gsk525762a and Leukemia

Bromodomain-containing protein 4 (BRD4), an epigenetic reader of acetyl lysine, has emerged as a promising therapeutic target for many diseases including cancer, inflammation and heart failure. Our previous study reported that nitroxoline, an FDA approved antibiotic, showed potential BRD4 inhibitory activity and antiproliferation activity against leukemia cell lines. In this study, we further explored the structure-activity relationship (SAR) around nitroxoline and employed our previously developed machine learning based activity scoring function BRD4LGR for further analysis. To improve the cellular level activity, physico-chemical properties were optimized using computational approaches. Then the candidates were tested for their ADME/T profiles. Finally, based on this rational hit-to-lead optimization strategy, 3 drug-like BRD4 inhibitors were obtained, with different profiles on cell line selectivity for multiple myeloma, leukemia and triple negative breast cancer. Further mechanism study showed these compounds could down-regulate c-Myc to inhibit cancer cell growth. This work illustrates the application of multiple computer-aided drug design techniques in a hit-to-lead optimization scenario, and provides novel potent BRD4 inhibitors with different phenotype propensities for future cancer treatment.

Topics: Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Computer-Aided Design; Drug Design; Humans; Imidazoles; Leukemia; Multiple Myeloma; Nitroquinolines; Nuclear Proteins; Proto-Oncogene Proteins c-myc; Quinolines; Structure-Activity Relationship; Transcription Factors; Triple Negative Breast Neoplasms

The discovery of inhibitors of bromodomain and extra terminal domain (BET) has achieved great progress, and at least seven inhibitors have progressed into clinical trials for the treatment of cancer or inflammatory diseases. Here, we describe the identification, optimization, and evaluation of benzo[cd]indol-2(1H)-one containing compounds as a new class of BET bromodomain inhibitors, starting from structure-based virtual screening (SBVS). Through structure-based optimization, potent compounds were obtained with significantly improved activity. The two most potent compounds bind to the BRD4 bromodomain, with Kd values of 124 and 137 nM. Selected compounds exhibited high selectivity over other non-BET subfamily members. Notably, compound 85 demonstrated a reasonable antiproliferation effect on MV4;11 leukemia cells and exhibited a good pharmacokinetic profile with high oral bioavailability (75.8%) and moderate half-life (T1/2 = 3.95 h). The resulting lead molecule 85 represents a new, potent, and selective class of BET bromodomain inhibitors for the development of therapeutics to treat cancer and inflammatory diseases.

Topics: Animals; Antineoplastic Agents; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Crystallography, X-Ray; Drug Discovery; Humans; Indoles; Leukemia; Molecular Docking Simulation; Nuclear Proteins; Rats; Structure-Activity Relationship; Transcription Factors

Small-molecule inhibitors of bromodomain and extra terminal proteins (BET), including BRD2, BRD3, and BRD4 proteins have therapeutic potential for the treatment of human cancers and other diseases and conditions. In this paper, we report the design, synthesis, and evaluation of γ-carboline-containing compounds as a new class of small-molecule BET inhibitors. The most potent inhibitor (compound 18, RX-37) obtained from this study binds to BET bromodomain proteins (BRD2, BRD3, and BRD4) with Ki values of 3.2-24.7 nM and demonstrates high selectivity over other non-BET bromodomain-containing proteins. Compound 18 potently and selectively inhibits cell growth in human acute leukemia cell lines harboring the rearranged mixed lineage leukemia 1 gene. We have determined a cocrystal structure of 18 in complex with BRD4 BD2 at 1.4 Å resolution, which provides a solid structural basis for the compound's high binding affinity and for its further structure-based optimization. Compound 18 represents a promising lead compound for the development of a new class of therapeutics for the treatment of human cancer and other conditions.

Topics: Antineoplastic Agents; Carbolines; Cell Cycle Proteins; Cell Line, Tumor; Crystallography, X-Ray; Humans; Leukemia; Molecular Docking Simulation; Nuclear Proteins; Protein Serine-Threonine Kinases; RNA-Binding Proteins; Transcription Factors

The transcription factor signal STAT5 is constitutively activated in a wide range of leukemias and lymphomas, and drives the expression of genes necessary for proliferation, survival, and self-renewal. Thus, targeting STAT5 is an appealing therapeutic strategy for hematologic malignancies. Given the importance of bromodomain-containing proteins in transcriptional regulation, we considered the hypothesis that a pharmacologic bromodomain inhibitor could inhibit STAT5-dependent gene expression. We found that the small-molecule bromodomain and extra-terminal (BET) bromodomain inhibitor JQ1 decreases STAT5-dependent (but not STAT3-dependent) transcription of both heterologous reporter genes and endogenous STAT5 target genes. JQ1 reduces STAT5 function in leukemia and lymphoma cells with constitutive STAT5 activation, or inducibly activated by cytokine stimulation. Among the BET bromodomain subfamily of proteins, it seems that BRD2 is the critical mediator for STAT5 activity. In experimental models of acute T-cell lymphoblastic leukemias, where activated STAT5 contributes to leukemia cell survival, Brd2 knockdown or JQ1 treatment shows strong synergy with tyrosine kinase inhibitors (TKI) in inducing apoptosis in leukemia cells. In contrast, mononuclear cells isolated form umbilical cord blood, which is enriched in normal hematopoietic precursor cells, were unaffected by these combinations. These findings indicate a unique functional association between BRD2 and STAT5, and suggest that combinations of JQ1 and TKIs may be an important rational strategy for treating leukemias and lymphomas driven by constitutive STAT5 activation.

Topics: Azepines; Benzodiazepines; Cell Line, Tumor; Cell Survival; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Hematologic Neoplasms; Humans; Leukemia; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; RNA, Small Interfering; STAT5 Transcription Factor; Transcription Factors; Triazoles

Topics: Anti-Inflammatory Agents, Non-Steroidal; Antineoplastic Agents; Azepines; Benzodiazepines; Cell Cycle Proteins; Cell Proliferation; Gene Expression; Humans; Leukemia; Nuclear Proteins; Protein Serine-Threonine Kinases; Quinazolines; Quinazolinones; RNA-Binding Proteins; Transcription Factors; Triazoles

Topics: Adult; Animals; Azepines; Benzodiazepines; Cell Cycle Proteins; Child; Epigenesis, Genetic; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Leukemia; Male; Mice; Mutation; Neoplasm Proteins; Neoplasms; Nuclear Proteins; Oncogene Proteins; Oncogene Proteins, Fusion; Proto-Oncogene Proteins c-myc; Transcription Factors; Triazoles; Vorinostat; Young Adult