Fabrication of Ultrafine Cu2 O Nanoparticles on W18 O49 Ultra-Thin Nanowires by In-Situ Reduction for Highly Efficient Photocatalytic Nitrogen Fixation.

Photocatalytic ammonia synthesis technology is one of the important methods to achieve green ammonia synthesis. Herein, two samples of Cu ion-doped W18 O49 with different morphologies, ultra-thin nanowires (Cu-W18 O49 -x UTNW) and sea urchin-like microspheres (Cu-W18 O49 -x SUMS), are synthesized by a simple solvothermal method. Subsequently, Cu2 O-W18 O49 -x UTNW/SUMS is synthesized by in situ reduction, where the NH3 production rate of Cu2 O-W18 O49 -30 UTNW is 252.4 µmol g-1  h-1 without sacrificial reagents, which is 11.8 times higher than that of the pristine W18 O49 UTNW. The Cu2 O-W18 O49 -30 UTNW sample is rich in oxygen vacancies, which promotes the chemisorption and activation of N2 molecules and makes the N≡N bond easier to dissociate by proton coupling. In addition, the in situ reduction-generated Cu2 O nanoparticles exhibit ideal S-scheme heterojunctions with W18 O49 UTNW, which enhances the internal electric field strength and improves the separation and transfer efficiency of the photogenerated carriers. Therefore, this study provides a new idea for the design of efficient nitrogen fixation photocatalysis.

Identification and human exposure prediction of two aldehyde oxidase-mediated metabolites of a methylquinoline-containing drug candidate.

1. Aldehyde oxidase (AO enzymes)-mediated oxidation predominantly occurs at a carbon atom adjacent to the nitrogen on aromatic azaheterocycles. In the current report, we identified that AO enzymes oxidation took place at both the C-2 and C-4 positions of the methylquinoline moiety of Compound A based on data from mass spectrometric analysis, AO enzymes "litmus" test, and comparison with authentic standards. 2. To assess the potential for inadequate coverage for these two AO enzyme-mediated metabolites in nonclinical safety studies, given concerns due to differences in AO enzymes expression between preclinical species and humans, the human circulating levels of the two AO enzyme-mediated metabolites were predicted prospectively using in vitro and in vivo models. Both formation clearance and elimination clearance of the two metabolites were predicted based on in vitro to in vivo correlation and comparison with in vivo data from rats. 3. The result showed that the 4-OH metabolite of Compound A would account for less than 3% of the total drug-related exposure in human plasma, while the exposure to the 2-oxo metabolite would be relatively high (∼70%). 4. The predicted human exposure levels for the two metabolites are in similar ranges as those observed in monkeys. These data taken together support the advancement to clinical development of Compound A.

In vitro drug-drug interactions of budesonide: inhibition and induction of transporters and cytochrome P450 enzymes.

1. Budesonide is a glucocorticoid used in the treatment of several respiratory and gastrointestinal inflammatory diseases. Glucocorticoids have been demonstrated to induce cytochrome P450 (CYP) 3A and the efflux transporter P-glycoprotein (P-gp). This study aimed to evaluate the potential of budesonide to act as a perpetrator or a victim of transporter- or CYP-mediated drug-drug interactions (DDIs). 2. In vitro studies were conducted for P-gp, breast cancer resistance protein and organic anion and cation transporters (OATP1B1, OATP1B3, OAT1, OAT3, OCT2) in transporter-transfected cells. Changes in mRNA expression in human hepatocytes and enzyme activity in human liver microsomes by budesonide were determined for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A. 3. The data indicated that budesonide is a substrate of P-gp but is not a substrate or an inhibitor of the other transporters investigated. Budesonide is neither an inducer nor an inhibitor of major CYP enzymes. The effect of P-gp on budesonide disposition is anticipated to be low owing to CYP3A-mediated clearance. 4. Collectively, our data indicate there is a low risk of budesonide perpetrating clinical DDIs mediated by the transporters or CYPs studied.

In vitro and in vivo characterisation of the metabolism and disposition of suvorexant in humans.

1. Suvorexant (MK-4305, Belsomra®) is a first-in-class dual orexin receptor antagonist approved in the USA and Japan for the treatment of insomnia. The current studies describe suvorexant's absorption, disposition and potential for CYP-mediated drug interactions in humans. 2. Following single oral administration of [(14)C]suvorexant to healthy human subjects, 90% of the radioactivity was recovered (66% in faeces, 23% in urine), primarily as oxidative metabolites. 3. In plasma, suvorexant and M9 were predominant, accounting for 30 and 37% of the total radioactivity, respectively. Metabolite M17 became more prominent (approaching 10%) following multiple daily doses of unlabelled suvorexant. M9 and M17 are not expected to contribute to the pharmacological activity of suvorexant due to reduced orexin receptor binding affinity and limited brain penetration. 4. CYP3A was determined to be the predominant enzyme mediating suvorexant oxidation. In vitro, suvorexant demonstrated reversible inhibition of CYP3A4 and 2C19 (IC50 ∼ 4-5 µM), and weak time-dependent inhibition of CYP3A4 (KI = 12 µM, kinact = 0.14 min(-1)). Suvorexant was also a weak inducer of CYP3A4, 1A2 and 2B6. Given the low plasma concentrations at clinical doses, suvorexant was not anticipated to cause significant drug interactions via inhibition and/or induction of major CYPs in vivo.

Contribution of metabolites to P450 inhibition-based drug-drug interactions: scholarship from the drug metabolism leadership group of the innovation and quality consortium metabolite group.

Recent European Medicines Agency (final) and US Food and Drug Administration (draft) drug interaction guidances proposed that human circulating metabolites should be investigated in vitro for their drug-drug interaction (DDI) potential if present at ≥ 25% of the parent area under the time-concentration curve (AUC) (US Food and Drug Administration) or ≥ 25% of the parent and ≥ 10% of the total drug-related AUC (European Medicines Agency). To examine the application of these regulatory recommendations, a group of scientists, representing 18 pharmaceutical companies of the Drug Metabolism Leadership Group of the Innovation and Quality Consortium, conducted a scholarship to assess the risk of contributions by metabolites to cytochrome P450 (P450) inhibition-based DDIs. The group assessed the risk of having a metabolite as the sole contributor to DDI based on literature data and analysis of the 137 most frequently prescribed drugs, defined structural alerts associated with P450 inhibition/inactivation by metabolites, and analyzed current approaches to trigger in vitro DDI studies for metabolites. The group concluded that the risk of P450 inhibition caused by a metabolite alone is low. Only metabolites from 5 of 137 drugs were likely the sole contributor to the in vivo P450 inhibition-based DDIs. Two recommendations were provided when assessing the need to conduct in vitro P450 inhibition studies for metabolites: 1) consider structural alerts that suggest P450 inhibition potential, and 2) use multiple approaches (e.g., a metabolite cut-off value of 100% of the parent AUC and the R(met) strategy) to predict P450 inhibition-based DDIs caused by metabolites in the clinic.

Discovery of piperidine ethers as selective orexin receptor antagonists (SORAs) inspired by filorexant.

Highly selective orexin receptor antagonists (SORAs) of the orexin 2 receptor (OX2R) have become attractive targets both as potential therapeutics for insomnia as well as biological tools to help further elucidate the underlying pharmacology of the orexin signaling pathway. Herein, we describe the discovery of a novel piperidine ether 2-SORA class identified by systematic lead optimization beginning with filorexant, a dual orexin receptor antagonist (DORA) that recently completed Phase 2 clinical trials. Changes to the ether linkage and pendant heterocycle of filorexant were found to impart significant selectivity for OX2R, culminating in lead compound PE-6. PE-6 displays sub-nanomolar binding affinity and functional potency on OX2R while maintaining >1600-fold binding selectivity and >200-fold functional selectivity versus the orexin 1 receptor (OX1R). PE-6 bears a clean off-target profile, a good overall preclinical pharmacokinetic (PK) profile, and reduces wakefulness with increased NREM and REM sleep when evaluated in vivo in a rat sleep study. Importantly, subtle structural changes to the piperidine ether class impart dramatic changes in receptor selectivity. To this end, our laboratories have identified multiple piperidine ether 2-SORAs, 1-SORAs, and DORAs, providing access to a number of important biological tool compounds from a single structural class.

Discovery of diazepane amide DORAs and 2-SORAs enabled by exploration of isosteric quinazoline replacements.

Dual orexin receptor antagonists (DORAs), or orexin 1 (OX1) and orexin 2 (OX2) receptor antagonists, have demonstrated clinical utility for the treatment of insomnia. Medicinal chemistry efforts focused on the reduction of bioactivation potential of diazepane amide 1 through the modification of the Western heterocycle resulted in the discovery of suvorexant, a DORA recently approved by the FDA for the treatment of insomnia. A second strategy towards reducing bioactivation risk is presented herein through the exploration of monocyclic quinazoline isosteres, namely substituted pyrimidines. These studies afforded potent DORAs with significantly reduced bioactivation risk and efficacy in rodent sleep models. Surprisingly, side products from the chemistry used to produce these DORAs yielded isomeric pyrimidine-containing diazepane amides possessing selective OX2R antagonist (2-SORA) profiles. Additional exploration of these isomeric pyrimidines uncovered potent 2-SORA diazepane amides with sleep efficacy in mouse EEG studies.

Discovery of dual orexin receptor antagonists with rat sleep efficacy enabled by expansion of the acetonitrile-assisted/diphosgene-mediated 2,4-dichloropyrimidine synthesis.

Recent clinical studies have demonstrated that dual orexin receptor antagonists (OX1R and OX2R antagonists or DORAs) represent a novel treatment option for insomnia patients. Previously we have disclosed several compounds in the diazepane amide DORA series with excellent potency and both preclinical and clinical sleep efficacy. Additional SAR studies in this series were enabled by the expansion of the acetonitrile-assisted, diphosgene-mediated 2,4-dichloropyrimidine synthesis to novel substrates providing an array of Western heterocycles. These heterocycles were utilized to synthesize analogs in short order with high levels of potency on orexin 1 and orexin 2 receptors as well as in vivo sleep efficacy in the rat.

Discovery of MK-3697: a selective orexin 2 receptor antagonist (2-SORA) for the treatment of insomnia.

Orexin receptor antagonists have demonstrated clinical utility for the treatment of insomnia. The majority of clinical efforts to date have focused on the development of dual orexin receptor antagonists (DORAs), small molecules that antagonize both the orexin 1 and orexin 2 receptors. Our group has recently disclosed medicinal chemistry efforts to identify highly potent, orally bioavailable selective orexin 2 receptor antagonists (2-SORAs) that possess acceptable profiles for clinical development. Herein we report additional SAR studies within the 'triaryl' amide 2-SORA series focused on improvements in compound stability in acidic media and time-dependent inhibition of CYP3A4. These studies resulted in the discovery of 2,5-disubstituted isonicotinamide 2-SORAs such as compound 24 that demonstrated improved stability and TDI profiles as well as excellent sleep efficacy across species.

g-C3N4@TiO2 photoanodes for high-efficiency QDSSCs: improved electron transfer and photochemical stability.

In QDSSCs, a photoanode is an important part of connecting the external circuit, providing support for the transmission of photogenerated carriers to the external circuit, and also providing an attachment site for QDs. In this study, we prepared a g-C3N4@TiO2 composite for the photoanode by a two-step process. The results show that the use of g-C3N4@TiO2 greatly increases the specific surface area of the material, effectively inhibits the "electron-hole" recombination, and optimizes the stability and catalytic performance of the photoanode. Among them, the cell equipped with the g-C3N4@TiO2 photoanode has improved performance: Jsc = 26.5 mA cm-2, PCE = 8.2%, Voc = 0.62 eV, and FF = 0.50. Based on the research in this paper, it can be seen that the g-C3N4@TiO2 composite applied to the photoanode can effectively improve the cell performance and provide a feasible idea for optimizing QDSSCs.

Core-shell ZnO@TiO2 hexagonal prism heterogeneous structures as photoanodes for boosting the efficiency of quantum dot sensitized solar cells.

In quantum dot sensitized solar cells (QDSSCs), the photoanode provides a stable support for the quantum dots, and promotes the production of photogenerated electrons and the transfer to external circuit. Therefore, it is very important to search for excellent photoanodes for the commercial application of QDSSCs. In this paper, a core-shell ZnO@TiO2 hexagonal prism heterogeneous structure was prepared by a two-step hydrothermal method. The ZnO@TiO2 heterogeneous structure not only has a unique 1D hexagonal prism morphology, but also can effectively inhibit the electron-hole recombination and has a greater light response and higher collection efficiency while speeding up the electron transmission rate. By adjusting the concentration of the TiO2 source, the best photoanode material Zn@Ti-2 was explored, and it showed excellent cell performance: Jsc = 25.4 mA cm-2, Voc = 0.71 V, PCE = 8.5%, and FF = 0.49. Compared with a single ZnO photoanode, the PCE value is increased by 25%. EIS, Tafel polarization and transient photocurrent responses confirm that the Zn@Ti-2 photoanode has higher catalytic activity and stability. Therefore, Zn@Ti-2 may be a promising photoanode material for QDSSCs.

Construction of Fe(III) Active Sites on Phenanthroline-Grafted g-C3N4: Reduced Work Function and Enhanced Intramolecular Charge Transfer for Efficient N2 Photofixation.

Photocatalytic nitrogen fixation is one of the important pathways for green and sustainable ammonia synthesis, but the extremely high bonding energy of the N≡N triple bond makes it difficult for conventional nitrogen fixation photocatalysts to directly activate and hydrogenate. Given this, we covalently grafted the phenanthroline unit onto graphitic carbon nitride nanosheets (CN) by the simple thermal oxidation method and complexed it with transition metal Fe3+ ions to obtain stable dispersed Fe active sites, which can significantly improve the photocatalytic activity. The Fe(III)-4-P-CN photocatalyst morphology consists of porous lamellar structures internally connected by nanowires. The special morphology of the catalysts gives them excellent nitrogen fixation performance, with an average NH3 yield of 492.9 µmol g-1 h-1, which is 6.5 times higher than that of the pristine CN, as well as better photocatalytic cycling stability. Comprehensive experiments and density-functional theory results show that Fe(III)-4-P-CN is more favorable than pristine CN for *N2 activation, effectively lowering the reaction energy barrier. Moreover, other byproducts (such as nitrate and H2O2) are also produced during the photocatalytic nitrogen fixation process, which also provides a new way for nitrogen-fixing photocatalysts to achieve multifunctional applications.

The duration of sleep promoting efficacy by dual orexin receptor antagonists is dependent upon receptor occupancy threshold.

BACKGROUND: Drugs targeting insomnia ideally promote sleep throughout the night, maintain normal sleep architecture, and are devoid of residual effects associated with morning sedation. These features of an ideal compound are not only dependent upon pharmacokinetics, receptor binding kinetics, potency and pharmacodynamic activity, but also upon a compound's mechanism of action. RESULTS: Dual orexin receptor antagonists (DORAs) block the arousal-promoting activity of orexin peptides and, as demonstrated in the current work, exhibit an efficacy signal window dependent upon oscillating levels of endogenous orexin neuropeptide. Sleep efficacy of structurally diverse DORAs in rat and dog was achieved at plasma exposures corresponding to orexin 2 receptor (OX2R) occupancies in the range of 65 to 80%. In rats, the time course of OX2R occupancy was dependent upon receptor binding kinetics and was tightly correlated with the timing of active wake reduction. In rhesus monkeys, direct comparison of DORA-22 with GABA-A modulators at similar sleep-inducing doses revealed that diazepam produced next-day residual sleep and both diazepam and eszopiclone induced next-day cognitive deficits. In stark contrast, DORA-22 did not produce residual effects. Furthermore, DORA-22 evoked only minimal changes in quantitative electroencephalogram (qEEG) activity during the normal resting phase in contrast to GABA-A modulators which induced substantial qEEG changes. CONCLUSION: The higher levels of receptor occupancy necessary for DORA efficacy require a plasma concentration profile sufficient to maintain sleep for the duration of the resting period. DORAs, with a half-life exceeding 8 h in humans, are expected to fulfill this requirement as exposures drop to sub-threshold receptor occupancy levels prior to the wake period, potentially avoiding next-day residual effects at therapeutic doses.

In vitro assessment of drug-drug interaction potential of boceprevir associated with drug metabolizing enzymes and transporters.

The inhibitory effect of boceprevir (BOC), an inhibitor of hepatitis C virus nonstructural protein 3 protease was evaluated in vitro against a panel of drug-metabolizing enzymes and transporters. BOC, a known substrate for cytochrome P450 (P450) CYP3A and aldo-ketoreductases, was a reversible time-dependent inhibitor (k(inact) = 0.12 minute(-1), K(I) = 6.1 µM) of CYP3A4/5 but not an inhibitor of other major P450s, nor of UDP-glucuronosyltransferases 1A1 and 2B7. BOC showed weak to no inhibition of breast cancer resistance protein (BCRP), P-glycoprotein (Pgp), or multidrug resistance protein 2. It was a moderate inhibitor of organic anion transporting polypeptide (OATP) 1B1 and 1B3, with an IC(50) of 18 and 4.9 µM, respectively. In human hepatocytes, BOC inhibited CYP3A-mediated metabolism of midazolam, OATP1B-mediated hepatic uptake of pitavastatin, and both the uptake and metabolism of atorvastatin. The inhibitory potency of BOC was lower than known inhibitors of CYP3A (ketoconazole), OATP1B (rifampin), or both (telaprevir). BOC was a substrate for Pgp and BCRP but not for OATP1B1, OATP1B3, OATP2B1, organic cation transporter, or sodium/taurocholate cotransporting peptide. Overall, our data suggest that BOC has the potential to cause pharmacokinetic interactions via inhibition of CYP3A and CYP3A/OATP1B interplay, with the interaction magnitude lower than those observed with known potent inhibitors. Conversely, pharmacokinetic interactions of BOC, either as a perpetrator or victim, via other major P450s and transporters tested are less likely to be of clinical significance. The results from clinical drug-drug interaction studies conducted thus far are generally supportive of these conclusions.

Discovery of 2,5-diarylnicotinamides as selective orexin-2 receptor antagonists (2-SORAs).

The orexin (or hypocretin) system has been identified as a novel target for the treatment of insomnia due to the wealth of biological and genetic data discovered over the past decade. Recently, clinical proof-of-concept was achieved for the treatment of primary insomnia using dual (OX1R/OX2R) orexin receptor antagonists. However, elucidation of the pharmacology associated with selective orexin-2 receptor antagonists (2-SORAs) has been hampered by the lack of orally bioavailable, highly selective small molecule probes. Herein, the discovery and optimization of a novel series of 2,5-diarylnicotinamides as potent and orally bioavailable orexin-2 receptor selective antagonists is described. A compound from this series demonstrated potent sleep promotion when dosed orally to EEG telemetrized rats.

Promotion of sleep by suvorexant-a novel dual orexin receptor antagonist.

Orexins/hypocretins are key neuropeptides responsible for regulating central arousal and reward circuits. Two receptors respond to orexin signaling, orexin 1 receptor (OX(1)R) and orexin 2 receptor (OX(2)R) with partially overlapping nervous system distributions. Genetic studies suggest orexin receptor antagonists could be therapeutic for insomnia and other disorders with disruptions of sleep and wake. Suvorexant (MK-4305) is a potent, selective, and orally bioavailable antagonist of OX(1)R and OX(2)R currently under clinical investigation as a novel therapy for insomnia. Examination of Suvorexant in radioligand binding assays using tissue from transgenic rats expressing the human OX(2)R found nearly full receptor occupancy (>90%) at plasma exposures of 1.1 µM. Dosed orally Suvorexant significantly and dose-dependently reduced locomotor activity and promoted sleep in rats (10, 30, and 100 mg/kg), dogs (1 and 3 mg/kg), and rhesus monkeys (10 mg/kg). Consistent cross-species sleep/wake architecture changes produced by Suvorexant highlight a unique opportunity to develop dual orexin antagonists as a novel therapy for insomnia.

Confirmation that cytochrome P450 2C8 (CYP2C8) plays a minor role in (S)-(+)- and (R)-(-)-ibuprofen hydroxylation in vitro.

Various groups have sought to determine the impact of CYP2C8 genotype (and CYP2C8 inhibition) on the pharmacokinetics (PK) of ibuprofen (IBU) enantiomers. However, the contribution of cytochrome P450 2C8 (CYP2C8) in human liver microsomes (HLMs) has not been reported. Therefore, in vitro cytochrome P450 (P450) reaction phenotyping was conducted with selective inhibitors of cytochrome P450 2C9 (CYP2C9) and CYP2C8. In the presence of HLMs, sulfaphenazole (CYP2C9 inhibitor), and anti-CYP2C9 monoclonal antibodies (mAbs) inhibited (73-100%) the 2- and 3-hydroxylation of both IBU enantiomers (1 and 20 microM). At a higher IBU concentration (500 microM), the same inhibitors were less able to inhibit the 2-hydroxylation of (S)-(+)-IBU (32-52%) and (R)-(-)-IBU (30-64%), whereas the 3-hydroxylation of (S)-(+)-IBU and (R)-(-)-IBU was inhibited 66 to 83 and 70 to 89%, respectively. In contrast, less inhibition was observed with montelukast (CYP2C8 inhibitor, < or =35%) and anti-CYP2C8 mAbs (< or =24%) at all concentrations of IBU. When (S)-(+)-IBU and (R)-(-)-IBU (1 microM) were incubated with a panel of recombinant human P450s, only CYP2C9 formed appreciable amounts of the hydroxy metabolites. At a higher IBU enantiomer concentration (500 microM), additional P450s catalyzed 2-hydroxylation (CYP3A4, CYP2C8, CYP2C19, CYP2D6, CYP2E1, and CYP2B6) and 3-hydroxylation (CYP2C19). When the P450 reaction phenotype and additional clearance pathways are considered (e.g., direct glucuronidation and chiral inversion), it is concluded that CYP2C8 plays a minor role in (R)-(-)-IBU (<10%) and (S)-(+)-IBU ( approximately 13%) clearance. By extension, one would not expect CYP2C8 inhibition (and genotype) to greatly affect the pharmacokinetic profile of either enantiomer. On the other hand, CYP2C9 inhibition and genotype are expected to have an impact on the PK of (S)-(+)-IBU.

Identification of the human enzymes involved in the oxidative metabolism of dasatinib: an effective approach for determining metabolite formation kinetics.

N-(2-Chloro-6-methylphenyl)-2-[[6-[4-(2-hydroxyethyl)-1-piperazinyl]-2-methyl-4-pyrimidinyl]amino]-5-thiazolecarboxamide (dasatinib, Sprycel, BMS-354825; Bristol-Myers Squibb, Princeton, NJ) is a potent protein kinase inhibitor to treat chronic myeloid leukemia. In vivo studies have shown that the primary oxidative metabolites of dasatinib are M4 (N-dealkylation), M5 (N-oxidation), M6 (carboxylic acid formation), M20, and M24 (hydroxylation). To identify the enzymes responsible for the formation of these metabolites, [(14)C]-dasatinib and nonradiolabeled dasatinib were incubated with human cDNA-expressed enzymes [cytochromes P450 (P450s) and flavin-containing monooxygenase (FMO) 3] or human liver microsome (HLM) in the presence of selective P450 inhibitors (antibodies and chemical inhibitors). The results of these experiments showed that metabolites M4, M20, and M24 were mainly generated by CYP3A4; M5 was primarily formed by FMO3; and M6 was formed by a cytosolic oxidoreductase. The enzyme kinetic analysis showed that the formation of M4 and M5 in HLM followed the Michaelis-Menten kinetics, and the formation data of M20 and M24 fitted well to a partial substrate inhibition kinetic model. The K(m) values were determined by the kinetic analysis of the substrate-dependent metabolite formation plots from a large number of incubations with the nonlabeled dasatinib; the V(max) values were calculated with the predetermined K(m) values and the metabolite formation rates from a limited number of incubations with [(14)C]dasatinib. The intrinsic formation clearance values (V(max)/K(m)) of 52, 14, 274, and 20 microl/mg protein/min for the formation of M4, M5, M20, and M24, respectively, suggested that the formation of M20 was more efficient than other metabolites. Collectively, multiple in vitro experiments showed that dasatinib was predominately metabolized by CYP3A4.

Biotransformation of [14C]dasatinib: in vitro studies in rat, monkey, and human and disposition after administration to rats and monkeys.

This study describes the in vitro metabolism of [(14)C]dasatinib in liver tissue incubations from rat, monkey, and human and the in vivo metabolism in rat and monkey. Across species, dasatinib underwent in vitro oxidative metabolism to form five primary oxidative metabolites. In addition to the primary metabolites, secondary metabolites formed from combinations of the oxidative pathways and conjugated metabolites of dasatinib and its oxidative metabolites were also observed in hepatocytes incubations. In in vivo studies in rats and monkeys, the majority of the radioactive dose was excreted in the bile and feces. In bile duct-cannulated monkeys after an i.v. dose, 13.7% of the radioactive dose was excreted in the feces through direct secretion. Dasatinib comprised 56 and 26% of the area under the curve (AUC) (0-8 h) of total radioactivity (TRA) in plasma, whereas multiple metabolites accounted for the remaining 44 and 74% of the AUC (0-8 h) of TRA for rats and monkeys, respectively. In rat and monkey bile, dasatinib accounted for < 12% of the excreted dose, suggesting that dasatinib was extensively metabolized before elimination. The metabolic profiles in bile were similar to the hepatocyte profiles. In both species, a large portion of the radioactivity excreted in bile (> or = 29% of the dose) was attributed to N-oxides and conjugated metabolites. In rat and monkey feces, only the oxidative metabolites and their further oxidation products were identified. The absence of conjugative or N-oxide metabolites in the feces suggests hydrolysis or reduction, respectively, in the gastrointestinal tract before elimination.

Metabolism and disposition of dasatinib after oral administration to humans.

SPRYCEL (dasatinib, BMS-354825; Bristol-Myers Squibb, Princeton, NJ), a multiple kinase inhibitor, is currently approved to treat chronic myelogenous leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia tumors in patients who are resistant or intolerant to imatinib mesylate (Gleevec; Novartis, Basel, Switzerland). After a 100-mg single p.o. dose of [(14)C]dasatinib to healthy volunteers, the radioactivity was rapidly absorbed (T(max) approximately 0.5 h). Both dasatinib and total radioactivity (TRA) plasma concentrations decreased rapidly with elimination half-life values of <4 h. Dasatinib was the major drug-related component in human plasma. At 2 h, dasatinib accounted for 25% of the TRA in plasma, suggesting that metabolites contributed significantly to the total drug-related component. There were many circulating metabolites detected that included hydroxylated metabolites (M20 and M24), an N-dealkylated metabolite (M4), an N-oxide (M5), an acid metabolite (M6), glucuronide conjugates (M8a,b), and products of further metabolism of these primary metabolites. Most of the administered radioactivity was eliminated in the feces (85%). Urine recovery accounted for <4% of the dose. Dasatinib accounted for <1 and 19% of the dose in urine and feces, respectively, suggesting that dasatinib was well absorbed after p.o. administration and extensively metabolized before being eliminated from the body. The exposures of pharmacologically active metabolites M4, M5, M6, M20, and M24 in patients, along with their cell-based IC(50) for Src and Bcr-Abl kinase inhibition, suggested that these metabolites were not expected to contribute significantly toward in vivo activity.