7-bromoindirubin-3--oxime and indirubin

Indirubin is the crucial ingredient of Danggui Longhui Wan and Qing-Dai, traditional Chinese medicine herbal formulas used for the therapy of chronic myelocytic leukemia in China for hundreds of years. Although the monomeric indirubin has been used in China for the treatment human chronic myelocytic leukemia. However, due to low water solubility, poor pharmacokinetic properties and low therapeutic effects are the major obstacle, and had significantly limited its clinical application. Consequently, the attractive anticancer profile of indirubin has enthused numerous researchers to discover novel indirubin derivatives with improved pharmacodynamic activity as well as good pharmacokinetic property. In this paper, we comprehensively review the recent progress of anticancer potential of indirubins, structural modification and structure-activity relationship, which may provide useful direction for the further development of novel indirubins with improved pharmacological profiles for the treatment of various types of cancer.

Topics: Antineoplastic Agents; Cell Survival; Chemistry, Pharmaceutical; Drugs, Chinese Herbal; Humans; Indoles; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Oximes; Structure-Activity Relationship

Drug resistance in chronic myelogenous leukemia (CML) requires the development of new CML chemotherapeutic drugs. Indirubin, a well-known mutikinase inhibitor, is the major active component of "Danggui Longhui Wan", a Chinese traditional medicine used for the treatment of CML symptoms. An in-house collection of indirubin derivatives was screened at 1 μM on wild-type and imatinib-resistant T315I mutant CML cells. Herein are reported that only 15 analogues of the natural 6-bromoindirubin displayed potent cytotoxicity in the submicromolar range. Kinase assays in vitro show that eight out of the 15 active molecules strongly inhibited both c-Src and Abl oncogenic kinases in the nanomolar range. Most importantly, these eight molecules blocked the activity of T315I mutant Abl kinase at the submicromolar level and with analogue 22 exhibiting inhibitory activity at the low nanomolar range. Docking calculations suggested that active indirubins might inhibit T315I Abl kinase through an unprecedented binding to both active and Src-like inactive conformations. Analogue 22 is the first derivative of a natural product identified as an inhibitor of wild-type and imatinib-resistant T315I mutant Abl kinases.

Topics: Apoptosis; Benzamides; Cell Line, Tumor; Cell Survival; Crystallography, X-Ray; CSK Tyrosine-Protein Kinase; Drug Resistance, Neoplasm; Humans; Imatinib Mesylate; Indoles; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Molecular Structure; Piperazines; Protein Kinase Inhibitors; Pyrimidines; src-Family Kinases

Phosphorylase kinase (PhK) has been linked with a number of conditions such as glycogen storage diseases, psoriasis, type 2 diabetes and more recently, cancer (Camus et al., 2012 [6]). However, with few reported structural studies on PhK inhibitors, this hinders a structure based drug design approach. In this study, the inhibitory potential of 38 indirubin analogues have been investigated. 11 of these ligands had IC50 values in the range 0.170-0.360μM, with indirubin-3'-acetoxime (1c) the most potent. 7-Bromoindirubin-3'-oxime (13b), an antitumor compound which induces caspase-independent cell-death (Ribas et al., 2006 [20]) is revealed as a specific inhibitor of PhK (IC50=1.8μM). Binding assay experiments performed using both PhK-holo and PhK-γtrnc confirmed the inhibitory effects to arise from binding at the kinase domain (γ subunit). High level computations using QM/MM-PBSA binding free energy calculations were in good agreement with experimental binding data, as determined using statistical analysis, and support binding at the ATP-binding site. The value of a QM description for the binding of halogenated ligands exhibiting σ-hole effects is highlighted. A new statistical metric, the 'sum of the modified logarithm of ranks' (SMLR), has been defined which measures performance of a model for both the "early recognition" (ranking earlier/higher) of active compounds and their relative ordering by potency. Through a detailed structure activity relationship analysis considering other kinases (CDK2, CDK5 and GSK-3α/β), 6'(Z) and 7(L) indirubin substitutions have been identified to achieve selective PhK inhibition. The key PhK binding site residues involved can also be targeted using other ligand scaffolds in future work.

Topics: Amino Acid Motifs; Binding Sites; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 5; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; High-Throughput Screening Assays; Humans; Hypoglycemic Agents; Indoles; Ligands; Molecular Docking Simulation; Molecular Sequence Data; Oximes; Phosphorylase Kinase; Protein Binding; Protein Kinase Inhibitors; Protein Structure, Secondary; Protein Structure, Tertiary; Structure-Activity Relationship; Thermodynamics; User-Computer Interface

The enzymes 5-lipoxygenase (5-LO) and glycogen synthase kinase (GSK)-3 represent promising drug targets in inflammation. We made use of the bisindole core of indirubin, present in GSK-3 inhibitors, to innovatively target 5-LO at the ATP-binding site for the design of dual 5-LO/GSK-3 inhibitors. Evaluation of substituted indirubin derivatives led to the identification of (3Z)-6-bromo-3-[(3E)-3-hydroxyiminoindolin-2-ylidene]indolin-2-one (15) as a potent, direct, and reversible 5-LO inhibitor (IC50 = 1.5 μM), with comparable cellular effectiveness on 5-LO and GSK-3. Together, we present indirubins as novel chemotypes for the development of 5-LO inhibitors, the interference with the ATP-binding site as a novel strategy for 5-LO targeting, and dual 5-LO/GSK-3 inhibition as an unconventional and promising concept for anti-inflammatory intervention.

Topics: Arachidonate 5-Lipoxygenase; Cytokines; Enzyme Inhibitors; Glycogen Synthase Kinase 3; HEK293 Cells; Humans; Indoles; Inhibitory Concentration 50; Molecular Structure; Monocytes

The bis-indole alkaloid indirubin and its analogues bear a very interesting natural pharmacophore. They are recognized mainly as kinase inhibitors, but several other activities make them possible candidates for preclinical studies. Based on the previously reported activity of 7-bromoindirubin-3'-oxime and its derivatives, the synthesis of indirubins bearing a heterocyclic nitrogen atom at position 7 was carried out. Herein, we report the first synthesis of 7-azaindirubin-3'-oxime (12) as well as its antiproliferative activity against 57 cancer cell lines and its inhibitory activity against a series of kinases. 7-Azaindirubin (10) and its 3'-oxime derivative (12) showed reduced activity as kinase inhibitors in comparison with other known indirubin derivatives, but antiproliferative activity with a best GI(50) value of 0.77 microM.

Topics: Amino Acid Sequence; Antineoplastic Agents; Cyclin-Dependent Kinase Inhibitor Proteins; Drug Screening Assays, Antitumor; Female; Humans; Indole Alkaloids; Indoles; Molecular Structure

A variation of the bromine substitution from 6- to 7-position converts the glycogen synthase kinase-3alpha/beta-(GSK-3-alpha/beta) selective inhibitor 6-bromoindirubin-3'-oxime (6BIO) to a potent inhibitor of Aurora B and C kinases. The novel indirubin analogue 7-bromoindirubin-3'-oxime (7BIO) demonstrated unexpected selectivity against these two kinases since the homologous kinase Aurora A was poorly inhibited. A hypothesis regarding the 7BIO selectivity profile was stated and validated by docking, molecular dynamics, and free energy perturbation calculations. The residue (Thr217AurA, Glu161AurB, Glu127AurC) located in the active site was identified as a major contributor to the enhanced affinity of 7BIO for Aurora B and C versus Aurora A. Furthermore, the docking events of 7BIO and several of its analogues were approached by quantitative models based on semiempirical scoring functions. In the course of model construction and optimization, a number of important factors influencing the quality of each model like the application of force constraints or the sampling method were determined. Among these factors, the presence and treatment of structurally important water molecules had a pronounced impact on the quality of each model. The final model was validated by use of free energy perturbation calculations.

Topics: Amino Acid Sequence; Aurora Kinases; Binding Sites; Indoles; Models, Molecular; Molecular Sequence Data; Oximes; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Quantitative Structure-Activity Relationship; Sequence Homology, Amino Acid; Thermodynamics

Indirubins are kinase inhibitory bis-indoles that can be generated from various plant, mollusk, mammalian, and bacterial sources or chemically synthesized. We here report on the synthesis and biological evaluation of 3'-substituted 7-halogenoindirubins. Molecular modeling and kinase assays suggest that steric hindrance prevents 3'-substituted 7-halogenoindirubins from interacting with classical kinase targets of other indirubins such as cyclin-dependent kinases and glycogen synthase kinase-3. Surprisingly 3'-substituted 7-halogenoindirubins induce cell death in a diversity of human tumor cell lines. Although some 3'-substituted 7-halogenoindirubins appear to induce effector caspase-independent, nonapoptotic cell death, others trigger the landmarks of classical apoptosis. A structure-activity relationship study was performed to optimize 3'-substituted 7-halogenoindirubins with respect to solubility and cell death induction. Despite their unidentified targets, 3'-substituted 7-halogenoindirubins constitute a new promising family of antitumor agents.

Topics: Antineoplastic Agents; Bromine; Cell Death; Cell Line, Tumor; Chlorine; Drug Screening Assays, Antitumor; Fluorine; Humans; Indoles; Iodine; Models, Molecular; Stereoisomerism; Structure-Activity Relationship