Inhibition of human UDP-glucuronosyltransferase enzyme by Dabrafenib: Implications for drug-drug interactions.

Dabrafenib is a novel small molecule tyrosine kinase inhibitor (TKI) which is used to treat metastatic melanoma. The aim of this research was to survey the effects of dabrafenib on human UDP-glucuronosyltransferases (UGTs) and to evaluate the risk of drug-drug interactions (DDIs). The formation rates for 4-methylumbelliferone (4-MU) glucuronide and trifluoperazine-glucuronide in 12 recombinant human UGT isoforms with or without dabrafenib were measured and HPLC was used to investigate the inhibitory effects of dabrafenib on UGTs. Inhibition kinetic studies were also conducted. In vitro-in vivo extrapolation approaches were further used to predict the risk of DDI potentials of dabrafenib via inhibition of UGTs. Our data indicated that dabrafenib had a broad inhibitory effect on 4-MU glucuronidation by inhibiting the activities of UGTs, especially on UGT1A1, UGT1A7, UGT1A8, and UGT1A9, and dabrafenib could increase the area under the curve of co-administered drugs. Dabrafenib is a strong inhibitor of several UGTs and the co-administration of dabrafenib with drugs primarily metabolized by UGT1A1, 1A7, 1A8 or 1A9 may induce potential DDIs.

High content phenotypic screening identifies serotonin receptor modulators with selective activity upon breast cancer cell cycle and cytokine signaling pathways.

Heterogeneity in disease mechanisms between genetically distinct patients contributes to high attrition rates in late stage clinical drug development. New personalized medicine strategies aim to identify predictive biomarkers which stratify patients most likely to respond to a particular therapy. However, for complex multifactorial diseases not characterized by a single genetic driver, empirical approaches to identifying predictive biomarkers and the most promising therapies for personalized medicine are required. In vitro pharmacogenomics seeks to correlate in vitro drug sensitivity testing across panels of genetically distinct cell models with genomic, gene expression or proteomic data to identify predictive biomarkers of drug response. However, the vast majority of in vitro pharmacogenomic studies performed to date are limited to dose-response screening upon a single viability assay endpoint. In this article we describe the application of multiparametric high content phenotypic screening and the theta comparative cell scoring method to quantify and rank compound hits, screened at a single concentration, which induce a broad variety of divergent phenotypic responses between distinct breast cancer cell lines. High content screening followed by transcriptomic pathway analysis identified serotonin receptor modulators which display selective activity upon breast cancer cell cycle and cytokine signaling pathways correlating with inhibition of cell growth and survival. These methods describe a new evidence-led approach to rapidly identify compounds which display distinct response between different cell types. The results presented also warrant further investigation of the selective activity of serotonin receptor modulators upon breast cancer cell growth and survival as a potential drug repurposing opportunity.

Pharmacological profile of neuroleptics at human monoamine transporters.

Using radioligand binding techniques, we determined the equilibrium dissociation constants (K(D)) for 37 neuroleptics and one metabolite of a neuroleptic (haloperidol metabolite) for the human serotonin, norepinephrine, and dopamine transporters with [3H]imipramine, [3H]nisoxetine, and [3H]WIN35428, respectively. Among neuroleptics, the four most potent compounds at the human serotonin transporter were triflupromazine, fluperlapine, chlorpromazine, and ziprasidone (K(D) 24-39 nM); and at the norepinephrine transporter, chlorpromazine, zotepine, chlorprothixene, and promazine (K(D) 19-25 nM). At the human dopamine transporter, only pimozide (K(D) = 69+/-3) ziprasidone (K(D) = 76+/-5) had notable potency. These data may be useful in predicting therapeutic and adverse effects, including drug interactions of neuroleptics.

Trifluopromazine late preventive effects on carbon tetrachloride-induced liver necrosis.

Trifluopromazine (TFPro) administration to rats (50 mg/kg, ip) 30 min before or 6 or 10 hr after CCl4 treatment (1 ml/kg ip in olive oil) partially prevented necrogenic effects of this compound at 24 hr. TFPro has only minor effects on the covalent binding (CB) of CCl4-reactive metabolites to cellular constituents and even an enhancing action on CCl4-promoted lipid peroxidation (LP). Determination of TFPro levels in liver 1 and 3 hr after administration by gas chromatography/mass spectrometry showed its presence in that tissue at concentrations well above those needed for calmodulin (CaM) inhibitory effects of this drug. TFPro lowered body temperature in CCl4-treated animals during the 24-hr observation period. Protective effects of TFPro at 6 or 10 hr, when most of the CB and all of the LP has already occurred, suggest but do not prove a role for CaM in late stages of CCl4-induced necrogenic effects. Decreases in the body temperature of CCl4-poisoned animals provoked by TFPro might also play a role in the preventive actions of this drug.

A theoretical study of the binding of phenothiazine derivatives to residues 82-93 of calmodulin.

A theoretical study was performed of the interaction of four phenothiazine derivatives, promethazine, promazine, trifluopromazine, and trifluoperazine, with a fragment (82-93) of calmodulin, held in the alpha-helical conformation. The computations were performed in the framework of the SIBFA 2 procedure (sum of interactions between fragments computed ab initio), which uses analytical formulas based on ab initio self-consistent field computations. The interaction energy is the sum of the intermolecular phenothiazine-oligopeptide interaction energy and of the separate intramolecular energy variations of the phenothiazine and of the side chains of the oligopeptide upon complex formation. The ordering of interaction energies of the four investigated phenothiazines parallels the ordering of their experimentally measured affinities for calmodulin, with a maximum affinity for trifluoperazine. The principal features of the trifluoperazine complex are a short hydrogen bond between the piperazinium proton and one anionic oxygen of Glu 87, and hydrophobic interactions between the piperazinium ring and Val 91 and between the methylene chain and Ala 88, together with partial insertion of the phenothiazine ring and the--CF3 substituent between Phe 89 and Phe 92.