Mean Recovery Of Radioactivity Research Articles

1120. Absorption, Metabolism, and Excretion of [14C]-Tebipenem Pivoxil Hydrobromide (TBP-PI-HBr) Following a Single Oral Dose in Healthy Male Subjects

BackgroundTebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral prodrug that is converted to tebipenem (TBP), the active moiety, with activity against multidrug-resistant gram-negative pathogens, including extended-spectrum-β-lactamase (ESBL)-producing Enterobacterales. TBP-PI-HBr is the first oral carbapenem intended for treating complicated urinary tract infections and acute pyelonephritis. This study evaluated the absorption, metabolism, and excretion (AME) of TBP-PI-HBr following a single oral dose of [14C]-TBP-PI-HBr to healthy males and characterized metabolites in plasma, urine, and feces.MethodsThis was a Phase 1, open-label, single-dose study in healthy subjects. Study drug was provided as radiolabeled and non-radiolabeled active pharmaceutical ingredient containing approximately 150 μCi of [14C]-TBP-PI-HBr. On Day 1, each subject received a 600 mg dose of TBP-PI-HBr. administered with 240 mL of water and fasted overnight for at least 10 hours. Blood samples were collected to determine TBP concentrations (whole blood), total radioactivity (whole blood and plasma), and metabolite profiling and identification were determined from plasma, urine, and feces. For mass balance, total radioactivity derived from urine and feces collections were determined. PK parameters were calculated using noncompartmental methods.ResultsTotal radioactivity in plasma and whole blood decreased rapidly with geometric mean t½ values of 6.0 hours and 3.5 hours, respectively and Tmax of 1 hour. The cumulative mean recovery of radioactivity was 38.7% in urine and 44.6% in feces. Most of the administered radioactivity was recovered in the first 144 hours post dose in urine and feces (80.0%). Six of 8 subjects achieved a mass balance recovery ranging from 80.1% to 85.0%. The TBP plasma to total radioactivity ratio of 0.536 indicated that other metabolites contribute to the total radioactivity AUC in plasma. Metabolite profiling and identification results indicated that TBP was the major component in plasma and urine. The inactive ring open metabolite of TBP (LJC 11,562) was also found in plasma ( >10%), urine (5.27%), and feces ( >10%) as a secondary metabolite.ConclusionThis study adequately characterized the AME of TBP-PI-HBr in humans.Disclosures Vipul K. Gupta, Ph.D., Spero Therapeutics (Employee, Shareholder) Gary Maier, PhD, Spero Therapeutics, Inc. (Consultant) Leanne Gasink, MD, Spero Therapeutics, Inc. (Consultant) Amanda Ek, MS, Spero Therapeutics, Inc. (Employee) Mary Fudeman, BA, MBA, Spero Therapeutics, Inc. (Employee) Praveen Srivastava, MS, BS, Spero Therapeutics, Inc. (Employee) Angela Talley, MD, Spero Therapeutics, Inc. (Employee)

Characterization of Clinical Absorption, Distribution, Metabolism, and Excretion and Pharmacokinetics of Velsecorat Using an Intravenous Microtracer Combined with an Inhaled Dose in Healthy Subjects.

This open-label, single-period study describes the human absorption, distribution, metabolism, excretion, and pharmacokinetics of velsecorat (AZD7594). Healthy subjects received inhaled velsecorat (non-radiolabeled; 720 µg) followed by intravenous infusion of carbon 14 (14C)-velsecorat (30 µg). Plasma, urine, and feces were collected up to 168 hours post-dose. Objectives included identification and quantification of velsecorat and its metabolites (i.e., drug-related material) in plasma and excreta, and determining the elimination pathways of velsecorat by measuring the rate and route of excretion, plasma half-life (t1/2), clearance, volume of distribution and mean recovery of radioactivity. On average, 76.0% of administered 14C dose was recovered by the end of the sampling period (urine = 24.4%; feces = 51.6%), with no unchanged compound recovered in excreta, suggesting that biliary excretion is the main elimination route. Compared with intravenous 14C-velsecorat, inhaled velsecorat had a longer t1/2 (27 versus 2 hours), confirming that plasma elimination is absorption-rate-limited from the lungs. Following intravenous administration, t1/2 of 14C-drug-related material was longer than for unchanged velsecorat, and 20% of the 14C plasma content was related to unchanged velsecorat. The geometric mean plasma clearance of velsecorat was high (70.7 l/h) and the geometric mean volume of distribution at steady state was 113 l. Velsecorat was substantially metabolized via O-dealkylation of the indazole ether followed by sulfate conjugation, forming the M1 metabolite, the major metabolite in plasma. There were 15 minor metabolites. Velsecorat was well tolerated, and these results support the progression of velsecorat to phase 3 studies. SIGNIFICANCE STATEMENT: This study describes the human pharmacokinetics and metabolism of velsecorat, a selective glucocorticoid receptor modulator, evaluated via co-administration of a radiolabeled intravenous microtracer dose and a non-radiolabeled inhaled dose. This study provides a comprehensive assessment of the disposition of velsecorat in humans. It also highlights a number of complexities associated with determining human absorption, distribution, metabolism, and excretion for velsecorat, related to the inhaled route, the high metabolic clearance, sequential metabolite formation and the low intravenous dose.

<p>Metabolism and Excretion of Intravenous, Radio-Labeled Amisulpride in Healthy, Adult Volunteers</p>

PurposeIntravenous amisulpride, a dopamine D2/D3 antagonist, has recently been shown in trials to be an effective antiemetic at low doses. This study was conducted to investigate the metabolism and elimination of a single dose of intravenous 14C-labeled amisulpride in healthy, adult volunteers.Patients and methodsSix healthy male volunteers aged 18–65 years were given a single 10 mg dose of 14C-labeled amisulpride containing not more than 1.8 MBq of radioactivity, infused over 4 mins. Concentrations of amisulpride and total radioactivity were measured in plasma, whole blood, urine and feces at various time points up to 168 hrs after dosing. Metabolites detected in plasma, urine and feces were characterized using liquid chromatography tandem mass spectrometry (LC-MS/MS) with in-line radiometric detection.ResultsThe mean recovery of radioactivity in excreta was 96.4% (range 92.0–98.5%), of which 73.6% (range 70.6–79.2%) was recovered from urine and 22.8% (range 18.9–25.7%) from feces. Four metabolites of amisulpride were detected in urine, representing 15.0% of the excreted dose; three of these were also present in feces, representing 6.1% of the excreted dose. No metabolites were detected in plasma. Excretion was initially rapid, with about two-thirds of the drug-related material eliminated within 12 hrs, primarily in the urine. A second, slower phase of excretion was predominantly fecal and was essentially complete by 96 hrs after dosing. The terminal plasma elimination half-life of parent amisulpride was 3.7 hrs and that of total 14C-labeled drug material was 4.2 hrs.ConclusionIntravenous amisulpride undergoes limited metabolism and is excreted primarily via the renal route.Clinical trial registry numberClinicalTrials.gov NCT02881840.

731. Pharmacokinetics of Gepotidacin (GSK2140944) in Subjects with Hepatic Impairment

BackgroundGepotidacin (GEP), a first in class novel triazaacenaphthylene bacterial topoisomerase inhibitor, inhibits bacterial replication and has in vitro and in vivo efficacy activity against key pathogens, including drug-resistant strains, associated with a range of infections. In a previous absorption, distribution, metabolism, and excretion study for GEP, the mean recovery of radioactivity in urine and feces accounted for approximately 31.2% and 52.5%, respectively, of [14C]-GEP administered as a single oral dose. GEP was eliminated mainly as parent in urine, accounting for approximately 20% of the administered dose. Elimination via metabolism accounted for a total of 13% to 19% of the dose. Average total intravenous clearance of approximately 43 L/hour and renal clearance (CLr) of approximately 16 L/hour provides a hepatic clearance of 27 L/hour, suggesting that hepatic clearance is a major route of elimination of GEP.MethodsParticipants with normal and varying degrees of hepatic impairment (HI) received a single oral dose of GEP 1,500 mg. PK collections of blood, urine and saliva were performed.ResultsRelative to normal hepatic function, GEP Cmax and AUC(0-∞) in plasma were increased by 1.2-fold in subjects with moderate, and between 1.7-fold to 1.9-fold in severe HI. The fraction of dose excreted in urine increased with an increase in hepatic impairment. GEP urine concentrations remained high over a 12-hour period. Saliva concentrations displayed a linear relationship with plasma (both total and unbound) concentrations (R2 = 0.76). The geometric mean ratio of saliva AUC to unbound plasma AUC values ranged from 0.746 to 0.839 across all groups. Administration of 1,500 mg oral GEP was generally tolerated.ConclusionAn increase in the dosing interval or dose reduction may be required in patients with severe hepatic impairment. Disclosures All authors: No reported disclosures.

Abstract CT159: Investigation of the absorption, metabolism, excretion, and mass balance of [14C]-pacritinib in healthy subjects: a phase I study

Abstract Introduction: Dysregulation in tyrosine kinase signaling has been implicated in development of hematologic malignancies including myelofibrosis and lymphomas. Pacritinib is an oral kinase inhibitor with specificity for JAK2, FLT3, CSF1R, and IRAK1. In mouse distribution studies of radiolabeled pacritinib, ∼91% of administered dose was recovered in the feces, suggesting an important role for biliary elimination in clearance of pacritinib. This phase 1 trial investigated clearance pathways, excretion, pharmacokinetics, and recovery of pacritinib, its major metabolites, and total radioactivity in healthy volunteers. Methods: Healthy male volunteers aged 18-55 y were eligible for inclusion. Study volunteers received a single 400 mg dose of pacritinib capsules plus a single dose of [14C]-pacritinib (100 μCi radioactivity per <1 mg of pacritinib as a 30 mL suspension). Blood, urine, and feces were sampled predose and up to 42 days postdose. Pacritinib and metabolites were identified using HPLC-MS/MS/radio flow-through detector (RFD), high resolution mass spectrometry, and authentic metabolite standards. Results: Six subjects were enrolled and received [14C]-pacritinib. Peak radioactivity in plasma was reached approximately 2 h following administration. Mean apparent volume of distribution and apparent clearance in plasma were 137 L and 1.73 L/h, respectively. Elimination half-life for total radioactivity in plasma was 55.1 h. Twelve pacritinib metabolites were identified: M1, M2, M3, M5, M6, M7, M8, M9, M12, M13, M14, and M14a and reflected metabolic pathways including oxidation, N-dealkylation, O-dealkylation, hydrolysis, and dehydrogenation. Pacritinib was the predominant radioactive component (72%) recovered in plasma from 0.5-120 h with mean maximum concentration (Cmax) of 4117.2 ng/mL. Mean Cmax for M2, M1, M3, and M8 were 887.0, 854.5, 292.3, and 148.6 ng/mL respectively. Mean metabolite exposure ratios for major metabolites, M1 and M2, in plasma relative to pacritinib were 0.0963 and 0.105, respectively. Mean recovery of radioactivity in urine (0-48 h) was 3.22% of administered dose; M7, a glucuronidated metabolite, was the predominant radioactive component (3.03% of administered dose). Pacritinib recovered in urine accounted for 0.12% of administered dose. From 0-240 h postdose, mean recovery of radioactivity in feces was 85.5% of administered dose. Pacritinib was detected by MS in fecal samples, but not by RFD. Metabolite M2 was the predominant radioactive fecal component, (24.1% of administered dose). Five individuals (83.3%) reported 9 total adverse events (AEs); all AEs were grade 1 and included diarrhea (5 events in 4 individuals) and nausea (1 event in 1 individual). There were no clinically significant abnormalities in vital signs, ECG, or by physical examination. Conclusions: Following oral administration, pacritinib was the predominant moiety recovered in plasma. Pacritinib was extensively metabolized; major metabolites (M1, oxidation; M2, dealkylation) have relatively low pharmacological potency and are unlikely to substantially contribute to the activity of pacritinib. Intact pacritinib was minimally excreted in urine and feces. Most radioactivity was recovered as metabolites in feces, suggesting extensive biliary clearance and hepatic metabolism of pacritinib. Citation Format: Suliman Al-Fayoumi, Sherri Amberg, Huafeng Zhou, Lindsey Millard, Jack W. Singer, James P. Dean. Investigation of the absorption, metabolism, excretion, and mass balance of [14C]-pacritinib in healthy subjects: a phase I study. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT159.

Pharmacokinetics, metabolism and excretion of [14C]-lanicemine (AZD6765), a novel low-trapping N-methyl-d-aspartic acid receptor channel blocker, in healthy subjects

1. (1S)-1-phenyl-2-(pyridin-2-yl)ethanamine (lanicemine; AZD6765) is a low-trapping N-methyl-d-aspartate (NMDA) channel blocker that has been studied as an adjunctive treatment in major depressive disorder. The metabolism and disposition of lanicemine was determined in six healthy male subjects after a single intravenous infusion dose of 150 mg [14C]-lanicemine.2. Blood, urine and feces were collected from all subjects. The ratios of Cmax and AUC(0–∞) of lanicemine to plasma total radioactivity were 84 and 66%, respectively, indicating that lanicemine was the major circulating component with T1/2 at 16 h. The plasma clearance of lanicemine was 8.3 L/h, revealing that lanicemine is a low-clearance compound. The mean recovery of radioactivity from urine was 93.8% of radioactive dose.3. In urine samples, 10 metabolites of lanicemine were identified. Among which, an O-glucuronide conjugate (M1) was the most abundant metabolite (∼11% of the dose in excreta). In plasma, the circulatory metabolites were identified as a para-hydroxylated metabolite (M1), an O-glucuronide (M2), an N-carbamoyl glucuronide (M3) and an N-acetylated metabolite (M6). The average amount of each of metabolite was less than 4% of total radioactivity detected in plasma or urine.4. In conclusion, lanicemine is a low-clearance compound. The unchanged drug and metabolites are predominantly eliminated via urinary excretion.

Etamicastat, a new dopamine-ß-hydroxylase inhibitor, pharmacodynamics and metabolism in rat

Despite the importance of sympathetic nervous system in pathophysiological mechanisms of cardiac heart failure and essential hypertension, therapy specifically targeting the sympathetic nervous system is currently underutilized. Etamicastat is a novel dopamine-ß-hydroxylase (DBH) inhibitor that is oxidized into BIA 5-965 and deaminated followed by oxidation to BIA 5-998, which represents 13% of total etamicastat and quantified metabolites. However, the primary metabolic pathway of etamicastat in rats was found to be the N-acetylation (BIA 5-961), which represents 44% of total etamicastat and quantified metabolites. Trace amounts of BIA 5-961 de-sulfated and S-glucuronide were also detected. All the main metabolites of etamicastat inhibited DBH with IC50 values of 306 (228, 409), 629 (534, 741), 427 (350, 522)nM for BIA 5-965, BIA 5-998 and BIA 5-961, respectively. However, only etamicastat (IC50 of 107 (94; 121)nM) was able to reduce catecholamine levels in sympathetic nervous system innervated peripheral tissues, without effect upon brain catecholamines. Quantitative whole body autoradiography revealed a limited transfer of etamicastat related radioactivity to brain tissues and the mean recovery of radioactivity was ~90% of the administered radioactive dose, eliminated primarily via renal excretion over 5 days. The absolute oral bioavailability of etamicastat was 64% of the administered dose. In conclusion, etamicastat is a peripheral selective DBH inhibitor mainly N-acetylated in the aminoethyl moiety and excreted in urine. Etamicastat main metabolites inhibit DBH, but only etamicastat demonstrated unequivocal pharmacological effects as a DBH inhibitor with impact upon the activity of the sympathetic nervous system under in vivo conditions.

Abstract 3367: Massbalance, excretion and metabolism of [14C]-Pralatrexate (PDX) incancer patients in a phase I trial.

Abstract Background: PDX is a novel 10-deaza-aminopterin analogue of methotrex[[Unsupported Character - Codename ­]]ate consisting of a mixture of R- and S-diastereomeric folate derivatives. PDX inhibits folate metabolism by binding to and inhibiting the enzyme dihydrofolate reductase (DHFR). PDX is the first drug approved by the US Food and Drug Admin[[Unsupported Character - Codename ­]]istration (FDA) specifically for the treatment of patients with relapsed or refractory peripheral T-cell lymphoma. Mass balance studies in animals and humans with radiolabeled compounds represent a standard part of the development process for new drugs. Isotopically labeled analogs of a drug or its metabolites play an important role in understanding the absorption, distribution, metabolism and excretion profiles of a compound. The objectives of this study were to determine the pharmacokinetics (PK), metabolism and routes of excretion of [14C]-PDX and to characterize its metabolites in human plasma and urine. Methods: Four patients were administered intravenously with a mixture of 50 μCi of [14C]-PDX (0.5 mg) and 224.5 mg of non radioactive PDX over a 3-5 minute infusion. Serial blood and plasma samples were drawn at: 0 (before PDX infusion), and up to 144 h after the start of infusion. Urine and fecal samples were collected for up to 168 h after the start of infusion. Expired air samples were collected up to 24 hours after administration. The radioactivity measurement in biological fluids was performed using liquid scintillation counting. Results: Mass balance was achieved with a mean recovery radioactivity in excreta= 82.9 % ± 20.0 % for the four patients. The mean recovery of radioactivity in urine, feces, and expired air were 34.1%, 38.7% and 10.1%, respectively, indicating renal and fecal excretions were the major route of elimination of [14C]-PDX. A three-compartment open model adequately described [14C]-PDX time radioactivity-concentration courses. The AUC0-∞, and clearance values for total radioactivity in plasma were 18.1 nCi.h/mL, and 3.95 L/h, respectively. Metabolite profiling will be performed using HPLC with beta radiation detector. Conclusions: This study quantified the mass balance of PDX and defined its substantial excretion in both urine and feces after IV administration. The PK of [14C]-PDX was best described by a three compartment open model. The metabolite profiling of PDX is ongoing. Citation Format: Elodie Odore, Keyvan Rezaï, Olivier Madar, Sophie Weill, Ahmad Awada, Bert Pronk, Esteban Cvitkovic, Francois Lokiec. Massbalance, excretion and metabolism of [14C]-Pralatrexate (PDX) incancer patients in a phase I trial. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3367. doi:10.1158/1538-7445.AM2013-3367

Pharmacokinetics, Biotransformation, and Mass Balance of Edoxaban, a Selective, Direct Factor Xa Inhibitor, in Humans

This study determined the mass balance and pharmacokinetics of edoxaban in humans after oral administration of [¹⁴C]edoxaban. After oral administration of 60 mg (as active moiety) of [¹⁴C]edoxaban to six healthy male subjects, serial blood/plasma and urinary and fecal samples were collected for up to 168 h postdose. All samples were analyzed for total radioactivity by liquid scintillation counting and for concentrations of edoxaban and four metabolites in plasma, urine, and fecal samples by either high-performance liquid chromatography/tandem mass spectrometry method using multiple reaction modes, or a liquid chromatography radiometric method. The mean recovery of radioactivity was >97% of the administered radioactive dose, with 62.2% eliminated in feces and 35.4% in urine. Unchanged edoxaban accounted for the majority of radioactivity, with 49.1 and 23.8% of the dose as parent observed in feces and urine, respectively. Unchanged edoxaban was the most abundant species in plasma, with a mean area under the curve (AUC)(0-∞) of 1596 ng · h/ml. The next most abundant species was metabolite M4, with a mean AUC(0-∞) 147 ng · h/ml. The mass balance of edoxaban was well described, with unchanged edoxaban as the most abundant component of total radioactivity. Edoxaban is eliminated through multiple pathways, but each accounts for only a small amount of overall elimination.

Abstract 751: Mass balance, excretion and metabolism of [14C] ASA404 in cancer patients in a phase I trial

Abstract Purpose: To determine the mass balance, excretion and metabolism of the small molecule flavonoid tumor vascular disrupting agent ASA404 in patients with advanced cancer. Methods: Seven cancer patients were given a single dose of 3000 mg [14C] ASA404 by intravenous infusion over 20 minutes prior to collection of samples of plasma, urine and faeces. Pharmacokinetic samples were analysed by HPLC, liquid scintillation counting, mass spectrometry, glusulase treatment and comparison to authentic standards. Descriptive pharmacokinetic parameters were generated by non-compartmental analysis. Results: Mass balance was achieved (mean recovery of radioactivity in excreta = 86.9% of the dose) with balanced excretion between urine (mean recovery of radioactivity in urine = 53.9% of dose) and faeces (mean recovery of radioactivity in faeces = 33.3% of dose). ASA404 was eliminated as parent drug, three known metabolites (6-hydroxy-ASA404, ASA404 acyl glucuronide and 6-hydroxy-ASA404 acyl glucuronide) and as two novel metabolites (an ASA404 dimer and an ASA404 dimer glucuronide conjugate). Unchanged ASA404 was the major radioactivity component detected in plasma within the first 24 hours after dosing. At later time-points, irreversibly protein bound ASA404 and all of the metabolites that had been detected in excreta, contributed to total plasma radioactivity. Conclusion: This study defined the substantial excretion of ASA404, mainly as metabolites, in both urine (over half of the dose) and faeces (about one third of the dose) after intravenous administration. Two novel metabolites were identified that were not reported by previous studies using nonradioactive techniques. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 751. doi:1538-7445.AM2012-751

Mass balance, excretion and metabolism of [14C] ASA404 in cancer patients in a phase I trial

To determine the mass balance, excretion and metabolism of the small molecule flavonoid tumour vascular disrupting agent ASA404 in patients with advanced cancer. Seven cancer patients were given a single dose of 3,000 mg [(14)C] ASA404 by intravenous infusion over 20 min prior to collection of samples of plasma, urine and faeces. Pharmacokinetic samples were analysed by HPLC, liquid scintillation counting, mass spectrometry, glusulase treatment and comparison to authentic standards. Descriptive pharmacokinetic parameters were generated by noncompartmental analysis. Mass balance was achieved (mean recovery of radioactivity in excreta = 86.9% of the dose) with balanced excretion between urine (mean recovery of radioactivity in urine = 53.9% of dose) and faeces (mean recovery of radioactivity in faeces = 33.3% of dose). ASA404 was eliminated as parent drug, three known metabolites (6-methylhydroxy-ASA404, ASA404 acyl glucuronide and 6-methylhydroxy-ASA404 acyl glucuronide) and two novel metabolites (an ASA404 dimer and an ASA404 dimer glucuronide conjugate). Unchanged ASA404 was the major radioactivity component detected in plasma within the first 24 h after dosing. At later time points, irreversibly protein bound ASA404 and all of the metabolites that had been detected in excreta contributed to total plasma radioactivity. This study defined the substantial excretion of ASA404, mainly as metabolites, in both urine (over half of the dose) and faeces (about one-third of the dose) after intravenous administration. Two novel metabolites were identified that were not reported by previous studies using nonradioactive techniques.

Metabolism and Disposition of Fluticasone Furoate, an Enhanced-Affinity Glucocorticoid, in Humans

The purpose of this study was to investigate the metabolism and disposition of fluticasone furoate, an enhanced-affinity glucocorticoid receptor agonist, in humans. In a two-part, open-label design study, five healthy male subjects received a p.o. dose of 2 mg of [(14)C]fluticasone furoate, followed 4 weeks later by an i.v. dose of 0.25 mg of [(14)C]fluticasone furoate (as a 30-min infusion). Oral absorption was rapid and estimated at approximately 30%, although the oral bioavailability was markedly lower at 1.6%, limited by extensive first-pass metabolism. Plasma clearance was 58.3 l/h, with a volume of distribution of 642 liters and a terminal elimination half-life of 15.3 h. The major circulating component identified in plasma extracts after i.v. and p.o. dosing was unchanged parent compound, with 17beta-carboxylic acid (GW694301X; M10) also being notable after p.o. administration. Mean recovery of radioactivity was approximately 92 and 102% at 216 and 168 h after i.v. and p.o. administration, respectively, with most (at least 90%) recovered in the feces. Fluticasone furoate was extensively metabolized, with only trace amounts of unchanged parent compound observed in feces following either route of administration. The predominant pathway was removal of the S-fluoromethyl carbothioate group to yield GW694301X (M10). Other pathways included oxidative defluorination to yield a hydroxyl at the C6 position. There was no evidence for metabolic loss of the furoate group from fluticasone furoate or any of its metabolites. Evidence presented suggests that enterocytes have a role in the metabolism of unabsorbed fluticasone furoate.

Absorption, metabolism, and excretion of 14C gimatecan (LBQ707) after oral administration in patients with advanced cancer

2564 Background: Gimatecan (Gim), a new potent oral topoisomerase I inhibitor is a lipophilic 7-oxyiminomethyl derivative of camptothecin. Its in vitro cytoxicity is more sustained than CPT-11 and topotecan, it has excellent anti-tumor activity in mouse xenografts, and shown good tolerability with Ph I activity. The study aim was to profile its disposition in cancer patients. Methods: 4 patients with advanced cancer received a single oral 1.5 mg dose of [14C] Gim (60 μCi) followed by standard Gim treatment on Day 15. Whole blood, plasma, urine, and feces were collected over 7 days with spot fecal collections up to Day 19. Total radioactivity was measured by liquid scintillation counting. Gim and metabolite concentrations in plasma and excreta were measured by LC- MS/MS and HPLC with radiometric detection. Results: Gim showed a rapid first-order absorption and a long elimination phase and was well tolerated. The median (range) Tmax for Gim was 1 h (0.5 to 3 h) and mean t1/2 and oral clearance values were 91 h and 0.6 L/h, respectively. Gim was the major moiety and its active metabolite LCF775 (t-butyl-mono-hydroxy Gim) was the main metabolite (albeit minor, 2–9%) in plasma. Trace glucuronide and sulfate metabolites were also detected in plasma. Mean recovery of radioactivity in urine (0-Day 7) and feces (0-Day 11) was 70.5 % (56.2–80.0%) of the dose. Incomplete recovery is attributed to opiates use in 2 patients and incomplete (sporadic) fecal sampling at later timepoints. Fecal excretion (0-Day 11) was prolonged and major in 3/4 patients (46- 73% of the dose, of which 14–23% is the unchanged Gim suggesting the drug is well absorbed). An additional 1.3–3.5% was recovered in spot collections (Days 14, 15 and 19). Urine excretion (0-Day 7) was 7.2–10.3% of the dose in 3 patients, one patient (cachectic, on opiates) excreted only 21% in feces and 46% in urine. Gim and several Gim metabolites (and glucuronide conjugates thereof) were the major components in excreta. Conclusions: Gim and its minor metabolite, LCF775 were the principal pharmacologically active components in plasma. Fecal excretion is the main elimination pathway in most patients. A long half-life (90hr) of Gim, uncomplicated metabolism, and good oral absorption make Gim an attractive candidate for Ph II development. [Table: see text]

Urinary testosterone measurement by gas chromatography after solid-phase extraction and high-performance liquid chromatography

A method was developed for the rapid determination of testosterone in urine. The procedure consists of solid-phase extraction (SPE) followed by high-performance liquid chromatographic (HPLC) clean-up before gas chromatographic determination. Recovery was evaluated by adding [ 3H]testosterone (10 4 cpm) to urine samples; the mean recovery of radioactivity after SPE and HPLC was 82%. Precision was estimated by repeated measurement of testosterone in four different urine samples; the coefficient of variation was 7.9% (95% confidence limits 6.1–11.4%). Accuracy was evaluated by standard addition and dilution assays; a linear relationship was found between the expected and observed values ( r 2 = 0.982). The method is rapid, effective and suitable for routine analysis.

The Pharmacokinetics of Omeprazole in Humans—A Study of Single Intravenous and Oral Doses

The pharmacokinetics of omeprazole, hydroxyomeprazole, omeprazolesulfone, and "remaining metabolites" have been studied in eight young healthy subjects following an acute i.v. and oral dose of 10 and 20 mg of 14C-labeled drug, respectively. The oral dose was given as a buffered solution. Two subjects exhibited essentially higher and more sustained plasma levels of omeprazole than the others. This was due to a higher bioavailability, lower clearance, and longer t1/2 of omeprazole in these two subjects. Maximum concentration (0.7-4.6 mumol/L) was reached between 10 and 25 min after oral dosing. The median bioavailability was 39% (25-117%) and the median systemic plasma clearance was 624 ml/min (range of 59-828 ml/min). The corresponding t1/2 for the i.v. dose was 35 min (16-150 min) and 39 min (14-186 min) after oral administration. The drug was rapidly distributed to extravascular sites (mean t1/2 lambda 1 = 3.0 +/- 0.8 min). Mean Vss was 0.23 +/- 0.04 L/kg. Low systemic clearance of omeprazole was associated with a decreased formation rate of hydroxyomepraxole and "remaining metabolites" while omeprazolesulfone formation seemed to be less affected. However, there was a clear-cut correlation between the t1/2 of omeprazole and of its omeprazolesulfone metabolite, indicating that the elimination of these two compounds is mediated by the same isoenzyme. The mean urinary recovery of the radioactive dose during 96 h was 78.3 +/- 2.3 and 75.7 +/- 2.6% for the i.v. and oral dose, respectively. Insignificant amounts were due to unchanged drug and omeprazolesulfone. The excretion of hydroxyomeprazole during the first 12 h varied between 4.6 to 15.5% of a given dose. The mean recovery of radioactivity in the feces was 19.3 +/- 3.1% of a given i.v. dose and 18.2 +/- 2.3% when given orally. It is concluded that omeprazole is mainly eliminated metabolically and that there is a substantial interindividual variation in the rate of formation of primary and secondary metabolites. This variation in omeprazole disposition is probably of limited clinical importance. The half-life, with a maximum of approximately 3 h, is too short to cause accumulation when the drug is administered in a once-daily regimen.

Metabolism of a new synthetic progestagen, Org 2969, in female volunteers. The distribution and excretion of radioactivity after an oral dose of the labelled drug.

The metabolism of a new synthetic progestagen, Org 2969 was studied in 4 healthy female volunteers. During the first part of the study (Phase I), the volunteers ingested 50 microgram (about 0.1 mCi) of [16-3H5Org 2969 together with 50 microgram of ethinyloestradiol as a single dose. During the second part of the study (Phase II), a 10-day pre-treatment with the same dosage of non-radioactive compound preceded the administration of the radioactive steroid. A peak level of total radioactivity, representing 3.16-5.02% of the dose given/l of serum, was achieved within 2-3 h in Phase I. During Phase II, the corresponding figures were 4.54-5.13% after 1.5-3 h. The difference was mainly due to an increase of freely-extractable steroids during Phase II. The difference can at least partly be explained by assuming a change in the kinetics of the metabolism of Org 2969 by pre-treatment with Org 2969 and ethinyloestradiol. The mean recovery of radio activity in urine and faeces was 83.0%/48.1%/34.9% (total/urine/faeces) of the total dose in Phase I and 76.1%/45.2%/30.9% during Phase II. The differences in the total excretion and in the radioactivity excreted in the faeces were significant.

Comparative Studies of the Intestinal Absorption of [3H]Pteroylmonoglutamate and [3H]Pteroylheptaglutamate in Man

Comparative efficiencies of absorption of crystalline folic acid polyglutamate and monoglutamyl folic acid were determined in 11 normal subjects by measurement of the excretion of radioisotope in the urine after oral administration of [3H]pteroylheptaglutamic acid ([3H]PteGlu7) synthesized in our laboratory and of [3H]pteroylglutamic acid ([3H]PGA). Following ingestion of 0.6 mumole of [3H]PteGlu7, urinary excretion of radioactivity over 48 hr averaged 56.1 +/- 11.2% of the total dose. By comparison the ingestion of 0.6 mumole of [3H]PGA resulted in an average urinary excretion of 70.8 +/- 13.0% for the same time period. Approximately 90% of the urinary radioactivity was excreted during the initial 24-hr collection period. The mean recovery of radioactivity in urine and stool was 94% and recovery exceeded 84% in all subjects. The principal radioactive compound in the urine chromatographed with standard pteroylmonoglutamates. By chromatography, urinary folates were monoglutamates whether [3H]PGA or [3H]PteGlu7 was administered. The time course of folate absorption for the study compounds was compared by measuring the rise in serum radioactivity after the oral folate dose. Peak values in serum folate radioactivity following [3H]PGA occurred at 1 hr, whereas the peak values after [3H]PteGlu7 more often occurred at 2 hr. Only monoglutamyl folate was detected in the serum. These studies demonstrate that in normal subjects physiological doses of crystalline monoglutamyl and crystalline heptaglutamyl folates are both absorbed with high degrees of efficiency.