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Purpose: Limited information is available regarding the drug–drug interaction (DDI) potential of molecular targeted agents and rituximab plus cyclophosphamide, doxorubicin (hydroxydaunorubicin), vincristine (Oncovin), and prednisone (R-CHOP) therapy. The addition of the Bruton tyrosine kinase (BTK) inhibitor ibrutinib to R-CHOP therapy results in increased toxicity versus R-CHOP alone, including higher incidence of peripheral neuropathy. Vincristine is a substrate of P-glycoprotein (P-gp, ABCB1); drugs that inhibit P-gp could potentially cause increased toxicity when co-administered with vincristine through DDI. While the combination of the BTK inhibitor acalabrutinib and R-CHOP is being explored clinically, the DDI potential between these therapies is unknown. Methods: A human mechanistic physiology-based pharmacokinetic (PBPK) model of vincristine following intravenous dosing was developed to predict potential DDI interactions with combination therapy. In vitro absorption, distribution, metabolism, and excretion and in vivo clinical PK parameters informed PBPK model development, which was verified by comparing simulated vincristine concentrations with observed clinical data. Results: While simulations suggested no DDI between vincristine and ibrutinib or acalabrutinib in plasma, simulated vincristine exposure in muscle tissue was increased in the presence of ibrutinib but not acalabrutinib. Extrapolation of the vincristine mechanistic PBPK model to other P-gp substrates further suggested DDI risk when ibrutinib (area under the concentration–time curve [AUC] ratio: 1.8), but not acalabrutinib (AUC ratio: 0.92), was given orally with venetoclax or digoxin. Conclusion: Overall, these data suggest low DDI risk between acalabrutinib and P-gp substrates with negligible increase in the potential risk of vincristine-induced peripheral neuropathy when acalabrutinib is added to R-CHOP therapy. [ABSTRACT FROM AUTHOR]

Regulation of gene expression by the aryl hydrocarbon (AHR) receptor is a much-studied pathway of molecular toxicology. Activation of AHR by the xenobiotic ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is hypothesized as the mechanism by which TCDD exerts its toxic and carcinogenic effects. Paradoxically, some studies have shown that TCDD acts as an antiestrogen. This has led to the hypothesis that so-called selective aryl hydrocarbon receptor modulators (SAhRMs), AHR ligands that retain the antiestrogenic effects but lack the transcriptional effects of TCDD associated with toxicity, may be utilized as cancer chemotherapeutics in conjunction with other antiestrogenic compounds such as tamoxifen. The present study attempts to further define the molecular mechanism of action of the putative SAhRMs, 6-alkyl-1,3,8-trichlorodibenzofuran (6-MCDF), and diindolylmethane (DIM), focusing particularly on the former. We tested 6-MCDF and DIM for the recruitment of AHR and RNA polymerase II (pol II) to the regulatory region of the AHR responsive gene, cytochrome P4501A1 (CYP1A1), using the chromatin immunoprecipitation (ChIP) assay in the mouse hepatoma cell line Hepa-1c1c7 (Hepa-1). We also tested the level of CYP1A1 induction in Hepa-1 cells using quantitative real-time PCR. We show no difference in the recruitment of AHR or pol II to the regulatory region of CYP1A1 in response to TCDD, 6-MCDF, or co-treatment with both TCDD and 6-MCDF. Our results also show no antagonism of CYP1A1 induction with co-treatment of Hepa-1 cells with TCDD and 6-MCDF. These data suggest that 6-MCDF exhibits agonist activity with respect to induction of CYP1A1 in the Hepa-1 cell line. [Copyright &y& Elsevier]

Genetic polymorphism in N-acetyltransferase-1 (NAT1) is associated with increased risk of various cancers, but epidemiological investigations are compromised by poor understanding of the relationship between NAT1 genotype and phenotype. Human reference NAT1*4 and 12 known human NAT1 allelic variants possessing nucleotide polymorphisms in the NAT1 coding region were cloned and expressed in yeast (Schizosaccharomyces pombe). Large reductions in the N-acetylation of 4-aminobiphenyl and the O-acetylation of N-hydroxy-2-aminofluorene were observed for recombinant NAT1 allozymes encoded by NAT1*14B, NAT1*15, NAT1*17, NAT1*19, and NAT1*22. Each of these alleles exhibited substantially lower expression of NAT1 protein than the reference NAT1*4 and the other NAT1 alleles. These results show an important effect of the NAT1 genetic polymorphism on the N- and O-acetylation of arylamine carcinogens, suggesting modification of cancer susceptibility following exposures to arylamine carcinogens. [Copyright &y& Elsevier]

A screening method is described for the detection of urinary bladder tumors in Syrian hamsters. The urinary bladder is removed, stained with 0.2% methylene blue in sodium phosphate buffer, pinned out flat, and fixed for 1 h in 4% paraformaldehyde in sodium phosphate buffer. The urinary bladder is examined with a dissecting microscope for the presence of stained and/or irregular areas and nodules, which are subjected to histological analysis. The screening method may reduce the possibility of missing small lesions with regular gross examination or the need to examine over 100 slides per animal. [ABSTRACT FROM AUTHOR]

Anticancer efficacy is driven not only by dose but also by frequency and duration of treatment. We describe a multiscale model combining cell cycle, cellular heterogeneity of B‐cell lymphoma 2 family proteins, and pharmacology of AZD5991, a potent small‐molecule inhibitor of myeloid cell leukemia 1 (Mcl‐1). The model was calibrated using in vitro viability data for the MV‐4‐11 acute myeloid leukemia cell line under continuous incubation for 72 hours at concentrations of 0.03–30 μM. Using a virtual screen, we identified two schedules as having significantly different predicted efficacy and showed experimentally that a "short" schedule (treating cells for 6 of 24 hours) is significantly better able to maintain the rate of cell kill during treatment than a "long" schedule (18 of 24 hours). This work suggests that resistance can be driven by heterogeneity in protein expression of Mcl‐1 alone without requiring mutation or resistant subclones and demonstrates the utility of mathematical models in efficiently identifying regimens for experimental exploration. [ABSTRACT FROM AUTHOR]

During drug discovery and prior to the first human dose of a novel candidate drug, the pharmacokinetic (PK) behavior of the drug in humans is predicted from preclinical data. This helps to inform the likelihood of achieving therapeutic exposures in early clinical development. Once clinical data are available, the observed human PK are compared with predictions, providing an opportunity to assess and refine prediction methods. Application of best practice in experimental data generation and predictive methodologies, and a focus on robust mechanistic understanding of the candidate drug disposition properties before nomination to clinical development, have led to maximizing the probability of successful PK predictions so that 83% of AstraZeneca drug development projects progress in the clinic with no PK issues; and 71% of key PK parameter predictions [64% of area under the curve (AUC) predictions; 78% of maximum concentration (C max) predictions; and 70% of half-life predictions] are accurate to within twofold. Here, we discuss methods to predict human PK used by AstraZeneca, how these predictions are assessed and what can be learned from evaluating the predictions for 116 candidate drugs. It is now universally recognized that an acceptable human PK profile increases the probability of a candidate drug becoming a successful therapy. A variety of tools are available to predict human PK behavior in advance of clinical data, including scaling clearance from in vitro metabolic stability data, and physiologically based scaling of volume of distribution. To improve PK prediction methods, it is crucial to continually assess the performance of predictions with first-time-in-human PK data for new candidate drugs. To date, AstraZeneca have compared observed PK to predictions for 116 candidate drugs, and since the launch of our five-dimensional framework in 2011, we have driven sustained improvements in the quality of PK predictions. [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate the pharmacokinetic profile after different subcutaneous (s.c.) administrations of nano- and microparticle suspensions of griseofulvin to mice. The solubility of the compound was determined as approximately 40 µM, at 37 °C, independent of particle size, stabilizer mixtures investigated and solvent used for measurement. The present in vivo studies demonstrated non-linear absorption kinetics (in peak concentration, C max) for griseofulvin up to 50 mg/kg after s.c. administration of nanocrystals and microsuspensions but linear increase in area under the curve (AUC) at all occasions investigated. C max was higher for smaller particles administered. Both investigated suspensions, at 10 and 50 mg/kg, showed significantly sustained plasma profiles compared to i.v. and p.o. administration. Administering 10 and 50 mg/kg of griseofulvin nanocrystals as 10 mL/kg, instead of 2.5 mL/kg, improved C max but AUC was unchanged. The present study showed that the bioavailability of griseofulvin, administered as nano- and microparticles, increased significantly after s.c. administration (60–100%) compared with p.o. dosing (17%). The drug is currently orally administered and clearly exposed to a significant first pass metabolism, i.e. an ideal candidate for an alternative administration route, like s.c. injection. [ABSTRACT FROM AUTHOR]

Abstract Adenosine is known to be an important signaling molecule in many physiological processes and has recently been shown to be an important molecule in oncology. A fit for purpose method has been developed for the quantification of adenosine in murine tumor samples using pre-column derivatization and liquid chromatography-mass spectrometry (LC-MS/MS). To overcome adenosine quantification challenges, derivatization with dansyl chloride was employed. This derivatization technique, following protein precipitation and liquid-liquid extraction, improved the sensitivity and selectivity of adenosine in tumor samples through the reduction of endogenous interference and matrix effects. This method utilizes a mouse plasma calibration curve, qualified over a range of 0.019 μM–37 μM. The 15 min derivatization incubation time and 1 min chromatographic run time allow for higher throughput. The following established method overcomes challenges associated with the quantification of low molecular weight, polar, endogenous molecules, such as adenosine, using derivatization and LC-MS/MS. With the additional analysis of murine tumors, this method will contribute to the understanding of the impact adenosine plays in the tumor microenvironment and the bearing it has on targeted cancer therapies. Highlights • Novel derivatization and LC-MS/MS method for quantifying adenosine in tissues. • Derivatization successfully stabilizes adenosine from degradation post extraction. • Rapid adenosine degradation in tissues, half-life of seconds to minutes observed. • Concentrations of adenosine vary in tumors, driving a need for characterization. [ABSTRACT FROM AUTHOR]

Here we report on novel, potent 3,3-dimethyl substituted N -aryl piperidine inhibitors of microsomal prostaglandin E synthases-1(mPGES-1). Example 14 potently inhibited PGE 2 synthesis in an ex vivo human whole blood (HWB) assay with an IC 50 of 7 nM. In addition, 14 had no activity in human COX-1 or COX-2 assays at 30 μM, and failed to inhibit human mPGES-2 at 62.5 μM in a microsomal prep assay. These data are consistent with selective mPGES-1-mediated reduction of PGE 2 . In dog, 14 had oral bioavailability (74%), clearance (3.62 mL/(min*kg)) and volume of distribution ( V d,ss = 1.6 L/kg) values within our target ranges. For these reasons, 14 was selected for further study. [ABSTRACT FROM AUTHOR]

1. Idasanutlin (RG7388) is a potent p53-MDM2 antagonist currently in clinical development for treatment of cancer. The purpose of the present studies was to investigate the cause of marked decrease in plasma exposure after repeated oral administration of RG7388 in monkeys and whether the autoinduction observed in monkeys is relevant to humans. 2. In monkey liver and intestinal microsomes collected after repeated oral administration of RG7388 to monkeys, significantly increased activities of homologue CYP3A8 were observed (ex vivo). Investigation using a physiologically based pharmacokinetic (PBPK) model suggested that the loss of exposure was primarily due to induction of metabolism in the gut of monkeys. 3. Studies in monkey and human primary hepatocytes showed that CYP3A induction by RG7388 only occurred in monkey hepatocytes but not in human hepatocytes, which suggests the observed CYP3A induction is monkey specific. 4. The human PK data obtained from the first cohorts confirmed the lack of relevant induction as predicted by the human hepatocytes and the PBPK modelling based on no induction in humans. [ABSTRACT FROM PUBLISHER]

TheIAPs are key regulators of the apoptotic pathways and are commonlyoverexpressed in many cancer cells. IAPs contain one to three BIRdomains that are crucial for their inhibitory function. The pro-survivalproperties of XIAP come from binding of the BIR domains to the pro-apoptoticcaspases. The BIR3 domain of XIAP binds and inhibits caspase 9, whilethe BIR2 domain binds and inhibits the terminal caspases 3 and 7.While XIAP BIR3 inhibitors have previously been reported, they alsoinhibit cIAP1/2 and promote the release of TNFα, potentiallylimiting their therapeutic utility. This paper will focus on the optimizationof selective XIAP BIR2 inhibitors leading to the discovery of highlypotent benzodiazepinone 36(IC50= 45 nM),which has high levels of selectivity over XIAP BIR3 and cIAP1 BIR2/3and shows efficacy in a xenograft pharmacodynamic model monitoringcaspase activity while not promoting the release of TNFα invitro. [ABSTRACT FROM AUTHOR]

XIAP is a key regulator of apoptosis,and its overexpression incancer cells may contribute to their survival. The antiapoptotic functionof XIAP derives from its BIR domains, which bind to and inhibit pro-apoptoticcaspases. Most known IAP inhibitors are selective for the BIR3 domainand bind to cIAP1 and cIAP2 as well as XIAP. Pathways activated uponcIAP binding contribute to the function of these compounds. Inhibitorsselective for XIAP should exert pro-apoptotic effects through competitionwith the terminal caspases. This paper details our synthetic explorationsof a novel XIAP BIR2-selective benzazepinone screening hit with afocus on increasing BIR2 potency and overcoming high in vivo clearance.These efforts led to the discovery of benzoxazepinone 40, a potent BIR2-selective inhibitor with good in vivo pharmacokineticproperties which potentiates apoptotic signaling in a manner mechanisticallydistinct from that of known pan-IAP inhibitors. [ABSTRACT FROM AUTHOR]

Lysophosphatidic acid is a class of bioactive phospholipidthatmediates most of its biological effects through LPA receptors, ofwhich six isoforms have been identified. The recent results from LPA1knockout mice suggested that blocking LPA1 signaling could providea potential novel approach for the treatment of idiopathic pulmonaryfibrosis. Here, we report the design and synthesis of pyrazole- andtriazole-derived carbamates as LPA1-selective and LPA1/3 dual antagonists.In particular, compound 2, the most selective LPA1 antagonistreported, inhibited proliferation and contraction of normal humanlung fibroblasts (NHLF) following LPA stimulation. Oral dosing ofcompound 2to mice resulted in a dose-dependent reductionof plasma histamine levels in a murine LPA challenge model. Furthermore,we applied our novel antagonists as chemistry probes and investigatedthe contribution of LPA1/2/3 in mediating the pro-fibrotic responses.Our results suggest LPA1 as the major receptor subtype mediating LPA-inducedproliferation and contraction of NHLF. [ABSTRACT FROM AUTHOR]

During routine safety evaluation of RO2910, a non-nucleoside reverse transcriptase inhibitor for HIV infection, histopathology findings concurrent with robust hepatocellular induction occurred in multiple organs, including a unique, albeit related, finding in the pituitary gland. For fourteen days, male and female rats were administered, by oral gavage vehicle, 100, 300, or 1000 mg/kg/day of RO2910. Treated groups had elevated serum thyroid-stimulating hormone and decreased total thyroxine, and hypertrophy in the liver, thyroid gland, and pituitary pars distalis. These were considered consequences of hepatocellular induction and often were dose dependent and more pronounced in males than in females. Hepatocellular centrilobular hypertrophy corresponded with increased expression of cytochrome P450s 2B1/2, 3A1, and 3A2 and UGT 2B1. Bilateral thyroid follicular cell hypertrophy occurred concurrent to increased mitotic activity and sometimes colloid depletion, which were attributed to changes in thyroid hormone levels. Males had hypertrophy of thyroid-stimulating hormone–producing cells (thyrotrophs) in the pituitary pars distalis. All findings were consistent with the well-established adaptive physiologic response of rodents to xenobiotic-induced hepatocellular microsomal enzyme induction. Although the effects on the pituitary gland following hepatic enzyme induction-mediated hypothyroidism have not been reported previously, other models of stress and thyroid depletion leading to pituitary stimulation support such a shared pathogenesis. [ABSTRACT FROM PUBLISHER]

1. The involvement of cytochrome P450 2B6 (CYP2B6) to the in vitro and in vivo metabolism of bupropion has been well studied. In these investigations we performed a detailed in vitro phenotyping study to characterize isoforms other than CYP2B6. 2. A total of nine metabolites were identified (M1-M9) in the incubations with cDNA-expressed P450s (rhCYP) and human liver microsomes (HLM). 3. Incubations in rhCYP identified CYP2B6 as the isoform responsible for the formation of hydroxybupropion (M3). CYP2C19 was involved in bupropion metabolism primarily through alternate hydroxylation pathways (M4-M6) with higher activity at lower substrate concentrations, near 1 μM. 4. The results from HLM inhibition studies using CYP2B6 and CYP2C19 inhibitory antibodies indicated that CYP2B6 contributed to approximately 90% of M3 formation, and CYP2C19 contributed to approximately 70-90% of M4, M5, and M6 formation. 5. Studies using single donor HLM with varying degrees of CYP2B6 and CYP2C19 activities showed a good relationship between M3 formation and CYP2B6 activity and M4/M5 formation and CYP2C19 activity. 6. These results confirmed the principle role of CYP2B6 in hydroxybupropion formation, as a selective CYP2B6 probe. In addition, the new findings revealed that CYP2C19 also contributes to bupropion metabolism through alternate hydroxylation pathways. [ABSTRACT FROM AUTHOR]