Radioactivity In Urine Research Articles

Mass balance and pharmacokinetic characterization ofzavegepant in healthy male subjects.

Zavegepant, a high-affinity, selective, small-molecule calcitonin gene-related peptide receptor antagonist, is approved as a nasal spray for acute treatment of migraine in adults. This phase I, open-label, single-center, single-period, nonrandomized study in six healthy male subjects assessed mass balance recovery after a single 15-min intravenous (IV) infusion dose of carbon-14 ([14C])-zavegepant. Blood, urine, and fecal samples were collected over 192 h for analysis of zavegepant in plasma and urine; total radioactivity (TR) in plasma, whole blood, urine, and feces; and zavegepant metabolite profiling and structural identification in plasma, urine, and feces. An average of 96.6% of radioactivity administered was recovered in excreta. Most TR (mean 84.9%) was recovered in the feces, indicating that biliary/fecal elimination was the main route. Volume of distribution of zavegepant based on the terminal phase (129 L) was higher than total body water (42 L), indicating substantial distribution into tissue. Total plasma clearance of zavegepant (220 mL/min) is identical to whole blood clearance given the blood/plasma partition ratio of 1, lower than typical hepatic blood flow (1450 mL/min). The observed plasma terminal half-life of zavegepant was 6.8 h. Exposure to zavegepant accounted for ~90% of circulating plasma TR, suggesting that very low levels of uncharacterized circulating metabolites were present. Metabolite profiling did not identify any metabolites representing ≥10% of radioactivity in plasma, urine, or feces. A single IV infusion of 5 mg [14C]-zavegepant was well tolerated in healthy male subjects. Disposition findings of IV [14C]-zavegepant are applicable to the disposition of the approved zavegepant nasal spray.

Disposition of [14C]-polystyrene microplastics after oral administration to lactating sheep

Microplastics have become a ubiquitous contaminant, but their fate in food animals is largely unknown. In this study, [14C]-polystyrene microplastic (PS-MP) particles were orally dosed to lactating sheep to evaluate their absorption and disposition. Elimination of the [14C]-PS-MP was predominately through faeces with faecal radioactivity peaking at 24 h post-dosing but continuing to be present throughout the entire 72 h study period. Only a small fraction (≤ 1%) of the dosed [14C]-PS-MP was present in blood, milk, and urine. Pharmacokinetic analysis of blood plasma radioactivity, using non-compartment modeling, indicated rapid absorption (T1/2 0.4 to 3 h) with slow elimination (T1/2 37 to 48 h). Radioactivity in milk and urine had similar elimination patterns with radiocarbon activities peaking 24 h post-dosing with detectable elimination throughout the 72 h study period. No radioactivity was quantifiable in tissues at the 72 h withdrawal period.

Radiation protection aspects in the design of a Boron Neutron Capture Therapy irradiation room

Boron Neutron Capture Therapy (BNCT) is a radiotherapy whose effect is due to the combination of low-energy neutron irradiation prior chemical targeting of tumour tissues with boron-10. The context of this work is the design of a clinical BNCT facility based on a Radio-Frequency Quadrupole proton accelerator, manufactured by the Italian National Institute of Nuclear Physics (INFN). Such a machine can provide a neutron beam suitable for the treatment of deep-seated tumours when coupled to a beryllium target and a Beam Shaping Assembly whose main constituent is densified lithiated aluminium fluoride. This paper refines the design of the facility, already addressed in preliminary studies, from the point of view of dosimetric quantities in the room and in the patient. The presented calculations have been performed with different Monte Carlo codes, and assess the time evolution of the dose due to the neutron activation of the irradiated materials. A comprehensive evaluation of the dose absorbed in the healthy organs of the patient is provided, with focus on the residual radioactivity of the patient urine, for three different treatment positions. Borated concrete is confirmed to be the best material for constructing the walls of the treatment room. A lead shielding at the beam-port is proposed to reduce the gamma dose at the irradiation position due to the activation of the Beam Shaping Assembly.

Pharmacokinetics, Mass Balance, Tissue Distribution and Metabolism of [14C]101BHG-D01, a Novel Muscarinic Receptor Antagonist, in Rats.

101BHG-D01, a novel long-acting and selective muscarinic receptor antagonist for the treatment of chronic obstructive pulmonary disease (COPD), is undergoing Phase Ib clinical trial in patients and has shown its potential efficacy. Its preparation method and medical use thereof have been patented in the United States (Patent No.US9751875B2). In this study, the pharmacokinetics, mass balance, tissue distribution and metabolism of radioactive 101BHG-D01 were investigated in rats after an intravenous dose of 1 mg/kg [14C]101BHG-D01 (100 μCi/kg). Radioactivity in rat plasma, urine, feces, and tissues was measured by liquid scintillation counting (LSC), and metabolite profiling and identification were conducted by UHPLC-β-RAM and UHPLC-Q-Exactive Plus MS. The total radioactivity of the study drug in rat plasma rapidly declined with an average terminal elimination half-life of 0.35 h. The radioactivity in most tissues reached the maximum concentration at 0.25 h post-- dosing. The radioactivity mainly concentrated in the kidney and pancreas. The drug-related substances tended to be distributed into the blood cells in the circulation. At 168 h post dosing, the mean recovery of the total radioactivity in urine and feces was 78.82%. Fecal excretion was the major excretion route, accounting for approximately 61% of the radioactive dose. The study drug was metabolized extensively, and a total of 17 metabolites were identified in rat plasma, urine, and feces. The major metabolic pathways involved oxidation, oxidation and dehydrogenation, and O-dephenylation. In conclusion, the study results are useful for better understanding the pharmacokinetic profiles of 101BHG-D01 and provide a robust foundation for subsequent clinical studies.

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.

An innovative phase I study in healthy subjects to determine the mass balance, elimination, metabolism, and absolute bioavailability of mitapivat.

Mitapivat, a first-in-class, oral, small-molecule, allosteric activator of the red blood cell-specific form of pyruvate kinase (PKR), was approved for the treatment of hemolytic anemia in adults with pyruvate kinase (PK) deficiency. In this phase I mass balance study in healthy males, we administered a single ~120 mg oral dose of [14 C]mitapivat and a concomitant intravenous ~0.1 mg microdose of [13 C6 ]mitapivat. We determined (1) the routes of total radioactivity excretion, including the mass balance of total radioactivity in urine and feces; (2) the pharmacokinetics of mitapivat and [13 C6 ]mitapivat in plasma and total radioactivity in whole blood and plasma; (3) the absolute oral bioavailability of mitapivat; and (4) the metabolite profiles in plasma and excreta. Mean recovery of the radioactive dose was 89.1% (49.6% in urine and 39.6% in feces). [14 C]Mitapivat was rapidly absorbed and extensively metabolized as <4% of the total radioactive dose was excreted unaltered in urine and feces. Mean absolute oral bioavailability was 72.7%. A total of 17 metabolites were identified. Mitapivat accounted for 57% and 34% of plasma radioactivity in AUC0-24 and AUC0-72 pooled samples, respectively. The remaining radioactivity was attributable to several metabolites, each representing <10% of the total radioactivity in pooled samples; none were disproportionate metabolites as defined by the US Food and Drug Administration and International Conference on Harmonisation M3 guidelines. Metabolite structures suggest that the primary metabolic pathways for [14 C]mitapivat in humans include N-dealkylation of the cyclopropylmethyl moiety, oxygenation of the quinoline-8-sulfonamide, oxidation/unsaturation, scission of the piperazine moiety, and amide hydrolysis.

The Absolute Bioavailability and Absorption, Metabolism, and Excretion of Ipatasertib, a Potent and Highly Selective Protein Kinase B (Akt) Inhibitor.

Ipatasertib (GDC-0068) is a potent, highly selective, small-molecule inhibitor of protein kinase B (Akt) being developed by Genentech/Roche as a single agent and in combination with other therapies for the treatment of cancers. To fully understand the absorption, metabolism, and excretion of ipatasertib in humans, an open-label study using 14C-radiolabeled ipatasertib was completed to characterize the absolute bioavailability (period 1) and mass balance and metabolite profiling (period 2). In period 1, subjects were administered a 200 mg oral dose of ipatasertib followed by an 80 μg (800 nCi) intravenous dose of [14C]-ipatasertib. In period 2, subjects received a single oral dose containing approximately 200 mg (100 μCi) [14C]-ipatasertib. In an integrated analytical strategy, accelerator mass spectrometry was applied to measure the 14C microtracer intravenous pharmacokinetics in period 1 and fully profile plasma radioactivity in period 2. The systemic plasma clearance and steady-state volume of distribution were 98.8 L/h and 2530 L, respectively. The terminal half-lives after oral and intravenous administrations were similar (26.7 and 27.4 hours, respectively) and absolute bioavailability of ipatasertib was 34.0%. After a single oral dose of [14C]-ipatasertib, 88.3% of the administered radioactivity was recovered with approximately 69.0% and 19.3% in feces and urine, respectively. Radioactivity in feces and urine was predominantly metabolites with 24.4% and 8.26% of dose as unchanged parent, respectively; indicating that ipatasertib had been extensively absorbed and hepatic metabolism was the major route of clearance. The major metabolic pathway was N-dealkylation mediated by CYP3A, and minor pathways were oxidative by cytochromes P450 and aldehyde oxidase. SIGNIFICANCE STATEMENT: The study provided definitive information regarding the absolute bioavailability and the absorption, metabolism, and excretion pathways of ipatasertib, a potent, novel, and highly selective small-molecule inhibitor of protein kinase B (Akt). An ultrasensitive radioactive counting method, accelerator mass spectrometry was successfully applied for 14C-microtracer absolute bioavailability determination and plasma metabolite profiling.

Pharmacokinetics, Mass Balance, Tissue Distribution, and Metabolism of [3H]Catalpol in Rats: the Main Bioactive Component of Rehmannia glutinosa for the Treatment of Ischemic Stroke.

Catalpol, one of the main bioactive components isolated from Rehmannia glutinosa, was developed by Suzhou Youseen for the treatment of ischemic stroke; however, preclinical information about its absorption, distribution, metabolism, and excretion (ADME) in animals is inadequate. This study aimed to illuminate the pharmacokinetics (PK), mass balance (MB), tissue distribution (TD), and metabolism of catalpol after a single intragastric administration of 30 mg/kg (300 μCi/kg) [3H]catalpol in rats. Radioactivity in plasma, urine, feces, bile, and tissues was measured by liquid scintillation counting (LSC), and metabolite profiling was characterized by UHPLC-β-ram and UHPLC-Q-Exactive plus MS. The radio pharmacokinetic results showed that catalpol was rapidly absorbed by Sprague‒Dawley (SD) rats, with a median Tmax of 0.75 h and an arithmetic mean half-life (t1/2) of the total radioactivity of approximately 1.52 h in plasma. The mean recovery of the total radioactive dose was 94.82%±1.96% over 168 h postdose (57.52%±12.50% in the urine and 37.30%±12.88% in the feces). The parent drug catalpol was the predominant drugrelated substance in rat plasma and urine, while M1 and M2, two unidentified metabolites, were detected in feces. When [3H]catalpol was incubated with β-glucosidase and rat intestinal flora, we found that the same metabolites M1 and M2 were produced in both incubation systems. Catalpol was excreted mainly through the urine. The drug-related substances were primarily concentrated in the stomach, large intestine, bladder, and kidney. Only the parent drug was detected in the plasma and urine, and M1 and M2 were detected in the feces. We speculate that the metabolism of catalpol in rats was mainly mediated by the intestinal flora, resulting in an aglycone-containing hemiacetal hydroxyl structure.

Absorption, metabolism, and excretion of [14 C]dersimelagon, an investigational oral selective melanocortin 1 receptor agonist, in preclinical species and healthy volunteers.

Dersimelagon (formerly MT-7117) is a novel, orally administered nonpeptide small molecule selective agonist for melanocortin 1 receptor currently being investigated for the treatment of erythropoietic protoporphyria, X-linked protoporphyria, and diffuse cutaneous systemic sclerosis (dcSSc). Findings of studies evaluating the absorption, distribution, metabolism, and excretion (ADME) of dersimelagon following a single dose of [14 C]dersimelagon in healthy adult volunteers (N = 6) who participated in phase 1, single-center, open-label, mass balance study (NCT03503266), and in preclinical animal models are presented. Rapid absorption and elimination were observed following oral administration of [14 C]dersimelagon in clinical and nonclinical studies, with a mean Tmax of 30 min in rats and 1.5 h in monkeys, and a median Tmax of 2 h in humans. In rats, there was a widespread distribution of [14 C]dersimelagon-related material, but little or no radioactivity was detected in the brain or fetal tissues. In humans, elimination of radioactivity in urine was negligible (excretion of radioactivity into the urine: 0.31% of dose), and the primary route of excretion was feces, with more than 90% of the radioactivity recovered through 5 days postdose. Based on these findings, dersimelagon is not retained in the human body. Findings from humans and animals suggest dersimelagon is extensively metabolized to the glucuronide in the liver, which is eliminated in bile, and hydrolyzed to unchanged dersimelagon in the gut. The results to date for this orally administered agent elucidate the ADME of dersimelagon in human and animal species and support its continued development for the treatment of photosensitive porphyrias and dcSSc.

Pharmacokinetics of small hyperbranched polyglycerols as an osmotic agent for peritoneal dialysis: Plasma exposure, organ distribution and excretion in rats.

Small hyperbranched polyglycerol (HPG) has been recently of interest for peritoneal dialysis, but its pharmacokinetics is barely understood. This study investigated the absorption, distribution and excretion of 1 and 3 kDa HPG. Rats (naive, 5/6 nephrectomy (5/6 Nx) or bilateral nephrectomy (BNx)) received a single dose of 3H-labelled HPG-containing solutions intraperitoneally (IP) or intravenously (IV). Radioactivity in tissues, urine and faeces was counted using a scintillation counter. Pharmacokinetic parameters were calculated using WinNonlin software. During 8-h dwell with IP injected therapeutic dose of HPG-based hypertonic solutions, the plasma levels of 1 kDa HPG reached the peak at 2 h, followed by a decrease to the end, whereas 3 kDa HPG increased for the duration of the 8 h. At the experimental endpoint, the distribution of both sizes of HPG in major organs was minimal, whereas most of 1 kDa HPG was excreted via urine, and of 3 kDa remained in peritoneal cavity. The elimination of both 1 and 3 kDa HPG after either IP or IV administration was significantly delayed by 5/6 Nx or BNx as compared to naive controls. Further, 24-h faecal excretion of HPG (3 kDa) was <5% of injected dose that was not different between healthy and BNx rats. Data suggest size-dependent peritoneal absorption of osmotic HPG that are not specifically absorbed by any of the organs tested. The clearance of small HPG mainly depends on kidney excretion, implying the risk of HPG accumulation in patients with end-stage kidney disease who receive maintenance dialysis with HPG.

RF34 | PMON202 The Human Metabolic Profile of Estetrol

Abstract Objectives Estetrol (E4), a native estrogen produced by the fetal human liver, has four hydroxyl-groups, making it structurally distinct from other estrogens. We determined the human metabolic profile of E4, which is recently marketed combined with drospirenone as a novel contraceptive and is currently in development for the relief of menopausal symptoms. Method: We studied the in vitro metabolism of E4 using human hepatocytes, human liver microsomes and recombinant CYP enzymes in reaction phenotyping studies to evaluate the role of human cytochrome P450 enzymes, UDP-glucuronosyltransferases (UGT) and sulfotransferases (SULT). Furthermore, we evaluated the in vivo metabolism of E4 in an open-label, non-randomised phase 1 human absorption, distribution, metabolism, and excretion study, in which six healthy postmenopausal participants received a single oral solution containing 15 mg [14C]-E4. We analysed blood (up to 240h), urine and faecal samples (up to 312h). Metabolite profiling and identification was performed using liquid chromatography with tandem mass spectrometry. Results The in vitro studies showed that E4 undergoes extensive phase 2 metabolism to form glucuronide and sulphate conjugates. UGT2B7 is the key enzyme catalysing the direct glucuronidation of E4 and SULT1E1 is the dominant sulfotransferase for sulphate conjugation in vitro. Unlike for other estrogens, oxidative phase 1 metabolism by P450 enzymes does not play a major role in the metabolism of E4. Following oral administration of E4 to humans, the major metabolites observed in human plasma were E4-16-glucuronide, E4-3-glucuronide and E4-glucuronide-sulfate (respectively 62%, 17% and 9% of radioactivity at the time of maximum plasma concentration [Tmax]). At Tmax, unchanged E4 accounts for only 7.5% of plasma radioactivity. Main metabolites quantified in urine during the first 6 hours after administration were E4-16-glucuronide and E4-3-glucuronide (respectively 77.4% and 16.5% of urine radioactivity). Approximately 69% of the total administered radioactivity was recovered in urine and 22% in faeces. Mass spectrometry showed that E4 was not present in urine but was detected in faeces and that E4 is not converted back into one of the other natural estrogens (estriol, estradiol, estrone). Conclusions Altogether, these data suggest that E4 has a unique metabolic profile. E4 is a terminal end-product of estrogen metabolism, which is not converted back, in vivo, into active metabolites like estriol, estradiol or estrone. Unlike for other estrogens, CYP450 enzymes do not play a major role in the metabolic pathway of E4. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m., Monday, June 13, 2022 12:48 p.m. - 12:53 p.m.

Absorption, metabolism and excretion of [14C]-sotorasib in healthy male subjects: characterization of metabolites and a minor albumin-sotorasib conjugate.

The objectives of this study were to characterize the absorption, metabolism, and excretion of sotorasib and determine the metabolites present in plasma, urine, and feces in healthy male subjects following a single oral 720mg dose containing approximately 1μCi of [14C]-sotorasib. Urine, feces, and plasma were collected post-dose and assayed for total radioactivity and profiled for sotorasib metabolites. Urine and plasma were also assayed for sotorasib pharmacokinetics. In addition, in vitro studies were performed to determine the enzymes responsible for formation of major circulating metabolites and protein adducts in human plasma. Sotorasib was rapidly absorbed, with a median time to peak concentration of 0.75h. Mean t1/2,z of plasma sotorasib, whole blood total radioactivity, and plasma total radioactivity were 6.35, 174, and 128h, respectively. The geometric mean cumulative recovery was 80.6%; the majority was excreted in feces (74.4%) with a low percentage excreted in urine (5.81%). M10, sotorasib, and M24 were present at 31.6%, 22.2%, and 13.7% of total radioactivity in plasma extracts, respectively. M10 and sotorasib were present at < 5% of administered radioactivity in urine, while only unchanged sotorasib, at 53% of administered radioactivity, was identified in feces. A sotorasib-albumin adduct was identified in plasma as a minor constituent, consistent with the observed radioactivity profile in plasma/blood. Sotorasib metabolism involves nonenzymatic glutathione conjugation, GGT-mediated hydrolysis of glutathione adduct, and direct CYP3A and CYP2C8-mediated oxidation. Elimination of sotorasib is predominantly fecal excretion, suggesting dose reduction is not necessary with renal impairment.

Absorption, metabolism, and excretion of [14C]-sebetralstat (KVD900) following a single oral dose in healthy male participants

Sebetralstat is an investigational oral plasma kallikrein inhibitor for the on-demand treatment of hereditary angioedema. Six healthy male participants received one dose of 600 mg (540 µCi) [14C]-sebetralstat. Plasma concentrations of sebetralstat and levels of total radioactivity in plasma, urine, and faeces were determined. Metabolite profiles of radioactivity were generated, and major metabolites structurally characterised. Radioactivity was rapidly absorbed and was excreted with a mean of 95.8% (63.4% faeces; 32.4% urine) recovered by 216 h. Sebetralstat was the major drug-related component in urine and faeces, although metabolism predominated overall (main metabolites: M19 (des-[methoxy-fluoro-methylpyridine]-sebetralstat), M10 (N-des-pyridone-sebetralstat-carboxylic acid), M3 (pyridine O-desmethyl-sebetralstat), and M34 (pyridine dioxy-dihydro-sebetralstat)). Sebetralstat was the main radiolabelled component in plasma (mean of 64.1% of the total radioactivity AUC0–24), followed by relatively low proportions of metabolites: M19 (7.10%), M3 (4.01%), and M10 (4.00%). Although M19 was >10% of the plasma radioactivity AUC0–24, in one participant it comprised a mean of <10% of AUC0–24. Plasma levels of M19 were measured at the NOAEL dose in a rat toxicology study, where higher exposure was observed vs. that in humans. Given these findings and the lack of pharmacological activity of M19, it was concluded that there was no unique or disproportionate circulating metabolite in humans.

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, metabolism, and excretion of [14C]YY-20394, a highly selective PI3K-Delta inhibitor in humans

YY-20394, a highly selective PI3Kδ inhibitor, is under NDA submission for treating follicular lymphoma in China. The absorption, metabolism, and excretion of YY-20394 were evaluated in healthy Chinese male subjects following a single oral dose of 80 mg [14C]YY-20394 (100 µCi). Within 264 h post-dose, 92.1% of the administered dose was recovered, with 58.1% from urine and 34.0% from faeces. YY-20394 was rapidly absorbed in humans, and the peak plasma concentrations occurred at 1.0 h. The absorbed drug fraction was at least 58.1% according to urine recovery. In addition to the parent drug, nine metabolites were identified in plasma, urine, and faeces. Unchanged YY-20394 was the predominant drug-related component in plasma (accounting for 68.4% of the total radioactivity), urine (accounting for 90.0% of the urinary radioactivity) and faeces (accounting for 41.7% of the faecal radioactivity). In humans, the major metabolic sites were the morphine ring and side chains of piperidine rings. The major metabolic pathways involved N-dealkylation, O-dealkylation, glucuronidation and acetylation. Overall, renal elimination played a significant role in the disposition of YY-20394, and the morphine ring and the side chain of the piperidine ring was the predominant metabolic sites.

Pharmacokinetics and metabolism of mirogabalin, a novel α2δ ligand, in rats and monkeys

The purpose of this study was to investigate the pharmacokinetic behaviour of mirogabalin in rats and monkeys. Pharmacokinetic parameters of mirogabalin after its oral and intravenous administration were determined. Distribution study, mass balance study and metabolite identification were also conducted after the oral administration of [14C]mirogabalin. Plasma exposure (Cmax and AUCinf) increased dose-proportionally after the oral administration of mirogabalin at 1, 3 and 10 mg/kg to rats and monkeys. Mean total body clearance (CLtot) after intravenous administration at 3 mg/kg was 13.5 mL/min/kg in rats and 9.02 mL/min/kg in monkeys, and absolute bioavailability at 3 mg/kg was 97.6% in rats and 85.2% in monkeys. There was greater recovery of radioactivity in urine than that in faeces after the oral administration of [14C]mirogabalin. The main radioactive component in the plasma, urine and faeces was mirogabalin. A204-4455 (lactam form), an oxidised metabolite of mirogabalin, mirogabalin N-glucuronide and O-glucuronide of oxidised A204-4455 were detected as minor components in monkeys and rats. Mirogabalin administered orally was almost completely eliminated via urinary excretion. A small part of the orally administered dose of mirogabalin was metabolised via glucuronidation at the amine and carboxylic acid moiety and oxidation as the primary metabolic pathway.

Radiolabeling of PSMA-617 with 89Zr: A novel use of DMSO to improve radiochemical yield and preliminary small-animal PET results

IntroductionNovel diagnostic and therapeutic options are urgently needed for patients with metastatic castration-resistant prostate cancer (CRPC). PSMA-617 is one of the most promising ligands that bind to prostate specific membrane antigen (PSMA), the cell surface biomarker of CRPC. Of the radiolabeled PSMA ligands developed to date, [68Ga]Ga-PSMA-617 is most commonly used for PSMA positron emission tomography (PET) prior to radioligand therapy (RLT) with [177Lu]Lu-PSMA-617. However, the presence of 68Ga radioactivity (half-life 68 m) in urine at the early PET imaging time point complicates optimization of the therapeutic dose of PSMA-617 labeled with 177Lu (half-life 6.7 d). Thus, PET imaging with the long-lived positron emitter 89Zr (half-life 3.3 d) would be better suited in order to optimize the dose of [177Lu]Lu-PSMA-617 as 89Zr PET allows scans after excretion of the radioactive urine. Until now, PSMA-617 could not be radiolabeled with 89Zr with high radiochemical yield due to poor incorporation of 89Zr into 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Here we report a novel method for radiolabeling PSMA-617 with 89Zr and the preliminary results of small-animal PET with [89Zr]Zr-PSMA-617. MethodsWe labeled PSMA-617 with 89Zr in a 1:1 mixture of DMSO and HEPES buffer at 90 °C for 30 min, followed by quality control analysis by HPLC. We then determined the dissociation constant (Kd) and logD values of [89Zr]Zr-PSMA-617. We obtained PET images of [89Zr]Zr-PSMA-617 at 24 h in mice bearing both LNCaP (PSMA-positive) and PC-3 (PSMA-negative) tumors (N = 5). The ex vivo [89Zr]Zr-PSMA-617 biodistribution was then examined separately using tissue samples of LNCaP-bearing mice at 2 h (N = 4) and 24 h (N = 4). Results[89Zr]Zr-PSMA-617 was prepared with a radiochemical yield of 70 ± 9%. The Kd value was 6.8 ± 3.5 nM. The logD value was −4.05 ± 0.20. PET images showed the highest uptake in LNCaP tumors (maximum standardized uptake value, SUVmax = 0.98 ± 0.32) and low uptake in kidneys (SUVmax = 0.18 ± 0.7) due to the absence of urine radioactivity. Conclusion[89Zr]Zr-PSMA-617 was successfully prepared using DMSO and HEPES buffer. [89Zr]Zr-PSMA-617 visualized PSMA-positive LNCaP tumors in the absence of radioactive urine 24 h p.i. Advances in knowledge and implications for patient careThis method of radiolabeling PSMA-617 with 89Zr using DMSO would be suitable for future clinical trials. Prediction of radiation dose by using [89Zr]Zr-PSMA-617 leads to the safe and effective RLT with [177Lu]Lu-PSMA-617.

Evobrutinib, a covalent Bruton's tyrosine kinase inhibitor: Mass balance, elimination route, and metabolism in healthy participants.

The highly selective, covalent Bruton’s tyrosine kinase inhibitor evobrutinib is under investigation for treatment of patients with multiple sclerosis (MS). Early clinical studies in healthy participants and patients with relapsing MS indicated that evobrutinib is well‐tolerated and effective. We undertook a mass balance study in six men who received a single 75‐mg oral dose of evobrutinib containing ~ 3.6 MBq (100 μCi) 14C‐evobrutinib, to determine the absorption, metabolic pathways, and routes of excretion of evobrutinib. The primary objectives of this phase I study (NCT03725072) were to (1) determine the rates and routes of total radioactivity excretion, including the mass balance of total drug‐related radioactivity in urine and feces, (2) assess the pharmacokinetics (PKs) of total radioactivity in blood and plasma, and (3) characterize the plasma PKs of evobrutinib. Exploratory end points included identifying and quantifying evobrutinib and its metabolites in plasma and excreta (urine and feces) and exploring key biotransformation pathways and clearance mechanisms. Evobrutinib was primarily eliminated in feces (arithmetic mean percentage, SD, 71.0, 2.1) and, to a lesser extent, in urine (20.6, 2.0), with most of the total radioactivity (85.3%) excreted in the first 72 h after administration. No unchanged evobrutinib was detected in excreta. Evobrutinib was rapidly absorbed and substantially metabolized upon absorption. Only one major metabolite M463‐2 (MSC2430422) was identified in plasma above the 10% of total drug exposure threshold, which classifies M463‐2 (MSC2430422) as a major metabolite according to the US Food and Drug Administration (FDA; metabolites in safety testing [MIST]) and the European Medicines Agency (EMA; International Conference on Harmonization [ICH] M3). These results support further development of evobrutinib and may help inform subsequent investigations.

Absorption, metabolism, excretion, and safety of [14C]almonertinib in healthy Chinese subjects

BackgroundAlmonertinib Mesilate Tablets (HS-10296, Hansoh Pharma, Shanghai, China) is a novel and selective third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). A phase I study of almonertinib in patients with non-small cell lung cancer (NSCLC) demonstrated a linear metabolic trend, a good tolerability/safety profile, and preliminary antitumor activity. However, the metabolism, excretion, and substance balance of almonertinib has not been clearly determined. Here, we investigated the pharmacokinetic characteristics and safety profile of almonertinib following a single oral dose (110 mg/50 µCi) in healthy Chinese male participants.MethodsTotal radioactivity (TRA) in whole blood, plasma, urine, and feces was measured by utilizing a liquid scintillation counter to obtain almonertinib substance balance data. The pharmacokinetic parameters of [14C]almonertinib and the parent drug almonertinib in whole blood and plasma were analyzed with noncompartmental analysis in the WinNonlin software (Pharsight Corp). The major metabolites in plasma, urine, and feces were analyzed by high-performance liquid chromatography (HPLC) coupled with an online or offline isotope detector. The safety of the drug was evaluated after administration.ResultsThe safety and tolerability of a single oral dose of 110 mg/50 µCi [14C] almonertinib suspension were good in healthy Chinese male participants. There was no significant abnormality or special adverse reaction. TRA peaked quickly in plasma, with a Tmax of 4.0 h; however, TRA was cleared slowly in vivo, with a mean terminal elimination phase (half-life, T1/2) of up to 863 h. In addition to the parent drug, a total of 26 metabolites in blood, urine, and feces were analyzed. In plasma, parent drug was the major drug-related component, accounting for 69.97% of TRA, and M440 (almonertinib-M2 demethyl product) was the major metabolite, accounting for 5.08% of TRA; in urine, parent drug accounted for 0.48% of the dose administered and HAS-719 was the major metabolite, accounting for 1.20% of the administered dose; in feces, parent drug was about 8.61% of the dose administered and HAS-719 was the major metabolite, accounting for 12.33% of the administered dose, which was followed by M541a/M470a and M617/M575, accounting for 11.8% and 6.76% of the administered dose, respectively.ConclusionsAlmonertinib has a good safety profile, with parent drug as its main circulating component. almonertinib is extensively metabolized in vivo before excretion and is excreted as a parent drug and metabolites mainly via feces.Trial registrationThe trial registration number: CTR20192291.

Perfluorooctanoic Acid Uptake by Alfalfa (Medicago sativa) and Bioavailability in Sprague-Dawley Rats

Perfluorooctanoic acid (PFOA) is a perfluorinated alkyl substance used as a surfactant in a wide variety of industrial and consumer products. Over the past decade, concern has increased over the presence of PFOA in biosolids from wastewater treatment plants used as fertilizer on agricultural lands because of the potential for PFOA to enter the food chain. In this study, the uptake of 14C-PFOA from soil by alfalfa and 14C-PFOA bioavailability from consumption of this alfalfa was evaluated in Sprague-Dawley rats. Alfalfa leaves accumulated 14C-PFOA up to 4 to 5 μg/g of dry leaf, approximately 10 times higher than accumulation in the stem. Alfalfa was ground for feeding to 15 female Sprague-Dawley rats (175 to 200 g). Animals within metabolism cages were fed 10 g of feed (6 g of alfalfa plus 4 g of ground rat chow) twice daily for 14 days (equivalent to 50 μg of 14C-PFOA per kg per day). At the end of the feeding period, three rats were euthanized for sample collection on each of withdrawal days 0, 3, 7, 11, and 14. During the feeding and withdrawal phases, urine and feces were collected daily. At necropsy, blood, liver, kidney, adipose, muscle, skin, brain, heart, adrenal glands, spleen, lungs, and thymus were removed and assayed for 14C-PFOA by combustion and liquid scintillation counting. Rats had eliminated 72.8% ± 3.4% of the total dose via urine at 14 days, but urinary radioactivity fell below the level of detection by day 3 of the withdrawal period. Fecal elimination was 6.5% ± 1.2% of the dose and fell below the level of detection by day 2 of the withdrawal period. The rapid and high elimination via urine indicates that a majority of the dose was absorbed. The uptake of 14C-PFOA into alfalfa was low from soil with a high organic concentration; however, 14C-PFOA was highly bioavailable from the alfalfa when used as a feed component for rats. This study provides data for regulators investigating 14C-PFOA bioavailability and disposition in animals or animal products exposed to contaminated feed.