Implementation of whole-exome sequencing for pharmacogenomics profiling and exploring its potential clinical utilities.

Whole-exome sequencing (WES) is widely used in clinical settings; however, the exploration of its use in pharmacogenomic analysis remains limited. Our study compared the variant callings for 28 core absorption, distribution, metabolism and elimination genes by WES and array-based technology using clinical trials samples. The results revealed that WES had a positive predictive value of 0.71-0.92 and a sensitivity of single-nucleotide variants between 0.68 and 0.95, compared with array-based technology, for the variants in the commonly targeted regions of the WES and PhamacoScan™ assay. Besides the common variants detected by both assays, WES identified 200-300 exclusive variants per sample, totalling 55 annotated exclusive variants, including important modulators of metabolism such as rs2032582 (ABCB1) and rs72547527 (SULT1A1). This study highlights the potential clinical advantages of using WES to identify a wider range of genetic variations and enabling precision medicine.

A phase I study of ATR inhibitor gartisertib (M4344) as a single agent and in combination with carboplatin in patients with advanced solid tumours.

BACKGROUND: Gartisertib is an oral inhibitor of ataxia telangiectasia and Rad3-related protein (ATR), a key kinase of the DNA damage response. We aimed to determine the safety and tolerability of gartisertib ± carboplatin in patients with advanced solid tumours. METHODS: This phase I open-label, multicenter, first-in-human study comprised four gartisertib cohorts: A (dose escalation [DE]; Q2W); A2 (DE; QD/BID); B1 (DE+carboplatin); and C (biomarker-selected patients). RESULTS: Overall, 97 patients were enroled into cohorts A (n = 42), A2 (n = 26), B1 (n = 16) and C (n = 13). The maximum tolerated dose and recommended phase II dose (RP2D) were not declared for cohorts A or B1. In cohort A2, the RP2D for gartisertib was determined as 250 mg QD. Gartisertib was generally well-tolerated; however, unexpected increased blood bilirubin in all study cohorts precluded further DE. Investigations showed that gartisertib and its metabolite M26 inhibit UGT1A1-mediated bilirubin glucuronidation in human but not dog or rat liver microsomes. Prolonged partial response (n = 1 [cohort B1]) and stable disease >6 months (n = 3) did not appear to be associated with biomarker status. Exposure generally increased dose-dependently without accumulation. CONCLUSION: Gartisertib was generally well-tolerated at lower doses; however, unexpected liver toxicity prevented further DE, potentially limiting antitumour activity. Gartisertib development was subsequently discontinued. CLINICALTRIALS: GOV: NCT02278250.

Evobrutinib pathway to its major metabolite M463-2 and insights from a biotransformation and DDI perspective.

Evobrutinib is a highly selective, covalent, central nervous system-penetrant Bruton's tyrosine kinase (BTK) inhibitor, currently in Phase III trials for the treatment of relapsing multiple sclerosis. One major circulating metabolite of evobrutinib has been previously identified as the racemic dihydro-diol M463-2 (MSC2430422) in a Phase I human mass balance study.Phenotyping experiments were conducted to confirm the metabolic pathway of evobrutinib to M463-2. Ratio of the enantiomers was determined by enantioselective liquid chromatography with tandem mass spectrometry analysis of plasma samples from humans and preclinical species. Drug-drug interaction (DDI) characterisation, evaluation of pharmacological activity on BTK, and off-target screening experiments followed assessing safety of the metabolite.The biotransformation of evobrutinib to M463-2 was determined to be a two-step process with a CYP-mediated oxidation acting to form an epoxide intermediate, which was further hydrolysed by soluble and mitochondrial epoxide hydrolase. Only the (S)-enantiomer was determined to be a major metabolite, the (R)-enantiomer was minor. In vitro studies demonstrated the (S)-enantiomer lacked clinically relevant pharmacological activity, off-target effects and DDIs.The biotransformation of evobrutinib to its major metabolite has been elucidated, with the major (S)-enantiomer being shown to pose no on/off target or DDI risks.

Challenges and Opportunities for In Vitro-In Vivo Extrapolation of Aldehyde Oxidase-Mediated Clearance: Toward a Roadmap for Quantitative Translation.

Underestimation of aldehyde oxidase (AO)-mediated clearance by current in vitro assays leads to uncertainty in human dose projections, thereby reducing the likelihood of success in drug development. In the present study we first evaluated the current drug development practices for AO substrates. Next, the overall predictive performance of in vitro-in vivo extrapolation of unbound hepatic intrinsic clearance (CLint,u) and unbound hepatic intrinsic clearance by AO (CLint,u,AO) was assessed using a comprehensive literature database of in vitro (human cytosol/S9/hepatocytes) and in vivo (intravenous/oral) data collated for 22 AO substrates (total of 100 datapoints from multiple studies). Correction for unbound fraction in the incubation was done by experimental data or in silico predictions. The fraction metabolized by AO (fmAO) determined via in vitro/in vivo approaches was found to be highly variable. The geometric mean fold errors (gmfe) for scaled CLint,u (mL/min/kg) were 10.4 for human hepatocytes, 5.6 for human liver cytosols, and 5.0 for human liver S9, respectively. Application of these gmfe's as empirical scaling factors improved predictions (45%-57% within twofold of observed) compared with no correction (11%-27% within twofold), with the scaling factors qualified by leave-one-out cross-validation. A road map for quantitative translation was then proposed following a critical evaluation on the in vitro and clinical methodology to estimate in vivo fmAO In conclusion, the study provides the most robust system-specific empirical scaling factors to date as a pragmatic approach for the prediction of in vivo CLint,u,AO in the early stages of drug development. SIGNIFICANCE STATEMENT: Confidence remains low when predicting in vivo clearance of AO substrates using in vitro systems, leading to de-prioritization of AO substrates from the drug development pipeline to mitigate risk of unexpected and costly in vivo impact. The current study establishes a set of empirical scaling factors as a pragmatic tool to improve predictability of in vivo AO clearance. Developing clinical pharmacology strategies for AO substrates by utilizing mass balance/clinical drug-drug interaction data will help build confidence in fmAO.

Alternatives to rifampicin: A review and perspectives on the choice of strong CYP3A inducers for clinical drug-drug interaction studies.

N-Nitrosamine (NA) impurities are considered genotoxic and have gained attention due to the recall of several marketed drug products associated with higher-than-permitted limits of these impurities. Rifampicin is an index inducer of multiple cytochrome P450s (CYPs) including CYP2B6, 2C8, 2C9, 2C19, and 3A4/5 and an inhibitor of OATP1B transporters (single dose). Hence, rifampicin is used extensively in clinical studies to assess drug-drug interactions (DDIs). Despite NA impurities being reported in rifampicin and rifapentine above the acceptable limits, these critical anti-infective drugs are available for therapeutic use considering their benefit-risk profile. Reports of NA impurities in rifampicin products have created uncertainty around using rifampicin in clinical DDI studies, especially in healthy volunteers. Hence, a systematic investigation through a literature search was performed to determine possible alternative index inducer(s) to rifampicin. The available strong CYP3A inducers were selected from the University of Washington DDI Database and their in vivo DDI potential assessed using the data from clinical DDI studies with sensitive CYP3A substrates. To propose potential alternative CYP3A inducers, factors including lack of genotoxic potential, adequate safety, feasibility of multiple dose administration to healthy volunteers, and robust in vivo evidence of induction of CYP3A were considered. Based on the qualifying criteria, carbamazepine, phenytoin, and lumacaftor were identified to be the most promising alternatives to rifampicin for conducting CYP3A induction DDI studies. Strengths and limitations of the proposed alternative CYP3A inducers, the magnitude of in vivo CYP3A induction, appropriate study designs for each alternative inducer, and future perspectives are presented in this paper.

Metabolism and Disposition of [14C]Pevonedistat, a First-in-Class NEDD8-Activating Enzyme Inhibitor, after Intravenous Infusion to Patients with Advanced Solid Tumors.

Metabolism and disposition of pevonedistat, an investigational, first-in-class inhibitor of the NEDD8-activating enzyme (NAE), were characterized in patients with advanced solid tumors after intravenous infusion of [14C]pevonedistat at 25 mg/m2 (∼60-85 µCi radioactive dose). More than 94% of the administered dose was recovered, with ∼41% and ∼53% of drug-related material eliminated in urine and feces, respectively. The metabolite profiles of [14C]pevonedistat were established in plasma using an accelerator mass spectrometer and excreta with traditional radiometric analysis. In plasma, unchanged parent drug accounted for approximately 49% of the total drug-related material. Metabolites M1 and M2 were major (>10% of the total drug-related material) circulating metabolites and accounted for approximately 15% and 22% of the drug-related material, respectively. Unchanged [14C]pevonedistat accounted for approximately 4% and 17% of the dose in urine and feces, respectively. Oxidative metabolites M1, M2, and M3 appeared as the most abundant drug-related components in the excreta and represented approximately 27%, 26%, and 15% of the administered dose, respectively. Based on the unbound plasma exposure in cancer patients and in vitro NAE inhibition, the contribution of metabolites M1 and M2 to overall in vivo pharmacological activity is anticipated to be minimal. The exposure to these metabolites was higher at safe and well tolerated doses in rat and dog (the two preclinical species used in toxicology evaluation) plasma than that observed in human plasma. Reaction phenotyping studies revealed that CYP3A4/5 are primary enzymes responsible for the metabolic clearance of pevonedistat. SIGNIFICANCE STATEMENT: This study details the metabolism and clearance mechanisms of pevonedistat, a first-in-class NEDD8-activating enzyme inhibitor, after intravenous administration to patients with cancer. Pevonedistat is biotransformed to two major circulating metabolites with higher exposure in nonclinical toxicological species than in humans. The pharmacological activity contribution of these metabolites is minimal compared to the overall target pharmacological effect of pevonedistat. Renal clearance was not an important route of excretion of unchanged pevonedistat (∼4% of the dose).

Absorption, Distribution, Metabolism, and Excretion of Therapeutic Proteins: Current Industry Practices and Future Perspectives.

Therapeutic proteins (TPs) comprise a variety of modalities, including antibody-based drugs, coagulation factors, recombinant cytokines, enzymes, growth factors, and hormones. TPs usually cannot traverse cellular barriers and exert their pharmacological activity by interacting with targets on the exterior membrane of cells or with soluble ligands in the tissue interstitial fluid/blood. Due to their large size, lack of cellular permeability, variation in metabolic fate, and distinct physicochemical characteristics, TPs are subject to different absorption, distribution, metabolism, and excretion (ADME) processes as compared with small molecules. Limited regulatory guidance makes it challenging to determine the most relevant ADME data required for regulatory submissions. The TP ADME working group was sponsored by the Translational and ADME Sciences Leadership Group within the Innovation and Quality (IQ) consortium with objectives to: (1) better understand the current practices of ADME data generated for TPs across IQ member companies, (2) learn about their regulatory strategies and interaction experiences, and (3) provide recommendations on best practices for conducting ADME studies for TPs. To understand current ADME practices and regulatory strategies, an industry-wide survey was conducted within IQ member companies. In addition, ADME data submitted to the U.S. Food and Drug Administration was also collated by reviewing regulatory submission packages of TPs approved between 2011 and 2020. This article summarizes the key learnings from the survey and an overview of ADME data presented in biologics license applications along with future perspectives and recommendations for conducting ADME studies for internal decision-making as well as regulatory submissions for TPs. SIGNIFICANCE STATEMENT: This article provides comprehensive assessment of the current practices of absorption, distribution, metabolism, and excretion (ADME) data generated for therapeutic proteins (TPs) across the Innovation and Quality participating companies and the utility of the data in discovery, development, and regulatory submissions. The TP ADME working group also recommends the best practices for condu-cting ADME studies for internal decision-making and regulatory submissions.

Current Practices, Gap Analysis, and Proposed Workflows for PBPK Modeling of Cytochrome P450 Induction: An Industry Perspective.

The International Consortium for Innovation and Quality (IQ) Physiologically Based Pharmacokinetic (PBPK) Modeling Induction Working Group (IWG) conducted a survey across participating companies around general strategies for PBPK modeling of induction, including experience with its utility to address various questions, regulatory interactions, and regulatory acceptance. The results highlight areas where PBPK modeling is used with high confidence and identifies opportunities where confidence is lower and further evaluation is needed. To enhance the survey results, the PBPK-IWG also collected case studies and analyzed recent literature examples where PBPK models were applied to predict CYP3A induction-mediated drug-drug interactions. PBPK modeling of induction has evolved and progressed significantly, proving to have great potential to accelerate drug discovery and development. With the aim of enabling optimal use for new molecular entities that are either substrates and/or inducers of CYP3A, the PBPK-IWG proposes initial workflows for PBPK application, discusses future trends, and identifies gaps that need to be addressed.

PBPK modeling to predict drug-drug interactions of ivosidenib as a perpetrator in cancer patients and qualification of the Simcyp platform for CYP3A4 induction.

Ivosidenib is a potent, targeted, orally active, small-molecule inhibitor of mutant isocitrate dehydrogenase 1 (IDH1) that has been approved in the United States for the treatment of adults with newly diagnosed acute myeloid leukemia (AML) who are greater than or equal to 75 years of age or ineligible for intensive chemotherapy, and those with relapsed or refractory AML, with a susceptible IDH1 mutation. Ivosidenib is an inducer of the CYP2B6, CYP2C8, CYP2C9, and CYP3A4 and an inhibitor of P-glycoprotein (P-gp), organic anion transporting polypeptide-1B1/1B3 (OATP1B1/1B3), and organic anion transporter-3 (OAT3) in vitro. A physiologically-based pharmacokinetic (PK) model was developed to predict drug-drug interactions (DDIs) of ivosidenib in patients with AML. The in vivo CYP3A4 induction effect of ivosidenib was quantified using 4ß-hydroxycholesterol and was subsequently verified with the PK data from an ivosidenib and venetoclax combination study. The verified model was prospectively applied to assess the effect of multiple doses of ivosidenib on a sensitive CYP3A4 substrate, midazolam. The simulated midazolam geometric mean area under the curve (AUC) and maximum plasma concentration (Cmax ) ratios were 0.18 and 0.27, respectively, suggesting ivosidenib is a strong inducer. The model was also used to predict the DDIs of ivosidenib with CYP2B6, CYP2C8, CYP2C9, P-gp, OATP1B1/1B3, and OAT3 substrates. The AUC ratios following multiple doses of ivosidenib and a single dose of CYP2B6 (bupropion), CYP2C8 (repaglinide), CYP2C9 (warfarin), P-gp (digoxin), OATP1B1/1B3 (rosuvastatin), and OAT3 (methotrexate) substrates were 0.90, 0.52, 0.84, 1.01, 1.02, and 1.27, respectively. Finally, in accordance with regulatory guidelines, the Simcyp modeling platform was qualified to predict CYP3A4 induction using known inducers and sensitive substrates.

Phase I study assessing the mass balance, pharmacokinetics, and excretion of [14C]-pevonedistat, a NEDD8-activating enzyme inhibitor in patients with advanced solid tumors.

Pevonedistat (TAK-924/MLN4924) is an investigational small-molecule inhibitor of the NEDD8-activating enzyme that has demonstrated preclinical and clinical activity across solid tumors and hematological malignancies. Here we report the results of a phase I trial characterizing the mass balance, pharmacokinetics, and clearance pathways of [14C]-pevonedistat in patients with advanced solid tumors (NCT03057366). In part A (n = 8), patients received a single 1-h intravenous infusion of [14C]-pevonedistat 25 mg/m2. In part B (n = 7), patients received pevonedistat 25 or 20 mg/m2 on days 1, 3, and 5 in combination with, respectively, docetaxel 75 mg/m2 or carboplatin AUC5 plus paclitaxel 175 mg/m2 on day 1 every 3 weeks. Following the single dose of [14C]-pevonedistat 25 mg/m2 in part A, there was a parallel log-linear decline in plasma and whole blood pevonedistat concentration, with systemic exposure of unchanged pevonedistat representing 41% of drug-related material (i.e., unchanged pevonedistat and its metabolites). The mean terminal half-life of pevonedistat and drug-related material in plasma was 8.4 and 15.6 h, respectively. Pevonedistat distributed preferentially in whole blood with a mean whole-blood-to-plasma ratio for pevonedistat AUC∞ of 40.8. By 1 week post dose, the mean recovery of administered radioactivity was 94% (41% in urine and 53% in feces). The pevonedistat safety profile during both study parts was consistent with previous clinical experience, with no new safety signals observed. In part B, pevonedistat in combination with docetaxel or carboplatin plus paclitaxel was generally well tolerated. ClinicalTrials.gov identifier: NCT03057366 .

Pharmacokinetics and Catabolism of [3H]TAK-164, a Guanylyl Cyclase C Targeted Antibody-Drug Conjugate.

TAK-164 is an antibody-drug conjugate (ADC) comprising human anti-guanylyl cyclase C (GCC) monoclonal antibody conjugated to indolinobenzodiazepine DNA alkylator IGN-P1 through a cleavable alanine-alanine dipeptide linker. TAK-164 is currently being evaluated for the treatment of gastrointestinal cancers expressing GCC. The catabolism of TAK-164 was studied using 3H-labeled ADC using GCC-expressing HEK-293 (GCC-HEK-293) cells, rat tritosomes, cathepsin B, and tumor-bearing mice. Time- and target-dependent uptake of [3H]TAK-164 was observed in GCC-HEK-293 cells with approximately 12% of radioactivity associated with DNA after 24 hours of incubation. Rat liver tritosomes and cathepsin B yielded IGN-P1 aniline, sulfonated IGN-P1 (s-IGN-P1) aniline, and a lysine conjugate of IGN-P1 (IGN-P1-Lys) aniline as catabolites. In tumor-bearing mice, [3H]TAK-164 exhibited a terminal half-life of approximately 41 and 51 hours in plasma and blood, respectively, with low plasma clearance (0.75 ml/h per kilogram). The extractable radioactivity in plasma and tumor samples revealed the presence of s-IGN-P1 aniline and IGN-P1 aniline as payload-related components. The use of a radiolabeled payload in the ADC in tumor uptake investigations provided direct and quantitative evidence for tumor uptake, DNA binding, and proof of mechanism of action of the payload. SIGNIFICANCE STATEMENT: Since payload-related species are potent cytotoxins, a thorough characterization of released products of ADCs, metabolites, and their drug interaction potential is necessary prior to clinical investigations. This study characterized in vitro and in vivo DNA binding mechanisms and released products of TAK-164. The methodologies described here will be highly useful for characterization of payload-related products of ADCs in general.

Preclinical Antitumor Activity and Biodistribution of a Novel Anti-GCC Antibody-Drug Conjugate in Patient-derived Xenografts.

Guanylyl cyclase C (GCC) is a unique therapeutic target with expression restricted to the apical side of epithelial cell tight junctions thought to be only accessible by intravenously administered agents on malignant tissues where GCC expression is aberrant. In this study, we sought to evaluate the therapeutic potential of a second-generation investigational antibody-dug conjugate (ADC), TAK-164, comprised of a human anti-GCC mAb conjugated via a peptide linker to the highly cytotoxic DNA alkylator, DGN549. The in vitro binding, payload release, and in vitro activity of TAK-164 was characterized motivating in vivo evaluation. The efficacy of TAK-164 and the relationship to exposure, pharmacodynamic marker activation, and biodistribution was evaluated in xenograft models and primary human tumor xenograft (PHTX) models. We demonstrate TAK-164 selectively binds to, is internalized by, and has potent cytotoxic effects against GCC-expressing cells in vitro A single intravenous administration of TAK-164 (0.76 mg/kg) resulted in significant growth rate inhibition in PHTX models of metastatic colorectal cancer. Furthermore, imaging studies characterized TAK-164 uptake and activity and showed positive relationships between GCC expression and tumor uptake which correlated with antitumor activity. Collectively, our data suggest that TAK-164 is highly active in multiple GCC-positive tumors including those refractory to TAK-264, a GCC-targeted auristatin ADC. A strong relationship between uptake of 89Zr-labeled TAK-164, levels of GCC expression and, most notably, response to TAK-164 therapy in GCC-expressing xenografts and PHTX models. These data supported the clinical development of TAK-164 as part of a first-in-human clinical trial (NCT03449030).

Prediction of Human Disproportionate and Biliary Excreted Metabolites Using Chimeric Mice with Humanized Liver.

The PXB-mouse is potentially a useful in vivo model to predict human hepatic metabolism and clearance. Four model compounds, [14C]desloratadine, [3H]mianserin, cyproheptadine, and [3H]carbazeran, all reported with disproportionate human metabolites, were orally administered to PXB- or control SCID mice to elucidate the biotransformation of each of them. For [14C]desloratadine in PXB-mice, O-glucuronide of 3-hydroxydesloratadine was observed as the predominant metabolite in both the plasma and urine. Both 3-hydroxydesloratadine and its O-glucuronide were detected as major drug-related materials in the bile, whereas only 3-hydroxydesloratadine was detected in the feces, suggesting that a fraction of 3-hydroxydesloratadine in feces was derived from deconjugation of its O-glucuronide by gut microflora. This information can help understand the biliary clearance mechanism of a drug and may fill the gap in a human absorption, distribution, metabolism, and excretion study, in which the bile samples are typically not available. The metabolic profiles in PXB-mice were qualitatively similar to those reported in humans in a clinical study in which 3-hydroxydesloratadine and its O-glucuronide were major and disproportionate metabolites compared with rat, mouse, and monkey. In the control SCID mice, neither of the metabolites was detected in any matrix. Similarly, for the other three compounds, all human specific or disproportionate metabolites were detected at a high level in PXB-mice, but they were either minimally observed or not observed in the control mice. Data from these four compounds indicate that studies in PXB-mice can help predict the potential for the presence of human disproportionate metabolites (relative to preclinical species) prior to conducting clinical studies and understand the biliary clearance mechanism of a drug. SIGNIFICANCE STATEMENT: Studies in PXB-mice have successfully predicted the human major and disproportionate metabolites compared with preclinical safety species for desloratadine, mianserin, cyproheptadine, and carbazeran. In addition, biliary excretion data from PXB-mice can help illustrate the human biliary clearance mechanism of a drug.

Metabolism of bioconjugate therapeutics: why, when, and how?

Bioconjugation of therapeutic agents has been used as a selective drug delivery platform for many therapeutic areas. Bioconjugates are prepared by the covalent linkage of active compounds (small or large molecule) to a carrier molecule (lipids, proteins, peptides, carbohydrates, and polymers) through a chemical linker. The linkage of the active component to a carrier molecule enhances the therapeutic window through a targeted delivery and by reducing toxicity. Bioconjugates also possess improved pharmacokinetic properties such as a long half-life, increased stability, and cleavage by intracellular enzymes/environment. However, premature cleavage of the bioconjugates and the resulting metabolites/catabolites may produce undesirable toxic effects and, hence, it is critical to understand cleavage mechanisms, metabolism of bioconjugates, and translatability to human in the discovery stages. This article provides a comprehensive overview of linker cleavage pathways and catabolism/metabolism of antibody-drug conjugates, glycoconjugates, polymer-drug conjugates, lipid-drug conjugates, folate-targeted small molecule-drug conjugates, and drug-drug conjugates.

Catabolism of antibody drug conjugates and characterization methods.

Antibody drug conjugates (ADCs) are large molecule therapeutics in which a cytotoxic payload is conjugated to a monoclonal antibody (mAb) via a linker. The molecules are designed to selectively bind to target-expressing cells, thus delivering therapeutic agents directly to the tumor. Chemical and enzymatic stability prior to reaching the target is an important factor for ADCs since it impacts their safety, efficacy, and pharmacokinetics (PK). One of the main reasons for off-target effects of ADCs is premature release of cytotoxic agents, either in the blood stream or at non-specific sites. Once an ADC is internalized by target-expressing cells, the cytotoxic payload and/or related catabolites are released through chemical or enzymatic cleavage within the cells. In some cases, the released payload and/or catabolites are effluxed into the systemic circulation and follow a small molecule disposition path. Since doses of ADCs are low, the concentration of cytotoxic payload and related catabolites/metabolites range from ng to µg levels in systemic circulation or tumors in clinical studies. Hence, it is challenging to identify these species without prior knowledge of the pathways of catabolism. The current review summarizes the mechanism of cleavage/catabolism of various types of linkers and available in vitro, in vivo, and bioanalytical methods for evaluation of catabolism of ADCs.

An accelerated background subtraction algorithm for processing high-resolution MS data and its application to metabolite identification.

BACKGROUND: Metabolite identification without radiolabeled compound is often challenging because of interference of matrix-related components. RESULTS: A novel and an effective background subtraction algorithm (A-BgS) has been developed to process high-resolution mass spectral data that can selectively remove matrix-related components. The use of a graphics processing unit with a multicore central processing unit enhanced processing speed several 1000-fold compared with a single central processing unit. A-BgS algorithm effectively removes background peaks from the mass spectra of biological matrices as demonstrated by the identification of metabolites of delavirdine and metoclopramide. CONCLUSION: The A-BgS algorithm is fast, user friendly and provides reliable removal of matrix-related ions from biological samples, and thus can be very helpful in detection and identification of in vivo and in vitro metabolites.

Carbon-carbon bond cleavage and formation reactions in drug metabolism and the role of metabolic enzymes.

Elimination of xenobiotics from the human body is often facilitated by a transformation to highly water soluble and more ionizable molecules. In general, oxidation-reduction, hydrolysis, and conjugation reactions are common biotransformation reactions that are catalyzed by various metabolic enzymes including cytochrome P450s (CYPs), non-CYPs, and conjugative enzymes. Although carbon-carbon (C-C) bond formation and cleavage reactions are known to exist in plant secondary metabolism, these reactions are relatively rare in mammalian metabolism and are considered exceptions. However, various reactions such as demethylation, dealkylation, dearylation, reduction of alkyl chain, ring expansion, ring contraction, oxidative elimination of a nitrile through C-C bond cleavage, and dimerization, and glucuronidation through C-C bond formation have been reported for drug molecules. Carbon-carbon bond cleavage reactions for drug molecules are primarily catalyzed by CYP enzymes, dimerization is mediated by peroxidases, and C-glucuronidation is catalyzed by UGT1A9. This review provides an overview of C-C bond cleavage and formation reactions in drug metabolism and the metabolic enzymes associated with these reactions.

Biotransformation and bioactivation reactions of alicyclic amines in drug molecules.

Aliphatic nitrogen heterocycles such as piperazine, piperidine, pyrrolidine, morpholine, aziridine, azetidine, and azepane are well known building blocks in drug design and important core structures in approved drug therapies. These core units have been targets for metabolic attack by P450s and other drug metabolizing enzymes such as aldehyde oxidase and monoamine oxidase (MAOs). The electron rich nitrogen and/or α-carbons are often major sites of metabolism of alicyclic amines. The most common biotransformations include N-oxidation, N-conjugation, oxidative N-dealkylation, ring oxidation, and ring opening. In some instances, the metabolic pathways generate electrophilic reactive intermediates and cause bioactivation. However, potential bioactivation related adverse events can be attenuated by structural modifications. Hence it is important to understand the biotransformation pathways to design stable drug candidates that are devoid of metabolic liabilities early in the discovery stage. The current review provides a comprehensive summary of biotransformation and bioactivation pathways of aliphatic nitrogen containing heterocycles and strategies to mitigate metabolic liabilities.

Glycyrrhiza uralensis flavonoids present in anti-asthma formula, ASHMI™, inhibit memory Th2 responses in vitro and in vivo.

Allergic asthma is associated with Th2-mediated inflammation. Several flavonoids were isolated from Glycyrrhiza uralensis, one of the herbs in the anti-asthma herbal medicine intervention. The aim of this investigation was to determine whether Glycyrrhiza uralensis flavonoids have inhibitory effects on memory Th2 responses in vitro and antigen-induced Th2 inflammation in vivo. The effects of three Glycyrrhiza uralensis flavonoids on effector memory Th2 cells, D10.G4.1 (D10 cells), were determined by measuring Th2 cytokine production. Isoliquiritigenin, 7, 4'-dihydroxyflavone (7, 4'-DHF) and liquiritigenin significantly suppressed IL-4 and IL-5 production in a dose-dependent manner, 7, 4'-DHF being most potent. It was also evaluated for effects on D10 cell proliferation, GATA-3 expression and IL-4 mRNA expression, which were suppressed, with no loss of cell viability. Chronic treatment with 7, 4'-DHF in a murine model of allergic asthma not only significantly reduced eosinophilic pulmonary inflammation, serum IgE levels, IL-4 and IL-13 levels, but also increased IFN-γ production in lung cell cultures in response to antigen stimulation.