Posaconazole is a potent, broad-spectrum triazole antifungal agent currently in clinical development for the treatment of refractory invasive fungal infections. Eight healthy male subjects received a single 399-mg (81.7 Ci) oral dose of [ 14 C]posaconazole after consuming a high-fat breakfast. Urine, feces, and blood samples were collected for up to 336 h postdose and assayed for total radioactivity; plasma and urine samples were also assayed for parent drug. Posaconazole was orally bioavailable, with a median maximum posaconazole concentration in plasma achieved by 10 h postdose. Thereafter, posaconazole was slowly eliminated, with a mean half-life of 20 h. The greatest peak in the radioactivity profile of pooled plasma extracts was due to posaconazole, with smaller peaks due to a monoglucuronide, a diglucuronide, and a smaller fragment of the molecule. The mean total amount of radioactivity recovered was 91.1%; the cumulative excretion of radioactivity in feces and in urine was 76.9 and 14.0% of the dose, respectively. Most of the fecal radioactivity was associated with posaconazole, which accounted for 66.3% of the administered dose; however, urine contained only trace amounts of unchanged posaconazole. The radioactivity profile of pooled urine extracts included two monoglucuronide conjugates and a diglucuronide conjugate of posaconazole. These observations suggest that oxidative (phase 1) metabolism by cytochrome P450 isoforms represents only a minor route of elimination for posaconazole, and therefore cytochrome P450-mediated drug interactions should have a limited potential to impact posaconazole pharmacokinetics.Posaconazole (SCH 56592) is a potent, extended-spectrum triazole antifungal agent currently in late-phase clinical development for the treatment and prophylaxis of invasive fungal infections due to a wide range of common, rare, and emerging molds and yeasts. Posaconazole has demonstrated in vitro activity against several commonly encountered pathogens, including Candida, Aspergillus, Cryptococcus, and Coccidioides species (1,7,12,13). In addition, its activity against several emerging pathogens, such as the filamentous fungus Scedosporium (3, 10), has been explored clinically. In an immunocompromised patient, posaconazole has been used to effectively treat Scedosporium-induced brain abscesses that were refractory to itraconazole and amphotericin B therapy (11).The anticipated clinical dosage regimen of posaconazole oral suspension for the treatment of refractory invasive fungal infections is 400 mg twice daily. The purpose of the present study was to determine the absorption, metabolism, and excretion of a single 400-mg dose of [ 14 C]posaconazole oral suspension in human subjects. MATERIALS AND METHODS Radiolabeled posaconazole and dosage forms. [14 C]posaconazole ( Fig. 1) was synthesized and formulated by the radiochemistry group at the Schering-Plough Research Institute (Kenilworth, N.J.). Its specific activity was 0.205 Ci/mg, and its radiochemical purity was 98.7%. The radiolabeled drug was ...

Acalabrutinib is a targeted, covalent inhibitor of Bruton tyrosine kinase (BTK) with a unique 2-butynamide warhead that has relatively lower reactivity than other marketed acrylamide covalent inhibitors. A human [ 14 C] microtracer bioavailability study in healthy subjects revealed moderate intravenous clearance (39.4 l/h) and an absolute bioavailability of 25.3% 6 14.3% (n = 8). Absorption and elimination of acalabrutinib after a 100 mg [ 14 C] microtracer acalabrutinib oral dose was rapid, with the maximum concentration reached in <1 hour and elimination half-life values of <2 hours. Low concentrations of radioactivity persisted longer in the blood cell fraction and a peripheral blood mononuclear cell subfraction (enriched in target BTK) relative to plasma. [ 14 C]Acalabrutinib was metabolized to more than three dozen metabolites detectable by liquid chromatography-tandem mass spectrometry, with primary metabolism by CYP3A-mediated oxidation of the pyrrolidine ring, thiol conjugation of the butynamide warhead, and amide hydrolysis. A major active, circulating, pyrrolidine ring-opened metabolite, ACP-5862 (4-[8-amino-3-[4-(but-2-ynoylamino)butanoyl]imidazo[1,5-a]pyrazin-1yl]-N-(2-pyridyl)benzamide), was produced by CYP3A oxidation. Novel enol thioethers from the 2-butynamide warhead arose from glutathione and/or cysteine Michael additions and were subject to hydrolysis to a b-ketoamide. Total radioactivity recovery was 95.7% 6 4.6% (n = 6), with 12.0% of dose in urine and 83.5% in feces. Excretion and metabolism characteristics were generally similar in rats and dogs. Acalabrutinib's highly selective, covalent mechanism of action, coupled with rapid absorption and elimination, enables high and sustained BTK target occupancy after twice-daily administration.

ABSTRACT:The metabolism and disposition of calcimimetic agent cinacalcet HCl was examined after a single oral administration to mice, rats, monkeys, and human volunteers. In all species examined, cinacalcet was well absorbed, with greater than 74% oral bioavailability of cinacalcet-derived radioactivity in monkeys and humans. In rats, cinacalcet-derived radioactivity was widely distributed into most tissues, with no marked gender-related differences. In all animal models examined, radioactivity was excreted rapidly via both hepatobiliary and urinary routes. In humans, radioactivity was cleared primarily via the urinary route (80%), with 17% excreted in the feces. Cinacalcet was not detected in the urine in humans. The primary routes of metabolism of cinacalcet were N-dealkylation leading to carboxylic acid derivatives (excreted in urine as glycine conjugates) and oxidation of naphthalene ring to form dihydrodiols (excreted in urine and bile as glucuronide conjugates). The plasma radioactivity in both animals and humans was primarily composed of carboxylic acid metabolites and dihydrodiol glucuronides, with <1% circulating radioactivity accounting for the unchanged cinacalcet. Overall, the circulating and excreted metabolite profile of cinacalcet in humans was qualitatively similar to that observed in preclinical animal models.Calcimimetic agents act as positive allosteric modulators of the calcium receptor located on the surface of the parathyroid cells (Nemeth et al., 1998;Cohen and Silverberg, 2002). Cinacalcet HCl (AMG 073; hereinafter referred to as cinacalcet), a calcimimetic agent, acts on the calcium-sensing receptor of the parathyroid, the principal regulator of parathyroid hormone release, to increase its sensitivity to activation by extracellular calcium, thus decreasing parathyroid hormone. The clinical efficacy of cinacalcet has been demonstrated in several studies in subjects with secondary hyperparathyroidism (Drueke et al., 2001;Goodman et al., 2002;Quarles et al., 2003).Nonclinical biodisposition studies (ADME) of a new chemical entity play a critical role in its initial selection as well as in its subsequent clinical development. Biodisposition studies provide important information regarding the absorption of the drug from the site of administration, distribution of the drug-related material into the target tissues, metabolic pathways to which the drug is subject, and the eventual excretion of the drug-related material from the body (Campbell, 1994;Caldwell et al., 1995;Miwa, 1995). The information generated from these studies is helpful in understanding the outcomes of the safety studies (e.g., toxic and reactive metabolites, covalent binding to macromolecules, species-specific toxicity) and in some instances the outcomes of pharmacology studies (e.g., the presence of active metabolites, distribution into target organ) (Wiltshire et al., 1997;Bischoff et al., 1998;Mutlib et al., 2000). These studies are also immensely helpful in understanding the potential behavior of a drug candidate in humans...

This paper describes a new strategy that utilizes the fast trap mode scan of the hybrid triple quadrupole linear ion trap (QqQ(LIT)) for the identification of drug metabolites. The strategy uses information-dependent acquisition (IDA) where the enhanced mass scan (EMS), the trap mode full scan, was used as the survey scan to trigger multiple dependent enhanced product ion scans (EPI), the trap mode product ion scans. The single data file collected with this approach not only includes full scan data (the survey), but also product ion spectra rich in structural information. By extracting characteristic product ions from the dependent EPI chromatograms, we can provide nearly complete information for in vitro metabolites that otherwise would have to be obtained by multiple precursor ion scan (prec) and constant neutral loss (NL) analysis. This approach effectively overcomes the disadvantages of traditional prec and NL scans, namely the slow quadrupole scan speed, and possible mass shift. Using nefazodone (NEF) as the model compound, we demonstrated the effectiveness of this strategy by identifying 22 phase I metabolites in a single liquid chromatography/tandem mass spectrometry (LC/MS/MS) run. In addition to the metabolites reported previously in the literature, seven new metabolites were identified and their chemical structures are proposed. The oxidative dechlorination biotransformation was also discovered which was not reported in previous literature for NEF. The strategy was further evaluated and worked well for the fast discovery setting when a ballistic gradient elution was used, as well as for a simulated in vivo setting when the incubated sample (phase I metabolites) was spiked to control human plasma extract and control human urine.

ABSTRACT:Bicifadine [DOV 220,075; (؎)-1-(4-methylphenyl)-3-azabicyclo-[3.1.0]hexane HCl)] is a non-narcotic analgesic that has proven to be effective for the treatment of acute pain in clinical studies. The pharmacokinetics, disposition, and metabolism of bicifadine were determined in eight healthy adult male subjects following a single oral dose of 200 mg of [ 14 C]bicifadine in solution. The maximum concentration of total drug equivalents and bicifadine in plasma was at approximately 1 h; the elimination half-life was 2.6 and 1.6 h for radioactivity and bicifadine, respectively. Unchanged bicifadine represented 15% of the area under the concentration-time curve for total drug equivalents; the rest was due mainly to the lactam (M12), the acid (M3), and the lactam acid (M9). Total recovery of the dose was 92%, with most of the radioactivity recovered in the urine in the first 24 h; fecal excretion accounted for only 3.5% of the dose. Approximately 64% of the dose was metabolized to M9 and its acyl glucuronide; another 23% was recovered as M3 and its acyl glucuronide. Neither bicifadine nor M12 were detected in urine or feces. There were no reported serious or severe adverse events during the study.Chronic peripheral neuropathic pain is difficult to treat, and side effects may limit the usefulness of a drug. Although opiates have been used for neuropathic pain management, tolerance develops to their analgesic efficacy, and they cause drowsiness and constipation. Empirical observations have demonstrated the efficacy of tricyclic antidepressants in treating peripheral neuropathy (Sindrup et al., 2005). Research has shown that this effect is produced by inhibition of the neuronal reuptake of NE and 5-HT and blocks the postsynaptic ␣-adrenergic, H 1 -histaminergic, and muscarinic cholinergic receptors. Duloxetine is a selective 5-HT and NE reuptake inhibitor that has been approved for treatment of diabetic neuropathy. Bupropion is a weak blocker of NE and DA, but not 5-HT, reuptake (Ascher et al., 1995) but was effective in reducing neuropathic pain in patients with human immunodeficiency virus (Semenchuck et al., 2001). The involvement of DA in analgesic mechanisms suggests that a broadened analgesic range may result from the ability to enhance dopaminergic neurotransmission, in addition to activating serotonergic and noradrenergic pathways. Thus, agents that simultaneously inhibit DA, NE, and 5-HT transporters may possess a unique analgesic profile, Bicifadine (Fig. 1) is being developed for the treatment of neuropathic pain. It inhibits NE (IC 50 , 55 nM) and 5-HT (117 nM) reuptake, with lesser potency in blocking DA reuptake (910 nM), as determined using recombinant human transporter systems (Basile et al., 2007). In vivo microdialysis studies in the brains of rats indicate that bicifadine increases the extracellular levels of all three neurotransmitters following oral administration of analgesic doses (Basile et al., 2007). Bicifadine was an effective antinociceptive agent in both the early (acute) and late (ton...

ABSTRACT:The in vitro metabolism of [ 14 C]bicifadine by hepatic microsomes and hepatocytes from mouse, rat, monkey, and human was compared using radiometric high-performance liquid chromatography and liquid chromatography/tandem mass spectrometry. Two main metabolic pathways were identified in all four species. One pathway was an NADPH-dependent pathway in which the methyl group was oxidized to form a hydroxymethyl metabolite (M2). Its formation was inhibited in human microsomes only by quinidine, a CYP2D6 inhibitor. In incubations with individual cDNA-expressed human cytochromes P450, M2 was formed only by CYP2D6 and CYP1A2, with CYP2D6 activity 6-fold greater than that of CYP1A2.

ABSTRACT:Bicifadine [DOV 220,075; (؎)-1-(4-methylphenyl)-3-azabicyclo[3.1.0]-hexane HCl)] is a non-narcotic analgesic that is effective in animal models of acute and chronic pain. In this study, the pharmacokinetics, disposition, and metabolism of bicifadine were determined in male and female mice, rats, and cynomolgus monkeys following single oral and i.v. doses. [ 14 C]Bicifadine was well absorbed in all three species. The oral bioavailability of bicifadine in mice and rats was 50 to 63% and 79 to 85%, respectively, and slightly lower in monkeys (33-42%). Based on the values of the area under the concentration-time curves, unchanged bicifadine comprised 7 to 12% of the plasma radioactivity after the oral dose and 14 to 26% after the i.v. dose in all three species. The major plasma metabolites were the lactam (M12), the lactam acid (M9), and the acid (M3) plus its glucuronide conjugate. At 0.5 h after the oral dose to rats, 63 to 64% of the radioactivity in the rat brain was bicifadine, and the remainder was the lactam. Most of the radioactivity after oral and i.v. dosing to the three species was recovered in the urine. The lactam acid was the major urinary metabolite in all species; bicifadine and the lactam were either not detected or were minor components in urine. Fecal radioactivity was due to the acid and lactam acid in the three species. Rat bile contained mainly the lactam acid and the acid plus its acyl glucuronide. Plasma protein binding of [ 14 C]bicifadine was moderate in the mouse (80-86%) and higher in the rat and monkey (95-97%). In summary, bicifadine was well absorbed, extensively metabolized, and excreted via the urine and feces as metabolites.Bicifadine (Fig. 1) is an inhibitor of norepinephrine and serotonin uptake that is being developed for the treatment of acute and chronic pain. The compound is a non-narcotic analgesic (Epstein et al., 1982) that is active in preclinical models of neuropathic pain. In animals, bicifadine has been shown to inhibit dopamine uptake, thus making it a functional triple reuptake inhibitor with antinociceptive and antiallodynic activity in acute, persistent, and chronic pain models (Basile et al., 2007). Clinically, it has been shown to be effective in the treatment of acute dental (Stern et al., 2005) and bunionectomy pain (Riff et al., 2006).The metabolites of bicifadine formed by mouse, rat, monkey, and human hepatocytes and microsomes were reported previously (Erickson et al., 2007). The two main metabolic pathways in all four species were formation of a lactam and the oxidation of the tolylmethyl group. When tested in human in vitro systems, MAO-B was the principal enzyme that formed the lactam, whereas CYP2D6 was responsible for the initial hydroxylation of the tolylmethyl group. The present studies were performed to determine the pharmacokinetics, metabolism, and disposition of bicifadine in the mouse, rat, and monkey, the species used in toxicological and carcinogenicity studies. Materials and MethodsChemicals and Reagents. [ Animal Studies. All experim...

The study reported herein examined the metabolism of 14C-labeled hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) resulting from a single oral gavage of 5 ml/kg to male and female Yucatan miniature pigs (43 mg/kg, 56 microCi/kg in 0.5% carboxymethylcellulose in water). Blood, urine, and feces were collected at selected times of 1, 6, 12, and 24 h postdose. At 24 h postdose, liver samples were collected. Blood, plasma, liver, and excreta were analyzed for total RDX-derived radioactivity and metabolites were identified. Urine was the major route of elimination of 14C-RDX-derived radioactivity in both males and females. Relatively low levels of radioactivity were found in gastrointestinal contents and in feces, suggesting nearly complete absorption of 14C-RDX following an oral dose. Analysis of urine by liquid chromatography-mass spectrometry (LC/MS) identified quantifiable levels of two ring-cleavage metabolites, 4-nitro-2,4-diazabutanal and 4-nitro-2,4-diaza-butanamide, as well as parent RDX. The 4-nitro-2,4-diazabutanal, was seen in earlier studies of aerobic metabolism of RDX. The 4-nitro-2,4-diaza-butanamide, an amide, was not previously reported but was tentatively identified in this study. Analysis by a more sensitive method (LC/MS/MS) also showed trace amounts of the RDX metabolites 1-nitroso-3,5-dinitro-1,3,5-triazacyclohexane (MNX) (in both male and female urine) and 1-nitro-3,5-dinitroso-1,3,5-triazacyclohexane (DNX) (in male urine). Analysis of plasma by LC/MS/MS also revealed quantifiable levels of RDX and trace levels of MNX, DNX, and 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNX). None of the liver extracts showed quantifiable levels of RDX or any identifiable metabolites. Most of the radioactivity was in the form of water-soluble high-molecular-weight compounds. RDX when given orally to pigs was rapidly metabolized by loss of two nitro groups followed by ring cleavage.