Structure design and development of double inhibitors of bromine domain protein 4 / Paolo like protein kinase 1

Bromine domain and super terminal structure (BET) protein family are very important for the recognition of acetyl lysine (KAC) on chromatin, and have broad application prospects as potential targets for the treatment of cancer, inflammation and viral infectious diseases At present, more than 12 bet inhibitors have been used in clinical trials for the treatment of hematological malignancies, solid tumors and cardiovascular diseases The latest research shows that the inhibition of Plk1, a key cell cycle regulator, has a synergistic effect with the inhibition of bet in prostate cancer and acute myeloid leukemia (AML) Plk1, bi-2536 and JAK2 inhibitors tg101209 (Fig 1) have moderate to excellent inhibitory activities on bet protein family, which provides a theoretical basis for the development of multi pharmacological compounds targeted at kinase and bet protein Recently, Zhang Wei group of UMass Boston and Jun Qi and James E Bradner group of Dana Farber Cancer Research Institute jointly modified the structure of small molecular compound bi-2536 (Figure 1), and obtained an effective Brd4 / Plk1 double inhibitor 23 and Plk1 selective inhibitor 6, and carried out structure-activity relationship (SAR) of similar compounds ）To understand the inhibitory mechanism of single drug on Brd4 and Plk1 (both bet family and Plk1 are targets of tumor therapy) The results were published in J Med Chem (DOI: 10.1021 / ACS Jmedchem 8b00765) (source: J Med Chem.) first, scientists investigated the combination of bi-2536 with brd4-bd1 and Plk1 by means of eutectic Research (Figure 2) In the complex of bi-2536 and brd4-bd1, formamido is used as acetyl lysine analogue, and the carbonyl oxygen and acetyl lysine of dihydropteridone form a water-mediated hydrogen bond in the pocket of asparagine (N140) Methyl extends into hydrophobic pockets formed by f83, i146, and C136 In addition, the imino and pyrimidine nitrogen atoms on aniline interact with the amide skeleton of q85 through water molecules The ethyl of dihydropteridone was located in hydrophobic pockets formed by v87, l92, L94 and y97, while cyclopentyl moiety and N-methylpiperidine were both exposed to solvents (source: J Med Chem.) in order to improve the binding affinity of the compound with brd4-bd1 and achieve the dual inhibition effect of Plk1 / brd4-bd1, based on the structure information of bi-2535, brd4-bd1 and Plk1 (Figure 2), the researchers designed several schemes to modify the structure of bi-2536 (Figure 3 ）。 (source: J Med Chem.) researchers prepared a series of bi-2536 analogues using the synthesis route shown in scheme 1 First, amino acids with different alkyl side chains (different R1 groups) are esterified with thionyl dichloride in methanol, then aminated with ketone to alkylate, and the secondary amine derivative E1, E1 reacts with 2,6-dichloro-5-nitropyrimidine to form tertiary aniline Next, the researchers reduced the nitro group on t-aniline with zinc powder in hot acetic acid to produce dihydropteridone ring system E2, which was alkylated with amide to produce E3 E3 reacted with aminobenzoic acid derivatives to form intermediate E4 E4 coupled with amine to form bi-2536 analog (source: J Med Chem.) further, the selectivity of bet subfamily and PLK kinase (plk1-3) as well as the selectivity of 32 BRD (bromoscan ®) and 468 kinase (kinomescan ®) were evaluated through the discoverx analysis platform The results showed that compound 5 had a good inhibitory effect on Brd4 (IC50 = 84 nm) and Plk1 (IC50 = 11 nm), and compound 6 had a good inhibitory activity on Brd4, but a high selectivity on Plk1 In order to improve the Brd4 selectivity of bi-2536 analogues, SAR studies were carried out on the methoxy groups around the terminal amine (site 5) and site 2 of compound 5 to investigate their effects on the activity and selectivity (see scheme 2 for the synthesis route) The results showed that compared with the positive control (+ - jq1) of bet inhibitor, the inhibitory activity of compound 23 on Brd4 was increased, but compared with bi-2536, the inhibitory activity of compound 23 on Plk1 was decreased Therefore, 23 is an inhibitor with good Brd4 inhibitory activity and high Plk1 selectivity (source: J Med Chem.) in order to better understand the efficacy of bi-2536 analogues and predict their binding patterns, the researchers used Plk1 and brd4-bd1 to conduct molecular simulation with the compounds (Table 3) The simulation results are in good agreement with the previous conclusions: Compound 23 shows good activity for Brd4 and Plk1, while compound 6 has the highest selective inhibition activity for Plk1 in this series (source: J Med Chem.) in conclusion, through SAR analysis of kinase inhibitor bi-2536, this study found an effective Brd4 / Plk1 double inhibitor (compound 23) and a highly selective Plk1 inhibitor (compound 6), and identified the binding site of Plk1 and bet protein.