Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

S31-201 (NSC 74859) is a chemical probe inhibitor of Stat3 activity, which was identified from the National Cancer Institute chemical libraries by using structure-based virtual screening with a computer model of the Stat3 SH2 domain bound to its Stat3 phosphotyrosine peptide derived from the x-ray crystal structure of the Stat3 beta homodimer. S31-201 inhibits Stat3-Stat3 complex formation and Stat3 DNA-binding and transcriptional activities. Furthermore, S31-201 inhibits growth and induces apoptosis preferentially in tumor cells that contain persistently activated Stat3. Constitutively climerized and active Stat3C and Stat3 SH2 domain rescue tumor cells from S31-201-induced apoptosis. Finally, S31-201 inhibits the expression of the Stat3-regulated genes encoding cyclin D1, BcI-xL, and survivin and inhibits the growth of human breast tumors in vivo. These findings strongly suggest that the antitumor activity of S31-201 is mediated in part through inhibition of aberrant Stat3 activation and provide the proof-of-concept for the potential clinical use of Stat3 inhibitors such as S31-201 in tumors harboring aberrant Stat3

Small molecule inhibitors of STAT3 with anti-tumor activity

The present invention concerns compounds, compositions containing these compounds, and methods of using these compounds and compositions as inhibitors of Stat3 signaling, Stat3 dimerization, Stat3-DNA binding, Stat5-DNA binding, and/or aberrant cell growth in vitro or in vivo, e.g., as anti-cancer agents for treatment of cancer, such as breast cancer. The compounds of the invention include, but are not limited to, NSC 74859 (S3I-201), NSC 42067, NSC 59263, NSC 75912, NSC 11421, NSC 91529, NSC 263435, and pharmaceutically acceptable salts and analogs of the foregoing. Other non-malignant diseases characterized by proliferation of cells that may be treated using the compounds of the invention, but are not limited to, cirrhosis of the liver; graft rejection; restenosis; and disorders characterized by a proliferation of T cells such as autoimmune diseases, e.g., type 1 diabetes, lupus and multiple sclerosis. The invention further includes an in-vitro screening test for the presence of malignant cells in a mammalian tissue; a method of identifying inhibitors of constitutive Stat3 activation, Stat3-DNA binding, Stat5-DNA binding, and/or Stat3 dimerization; and a method of identifying anti-cancer agents

Reversible, Allosteric Small-Molecule Inhibitors of Regulator of G Protein Signaling ProteinsS⃞

Regulators of G protein signaling (RGS) proteins are potent negative modulators of G protein signaling and have been proposed as potential targets for small-molecule inhibitor development. We report a high-throughput time-resolved fluorescence resonance energy transfer screen to identify inhibitors of RGS4 and describe the first reversible small-molecule inhibitors of an RGS protein. Two closely related compounds, typified by CCG-63802 [((2E)-2-(1,3-benzothiazol-2-yl)-3-[9-methyl-2-(3-methylphenoxy)-4-oxo-4H-pyrido[1,2-a]pyrimidin-3-yl]prop-2-enenitrile)], inhibit the interaction between RGS4 and Gαo with an IC50 value in the low micromolar range. They show selectivity among RGS proteins with a potency order of RGS 4 > 19 = 16 > 8 ≫ 7. The compounds inhibit the GTPase accelerating protein activity of RGS4, and thermal stability studies demonstrate binding to the RGS but not to Gαo. On RGS4, they depend on an interaction with one or more cysteines in a pocket that has previously been identified as an allosteric site for RGS regulation by acidic phospholipids. Unlike previous small-molecule RGS inhibitors identified to date, these compounds retain substantial activity under reducing conditions and are fully reversible on the 10-min time scale. CCG-63802 and related analogs represent a useful step toward the development of chemical tools for the study of RGS physiology

Orvinols with Mixed Kappa/Mu Opioid Receptor Agonist Activity

Dual-acting kappa opioid receptor (KOR) agonist and mu opioid receptor (MOR) partial agonist ligands have been put forward as potential treatment agents for cocaine and other psychostimulant abuse. Members of the orvinol series of ligands are known for their high binding affinity to both KOR and MOR, but efficacy at the individual receptors has not been thoroughly evaluated. In this study, it is shown that a predictive model for efficacy at KOR can be derived, with efficacy being controlled by the length of the group attached to C20 and by the introduction of branching into the side chain. In vivo evaluation of two ligands with the desired in vitro profile confirms both display KOR, and to a lesser extent MOR, activity in an analgesic assay suggesting that, in this series, in vitro measures of efficacy using the [³⁵S]­GTPγS assay are predictive of the in vivo profile

Fumaroylamino-4,5-epoxymorphinans and Related Opioids with Irreversible μ Opioid Receptor Antagonist Effects

We have previously shown that cinnamoyl derivatives of 14β-amino-17-cyclopropylmethyl-7,8-dihydronormorphinone and 7α-aminomethyl-6,14-endoethanonororipavine have pronounced pseudoirreversible μ opioid receptor (MOR) antagonism. The present communication describes the synthesis and evaluation of fumaroylamino analogues of these cinnamoylamino derivatives together with some related fumaroyl derivatives. The predominant activity of the new ligands was MOR antagonism. The fumaroylamino analogues (<b>2a</b>, <b>5a</b>) of the pseudoirreversible antagonist cinnamoylamino morphinones and oripavines (<b>2b</b>, <b>5b</b>) were themselves irreversible antagonists in vivo. However the fumaroylamino derivatives had significantly higher MOR efficacy than the cinnamoylamino derivatives in mouse antinociceptive tests. Comparison of <b>2a</b> and <b>5a</b> with the prototypic fumaroylamino opioid β-FNA (<b>1a</b>) shows that they have similar MOR irreversible antagonist actions but differ in the nature of their opioid receptor agonist effects; <b>2a</b> is a predominant MOR agonist and <b>5a</b> shows no opioid receptor selectivity, whereas the agonist effect of β-FNA is clearly κ opioid receptor (KOR) mediated