Total Recovery Of Radioactivity Research Articles

Metabolism and Excretion of [14C]Mobocertinib, a Selective Covalent Inhibitor of Epidermal Growth Factor Receptor (EGFR) Exon 20 Insertion Mutations, in Healthy Male Subjects.

Mobocertinib (formerly known as TAK-788) is a targeted covalent tyrosine kinase inhibitor of epidermal growth factor receptor with exon 20 insertion mutations. This article describes the metabolism and excretion of mobocertinib in healthy male subjects after a single oral administration of [14C]mobocertinib. Mobocertinib-related materials were highly covalently bound to plasma proteins such as human serum albumin. The mean extraction recovery of total radioactivity was only 3.9% for six individual Hamilton pooled plasma samples. After extraction, mobocertinib was the most abundant component accounting for 7.7% of total extracted circulating radioactivity (TECRA) in the supernatant. Each of identified metabolites accounted for <10% of TECRA. Mobocertinib underwent extensive first-pass metabolism with the fraction of the dose absorbed estimated to be approximately 91.7%. Fecal excretion of mobocertinib metabolites was the major elimination route. Mobocertinib was mainly eliminated via oxidative metabolism with a fraction of approximately 88% metabolized by CYP3A4/5. The other minor elimination pathways included cysteine conjugation, metabolism by other cytochrome P450s, and renal excretion of unchanged mobocertinib. SIGNIFICANCE STATEMENT: This article describes the metabolism and excretion of a targeted covalent inhibitor mobocertinib in humans after a single oral administration of [14C]mobocertinib. Mobocertinib was highly covalently bound to human plasma proteins. No metabolite accounted for >10% of total extracted circulating radioactivity in human plasma. Mobocertinib was mainly eliminated via CYP3A4/5 mediated oxidative metabolism followed by fecal excretion after approximately 91.7% of the dose was absorbed.

Mass Balance, Metabolic Pathways, Absolute Bioavailability, and Pharmacokinetics of Giredestrant in Healthy Subjects.

Giredestrant is a potent and selective small-molecule estrogen receptor degrader. The objectives of this study were to assess the absolute bioavailability (aBA) of giredestrant and to determine the mass balance, routes of elimination, and metabolite profile of [14C]giredestrant. In part 1 (mass balance), a single 30.8-mg oral dose of [14C]giredestrant (105 µCi) was administered to women of nonchildbearing potential (WNCBP; n = 6). The mean recovery of total radioactivity in excreta was 77.0%, with 68.0% of the dose excreted in feces and 9.04% excreted in urine over a 42-day sample collection period. The majority of the circulating radioactivity (56.8%) in plasma was associated with giredestrant. Giredestrant was extensively metabolized, with giredestrant representing only 20.0% and 1.90% of the dose in feces and urine, respectively. All metabolites in feces resulted from oxidative metabolism and represented 44.7% of the dose. In part 2 (aBA), WNCBP (n = 10) received an oral (30-mg capsule) or intravenous (30-mg solution) dose of giredestrant. The aBA of giredestrant after oral administration was 58.7%. Following the intravenous dose, giredestrant had a plasma clearance and volume of distribution of 5.31 L/h and 266 L, respectively. In summary, giredestrant was well tolerated, rapidly absorbed, and showed moderate oral bioavailability with low recovery of the dose as parent drug in excreta. Oxidative metabolism followed by excretion in feces was identified as the major route of elimination of giredestrant. SIGNIFICANCE STATEMENT: This study provides definitive insight into the absorption, distribution, metabolism, and excretion of giredestrant in humans. The results show that giredestrant exhibits low clearance, a high volume of distribution, and moderate oral bioavailability in humans. In addition, the data show that oxidative metabolism followed by excretion in feces is the primary elimination route of giredestrant in humans. These results will be used to further inform the clinical development of giredestrant.

Mass Balance and Metabolic Pathways of Eliapixant, a P2X3 Receptor Antagonist, in Healthy Male Volunteers.

Overactive adenosine triphosphate signaling via P2X3 homotrimeric receptors is implicated in multiple conditions. To fully understand the metabolism and elimination pathways of eliapixant, a study was conducted to assess the pharmacokinetics, mass balance, and routes of excretion of a single oral dose of the selective P2X3 receptor antagonist eliapixant, in addition to an invitro characterization. In this single-center open-label non-randomized non-placebo-controlled phase I study, healthy male subjects (n=6) received a single dose of 50mg eliapixant blended with 3.7MBq [14C]eliapixant as a PEG 400-based oral solution. Total radioactivity and metabolites excreted in urine and feces, and pharmacokinetics of total radioactivity, eliapixant, and metabolites in plasma were assessed via liquid scintillation counting and high-performance liquid chromatography-based methods coupled to radiometric and mass spectrometric detection. Metabolite profiles of eliapixant in human invitro systems and metabolizing enzymes were also investigated. After administration as an oral solution, eliapixant was rapidly absorbed, reaching maximum plasma concentrations within 2h. Eliapixant was eliminated from plasma with a mean terminal half-life of 48.3h. Unchanged eliapixant was the predominant component in plasma (72.6% of total radioactivity area under the curve). The remaining percentage of drug-related components in plasma probably represented the sum of many metabolites, detected in trace amounts. Mean recovery of total radioactivity was 97.9% of the administered dose (94.3-99.4%) within 14 days, with 86.3% (84.8-88.1%) excreted via feces and 11.6% (9.5-13.1%) via urine. Excretion of parent drug was minimal in feces (0.7% of dose) and urine (≈0.5%). In feces, metabolites formed by oxidation represented > 90% of excreted total radioactivity. The metabolites detected in the invitro experiments were similar to those identified invivo. Complete recovery of administered eliapixant-related radioactivity was observed in healthy male subjects with predominant excretion via feces. Eliapixant was almost exclusively cleared by oxidative biotransformation (>90% of dose), with major involvement of cytochrome P450 3A4. Excretion of parent drug was of minor importance (~1% of dose). ClinicalTrials.gov: NCT04487431 (registered 27 July 2020)/EudraCT number: 2020-000519-54 (registered 3 February 2020), NCT02817100 (registered 26 June 2016), NCT03310645 (registered 16 October 2017).

Study of the mass balance, biotransformation and safety of [14C]SHR8554, a novel μ-opioid receptor injection, in healthy Chinese subjects.

Background: SHR8554 is a novel μ-opioid receptor-biased agonist. It has analgesic effects by selectively activating the G protein-coupled pathway. Additionally, it can weakly activate the ß-arrestin-2 pathway, resulting in a limited number of side effects, such as gastrointestinal inhibition. Previous studies have shown that SHR8554 has good analgesic effects, safety and tolerability, but the pharmacokinetic characteristics of SHR8554 in humans have not been reported. This study was designed to investigate the pharmacokinetics and safety of SHR8554 in healthy Chinese male subjects. Methods: A single 1mg/41.3μCi intravenous dose of [14C]SHR8554 was administered to six healthy male subjects. Blood, urine and faecal samples were collected at continuous time points to analyse SHR8554 parent drug levels and their metabolites. The total radioactivity in blood, plasma, urine and faeces was detected by using a liquid scintillation counter. The dynamic changes of SHR8554 and its metabolite concentration were by liquid chromatography-tandem mass spectrometry (LC/MS), and then pharmacokinetic analysis. The safety of the drug on the subjects was also observed after a single intravenous injection. Results: The total recovery of radioactivity in urine and faeces was 99.68% ± 0.79% in 216h, including 76.22% ± 1.12% in urine and 23.46% ± 1.36% in faeces. Seventeen major metabolites in blood, urine and faeces were analysed and identified. The main metabolic pathways of SHR8554 in the human body involve 1) N-dealkylation; 2) O-deethylation; 3) mono-oxidation; 4) glucuronidation, etc. The primary mechanism of SHR8554 clearance in the human body is through urinary excretion, primarily in its parent drug and metabolite forms. The drug has good safety, and no serious adverse effects were observed. Conclusion: SHR8554 showed favourable pharmacokinetic characteristics and safety profiles in this study. SHR8554 is extensively metabolized in human body. The main metabolic pathways include N-dealkylation and O-deethylation, as well as mono-oxidation and glucuronidation. The main excretion route of SHR8554 and its metabolites is through urine. Clinical Trial Registration: http://www.chinadrugtrials.org.cn/, identifier CTR20220450.

Disposition study of the novel dipeptidyl peptidase 4 inhibitor cetagliptin in rats

Dipeptidyl peptidase-4 (DPP-4) inhibitor is a class of oral antihyperglycemic agents and therapeutic approach for type 2 diabetes. Cetagliptin is a novel oral and selective DPP-4 inhibitor and developed as a promising candidate for treatment of type 2 diabetes mellitus. This study aimed to evaluate the metabolism and excretion of cetagliptin in Sprague-Dawley (SD) rats, and to detect and identify metabolites of cetagliptin. The SD rats were administered with a single oral dose of 6 mg/kg with approximately 100 µCi of [14C] cetagliptin. The mean total recovery of radioactivity was 90.20% within 168h in SD rats excreta. Cetagliptin was the major radioactive component in SD rats plasma, urine and eliminated primarily by faecal excretion. The recovery of cetagliptin in urine and feces was 25.15% and 13.85% of the dose, respectively. Cetagliptin was well absorbed after oral administration in SD rats based on the total recovery of radioactivity in BDC SD rats bile and urine. Six major metabolites were observed and identified in SD rats, comprising 0.20 to 4.53% of total plasma AUC. These major metabolites were the hydroxylated, N-sulphate and N-carbamoyl glucuronic acid conjugates of the cetagliptin, two metabolites formed by glucuronide of a hydroxylated metabolite.

Absorption, distribution, metabolism, and excretion of [14C]TPN729 after oral administration to rats

TPN729, a novel phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), is in phase II clinical trials in China. Previous studies suggested that TPN729 possesses promising therapeutic value. In previous non-radiolabeled rat excretion studies, the recovery of TPN729 and its major metabolites accounted for approximately 8.58% of the administration dose in urine and feces by 48 h post-dose. To solve this problem and further study the metabolism of TPN729 in rats, we used the radio-isotopic tracing technique for the first time. In this study, the mass balance, tissue distribution, and metabolism of TPN729 were evaluated in rats after a single oral dose of 25 mg/kg [14C]TPN729 (150 μCi/kg). At 168 h post-dose, the mean total radioactivity recovery of the dose was 92.13%. Feces was the major excretion route, accounting for 74.63% of the dose, and urine excretion accounted for 17.50%. After oral administration of [14C]TPN729, radioactivity was widely distributed in all examined tissues, and a higher radioactivity concentration was observed in the stomach, large intestine, lung, liver, small intestine, and eyes. The concentration of drug-related materials were similar in plasma and blood cells. A total of 51 metabolites were identified in rat plasma, urine, feces, and bile, and the predominant metabolically susceptible position of TPN729 was the pyrrolidine moiety. The main metabolic pathways were N-dealkylation, oxidation, dehydrogenation, and glucuronidation. In summary, we solved the previous problem of low drug recovery, elucidated the major excretion pathway, determined the tissue distribution patterns, and investigated the metabolism of TPN729 in rats by using a radioisotopic tracing technique.

Excretion and Distribution of the 60-kDa PEG Moiety Used in BAY 94-9027 in Male Wistar Rats

Introduction: PEGylation is a widely used method to prolong the half-life of therapeutic proteins. Long-acting factor VIII (FVIII) products developed through PEGylation may potentially reduce the burden associated with prophylaxis in patients with hemophilia A. BAY 94-9027 is a prolonged-half-life FVIII product modified through site-specific addition of a 60-kDa (2 × 30-kDa branched) PEG via a maleimide linker to a cysteine amino acid. BAY 1025662 is the 60-kDa PEG moiety used for PEGylation including linker and cysteine (PEG-60-Mal-Cys). In toxicology studies, BAY 94-9027 and BAY 1025662 were not associated with any adverse events or PEG-related cellular vacuolation (Ivens et al. Haemophilia. 2013;19:11-20). The rate-limiting clearance of the PEG part of PEGylated proteins after metabolism is expected to be similar to that when the corresponding PEG is administered alone (Baumann et al. Drug Discov Today . 2014;19:1623-1631). The study objective was to investigate the pharmacokinetics and mass balance of total radioactivity in male Wistar rats after a single intravenous (IV) administration of [14C]-labeled BAY 1025662, including size exclusion chromatography profiles of urine at selected time points.Methods: Radiolabeled BAY 1025662 ([prop-14C]BAY 1025662) was synthesized using a 2-step process resulting in a maleimide linker bearing the [14C] label at the propionic acid moiety. Radioactivity following a single IV dose of 11 mg/kg (the estimated maximal human PEG dose over ~30 years' treatment with BAY 94-9027) was determined in body fluids, organs and tissues, and in excreta by liquid scintillation counting after appropriate sample preparation and by quantitative whole-body autoradiography during and at the end of the study.Results: Single-dose mass balance studies using [prop-14C]BAY 1025662 showed that 30.4% of administered radioactivity was excreted within 1 week (23.7% in urine and 6.3% in feces); cumulative excretion at day 168 via urine and feces was 82.6% of the administered dose (68.4% via urine, 13.8% via feces). High-performance liquid chromatography profiling analysis of rat urine suggested that BAY 1025662 is excreted nearly unchanged (74% of total radioactivity, corresponding to 17.6% of dose, present unchanged in urine in the 0- to 168-hour interval). Radioactivity was continuously, albeit slowly, eliminated throughout the study; elimination half-life was 23 and 24 days in blood and plasma, respectively. The corresponding elimination half-lives of radioactivity were 33, 31, 39, 54, and 68 days in the liver, skin, carcass, testes, and kidneys, respectively. Elimination was almost complete at the end of experiment, with a total recovery of radioactivity (cumulative excretion plus residues in animals) of 89% on day 168. Following [prop-14C]BAY 1025662 administration, radioactivity was slowly distributed from blood to peripheral organs, reaching maximum concentration 2 hours postdose; highest maximum concentration was observed in blood, followed by lung and liver. At day 168, only ~4% of the administered radioactive dose was still present in the animal body, partially localized in endocrine/exocrine glands and lymphatic organs. No residual radioactivity was observed in the brain, indicating no crossing of the blood-brain barrier.Conclusions: Following single-dose administration of [prop-14C]BAY 1025662, elimination was almost complete by the end of the experiment on day 168. These results suggest that there are excretion processes in place for high-molecular-weight PEGs such as the PEG 60 moiety used in BAY 94-9027. Two clearance processes are proposed for large PEGs (>30 kDa), as indicated by a faster initial excretion over the first 1-2 weeks, followed by a nonspecific uptake into cells by pinocytosis leading to a longer elimination half-life. The PEG moiety can be recycled from inside the cells back to the plasma, possibly by exocytosis, to then undergo further (mainly renal) excretion (Baumann et al. Drug Discov Today . 2014;19:1623-1631). DisclosuresBaumann:Bayer AG: Employment. Schwarz:Bayer AG: Employment. Hucke:Bayer AG: Employment. Piel:Bayer AG: Employment. Sandmann:Bayer AG: Employment.

Pharmacokinetics, metabolism, and excretion of licogliflozin, a dual inhibitor of SGLT1/2, in rats, dogs, and humans

Absorption, metabolism, and excretion (AME) of licogliflozin, a sodium-glucose co-transporters (SGLTs) 1 and 2 inhibitor, were studied in male rats, dogs, and healthy male volunteers and reported. Oral absorption of licogliflozin was rapid (t max < 1 h) with absorption estimated at 87%, 100% and 77% in rats, dogs and humans, respectively. Excretion of licogliflozin-related radioactivity was rapid and nearly complete following oral administration with total radioactivity recovery ranging from 73% in dogs, 92.5% in humans, to 100% in rats. Dose-related radioactivity was excreted in both urine and faeces with urinary excretion playing a slightly more important role in humans (∼56%) than in animal species (∼19–41%). Elimination of licogliflozin was predominantly via metabolism with the majority of the radioactivity dose (∼54–74%) excreted as metabolites across species. The principal biotransformation pathways involved direct glucuronidation and oxidation across all species. In humans, direct glucuronidation to M17 and M27 was the major pathway observed, accounting for ∼38% of the dose in excreta while oxidative metabolism also contributed to >29% of the dose in excreta. Oxidative pathways were predominant in animal species.

940-P: 14C-Tirzepatide ADME Studies in Rat and Monkey

Novel dual GIP and GLP-1 receptor agonist, tirzepatide (TZP), is being developed as a potential weekly treatment for type 2 diabetes (T2DM), weight management and nonalcoholic steatohepatitis. The absorption, metabolism and excretion of a single subcutaneous (SC) dose of 14C-tirzepatide was investigated in Sprague Dawley rat and cynomolgus monkey. In addition, tissue distribution of 14C-tirzepatide was assessed in quantitative whole-body autoradiography (QWBA) study in pigmented Long Evans rat following a single SC dose. 14C-Tirzepatide was prepared by incorporating four 14C’s in the mini-PEG linker between the peptide backbone and the di-acid chain to provide a specific activity of ∼ 40 µCi/mg. Following a single SC dose of 14C-tirzepatide in rat (3 mg/kg) and monkey (0.5 mg/kg), total radioactivity recovery was &amp;gt; 97% over the course of study (336 hours for rat and 672 hours for monkey). The dosed radioactivity was similarly excreted via urine and feces in rats and monkeys. Metabolism of 14C-tirzepatide was characterized in plasma and excreta. Parent drug was the major component in circulation accounting for approximately 87% of total radioactivity in rat and 84% in monkey. Tirzepatide was primarily metabolized via catabolism of the peptide backbone and β-oxidation of the di-acid chain. Following a single SC dose of 14C-tirzepatide in rats (3 mg/kg), radioactivity was distributed to tissues as early as the first collection time point at 1-hour post dose. The tissues with the highest radioactivity concentrations were observed in the dose site, kidney, cecum, urinary bladder, intervertebral ligaments, arterial wall, lungs, and liver, generally at 12 to 48 hours post dose. Disclosure J. Martin: Employee; Self; Eli Lilly and Company. K. Cassidy: Employee; Self; Eli Lilly and Company. B. Czeskis: None. J. Alberts: Employee; Self; Eli Lilly and Company. Y. Lao: Employee; Spouse/Partner; Eli Lilly and Company. J. Gluff: None. A.M. Niedenthal: None.

A phase I study investigation of metabolism, and disposition of [14C]-anlotinib after an oral administration in patients with advanced refractory solid tumors

PurposeAnlotinib is a novel oral multi-targeted receptor tyrosine kinase inhibitor, which selectively inhibits VEGFR2/3, FGFR1-4, PDGFR α/β, c-kit, and Ret. It shows antitumor effect in patients with advanced refractory solid tumors. The detailed absorption, metabolism, and excretion pathways of anlotinib have not yet been fully investigated.MethodsSix male patients were enrolled and divided into two groups. Group A (containing two patients) received 14.15 mg/80 µCi/subject [14C]-anlotinib hydrochloride. Group B (containing four patients) received 14.15 mg/120 µCi/subject [14C]-anlotinib hydrochloride. The blood, urine, and feces of all the six patients after orally administration of [14C]-anlotinib were collected. The absorption, metabolism, and excretion of [14C]-anlotinib were investigated, and the efficacy and safety of anlotinib were evaluated.ResultsIn plasma, the average time to peak concentration (Tmax) of total radioactivity was 4.42 h and the average peak concentration (Cmax) of total radioactivity was 18.80 ng Eq./g. The average values of AUC0-last, AUC0-∞, and MRT0-t were 4071 h.ng Eq./g, 13,555 h.ng Eq./g, and 125 h, respectively. The average recovery of total radioactivity (TRA) in urine and feces was 62.03%, accounting for 48.52% and 13.51% in feces and urine of the total dosage, respectively. The parent drug, a carboxylic metabolite (M30), and mono-oxidation products (M46/M66) were major drug-related components in human plasma. Oxidative metabolism played the major role in drug clearance in human. The major metabolic pathways include oxidative deamination to M2, mono-oxidation to M1, and the formation of M30. Adverse events occurred in five patients and severe adverse events (SAE) occurred in one. Tumor response were evaluated as stable disease (SD) in three, partial response (PR) in one, and progressive disease (PD) in one of the patients, respectively.ConclusionsAnlotinib had a good pharmacokinetic profile with rapid absorption, long half-life, and extensive hepatic metabolism. The adverse events and efficacy were as expected.

Absorption, Distribution and Excretion of [14C] Zamicastat after Single Oral and Intravenous Administration in Rats and Dogs

BackgroundZamicastat is a dopamine‐β‐hydroxylase inhibitor (1), previously showed to increase the survival rate in the monocrotaline rat model of pulmonary arterial hypertension.ObjectivesThe purpose of this study was to characterize the absorption, distribution and elimination of 14C‐zamicastat in rat and dog, after single oral (p.o.) or intravenous (i.v.) administration.MethodsWistar rats and Beagle dogs were administered with 14C‐zamicastat at 30 mg/kg orally or intravenously with 2.5 mg/kg (rat) and 0.1 mg/kg (dog). Plasma, urine and faeces samples were collected at different time‐points to measure the plasma exposure and the recovery of total radioactivity up to 168 h post‐dose. Whole body phosphor imaging (WBPI) was evaluated in rat after p.o. administration of 30 mg/kg of 14C‐zamicastat. The extent of plasma protein binding was determined by equilibrium dialysis and blood cell binding was determined, using centrifugation, on pooled male samples from each species.ResultsAfter single oral dosing of 14C‐zamicastat, more than 95% of total radioactivity was recovered at five and seven days from rats and dogs, respectively. The radioactivity peaked in plasma between 6 to 8 h and 2 to 4 h post‐dosing in rats and dogs, respectively, followed by a slow elimination over time. Zamicastat related radioactivity was mainly recovered in faeces with very low levels (less than 20% of total radioactivity) excreted in urine in both species. Following i.v. administration more than 80% of radioactivity was recovered in both species mainly via feaces excretion. The WBPI study indicates that radioactivity was distributed throughout the body with the majority of tissues achieving a tissue:blood ratio greater than 2. Elimination of radioactivity progressed over time with most tissues reaching the low limit of quantification at 168h. The highest tissue:blood ratios were noted in thyroid gland, lung and harderian gland at, respectively, 168h, 8h and 8h post‐dosing. Protein binding data indicates that zamicastat is preferentially bound to plasma proteins in a concentration independent manner, with 98% and 96% bound to rat and dog plasma proteins, respectively.ConclusionZamicastat is a highly plasma protein bound compound after oral administration and it is extensively distributed to tissues. After oral administration to rats and dogs, radioactivity was almost completely recovered with most of zamicastat‐related radioactivity excreted through faeces.

Metabolism, Excretion, and Pharmacokinetics of [14 C]-Cefiderocol (S-649266), a Siderophore Cephalosporin, in Healthy Subjects Following Intravenous Administration.

The objectives of this study were to characterize the concentration‐time profiles of total radioactivity equivalent and unchanged cefiderocol, the route(s) of elimination and mass balance, and safety of cefiderocol after intravenous administration of a single 1000‐mg (100 μCi) dose of [14C]‐cefiderocol as a 1‐hour infusion in healthy adult male subjects. Unchanged cefiderocol accounted for the majority of total radioactivity in plasma, and the partitioning of total radioactivity into red blood cells was negligible. The recovery of total radioactivity was complete in all subjects within 120 hours after initiation of the infusion (101.5% of the administered dose). Cefiderocol‐related material was primarily excreted into urine, with 98.7% of the administered dose of [14C]‐cefiderocol excreted as total radioactivity into urine and negligible excretion into feces. Based on the results of metabolite profiling, cefiderocol accounted for 92.3% of area under the concentration‐time curve of total radioactivity in plasma and accounted for 90.6% of the administered dose excreted into urine. Metabolism was a minor route of elimination for cefiderocol. Cefiderocol was generally safe and well tolerated in healthy adult male subjects. In conclusion, unchanged cefiderocol represents the majority of total radioactivity in plasma. Cefiderocol is primarily excreted as unchanged drug into urine. This study indicates that cefiderocol and drug‐related material did not remain in the body.

Absorption, distribution, metabolism, and excretion of radiolabeled naldemedine in healthy subjects

1. Naldemedine is a peripherally acting μ-opioid receptor antagonist for the treatment of opioid-induced constipation.2. This phase 1 study investigated the absorption, distribution, metabolism and excretion of naldemedine, following a single oral 2-mg dose of [oxadiazole-14C]-naldemedine or [carbonyl-14C]-naldemedine to 12 healthy adult male subjects. Pharmacokinetic assessments were performed on blood, urine and fecal samples collected at defined intervals.3. Naldemedine was the major circulating component in plasma with a median Tmax of approximately 0.8–0.9 h and a geometric mean t1/2,z of approximately 11 h. Total systemic exposures, AUC, of metabolites nor-naldemedine were less abundant than those of naldemedine (9% or 13% of AUC of naldemedine) and 16.2% or 18.1% of naldemedine was excreted as unchanged in urine after administration of [oxadiazole-14C]-naldemedine or [carbonyl-14C]-naldemedine, respectively, and benzamidine was the major radioactive component after administration of [oxadiazole-14C]-naldemedine (32.5% of administered dose). Overall, the recovery of total radioactivity was 92% (57.3% in urine; 34.8% in feces) after administration of [oxadiazole-14C]-naldemedine and 85% (20.4% in urine; 64.3% in feces) after administration of [carbonyl-14C]-naldemedine.4. Our findings suggest that naldemedine is mainly metabolized to nor-naldemedine. Naldemedine was rapidly absorbed and well tolerated, with no major safety signals observed.

Bioavailability, Biotransformation, and Excretion of the Covalent Bruton Tyrosine Kinase Inhibitor Acalabrutinib in Rats, Dogs, and Humans

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 [14C] microtracer bioavailability study in healthy subjects revealed moderate intravenous clearance (39.4 l/h) and an absolute bioavailability of 25.3% ± 14.3% (n = 8). Absorption and elimination of acalabrutinib after a 100 mg [14C] 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. [14C]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-1-yl]-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 β-ketoamide. Total radioactivity recovery was 95.7% ± 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.

Absorption, Metabolism and Excretion of GBT440, a Novel Hemoglobin S (HbS) Polymerization Inhibitor for the Treatment of Sickle Cell Disease (SCD), in Healthy Male Subjects

Background: SCD is caused by a point mutation in the β-globin gene producing hemoglobin S (HbS) that polymerizes upon deoxygenation with subsequent formation of sickled red blood cells (RBCs). GBT440 is a novel, orally bioavailable small molecule that inhibits HbS polymerization by increasing the affinity of O2 to hemoglobin (Hb).Methods: The pharmacokinetics, mass balance, and metabolite profile of [14C]-GBT440 were evaluated in 7 healthy male subjects in this open-label study. In order to evaluate the disposition kinetics of GBT440 at steady-state concentrations, a loading/maintenance dose schema was employed. Each subject received an oral loading dose of 2000 mg GBT440 on Day 1 followed by oral maintenance doses of 400 mg once daily on Day 2 to Day 4. Once the target steady-state was achieved, a single [14C]-GBT440 400 mg dose (approximately 100 μCi) was administered orally on Day 5. Blood, plasma, urine and feces were collected serially up to 26 days postdose.Results: There were no serious adverse events or discontinuations due to adverse events for any of the healthy subjects participating in this study. GBT440 reached Cmax in plasma and whole blood with median time to maximum concentration (Tmax) values of 2.00 hours in plasma and whole blood and in 6.00 hours in RBCs. After reaching Cmax, GBT440 concentrations appeared to decline in a monophasic manner, with the terminal elimination phase for GBT440 in plasma, whole blood, and RBCs appearing to decline in a parallel manner, with geometric mean T1/2 values of 98.0 hours in plasma, 66.3 hours in whole blood, and 65.8 hours in RBCs. This study achieved 98.0% average recovery of total radioactivity in urine and feces over the course of the study. Most of the administered radioactivity (88.2%) was recovered by 144 hours postdose (Day 7). GBT440 was eliminated primarily in feces (62.6% of the total radioactive dose) with urinary excretion accounting for 35.4% of the total radioactive dose.In whole blood, the majority of the total radioactivity (TRA) was unchanged GBT440 (97.5%) while three metabolites accounted for the remaining TRA (2.5%). In plasma, unchanged GBT440 was the prominent circulating radioactive component, accounting for 48.8% of the TRA. Eleven circulating metabolites with corresponding radioactive peaks were identified. There was one major Phase II metabolite (GBT440 O-dealkylation-sulfation), accounting for 16.8% of the TRA. Two potential active metabolites were identified but only accounted for 2.5% of the dose in whole blood.GBT440 was eliminated predominately in feces. Unchanged GBT440 was the most abundant radioactive component, accounting for 33.3% of the administered dose. Four metabolites were identified, each accounting for 5.62%, 2.66%, 1.66% and less than 6% of the dose in the 0-216-hr human feces. Urine was a relatively minor excretion route for GBT440 in humans. An average of 34.3% of the dose was recovered in the urine samples. Unchanged GBT440 accounted for 0.08% of the administered dose and the rest were metabolites. GBT440 glucuronidation and reduction-glucuronidation products, which are Phase II metabolites, were the most abundant metabolites in urine, accounting for a combined 9.22% of dose. Because GBT440 does not undergo renal elimination, patients with renal disorders should not experience changes in pharmacokinetics of GBT440.Conclusions: Although GBT440 has high specific binding to hemoglobin, it was completely excreted from the body with a half-life of approximately three days in healthy subjects. Since the half-life of GBT440 was much shorter than RBC lifespan (~ 120 days), this supports the hypothesis that the binding between GBT440 to hemoglobin is a reversible process. Following an oral administration, approximately one-third of the dose was excreted as the unchanged drug into the feces (unabsorbed and/or via biliary excretion). Two-thirds of the administered dose was metabolized and excreted into urine and feces. The major metabolic pathway was via Phase I and Phase II metabolism. Because GBT440 was not excreted directly into the urine, the pharmacokinetics are unlikely to be affected in patients with renal disorders. DisclosuresRademacher:Global Blood Therapeutics: Employment, Equity Ownership. Hutchaleelaha:Global Blood Therapeutics: Employment, Equity Ownership. Washington:Global Blood Therapeutics: Employment, Equity Ownership. Lehrer:Global Blood Therapeutics: Employment, Equity Ownership. Ramos:Global Blood Therapeutics: Employment, Equity Ownership.

Investigation of the “true” extraction recovery of analytes from multiple types of tissues and its impact on tissue bioanalysis using two model compounds

LC-MS/MS has been widely applied to the quantitative analysis of tissue samples. However, one key remaining issue is that the extraction recovery of analyte from spiked tissue calibration standard and quality control samples (QCs) may not accurately represent the “true” recovery of analyte from incurred tissue samples. This may affect the accuracy of LC-MS/MS tissue bioanalysis. Here, we investigated whether the recovery determined using tissue QCs by LC-MS/MS can accurately represent the “true” recovery from incurred tissue samples using two model compounds: BMS-986104, a S1P1 receptor modulator drug candidate, and its phosphate metabolite, BMS-986104-P. We first developed a novel acid and surfactant assisted protein precipitation method for the extraction of BMS-986104 and BMS-986104-P from rat tissues, and determined their recoveries using tissue QCs by LC-MS/MS. We then used radioactive incurred samples from rats dosed with 3H-labeled BMS-986104 to determine the absolute total radioactivity recovery in six different tissues. The recoveries determined using tissue QCs and incurred samples matched with each other very well. The results demonstrated that, in this assay, tissue QCs accurately represented the incurred tissue samples to determine the “true” recovery, and LC-MS/MS assay was accurate for tissue bioanalysis. Another aspect we investigated is how the tissue QCs should be prepared to better represent the incurred tissue samples. We compared two different QC preparation methods (analyte spiked in tissue homogenates or in intact tissues) and demonstrated that the two methods had no significant difference when a good sample preparation was in place. The developed assay showed excellent accuracy and precision, and was successfully applied to the quantitative determination of BMS-986104 and BMS-986104-P in tissues in a rat toxicology study.

Evaluation of rosuvastatin as an organic anion transporting polypeptide (OATP) probe substrate: in vitro transport and in vivo disposition in cynomolgus monkeys.

Organic anion transporting polypeptides (OATPs) mediate hepatic drug uptake and serve as the loci of drug-drug interactions (DDIs). Consequently, there is a major need to develop animal models and refine in vitro-in vivo extrapolations. Therefore, the in vivo disposition of a model OATP substrate, [(3)H]rosuvastatin (RSV), was studied in the cynomolgus monkey and reported for the first time. After monkeys had received a 3-mg/kg oral dose, mass balance was achieved after bile duct cannulation (mean total recovery of radioactivity of 103.6%). Forty-two percent of the RSV dose was recovered in urine and bile, and the elimination pathways were similar to those reported for human subjects; 61.7%, 39.0%, and 2.9% of the dose was recovered in the feces, bile, and urine, respectively. The high levels of unchanged RSV recovered in urine and bile (26% of the dose) and the relatively low levels of metabolites observed indicated that RSV was eliminated largely by excretion. Also, for the first time, the in vitro inhibitory potential of cyclosporin A (CsA) toward cynomolgus monkey OATPs and sodium-taurocholate cotransporting polypeptide was studied in vitro (primary hepatocytes and transporter-transfected cells). It is concluded that one can study the CsA-RSV DDI in the cynomolgus monkey. For example, the in vitro IC50 values were within 2-fold (monkey versus human), and the increase (versus vehicle control) in the RSV AUC0-inf (6.3-fold) and Cmax (10.2-fold) with CsA (100 mg/kg) was similar to that reported for humans. The results further support the use of the cynomolgus monkey as a model to assess interactions involving OATP inhibition.

Pharmacokinetics and Excretion of 14C-Labeled Polyethylene Glycol (60 kDa) in Rats

Introduction: Although there is no evidence for PEG-related safety issues with PEGylated proteins in the clinic, questions relating to the pharmacokinetics including disposition and excretion of PEG are being raised more frequently by health authorities nowadays, particularly for PEGylated proteins used chronically and/or in the pediatric population (http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2012/11/WC500135123.pdf).BAY 94-9027, a B-domain–deleted recombinant FVIII with a 60-kDa branched PEG molecule attached via a maleimide linker to an amino acid using site-specific PEGylation, is in clinical development for acute and prophylactic intravenous treatment of hemophilia A. The objective of this study was to investigate the pharmacokinetics and excretion of radioactivity (unchanged compound and radioactive metabolites) after single intravenous administration of 14C-labeled BAY 1025662 (cysteine linker-[60-kDa] PEG part of BAY 94-9027 with the 14C label covalently integrated in the linker) in male Wistar rats.Methods: The administered dose was 11 mg/kg body weight related to BAY 1025662 (approximated human lifetime dose of PEG 60 kDa resulting from treatment with BAY 94-9027). The concentrations and amounts of radioactivity in urine, feces, blood, plasma, and selected organs and tissues were investigated in order to determine the excretion via urine and feces, and the pharmacokinetics of total radioactivity and radioactive residues in the animal body.Results: After single intravenous administration of 14C-BAY 1025662 to rats, a fast initial elimination of 14C radioactivity was observed; 63.2% of administered radioactivity was excreted within the first 24 hours (51.4% in urine, 11.8% in feces). Up to day 7, 75.6% of administered radioactivity was excreted predominantly via urine. The balance/recovery of radioactivity on day 7 amounted to 99.0% in relation to the administered radioactive dose. The radioactive residue in the animals amounted to 23.4% of administered dose. The majority of the residual radioactivity was recovered in the carcass and skin, followed by liver and kidneys. The excretion of radioactivity continued at steadily decreasing levels until the end of the study. The daily radioactivity excretion decreased from 2.1% at 72 hours to 0.013% of dose at 6 months after administration of 14C-BAY 1025662. The cumulative excretion of radioactivity via urine and feces was calculated (partly interpolated) to 92.2% of the administered radioactive dose by the end of the experiment on day 168 (74.5% via urine, 17.4% via feces, and 0.294% recovered in the cage wash). The radioactivity was continuously albeit slowly eliminated from the investigated organs and tissues. The elimination half-life of radioactivity was 26 and 23 days in blood and plasma, respectively. The corresponding elimination half-lives of radioactivity were 35, 41, and 31 days in the liver, carcass, and skin, respectively. Radioactivity elimination from kidneys was biphasic with a terminal half-life of 92 days. The radioactive residues in the animals excluding the gastrointestinal tract decreased during the study from 22.5% on day 7 to 1.79% of dose at the end of the study on day 168. There was no indication for any retention or irreversible binding of radioactivity in the animal body. The total recovery of radioactivity (cumulative excretion plus residues in the animals) was 94% in relation to the administered dose at the end of the experiment on day 168.Conclusions: In this study, nearly complete excretion of the 60-kDa PEG molecule (measured as total radioactivity) could be observed, with a fast initial elimination in the first few days and a subsequent considerably slower process until the end of the observation period (6 months). These results are in agreement with recently proposed fast and slow processes for the renal excretion of large PEG and PEG proteins (Baumann, A. et al. Drug Discov Today. 2014:[Epub ahead of print, http://dx.doi.org/10.1016/j.drudis.2014.06.002]). DisclosuresBaumann:Bayer Pharma AG: Employment. Schwarz:Bayer Pharma AG: Employment. Seidel:Bayer Pharma AG: Employment. Hucke:Bayer Pharma AG: Employment. Steinke:Bayer Pharma AG: Employment. Buehner:Bayer Pharma AG: Employment.

Disposition and metabolism of LY2603618, a Chk-1 inhibitor following intravenous administration in patients with advanced and/or metastatic solid tumors

1. The disposition and metabolism of a Chk-1 inhibitor (LY2603618) was characterized following a 1-h intravenous administration of a single 250-mg dose of [14C]LY2603618 (50 µCi) to patients with advanced or metastatic solid tumors.2. LY2603618 was well tolerated with no clinically significant adverse events. Study was limited to three patients due to challenges of conducting ADME studies in patients with advanced cancer. Plasma, urine and feces were analyzed for radioactivity, LY2603618 and metabolites. LY2603618 had a half-life of 10.5 h and was the most abundant entity in plasma, accounting for approximately 69% of total plasma radioactivity. The second most abundant metabolites, H2 and H5, accounted for <10% of total circulating radioactivity. The major route of clearance was via CYP450 metabolism. The mean total recovery of radioactivity was 83%, with approximately 72% of the radioactivity recovered in the feces and approximately 11% in the urine. LY2603618 represented approximately 6% and 3% of the administered dose in feces and urine, respectively.3. A total of 12 metabolites were identified. In vitro phenotyping indicated that CYP3A4 was predominantly responsible for the metabolic clearance of LY2603618. Additionally, aldehyde oxidase was involved in the formation of a unique human and non-human primate metabolite, H5.

The metabolic fate of [14C]-fenclozic acid in the hepatic reductase null (HRN) mouse

1. The distribution, metabolism, excretion and hepatic effects of fenclozic acid were investigated following a single oral dose of 10 mg/kg to hepatic reductase null (HRN) mice.2. The majority of the [14C]-fenclozic acid was eliminated via the urine/aqueous cage wash, (55 %) with a smaller portion excreted in the faeces, (5 %). The total recovery of radioactivity in the excreta over the 72 h period studied was ca. 60%.3. Metabolism of fenclozic acid in the HRN mice was entirely to the carboxylic acid function and was dominated by amino acid conjugation to glycine and taurine, with lesser amounts of an acyl glucuronide.4. Whole body autoradiography of mice showed general distribution into all tissues except the brain. Radioactivity was still detectable in the kidney and liver of the HRN mice at 72 h post-dose. Covalent binding studies showed evidence of binding to kidney, liver and plasma proteins however, the degree of binding was less than 50 pmol equiv/mg protein for all tissues.5. The HRN mouse appears to be a useful in vivo model for the study of the Phase II conjugation metabolism of fenclozic acid in the absence of hepatic cytochrome P450-related oxidative metabolism.