Discovery of 1-(5-(1H-benzo[d]imidazole-2-yl)-2,4-dimethyl-1H-pyrrol-3-yl)ethan-1-one derivatives as novel and potent bromodomain and extra-terminal (BET) inhibitors with anticancer efficacy

Structure-Guided Design and Synthesis of Pyridinone-Based Selective Bromodomain and Extra-Terminal Domain (BET)-First Bromodomain (BD1) Inhibitors

The bromodomain and extra-terminal domain (BET) proteins are epigenetic readers, regulating transcription via two highly homologous tandem bromodomains, BD1 and BD2. Clinical development of nonselective pan-BD BET inhibitors has been challenging, partly due to dose-limiting side effects such as thrombocytopenia. This has prompted the push for domain-selective BET inhibitors to achieve a more favorable therapeutic window. We report a structure-guided drug design campaign that led to the development of a potent BD1-selective BET inhibitor, 33 (XL-126), with a Kd of 8.9 nM and 185-fold BD1/BD2 selectivity. The high selectivity was first assayed by SPR, validated by a secondary time-resolved fluorescence energy transfer assay, and further corroborated by BROMOscan (∼57-373 fold selectivity). The cocrystal of 33 with BRD4 BD1 and BD2 demonstrates the source of selectivity: repulsion with His437 and lost binding with the leucine clamp. Notably, the BD1 selectivity of BET inhibitor 33 leads to both the preservation of platelets and potent anti-inflammatory efficacy.

Discovery of (R)-4-(8-methoxy-2-methyl-1-(1-phenylethy)-1H-imidazo[4,5-c]quinnolin-7-yl)-3,5-dimethylisoxazole as a potent and selective BET inhibitor for treatment of acute myeloid leukemia (AML) guided by FEP calculation

The functions of the bromodomain and extra terminal (BET) family of proteins have been proved to be involved in various diseases, particularly the acute myeloid leukemia (AML). In this work, guided by free energy perturbation (FEP) calculation, a methyl group was selected to be attached to the 1H-imidazo[4,5-c]quinoline skeleton, and a series of congeneric compounds were synthesized. Among them, compound 10 demonstrated outstanding activity against BRD4 BD1 with an IC50 value of 1.9 nM and exhibited remarkable antiproliferative effects against MV4-11 cells. The X-ray cocrystal structure proved that 10 occupied the acetylated lysine (KAc) binding cavity and the WPF shelf of BRD4 BD1. Additionally, 10 displayed high selectivity towards BET family members, effectively inhibiting the growth of AML cells, promoting apoptosis, and arresting the cell cycle at the G0/G1 phase. Further mechanistic studies demonstrated that compound 10 could suppress the expression of c-Myc and CDK6 while enhancing the expression of P21, PARP, and cleaved PARP. Moreover, 10 exhibited remarkable pharmacokinetic properties and significant antitumor efficacy in vivo. Therefore, compound 10 may represent a new, potent and selective BET bromodomain inhibitor for the development of therapeutics to treat AML.

Selectivity Mechanism of Pyrrolopyridone Analogues Targeting Bromodomain 2 of Bromodomain-Containing Protein 4 from Molecular Dynamics Simulations

Bromodomain and extra-terminal domain (BET) proteins play an important role in epigenetic regulation and are linked to several diseases; therefore, they are interesting targets. BET has two bromodomains: bromodomain 1 (BD1) and BD2. Selective targeting of BD1 or BD2 may produce different activities and greater effects than pan-BD inhibitors. However, the selective mechanism of the specific core must be studied at the atomic level. This study determined the effectiveness of pyrrolopyridone analogues to selectively inhibit BD2 using a pan-BD inhibitor (ABBV-075) and a selective-BD2 inhibitor (ABBV-744). Molecular dynamics simulations and calculations of binding free energies were used to systematically study the selectivity of BD2 inhibition by the pyrrolopyridone analogues. Overall, the pyrrolopyridone analogue inhibitors targeting BD2 interacted mainly with the following amino acid pairs between bromodomain-containing protein 4 (BRD4)-BD1 and BRD4-BD2 complexes: I146/V439, N140/N433, D144/H437, P82/P375, V87/V380, D88/D381, and Y139/Y432. The pyrrolopyridone analogues targeting BRD4-BD2 were divided into five regions based on selectivity mechanism. These results suggest that the R3 and R5 regions of pyrrolopyridone analogues can be modified to improve the selectivity between BRD4-BD1 and BRD4-BD2. The selectivity of BD2 inhibition by pyrrolopyridone analogues can be used to design novel BD2 inhibitors based on a pyrrolopyridone core.

Novel Aminopyrimidine-2,4-diones, 2-Thiopyrimidine-4-ones, and 6-Arylpteridines as Dual-Target Inhibitors of BRD4/PLK1: Design, Synthesis, Cytotoxicity, and Computational Studies

Structural-based drug design and solvent-free synthesis were combined to obtain three novel series of 5-arylethylidene-aminopyrimidine-2,4-diones (4, 5a-c, 6a,b), 5-arylethylidene-amino-2-thiopyrimidine-4-ones (7,8), and 6-arylpteridines (9,10) as dual BRD4 and PLK1 inhibitors. MTT assays of synthesized compounds against breast (MDA-MB-231), colorectal (HT-29), and renal (U-937) cancer cells showed excellent-to-good cytotoxic activity, compared to Methotrexate; MDA-MB-231 were the most sensitive cancer cells. The most active compounds were tested against normal Vero cells. Compounds 4 and 7 significantly inhibited BRD4 and PLK1, with IC50 values of 0.029, 0.042 µM, and 0.094, 0.02 µM, respectively, which are nearly comparable to volasertib (IC50 = 0.017 and 0.025 µM). Compound 7 triggered apoptosis and halted cell growth at the G2/M phase, similarly to volasertib. It also upregulated the BAX and caspase-3 markers while downregulating the Bcl-2 gene. Finally, active compounds fitted the volasertib binding site at BRD4 and PLK1 and showed ideal drug-like properties and pharmacokinetics, making them promising anticancer candidates.

Bromodomain inhibitors and therapeutic applications

The bromodomain acts to recognize acetylated lysine in histones and transcription proteins and plays a fundamental role in chromatin-based cellular processes including gene transcription and chromatin remodeling. Many bromodomain proteins, particularly the bromodomain and extra terminal domain (BET) protein BRD4 have been implicated in cancers and inflammatory disorders and recognized as attractive drug targets. Although clinical studies of many BET bromodomain inhibitors have made substantial progress toward harnessing the therapeutic potential of targeting the bromodomain proteins, the development of this new class of epigenetic drugs is met with challenges, especially on-target dose-limiting toxicity. In this review, we highlight the current development of new-generation small molecule inhibitors for the BET and non-BET bromodomain proteins and discuss the research strategies used to target different bromodomain proteins for a wide array of human diseases including cancers and inflammatory disorders.

Current development of pyrazole-azole hybrids with anticancer potential

Chemotherapy is a critical treatment modality for cancer patients, but multidrug resistance remains one of the major challenges in cancer therapy, creating an urgent need for the development of novel potent chemical entities. Azoles, particularly pyrazole, could interact with different biological targets and exhibit diverse biological properties including anticancer activity. Many clinically used anticancer agents own an azole moiety, demonstrating that azoles are privileged and pivotal templates in the discovery of novel anticancer chemotherapeutics. The present article is an attempt to highlight the recent advances in pyrazole-azole hybrids with anticancer potential and discuss the structure-activity relationships, covering articles published from 2018 to present, to facilitate the rational design of more effective anticancer candidates.

Discovery of Benzo[d]imidazole-6-sulfonamides as Bromodomain and Extra-Terminal Domain (BET) Inhibitors with Selectivity for the First Bromodomain

The bromodomain and extra-terminal (BET) family of proteins includes BRD2, BRD3, BRD4, and the testis-specific protein, BRDT, each containing two N-terminal tandem bromodomain (BRD) modules. Potent and selective inhibitors targeting the two bromodomains are required to elucidate their biological role(s), with potential clinical applications. In this study, we designed and synthesized a series of benzimidazole-6-sulfonamides starting from the azobenzene compounds MS436 (7 a) and MS611 (7 b) that exhibited preference for the first (BD1) over the second (BD2) BRD of BET family members. The most-promising compound (9 a) showed good binding potency and improved metabolic stability and selectivity towards BD1 with respect to the parent compounds.

Intravenous Immunoglobulin Inhibits Liver Cancer Progression by Promoting p38MAPK-Associated Apoptosis

OBJECTIVE

The aim of this study is to explore the effect of intravenous immunoglobulin (IVIG) on the development of rat hepatocellular carcinoma and its possible molecular mechanism.

METHODS

Sixty adult male Sprague-Dawley (SD) rats were randomly divided into three groups: control, diethylnitrosamine(DEN) + normal saline(NS), and DEN + IVIG groups, with 20 rats in each group. The  rats in the DEN + NS group and DEN + IVIG group were given DEN 0.2 g/kg intraperitoneal injection once on day 1 and then 0.05% DEN aqueous solution in drinking water to establish a rat liver cancer model. Immunoglobulin (IgG) was injected intraperitoneally into the DEN + IVIG group twice a week at the dose of 100 mg/kg, and saline was administered intraperitoneally into the control group at a 50 mg/kg dosage. The body weight of each group of rats was recorded twice a week. All treatments were maintained continuously for 12 weeks. After the intervention, the liver function indexes of rats were measured by a fully automated biochemical analysis instrument. The liver histopathology was observed by hematoxylin-eosin(HE) staining. Immunohistochemistry was used to detect c-myc protein expression, and Western blotting was used to determine p38MAPK and p-p38MAPK protein expressions, as well as apoptosis-related proteins such as Bcl-2, Bax, and cleaved caspase-3.

RESULTS

Compared with the rats in the DEN + NS group, rats in the DEN + IVIG group showed substantially higher body mass (P < 0.05), higher survival rate (P < 0.05), and lower liver function indexes (P < 0.05). Few focal necrosis of cancer cells and few nuclear division were observed in the rats in the DEN + IVIG group. The rats in the DEN + NS group showed lamellar necrosis of cancer foci, destruction of normal liver lobular structure, and hepatocellular carcinoma cells. Immunohistochemical analysis results revealed that the expression of c-myc was reduced in the DEN + IVIG group (P < 0.05), and Western blotting confirmed that the Bcl-2 expression was decreased (P < 0.05), while Bax, p38 MAPK, p-p38 MAPK, and cleaved caspase-3 protein expressions were increased (P < 0.05).

CONCLUSION

IVIG prophylactic injection can delay tumor development and induce apoptosis in primary hepatocellular carcinoma in rats. The mechanism is connected to the activation of the p38MAPK signaling pathway by upregulating the level of cleaved caspase-3 and Bax proteins while downregulating the level of Bcl-2 and c-myc proteins.

New Potential Agents for Malignant Melanoma Treatment-Most Recent Studies 2020-2022

Malignant melanoma (MM) is the most lethal skin cancer. Despite a 4% reduction in mortality over the past few years, an increasing number of new diagnosed cases appear each year. Long-term therapy and the development of resistance to the drugs used drive the search for more and more new agents with anti-melanoma activity. This review focuses on the most recent synthesized anti-melanoma agents from 2020-2022. For selected agents, apart from the analysis of biological activity, the structure-activity relationship (SAR) is also discussed. To the best of our knowledge, the following literature review delivers the latest achievements in the field of new anti-melanoma agents.

Bromodomain and Extra-Terminal Inhibitor BMS-986158 Reverses Latent HIV-1 Infection In Vitro and Ex Vivo by Increasing CDK9 Phosphorylation and Recruitment

Latent reservoir persistence remains a major obstacle for curing human immunodeficiency virus type 1 (HIV-1) infection. Thus, strategies for the elimination of latent HIV-1 are urgently needed. As a bromodomain and extra-terminal (BET) inhibitor, BMS-986158 has been used in clinical trials for advanced solid tumors and hematological malignancies. Here, we found that BMS-986158 reactivated latent HIV-1 in three types of HIV-1 latency cells in vitro, and in combination antiretroviral therapy (cART)-treated patient-derived peripheral blood mononuclear cells ex vivo, without influencing global immune cell activation. BMS-986158 reactivated latent HIV-1 by increasing phosphorylation of CDK9 at Thr186 and promoting recruitment of CDK9 and RNA polymerase II to the HIV-1 long terminal repeat in J-Lat cells. Furthermore, BMS-986158 exerted strong synergism in reactivating latent HIV-1 when combined with prostratin and vorinostat and enhanced the antiviral activity of anti-HIV-1 drugs. Finally, BMS-986158 showed antiviral activity in an HIV-1 acute infection model, possibly by arresting the cell cycle in infected cells. Thus, these results suggest that BMS-986158 is a potential candidate for AIDS/HIV-1 therapy.