Inhibition Of 2D6 Research Articles

Vortioxetine: Clinical Pharmacokinetics and Drug Interactions.

Vortioxetine is a novel antidepressant with multimodal activity currently approved for the treatment of major depressive disorder. Vortioxetine is orally administered once daily at 5- to 20-mg doses. The pharmacokinetics of vortioxetine are linear and dose proportional, with a mean terminal half-life of approximately 66 h and steady-state plasma concentrations generally achieved within 2 weeks of dosing. The mean absolute oral bioavailability of vortioxetine is 75%. No food effect on pharmacokinetics was observed. Vortioxetine is metabolized by cytochrome P450 enzymes and subsequently by uridine diphosphate glucuronosyltransferase. The major metabolite is pharmacologically inactive, and the minor pharmacologically active metabolite is not expected to cross the blood–brain barrier, making the parent compound primarily responsible for in-vivo activity. No clinically relevant differences were observed in vortioxetine exposure by sex, age, race, body size, and renal or hepatic function. Dose adjustment is only recommended for cytochrome P450 2D6 poor metabolizers based on polymorphism of the cytochrome P450 enzymes involved. Similarly, except for bupropion, a strong cytochrome P450 2D6 inhibitor, and rifampin, a broad cytochrome P450 inducer, co-administration of other drugs evaluated did not affect the vortioxetine exposure or safety profile in any clinically meaningful way. Pharmacodynamic studies demonstrated that vortioxetine achieved high levels of serotonin transporter occupancy in relevant brain areas, affected neurotransmitter levels in the cerebrospinal fluid, and modified abnormal resting state networks in the brain over the therapeutic dose range. Overall, vortioxetine can be administered in most populations studied to date without major dose adjustments; however, dose adjustments should be considered on a patient-by-patient basis.Electronic supplementary materialThe online version of this article (10.1007/s40262-017-0612-7) contains supplementary material, which is available to authorized users.

A combinatorial approach for the discovery of cytochrome P450 2D6 inhibitors from nature

The human cytochrome P450 2D6 (CYP2D6) enzyme is part of phase-I metabolism and metabolizes at least 20% of all clinically relevant drugs. Therefore, it is an important target for drug-drug interaction (DDI) studies. High-throughput screening (HTS) assays are commonly used tools to examine DDI, but show certain drawbacks with regard to their applicability to natural products. We propose an in silico – in vitro workflow for the reliable identification of natural products with CYP2D6 inhibitory potential. In order to identify candidates from natural product-based databases that share similar structural features with established inhibitors, a pharmacophore model was applied. The virtual hits were tested for the inhibition of recombinant human CYP2D6 in a bioluminescence-based assay. By controlling for unspecific interferences of the test compounds with the detection reaction, the number of false positives were reduced. The success rate of the reported workflow was 76%, as most of the candidates identified in the in silico approach were able to inhibit CYP2D6 activity. In summary, the workflow presented here is a suitable and cost-efficient strategy for the discovery of new CYP2D6 inhibitors with natural product libraries.

In Vitro Inhibition of Human CYP450s 1A2, 2C9, 3A4/5, 2D6 and 2E1 by Grandisin.

Grandisin, a lignan isolated from many species of plants, such as Virola surinamensis, is a potential drug candidate due to its biological properties, highlighted by its antitumor and trypanocidal activities. In this study, the inhibitory effects of grandisin on the activities of human cytochrome P450 enzymes were investigated by using human liver microsomes. Results showed that grandisin is a competitive inhibitor of CYP2C9 and a competitive and mechanism-based inhibitor of CYP3A4/5. The apparent Ki value for CYP2C9 was 50.60 µM and those for CYP3A4/5 were 48.71 µM and 31.25 µM using two different probe substrates, nifedipine and midazolam, respectively. The apparent KI, kinact, and kinact/KI ratio for the mechanism-based inhibition of CYP3A4/5 were 6.40 µM, 0.037 min-1, and 5.78 mL · min-1 µmol-1, respectively, by examining nifedipine oxidation, and 31.53 µM, 0.049 min-1, and 1.55 mL · min-1 µmol-1, respectively, by examining midazolam 1'-hydroxylation. These apparent kinact/KI values were comparable to or even higher than those for several therapeutic drugs that act as mechanism-based inhibitors of CYP3A4/5. CYP1A2 and CYP2D6 activities, in turn, were not substantially inhibited by grandisin (IC50 > 200 µM and 100 µM, respectively). In contrast, from a concentration of 4 µM, grandisin significantly stimulated CYP2E1 activity. These results improve the prediction of grandisin-drug interactions, suggesting that the risk of interactions with drugs metabolized by CYP3A4/5 and CYP2E1 cannot be overlooked.

Preclinical Evaluation of Safety of Fucoidan Extracts From Undaria pinnatifida and Fucus vesiculosus for Use in Cancer Treatment.

Objectives: To evaluate potential hepatic metabolism-mediated drug interactions with fucoidan from Undaria pinnatifida (UPF) or Fucus vesiculosus (FVF) and potential growth inhibition activity with either fucoidan alone or with chemotherapy. In vivo studies were done to confirm safety and investigate fucoidan-mediated immune modulation. Methods: Cytochrome P450 (CYP450) 3A4, 2C8, 2C9, and 2D6 inhibition experiments were conducted in vitro followed by an ex vivo human hepatocytes model to evaluate the CYP450 induction potential of each fucoidan at highest theoretical concentrations. Four hepatic metabolism phase II pathways—glutathione S transferase (GST), quinone oxidoreductase (QOR), catechol-O-methyltransferases (COMT), and uridine di-phosphate (UDP)-glucuronosyltransferase (UGT)—were evaluated with validated immunoassays. Growth inhibition assays were performed with each fucoidan alone and in combination with chemotherapy agents in a panel of human cancer cell lines. In vivo studies evaluated safety and immune modualtion. Results: CYP450 inhibition was observed with FVF. The GST, QOR, and UGT pathways had no changes. UPF and FVF both interacted with COMT. No growth inhibitory activity in cancer cell lines was observed. UPF and FVF had synergistic activity with paclitaxel or tamoxifen and additive activity with topotecan. In vivo, FVF decreased HeLa human cervical tumor growth and both FVF and UPF decreased TOV-112D human ovarian tumor growth. Otherwise, no significant change in tumor growth was observed. FVF immune modulation of IgG and IL-6 was observed (p<0.03). Conclusion: At higher doses, UPF and FVF may have limited potential for drug-supplement interactions, with either CYP450 or COMT hepatic metabolism pathways. Additional studies are warranted to evaluate to confirm findings of fucoidans in combination with chemotherapy.

Evaluating the Role of Drug Metabolism and Reactive Intermediates in Trazodone-Induced Cytotoxicity toward Freshly-Isolated Rat Hepatocytes.

Background: Trazodone is an antidepressant agent widely administered for the treatment of depressive disorders. On the other hand, several cases of hepatic injury have been reported after Trazodone administration. Although the precise mechanism(s) of trazodone-induced liver injury is not known, some investigations proposed the role of reactive intermediates in this complication. This study was designed to investigate the role of reactive metabolites in hepatocytes injury induced by trazodone. Methods: Isolated rat hepatocytes were prepared by the method of collagenase enzyme perfusion via the portal vein. Cells were treated with trazodone, its cytotoxic metabolite, and different enzyme inhibitors and cytoprotective agents. Results: It was found that trazodone was toxic towards hepatocytes and caused 50% cell death after 2 h of incubation at a dose of 450 µM. The trazodone postulated reactive metabolite; m-chlorophenyl piperazine (m-CPP) was less toxic and caused 50% cell death at a dose of 750 µM at a similar time period. Cellular glutathione (GSH) depletion and lipid peroxidation were detected when hepatocytes were treated with trazodone and/or m-CPP. Depleting hepatocytes GSH beforehand, increased cytotoxicity of both trazodone and m-CPP. Troleandomycin as the CYP3A4 inhibitor prevented cytotoxicity of trazodone but slightly affected m-CPP-induced cell injury. Inhibition of CYP2D6 by quinidine and cimetidine increased the cytotoxicity of both trazodone and m-CPP. Antioxidants and ATP suppliers slightly prevented cytotoxicity of trazodone and m-CPP. Conclusion: As inhibitors of CYP3A4 and 2D6 affected trazodone cytotoxicity, it is suggested that trazodone -induced cytotoxicity, at least in part, is mediated by its reactive metabolites.

Pathway-specific inhibition of primaquine metabolism by chloroquine/quinine.

BackgroundThere has been some evidence to suggest that the addition of chloroquine (CQ) or quinine (QN) to 8-aminoquinoline (8-AQ) treatment regimens may increase the therapeutic efficacy of the 8-AQ and simultaneously mitigate against its haemolytic toxicity. However, both CQ and QN are considered effective, although perhaps moderate inhibitors of CYP2D6, an enzyme now regarded as necessary for primaquine (PQ) pharmacologic activity. An understanding of the influence of CQ and QN on the metabolism of PQ may shed light on the potential mechanisms of the beneficial interaction.MethodsDifferential metabolism of PQ enantiomers by recombinant human CYP2D6, monoamine oxidase A (MAO), and cryopreserved human hepatocytes in the presence/absence of CQ and QN.ResultsBoth CQ and QN significantly inhibited the activity of CYP2D6. PQ depletion by MAO and human hepatocytes was not affected significantly by the presence of CQ and QN. CYP2D6-mediated hydroxylation was largely suppressed by both CQ and QN. The formation of the primary deaminated metabolites, including carboxyprimaquine (CPQ) and cyclized side chain derivative from the aldehyde (m/z 241), was not sensitive to the presence of CQ and QN. However, the appearance of the glucuronides of CPQ and PQ alcohol were significantly suppressed. CQ and QN also inhibited the appearance of the m/z 257 metabolite with a similar pattern, suggesting that it may be derived from the CPQ conjugate. The apparent quinone-imine of CPQ (m/z 289) was only partially suppressed by both QN and CQ, but with a differential pattern of inhibition for the two drugs. The m/z 274 (quinone-imine of a ring-hydroxylated PQ metabolite) and m/z 422 (an apparent glucose conjugate of PQ) metabolites in hepatocytes were strongly suppressed by both QN and CQ, perhaps a reflection of the 2D6 inhibition by these drugs. The formation of the carbamoyl glucuronide of PQ (m/z 480) was not affected by CQ/QN.ConclusionThe metabolite-specific interactions in the current studies seem at variance with earlier reports of the dependence of PQ on CYP2D6 metabolism, and enhanced PQ anti-malarial activity/reduced toxicity in the presence of CQ/QN. These results suggest a complex picture in which CQ/QN may shift metabolite pathway balances towards a profile that retains efficacy, while reducing the formation or availability of toxic metabolites to erythrocytes. Alternatively, these drugs may alter transport or distribution of PQ metabolites in a fashion that reduces toxicity while maintaining efficacy against the parasite.

Development of an automated, high-throughput hepatocyte spheroid screen for use within the pharmaceutical industry

Silymarin was assessed for drug–drug interaction by permeability studies with Caco-2 cells, for cytochrome P450 induction with human primary hepatocytes and for cytochrome P450 inhibition with human liver microsomes. Studies with Caco-2 cells revealed no interference of silymarin with the permeability of nifedipine. Silymarin did not induce cytochromes P450 2C9 and 3A4 at concentrations of 0.1; 1; and 100 μM, measured as silibinin. The inhibitory effect was tested on the nine major cytochromes P450 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 at concentrations of 1 and 100 μM silymarin. At 1 μM concentration no or negligible inhibition of cytochromes P450 1A2, 2A6, 2B6, 2C8, 2C9, and 2E1, minor inhibition of 3A4 (<20%), and moderate inhibition of 2C19 and 2D6 (<40%) were observed. Inhibition constant Ki of silymarin was determined for cytochromes P450 3A4 with 12 μM, 2C19 with 2 μM, and 2D6 with 12 μM. Only at the high concentration of 100 μM silymarin, inhibition at >50% of the cytochromes P450 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4 was observed, and no or moderate inhibition was for the cytochromes P450 1A2, 2A6, and 2E1. However, in view of the clinically relevant plasma concentration of approx. 0.2 μM measured as silibinin, it is evident that there is no drug–drug interaction problem with silymarin.

Pre-clinical evaluation of CYP 2D6 dependent drug-drug interactions between primaquine and SSRI/SNRI antidepressants.

BackgroundThe liver-stage anti-malarial activity of primaquine and other 8-aminoquinoline molecules has been linked to bio-activation through CYP 2D6 metabolism. Factors such as CYP 2D6 poor metabolizer status and/or co-administration of drugs that inhibit/interact with CYP 2D6 could alter the pharmacological properties of primaquine.MethodsIn the present study, the inhibitory potential of the selective serotonin reuptake inhibitor (SSRI) and serotonin norepinephrine reuptake inhibitor (SNRI) classes of antidepressants for CYP 2D6-mediated primaquine metabolism was assessed using in vitro drug metabolism and in vivo pharmacological assays.ResultsThe SSRI/SNRI classes of drug displayed a range of inhibitory activities on CYP 2D6-mediated metabolism of primaquine in vitro (IC50 1–94 μM). Fluoxetine and paroxetine were the most potent inhibitors (IC50 ~1 µM) of CYP 2D6-mediated primaquine metabolism, while desvenlafaxine was the least potent (IC50 ~94 µM). The most potent CYP 2D6 inhibitor, fluoxetine, was chosen to investigate the potential pharmacological consequences of co-administration with primaquine in vivo. The pharmacokinetics of a CYP 2D6-dependent primaquine metabolite were altered upon co-administration with fluoxetine. Additionally, in a mouse malaria model, co-administration of fluoxetine with primaquine reduced primaquine anti-malarial efficacy.ConclusionsThese results are the first from controlled pre-clinical experiments that indicate that primaquine pharmacological properties can be modulated upon co-incubation/administration with drugs that are known to interact with CYP 2D6. These results highlight the potential for CYP 2D6-mediated drug–drug interactions with primaquine and indicate that the SSRI/SNRI antidepressants could be used as probe molecules to address the primaquine-CYP 2D6 DDI link in clinical studies. Additionally, CYP 2D6-mediated drug–drug interactions can be considered when examining the possible causes of human primaquine therapy failures.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1329-z) contains supplementary material, which is available to authorized users.

Evaluation of the Effects of &lt;i&gt;S&lt;/i&gt;-Allyl-L-cysteine, &lt;i&gt;S&lt;/i&gt;-Methyl-L-cysteine, &lt;i&gt;trans&lt;/i&gt;-&lt;i&gt;S&lt;/i&gt;-1-Propenyl-L-cysteine, and Their &lt;i&gt;N&lt;/i&gt;-Acetylated and &lt;i&gt;S&lt;/i&gt;-Oxidized Metabolites on Human CYP Activities

Three major organosulfur compounds of aged garlic extract, S-allyl-L-cysteine (SAC), S-methyl-L-cysteine (SMC), and trans-S-1-propenyl-L-cysteine (S1PC), were examined for their effects on the activities of five major isoforms of human CYP enzymes: CYP1A2, 2C9, 2C19, 2D6, and 3A4. The metabolite formation from probe substrates for the CYP isoforms was examined in human liver microsomes in the presence of organosulfur compounds at 0.01-1 mM by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Allicin, a major component of garlic, inhibited CYP1A2 and CYP3A4 activity by 21-45% at 0.03 mM. In contrast, a CYP2C9-catalyzed reaction was enhanced by up to 1.9 times in the presence of allicin at 0.003-0.3 mM. SAC, SMC, and S1PC had no effect on the activities of the five isoforms, except that S1PC inhibited CYP3A4-catalyzed midazolam 1'-hydroxylation by 31% at 1 mM. The N-acetylated metabolites of the three compounds inhibited the activities of several isoforms to a varying degree at 1 mM. N-Acetyl-S-allyl-L-cysteine and N-acetyl-S-methyl-L-cysteine inhibited the reactions catalyzed by CYP2D6 and CYP1A2, by 19 and 26%, respectively, whereas trans-N-acetyl-S-1-propenyl-L-cysteine showed weak to moderate inhibition (19-49%) of CYP1A2, 2C19, 2D6, and 3A4 activities. On the other hand, both the N-acetylated and S-oxidized metabolites of SAC, SMC, and S1PC had little effect on the reactions catalyzed by the five isoforms. These results indicated that SAC, SMC, and S1PC have little potential to cause drug-drug interaction due to CYP inhibition or activation in vivo, as judged by their minimal effects (IC50>1 mM) on the activities of five major isoforms of human CYP in vitro.

Cytochrome P450 2D6 and 3A4 enzyme inhibition by amine stimulants in dietary supplements.

A number of dietary supplements used for weight loss and athletic performance enhancement have been recently shown to contain a variety of stimulants, for which there is a lack of pharmacological and toxicological information. One concern for these emerging compounds is their potential to inhibit metabolic enzymes in the liver such as cytochromes P450 (CYP), which can lead to unexpected interactions among dietary supplements, drugs, and other xenobiotics. In this study, inhibition of human recombinant CYP2D6 and CYP3A4 by 27 amine stimulants associated with dietary supplements and their analogs was evaluated by luminescence assays. The strongest CYP2D6 inhibitors were coclaurine (IC50 = 0.14 ± 0.01 μM) and N-benzylphenethylamine (IC50 = 0.7 ± 0.2 μM), followed by several other relatively strong inhibitors (IC50 , 2-12 μM) including β-methylphenethylamine, N,β-dimethylphenethylamine (phenpromethamine), 1,3-dimethylamylamine (DMAA), N,α-diethylphenethylamine, higenamine (norcoclaurine) and N,N-diethylphenethylamine. Only nine compounds inhibited CYP3A4 by 20-55% at 100 μM. Results of this study illustrate that several amine stimulants associated with dietary supplements inhibit CYP2D6 and CYP3A4 in vitro, and these compounds may participate in adverse drug-dietary supplement interactions in vivo. Copyright © 2015 John Wiley & Sons, Ltd.

Human microsomal cyttrochrome P450-mediated reduction of oxysophocarpine, an active and highly toxic constituent derived from Sophora flavescens species, and its intestinal absorption and metabolism in rat

Oxysophocarpine (OSC), an active and toxic quinolizidine alkaloid, is highly valued in Sophora flavescens Ait. and Subprostrate sophora Root. OSC is used to treat inflammation and hepatitis for thousands of years in China. This study aims to investigate the CYP450-mediated reduction responsible for metabolizing OSC and to evaluate the absorption and metabolism of OSC in rat in situ. Four metabolites were identified, with sophocarpine (SC) as the major metabolite. SC formation was rapid in human and rat liver microsomes (HLMs and RLMs, respectively). The reduction rates in the liver are two fold higher than in the intestine, both in humans and rats. In HLMs, inhibitors of CYP2C9, 3A4/5, 2D6, and 2B6 had strong inhibitory effects on SC formation. Meanwhile, inhibitors of CYP3A and CYP2D6 had significant inhibition on SC formation in RLMs. Human recombinant CYP3A4/5, 2B6, 2D6, and 2C9 contributed significantly to SC production. The permeability in rat intestine and the excretion rates of metabolites were highest in the duodenum (p<0.05), and the absorbed amount of OSC in duodenum and jejunum was concentration-dependent. The metabolism could be significantly decreased by CYP3A inhibitor ketoconazole. In conclusion, the liver was the main organ responsible for OSC metabolism. First-pass metabolism via CYP3A4/5, 2B6, 2D6, and 2C9 may be the main reason for the poor OSC bioavailability.

Contributions of Ionic Interactions and Protein Dynamics to Cytochrome P450 2D6 (CYP2D6) Substrate and Inhibitor Binding

P450 2D6 contributes significantly to the metabolism of >15% of the 200 most marketed drugs. Open and closed crystal structures of P450 2D6 thioridazine complexes were obtained using different crystallization conditions. The protonated piperidine moiety of thioridazine forms a charge-stabilized hydrogen bond with Asp-301 in the active sites of both complexes. The more open conformation exhibits a second molecule of thioridazine bound in an expanded substrate access channel antechamber with its piperidine moiety forming a charge-stabilized hydrogen bond with Glu-222. Incubation of the crystalline open thioridazine complex with alternative ligands, prinomastat, quinidine, quinine, or ajmalicine, displaced both thioridazines. Quinine and ajmalicine formed charge-stabilized hydrogen bonds with Glu-216, whereas the protonated nitrogen of quinidine is equidistant from Asp-301 and Glu-216 with protonated nitrogen H-bonded to a water molecule in the access channel. Prinomastat is not ionized. Adaptations of active site side-chain rotamers and polypeptide conformations were evident between the complexes, with the binding of ajmalicine eliciting a closure of the open structure reflecting in part the inward movement of Glu-216 to form a hydrogen bond with ajmalicine as well as sparse lattice restraints that would hinder adaptations. These results indicate that P450 2D6 exhibits sufficient elasticity within the crystal lattice to allow the passage of compounds between the active site and bulk solvent and to adopt a more closed form that adapts for binding alternative ligands with different degrees of closure. These crystals provide a means to characterize substrate and inhibitor binding to the enzyme after replacement of thioridazine with alternative compounds.

Evaluation of drug interaction potential of Labisia pumila (Kacip Fatimah) and its constituents.

Labisia pumila (Kacip Fatimah) is a popular herb in Malaysia that has been traditionally used in a number of women’s health applications such as to improve libido, relieve postmenopausal symptoms, and to facilitate or hasten delivery in childbirth. In addition, the constituents of this plant have been reported to possess anticancer, antioxidant, and anti-inflammatory properties. Clinical studies have indicated that cytochrome P450s (CYPs), P-glycoprotein (P-gp), and Pregnane X receptor (PXR) are the three main modulators of drug-drug interactions which alter the absorption, distribution, and metabolism of drugs. Given the widespread use of Kacip Fatimah in dietary supplements, the current study focuses on determining the potential of its constituents to affect the activities of CYPs, P-gp, or PXR using in vitro assays which may provide useful information toward the risk of herb-drug interaction with concomitantly used drugs. Six compounds isolated from the roots of L. pumila (2 saponins and 4 alkyl phenols) were tested, in addition to the methanolic extract. The extract of L. pumila showed a significant time dependent inhibition (TDI) of CYP3A4, reversible inhibition of CYP2C9 and 2C19 and a weak inhibition of 1A2 and 2D6 as well as an inhibition of P-gp and rifampicin-induced PXR activation. The alkyl phenols inhibited CYP3A4 (TDI), CYP2C9, and 2C19 (reversible) while saponins inhibited P-gp and PXR. In conclusion, L. pumila and its constituents showed significant modulation of all three regulatory proteins (CYPs, P-gp, and PXR) suggesting a potential to alter the pharmacokinetic and pharmacodynamic properties of conventional drugs if used concomitantly.

An Evaluation of the Potential for Pharmacokinetic Interaction between Tramadol and Cytochrome P450 2D6 Inhibitor Promethazine

In this single-center, randomized, open-label, 3-way crossover study, subjects received each of the following: a single dose of Tramadol Hydrochloride Injection (THI) 35 mg, a single dose of Promethazine Hydrochloride Injection (PHI) 45 mg, and single dose of Compound Tramadol Hydrochloride Injection (CTHI) 80mg. Blood was collected and plasma was analyzed for the pharmacokinetic parameters (maximum plasma concentration [Cmax], time to Cmax [Tmax], area under the plasma concentration-time curve, plasma elimination half-life, clearance, and apparent volume of distribution) of Tramadol and Promethazine. In general, several pharmacokinetic interactions were observed between Tramadol and Promethazine in the present study.

Review of Dextromethorphan 20mg/Quinidine 10mg (NUEDEXTA(®)) for Pseudobulbar Affect.

Pseudobulbar affect (PBA) is a dysfunction of emotional expression characterized by involuntary outbursts of crying or laughing disproportionate or unrelated to mood, occurring in patients with various underlying neurologic disorders. This review describes the clinical data supporting dextromethorphan (DM) hydrobromide combined with quinidine sulfate (Q) as treatment of PBA and briefly surveys the ongoing debates concerning the terminology for dysfunction of emotional expression, as well as the ongoing searches for its brain substrates. Until recently, pharmacologic intervention consisted chiefly of off-label antidepressants. In October 2010, however, DM/Q at 20/10 mg twice daily received approval from the United States Food and Drug Administration for PBA in any setting, and in June 2013, dosages of 20/10 and 30/10 mg twice daily (labeled as 15/9 and 23/9 mg, respectively, DM/Q base) received approval from the European Medicines Agency. DM is an uncompetitive N-methyl-d-aspartate (NMDA) glutamate receptor antagonist, a sigma-1 receptor agonist, and a serotonin and norepinephrine reuptake inhibitor. To block DM hepatic metabolism, thereby increasing DM bioavailability, Quinidine, a cytochrome P450 2D6 inhibitor, is coadministered at a dosage well below those for treating cardiac arrhythmia. Three large-scale DM/Q trials have utilized PBA-episode counts and the Center for Neurologic Study-Lability Scale (CNS-LS), a validated PBA rating scale, to measure efficacy. In a 4-week study of patients with PBA in amyotrophic lateral sclerosis (ALS), DM/Q 30/30 mg was superior to its component drugs. A 12-week, double-blind, placebo-controlled study of DM/Q 30/30 mg showed similar efficacy in patients with PBA in multiple sclerosis (MS). A subsequent 12-week study of patients with PBA and ALS or MS showed superiority to placebo for the 20/10 and 30/10 mg doses. Efficacy was maintained during a 12-week, open-label extension (30/10 mg dose), with further improvement of mean CNS-LS scores. Across these studies, DM/Q was generally safe and well tolerated, with no evidence of clinically relevant cardiac or respiratory effects. DM/Q is being studied (currently unapproved) for conditions including agitation in autism and in dementia.Electronic supplementary materialThe online version of this article (doi:10.1007/s40120-014-0018-5) contains supplementary material, which is available to authorized users.

Involvement of sigma-1 receptors in the antidepressant-like effects of dextromethorphan.

Dextromethorphan is an antitussive with a high margin of safety that has been hypothesized to display rapid-acting antidepressant activity based on pharmacodynamic similarities to the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine. In addition to binding to NMDA receptors, dextromethorphan binds to sigma-1 (σ1) receptors, which are believed to be protein targets for a potential new class of antidepressant medications. The purpose of this study was to determine whether dextromethorphan elicits antidepressant-like effects and the involvement of σ1 receptors in mediating its antidepressant-like actions. The antidepressant-like effects of dextromethorphan were assessed in male, Swiss Webster mice using the forced swim test. Next, σ1 receptor antagonists (BD1063 and BD1047) were evaluated in conjunction with dextromethorphan to determine the involvement of σ receptors in its antidepressant-like effects. Quinidine, a cytochrome P450 (CYP) 2D6 inhibitor, was also evaluated in conjunction with dextromethorphan to increase the bioavailability of dextromethorphan and reduce exposure to additional metabolites. Finally, saturation binding assays were performed to assess the manner in which dextromethorphan interacts at the σ1 receptor. Our results revealed dextromethorphan displays antidepressant-like effects in the forced swim test that can be attenuated by pretreatment with σ1 receptor antagonists, with BD1063 causing a shift to the right in the dextromethorphan dose response curve. Concomitant administration of quinidine potentiated the antidepressant-like effects of dextromethorphan. Saturation binding assays revealed that a Ki concentration of dextromethorphan reduces both the Kd and the Bmax of [3H](+)-pentazocine binding to σ1 receptors. Taken together, these data suggest that dextromethorphan exerts some of its antidepressant actions through σ1 receptors.

Multivariate Modeling of Cytochrome P450 Enzymes for 4- Aminoquinoline Antimalarial Analogues using Genetic- Algorithms Multiple Linear Regression

Purpose: To develop QSAR modeling of the inhibition of cytochrome P450s (CYPs) by chloroquine and a new series of 4-aminoquinoline derivatives in order to obtain a set of predictive in-silico models using genetic algorithms-multiple linear regression (GA-MLR) methods. Methods: Austin model 1 (AM1) semi-empirical quantum chemical calculation method was used to find the optimum 3D geometry of the studied molecules. The relevant molecular descriptors were selected by genetic algorithm-based multiple linear regression (GA-MLR) approach. In silico predictive models were generated to predict the inhibition of CYP 2B6, 2C9, 2C19, 2D6, and 3A4 isoforms using a set of descriptors. Results: The results obtained demonstrate that our model is capable of predicting the potential of new drug candidates to inhibit multiple CYP isoforms. A cross-validated Q 2 test and external validation showed that the models were robust. By inspection of R 2 pred , and RMSE test sets, it can be seen that the predictive ability of the different CYP models varies considerably. Conclusion : Apart from insights into important molecular properties for CYP inhibition, the findings may also guide further investigations of novel drug candidates that are unlikely to inhibit multiple CYP sub-types. Keywords : Antimalarial, Chloroquine, Cytochrome P450, Genetic algorithm-based multiple linear regression, QSAR.

Observations on the Urine Metabolic Profile of Codeine in Pain Patients

This retrospective data analysis explored the relationship between codeine and its metabolites morphine, hydrocodone and hydromorphone. The objectives were: (i) to determine urine concentrations and mole fractions of codeine and metabolites and (ii) to examine the effect of cytochrome P450 (CYP) 2D6 inhibition on metabolite mole fractions. De-identified urine specimens were collected between September 2010 and July 2011 and analyzed using LC-MS-MS to determine codeine, morphine, hydrocodone and hydromorphone concentrations. Geometric mean urine concentrations were 0.833, 0.085 and 0.055 for morphine, hydrocodone and hydromorphone, respectively. Mole fractions were 0.23, 0.025 and 0.014 for morphine, hydrocodone and hydromorphone, respectively. The fraction of excreted codeine in the urine increased (slope = 0.06 ± .01, R² = 0.02) with total moles. As the total amount of codeine and metabolites increased, the fraction of codeine increased, while the fraction of active metabolites decreased. CYP2D6 inhibition with paroxetine, fluoxetine, bupropion and methadone significantly decreased the fraction of morphine excreted. The prevalence of codeine metabolism to morphine was considerably higher than codeine to hydrocodone. The urine concentration of codeine excreted was the greatest, followed by morphine and hydrocodone. Subjects should be monitored during concomitant use of codeine and CYP2D6 inhibitors as this affects the amount of morphine metabolite formation.

Identification of Key Licorice Constituents Which Interact with Cytochrome P450: Evaluation by LC/MS/MS Cocktail Assay and Metabolic Profiling

Licorice has been shown to affect the activities of several cytochrome P450 enzymes. This study aims to identify the key constituents in licorice which may affect these activities. Bioactivity assay was combined with metabolic profiling to identify these compounds in several complex licorice extracts. Firstly, the inhibition potencies of 40 pure licorice compounds were tested using an liquid chromatography/tandem mass spectrometry cocktail method. Significant inhibitors of human P450 isozymes 1A2, 2C9, 2C19, 2D6, and 3A4 were then selected for examination of their structural features by molecular docking to determine their molecular interaction with several P450 isozymes. Based on the present in vitro inhibition findings, along with our previous in vivo metabolic studies and the prevalence of individual compounds in licorice extract, we identified several licorice constituents, viz., liquiritigenin, isoliquiritigenin, together with seven isoprenylated flavonoids and arylcoumarins, which could be key components responsible for the herb-drug interaction between cytochrome P450 and licorice. In addition, hydrophilic flavonoid glycosides and saponins may be converted into these P450 inhibitors in vivo. These studies represent a comprehensive examination of the potential effects of licorice components on the metabolic activities of P450 enzymes.

Abstract C83: Nonclinical in vitro ADME, disposition, and pharmacokinetic assessment of ARQ 092, a selective AKT inhibitor.

Abstract Introduction: ARQ 092 is a potent and selective pan-AKT inhibitor currently in Phase 1 clinical studies for the treatment of advanced solid tumors. Here, we present preclinical in vitro drug-drug interaction, metabolism, disposition, and pharmacokinetic studies with ARQ 092. Methods: ARQ 092 was assessed in vitro for cross-species metabolic stability; CYP450 (cytochrome P450) and UGT (UDP-glucuronosyltransferase) reaction phenotyping; CYP450 inhibition/induction; Caco-2 absorption and efflux; and P-gp (P-glycoprotein), BCRP (Breast Cancer Resistance Protein), and MRP2 (Multidrug Resistance-associated Protein 2) mediated ATPase stimulation. Distribution of ARQ 092 to various tissues was measured after single and repeat dosing to mice as well as pharmacokinetics in mice, rats, and monkeys. Results: Cross-species NADPH-dependent metabolism studies revealed that ARQ 092 metabolism was highly species dependent with ARQ 092 being most stable in rat and human liver microsomes (t1/2 &amp;gt; 52 min) and least stable in mouse, dog, and monkey liver microsomes (t1/2 &amp;gt; 13-33 min). Reaction phenotyping with CYP450 and UGT isozymes and CYP450 inhibitors/antibodies indicated that CYP2D6, CYP3A, UGT1A4, and possibly CYP2C9 are involved in ARQ 092 metabolism. ARQ 092 inhibited CYP2D6, 2C9, and 2C19 in HLM with IC50 values of 10.2, 3.0, and 4.0 µM, respectively, but had little activity against other isozymes tested; and no induction of CYP3A, 2B6, or 1A2 was observed. Based on these in vitro results, interactions with CYP3A4, 2D6, CYP2C9, or CYP2C19 substrates and/or inhibitors in the clinic are possible. Caco-2 and ATPase transporter studies showed that ARQ 092 was highly permeable with little efflux in Caco-2 monolayers but may be an inhibitor/substrate of P-gp and mutant BCRP. Oral bioavailability values of 23, 62, and 50% were determined in mice, rats, and monkeys, respectively, with half-lives ranging widely from 1.6 to 13.6 hrs with iv dosing and 4.3 to 16.6 hrs with po dosing. In mice, ARQ 092 was highly distributed to tissues with liver, lung, and kidney having the highest concentrations. This result correlates with the high volume of distribution of the compound in mice of 24.5 L/kg. In toxicokinetic studies, increases in Cmax and AUC were generally greater than dose proportional with repeat dosing and accumulation was observed in rats but not monkeys. Conclusion: Collectively, these data indicate that ARQ 092 has sufficient oral bioavailability to advance into clinical testing. However, the potential for drug-drug interactions with ARQ 092 in the clinic will need to be investigated further. Additionally, careful selection of dosing regimens for ARQ 092 may be crucial based on the high volume of distribution and accumulation observed preclinically. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C83. Citation Format: Laurie P. Volak, Karen R. Bresciano, Terence Hall, David Vensel, Jean-Marc Lapierre, Inese Smukste, David K. McKearn, Ronald E. Savage. Nonclinical in vitro ADME, disposition, and pharmacokinetic assessment of ARQ 092, a selective AKT inhibitor. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C83.