Vascular disrupting activity and the mechanism of action of EHT 6706, a novel anticancer tubulin polymerization inhibitor.

Tumor blood vessels are an important emerging target for anticancer therapy. Here, we characterize the in vitro antiproliferative and antiangiogenic properties of the synthetic small molecule, 7-ethoxy-4-(3,4,5-trimethoxybenzyl)isoquinolin-8-amine dihydrochloride, EHT 6706, a novel microtubule-disrupting agent that targets the colchicine-binding site to inhibit tubulin polymerization. At low nM concentrations, EHT 6706 exhibits highly potent antiproliferative activity on more than 60 human tumor cell lines, even those described as being drug resistant. EHT 6706 also shows strong efficacy as a vascular-disrupting agent, since it prevents endothelial cell tube formation and disrupts pre-established vessels, changes the permeability of endothelial cell monolayers and inhibits endothelial cell migration. Genome-wide transcriptomic analysis of EHT 6706 effects on human endothelial cells shows that the antiangiogenic activity elicits gene deregulations of antiangiogenic pathways. These findings indicate that EHT 6706 is a promising tubulin-binding compound with potentially broad clinical antitumor efficacy.

Structure-activity relationship of isoform selective inhibitors of Rac1/1b GTPase nucleotide binding.

The synthesis of a series of berberine, phenantridine and isoquinoline derivatives was realized to explore their Rho GTPase nucleotide inhibitory activity. The compounds were evaluated in a nucleotide binding competition assay against Rac1, Rac1b, Cdc42 and in a cellular Rac GTPase activation assay. The insertion of 19 AA in the splice variant Rac1b is shown to be sufficient to introduce a conformational difference that allows compounds 4, 21, 22, and 26 to exhibit selective inhibition of Rac 1b over Rac1.

Yawning and hypothermia in rats: effects of dopamine D3 and D2 agonists and antagonists.

RATIONALE: Identification of behaviors specifically mediated by the dopamine D2 and D3 receptors would allow for the determination of in vivo receptor selectivity and aide the development of novel therapeutics for dopamine-related diseases. OBJECTIVES: These studies were aimed at evaluating the specific receptors involved in the mediation of D2/D3 agonist-induced yawning and hypothermia. MATERIALS AND METHODS: The relative potencies of a series of D2-like agonists to produce yawning and hypothermia were determined. The ability of D3-selective and D2-selective antagonists to inhibit the induction of yawning and hypothermia were assessed and a series of D2/D3 antagonists were characterized with respect to their ability to alter yawning induced by a low and high dose of PD-128,907 and sumanirole-induced hypothermia. RESULTS: D3-preferring agonists induced yawning at lower doses than those required to induce hypothermia and the D2-preferring agonist, sumanirole, induced hypothermia at lower doses than were necessary to induce yawning. The rank order of D3 selectivity was pramipexole > PD-128,907 = 7-OH-DPAT = quinpirole = quinelorane > apomorphine = U91,356A. Sumanirole had only D2 agonist effects. PG01,037, SB-277,011A, and U99,194 were all D3-selective antagonists, whereas haloperidol and L-741,626 were D2-selective antagonists and nafadotride's profile of action was more similar to the D2 antagonists than to the D3 antagonists. CONCLUSIONS: D3 and D2 receptors have specific roles in the mediation of yawning and hypothermia, respectively, and the analysis of these effects allow inferences to be made regarding the selectivity of D2/D3 agonists and antagonists with respect to their actions at D2 and D3 receptors.

Major effect of pyrrolic N-benzylation in norbinaltorphimine, the selective kappa-opioid receptor antagonist.

Indolic N-benzylation of naltrindole reportedly extends the duration of delta-opioid receptor (DOR) antagonism. Similar modification of the kappa-opioid receptor (KOR) antagonist norBNI (1a) and its 17,17'-diNMe analogue (1d), a low potency mu-opioid receptor (MOR) partial agonist, was found to affect predominantly their MOR activity. When administered systemically in mouse antinociceptive assays, N-benzyl-norBNI (1b) had only MOR agonist activity of relatively short duration whereas on central administration it had only a KOR-antagonist action of extremely long duration.

Guanidino N-substituted and N,N-disubstituted derivatives of the kappa-opioid antagonist GNTI.

Derivatives of the highly selective kappa-opioid receptor antagonist GNTI (2a) have been prepared. Binding and functional studies conducted on cloned human opioid receptors expressed in Chinese hamster ovarian (CHO) cells suggested that adding a benzyl or a substituted benzyl group to the guanidino moiety led, in general, to a retention of high kappa-affinity and antagonist potency. Disubstitution of the guanidino moiety led to reduced kappa-selectivity.