Considerations from the Innovation and Quality Induction Working Group in Response to Drug-Drug Interaction Guidance from Regulatory Agencies: Guidelines on Model Fitting and Recommendations on Time Course for In Vitro Cytochrome P450 Induction Studies Including Impact on Drug Interaction Risk Assessment.

Translational and ADME Sciences Leadership Group Induction Working Group (IWG) presents an analysis on the time course for cytochrome P450 induction in primary human hepatocytes. Induction of CYP1A2, CYP2B6, and CYP3A4 was evaluated by seven IWG laboratories after incubation with prototypical inducers (omeprazole, phenobarbital, rifampicin, or efavirenz) for 6-72 hours. The effect of incubation duration and model-fitting approaches on induction parameters (E and EC) and drug-drug interaction (DDI) risk assessment was determined.

Discovery and in Vivo Evaluation of Macrocyclic Mcl-1 Inhibitors Featuring an α-Hydroxy Phenylacetic Acid Pharmacophore or Bioisostere.

Overexpression of the antiapoptotic protein Mcl-1 provides a survival advantage to some cancer cells, making inhibition of this protein an attractive therapeutic target for the treatment of certain types of tumors. Herein, we report our efforts toward the identification of a novel series of macrocyclic Mcl-1 inhibitors featuring an α-hydroxy phenylacetic acid pharmacophore or bioisostere. This work led to the discovery of , a potent Mcl-1 inhibitor (IC = 19 nM in an OPM-2 cell viability assay) with good pharmacokinetic properties and excellent in vivo efficacy in an OPM-2 multiple myeloma xenograft model.

Development of a mass spectrometry-based tryptophan 2, 3-dioxygenase assay using liver cytosol from multiple species.

A novel and rapid method to determine the potency of inhibitors for tryptophan 2, 3-dioxygenase (TDO2) activities in human and preclinical species was successfully developed and validated utilizing LC-MS/MS. Previously reported TDO2 activity assays are resource intensive, requiring cloning and overexpression of TDO2. Here, we demonstrated that liver cytosol contained sufficient active TDO2 for evaluating the potency of TDO2 inhibitors across multiple species.

Single concentration loss of activity assay provides an improved assessment of drug-drug interaction risk compared to IC50-shift.

1. The utility of two abbreviated, higher-throughput assays [IC50-shift and the loss of activity (LOA) assay] to evaluate time-dependent inhibition (TDI) of 24 structurally related compounds was compared. 2.

Solving time-dependent CYP3A4 inhibition for a series of indole-phenylacetic acid dual antagonists of the PGD(2) receptors CRTH2 and DP.

Based on their structural similarity to previously described compound AMG 009, indole-phenyl acetic acids were proposed to be potent dual inhibitors of chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2 or DP2) and prostanoid D receptor (DP or DP1). This series was equipotent to AMG 009 in binding assays against both receptors but exhibited decreased serum shift. We discovered early in the optimization of these indole-phenylacetic acid compounds that they demonstrated CYP3A4 time-dependent inhibition (TDI).

Sequential metabolism of AMG 487, a novel CXCR3 antagonist, results in formation of quinone reactive metabolites that covalently modify CYP3A4 Cys239 and cause time-dependent inhibition of the enzyme.

CYP3A4-mediated biotransformation of (R)-N-(1-(3-(4-ethoxyphenyl)-4-oxo-3,4-dihydropyrido[2,3-d]pyrimidin-2-yl)ethyl)-N-(pyridin-3-ylmethyl)-2-(4-(trifluoromethoxy)phenyl)acetamide (AMG 487) was previously shown to generate an inhibitory metabolite linked to dose- and time-dependent pharmacokinetics in humans. Although in vitro activity loss assays failed to demonstrate CYP3A4 time-dependent inhibition (TDI) with AMG 487, its M2 phenol metabolite readily produced TDI when remaining activity was assessed using either midazolam or testosterone (K(I) = 0.73-0.

Prediction of drug-drug interactions arising from mechanism-based inactivation: key input parameters and impact on risk assessment.

As the prevalence of polypharmacy increases with our aging population, the propensity for adverse drug-drug interactions arising from the altered metabolism of co-administered medicines remains an important consideration for drug development. Mechanism-based inactivation (MBI) of the cytochrome P450 enzyme system is responsible for many clinically relevant drug-drug interactions (DDIs) due to the irreversible and long-lasting effects of the enzyme inactivation. Unlike competitive inhibition, MBI persists after the inactivator has been cleared from the system, since de novo enzyme synthesis is required to restore metabolic activity.

Bioactivation of a novel 2-methylindole-containing dual chemoattractant receptor-homologous molecule expressed on T-helper type-2 cells/D-prostanoid receptor antagonist leads to mechanism-based CYP3A inactivation: glutathione adduct characterization and prediction of in vivo drug-drug interaction.

The 2-methyl substituted indole, 2MI [2-(4-(4-(2,4-dichlorophenylsulfonamido)-2-methyl-1H-indol-5-yloxy)-3-methoxyphenyl)acetic acid] is a potent dual inhibitor of 1) chemoattractant receptor-homologous molecule expressed on T-helper type-2 cells and 2) d-prostanoid receptor. During evaluation as a potential treatment for asthma and allergic rhinitis, 2MI was identified as a mechanism-based inactivator of CYP3A4 in vitro. The inactivation was shown to be irreversible by dialysis and accompanied by an NADPH-dependent increase in 2MI covalent binding to a 55- to 60-kDa microsomal protein, consistent with irreversible binding to CYP3A4.

An inhibitory metabolite leads to dose- and time-dependent pharmacokinetics of (R)-N-{1-[3-(4-ethoxy-phenyl)-4-oxo-3,4-dihydro-pyrido[2,3-d]pyrimidin-2-yl]-ethyl}-N-pyridin-3-yl-methyl-2-(4-trifluoromethoxy-phenyl)-acetamide (AMG 487) in human subjects after multiple dosing.

(R)-N-{1-[3-(4-Ethoxy-phenyl)-4-oxo-3,4-dihydro-pyrido[2,3-d]-pyrimidin-2-yl]-ethyl}-N-pyridin-3-yl-methyl-2-(4-trifluoromethoxyphenyl)-acetamide (AMG 487) is a potent and selective orally bioavailable chemokine (C-X-C motif) receptor 3 (CXCR3) antagonist that displays dose- and time-dependent pharmacokinetics in human subjects after multiple oral dosing. Although AMG 487 exhibited linear pharmacokinetics on both days 1 and 7 at the 25-mg dose, dose- and time-dependent kinetics were evident at the two higher doses. Nonlinear kinetics were more pronounced after multiple dosing.