR and VEGFR-2 are important targets for cancer therapy, the combined inhibition of both EGFR and VEGFR-2 signaling pathway represents a promising approach to the treatment of cancers with a synergistic effect. In this study, a series of novel 4-anilinoquinazoline-acylamino derivatives designed as EGFR and VEGFR-2 dual inhibitors were synthesized and evaluated for biological activities. Most of them exhibited interesting inhibitory potencies against EGFR and VEGFR-2 as well as good antiproliferative activities. Compounds 15a, 15b and 15e exhibited the most potent inhibitory activity against EGFR (IC50 = 0.13 µM, 0.15 µM and 0.69 µM, respectively) and VEGFR-2 (IC50 = 0.56 µM, 1.81 µM and 0.87 µM, respectively), among them, compound 15b showed the highest antiproliferative activities against three cancer cell lines (HT-29, MCF-7 and H460) with IC50 of 5.27 µM, 4.41 µM and 11.95 µM, respectively. Molecular docking established the interaction of 15a with the DFG-out conformation of VEGFR-2, suggesting that they might be type II kinase inhibitors.

Design, synthesis and biological evaluation of N-phenylquinazolin-4-amine hybrids as dual inhibitors of VEGFR-2 and HDAC.

A single agent that simultaneously inhibits multiple targets may offer greater therapeutic benefits in cancer than single-acting agents through interference with multiple pathways and potential synergistic action. In this work, a series of hybrids bearing N-phenylquinazolin-4-amine and hydroxamic acid moieties were designed and identified as dual VEGFR-2/HDAC inhibitors. Compound 6fd exhibited the most potent inhibitory activity against HDAC with IC50 of 2.2 nM and strong inhibitory effect against VEGFR-2 with IC50 of 74 nM. It also showed the most potent inhibitory activity against a human breast cancer cell line MCF-7 with IC50 of 0.85 µM. Docking simulation supported the initial pharmacophoric hypothesis and suggested a common mode of interaction at the active binding sites of VEGFR-2 and HDLP ((Histone Deacetylase-Like Protein), which demonstrates that compound 6fd is a potential agent for cancer therapy deserving further researching.

Discovery, stereospecific characterization and peripheral modification of 1-(pyrrolidin-1-ylmethyl)-2-[(6-chloro-3-oxo-indan)-formyl]-1,2,3,4-tetrahydroisoquinolines as novel selective κ opioid receptor agonists.

A novel series of 1-(pyrrolidin-1-ylmethyl)-2-[(3-oxo-indan)-formyl]-1,2,3,4-tetrahydroisoquinoline derivatives maj-3a-maj-3u were synthesized and evaluated in vitro for their binding affinity at κ-opioid receptors. Maj-3c displayed the highest affinity for κ-opioid receptors (Ki = 0.033 nM) among all the compounds evaluated. Furthermore, all four stereoisomers of compound 3c were prepared, and (1S,18S)-3c was identified as the most potent (Ki = 0.0059 nM) κ-opioid receptor agonist among the four stereoisomers. Maj-3c produced significant antinociception (ED50 = 0.000406 mg kg(-1)) compared to U-50,488H and original BRL 52580 in the acetic acid writhing assay, but its strong sedative effect (ED50 = 0.000568 mg kg(-1)) observed in the mouse rotation test reduced its druggability. To minimize the central nervous system side effects, a series of hydroxyl-containing analogs of maj-3c were synthesized, and maj-11a was found to be a potent κ-opioid receptor agonist (Ki = 35.13 nM). More importantly, the dose for the sedative effect (ED50 = 9.29 mg kg(-1)) of maj-11a was significantly higher than its analgesic dose (ED50 = 0.392 mg kg(-1)), which made it a promising peripheral analgesic candidate compound with weak sedative side effects.

Novel κ-opioid receptor agonist MB-1C-OH produces potent analgesia with less depression and sedation.

AIM: To characterize the pharmacological profiles of a novel κ-opioid receptor agonist MB-1C-OH. METHODS: [(3)H]diprenorphine binding and [(35)S]GTPγS binding assays were performed to determine the agonistic properties of MB-1C-OH. Hot plate, tail flick, acetic acid-induced writhing, and formalin tests were conducted in mice to evaluate the antinociceptive actions. Forced swimming and rotarod tests of mice were used to assess the sedation and depression actions. RESULTS: In [(3)H]diprenorphine binding assay, MB-1C-OH did not bind to µ- and δ-opioid receptors at the concentration of 100 µmol/L, but showed a high affinity for κ-opioid receptor (Ki=35 nmol/L). In [(35)S]GTPγS binding assay, the compound had an Emax of 98% and an EC50 of 16.7 nmol/L for κ-opioid receptor. Subcutaneous injection of MB-1C-OH had no effects in both hot plate and tail flick tests, but produced potent antinociception in the acetic acid-induced writhing test (ED50=0.39 mg/kg), which was antagonized by pretreatment with a selective κ-opioid receptor antagonist Nor-BNI. In the formalin test, subcutaneous injection of MB-1C-OH did not affect the flinching behavior in the first phase, but significantly inhibited that in the second phase (ED50=0.87 mg/kg). In addition, the sedation or depression actions of MB-1C-OH were about 3-fold weaker than those of the classical κ agonist (-)U50,488H. CONCLUSION: MB-1C-OH is a novel κ-opioid receptor agonist that produces potent antinociception causing less sedation and depression.

Design, synthesis, and evaluation of non-ATP-competitive small-molecule Polo-like kinase 1 (Plk1) inhibitors.

A series of small-molecule Plk1 inhibitors targeting the substrate-binding pocket were designed through rational drug design for the first time. The designed compounds were synthesized and their activities were evaluated in vitro. Some of the targeted compounds showed potent Plk1 inhibitory activities and anti-proliferative characters. Particularly, 5i showed Plk1 inhibitory activity with an IC50 value of 0.68 µM. Compound 5i also showed cell growth inhibitory activity on HeLa cells with an IC50 value of 0.51 µM, which is about four times more potent compared to thymoquinone. The mechanism of action suggested that 5i was an ATP-independent and substrate-dependent Plk1 inhibitor. Compound 5i demonstrated excellent Plk1 inhibitory selectivity against Plk2, Plk3, and five serine/threonine and tyrosine kinases. Our discovery and structure-activity relationship study may provide useful lead compounds for further optimization of non-ATP-competitive Plk1 inhibitors.

Discovery of quinazolin-4-amines bearing benzimidazole fragments as dual inhibitors of c-Met and VEGFR-2.

Both c-Met and VEGFR-2 are important targets for the treatment of cancers. In this study, a series of N-(2-phenyl-1H-benzo[d]imidazol-5-yl)quinazolin-4-amine derivatives were designed and identified as dual c-Met and VEGFR-2 inhibitors. Among these compounds bearing quinazoline and benzimidazole fragments, compound 7j exhibited the most potent inhibitory activity against c-Met and VEGFR-2 with IC50 of 0.05µM and 0.02µM, respectively. It also showed the highest anticancer activity against the tested cancer cell lines with IC50 of 1.5µM against MCF-7 and 8.7µM against Hep-G2. Docking simulation supported the initial pharmacophoric hypothesis and suggested a common mode of interaction at the ATP-binding site of c-Met and VEGFR-2, which demonstrates that compound 7j is a potential agent for cancer therapy deserving further researching.

Discovery of N-(2-phenyl-1H-benzo[d]imidazol-5-yl)quinolin-4-amine derivatives as novel VEGFR-2 kinase inhibitors.

Inhibition of the VEGF signaling pathway has become a valuable approach in the treatment of cancers. In this work, a series of N-(2-phenyl-1H-benzo[d]imidazol-5-yl)quinolin-4-amine derivatives were designed and identified as potent inhibitors of VEGFR-2 (KDR) kinase. These compounds with quinoline scaffold and benzimidazole moiety were synthesized and their biological activities against VEGFR-2 and two human cancer cell lines were evaluated. Among them, compound 7s exhibited the most potent inhibitory activity against VEGFR-2 with IC50 of 0.03 µM and it also showed the highest anticancer activity against the tested cancer cell lines with IC50 of 1.2 µM against MCF-7 and 13.3 µM against Hep-G2. Docking simulation supported the initial pharmacophoric hypothesis and suggested a common mode of interaction at the ATP-binding site of VEGFR-2, which demonstrates that compound 7s is a potential agent for cancer therapy deserving further researching.

Design, synthesis and antithrombotic evaluation of novel dabigatran prodrugs containing methyl ferulate.

A novel series of prodrugs containing dabigatran and methyl (E)-3-(4-hydroxy-2-methoxyphenyl)propenoate (methyl ferulate) were synthesized. All of them reveal the effect of thrombin-induced anti-platelet aggregation in vitro. In addition, in vivo experiment shows that one of the target compounds, X-2 (ED50=3.7 ± 1.0 µmol/kg) possesses a more potent activity for inhibiting venous thrombosis than that of dabigatran etexilate (ED50=7.8 ± 1.5 µmol/kg).