Mass Balance Studies Research Articles

Establishing a physiologically based pharmacokinetic framework for aldehyde oxidase and dual aldehyde oxidase-CYP substrates.

Aldehyde oxidase (AO) contributes to the clearance of many approved and investigational small molecule drugs, which are often dual substrates of AO and drug-metabolizing enzymes such as cytochrome P450s (CYPs). As such, the lack of established framework for quantitative translation of the clinical pharmacologic correlates of AO-mediated clearance represents an unmet need. This study aimed to evaluate the utility of physiologically based pharmacokinetic (PBPK) modeling in the development of AO and dual AO-CYP substrates. PBPK models were developed for capmatinib, idelalisib, lenvatinib, zaleplon, ziprasidone, and zoniporide, incorporating invitro functional data from human liver subcellular fractions and human hepatocytes. Prediction of metabolic elimination with/without the additional empirical scaling factors (ESFs) was assessed. Clinical pharmacokinetics, human mass balance, and drug-drug interaction (DDI) studies with CYP3A4 modulators, where available, were used to refine/verify the models. Due to the lack of clinically significant AO-DDIs with known AO inhibitors, the fraction metabolized by AO (fmAO) was verified indirectly. Clearance predictions were improved by using ESFs (GMFE ≤1.4-fold versus up to fivefold with physiologically-based scaling only). Observed fmi from mass balance studies were crucial for model verification/refinement, as illustrated by capmatinib, where the fmAO (40%) was otherwise underpredicted up to fourfold. Subsequently, independent DDI studies with ketoconazole, itraconazole, rifampicin, and carbamazepine verified the fmCYP3A4, with predicted ratios of the area under the concentration-time curve (AUCR) within 1.5-fold of the observations. In conclusion, this study provides a novel PBPK-based framework for predicting AO-mediated pharmacokinetics and quantitative assessment of clinical DDI risks for dual AO-CYP substrates within a totality-of-evidence approach.

19F qNMR based pharmacokinetics, metabolism and mass balance studies of SARS-CoV-2-3CL protease inhibitor simnotrelvir (SIM0417) in humans.

Simnotrelvir (SIM0417), an inhibitor of the 3CL protease of SARS-CoV-2, has been identified as a CYP3A sensitive substrate. This study investigated the pharmacokinetics, metabolism, and mass balance of simnotrelvir following a single oral dose of 750 mg in six healthy Chinese male subjects, co-administered with four doses of 100 mg ritonavir. Analysis using 19F qNMR combined with LC-MS/MS showed that the parent drug M0 constituted over 90% of the drug-related components in plasma. Of the administered dose, 55.4% (54.3% of M0) was recovered in urine, while 36.7% (4.57% of M0) was excreted in feces. UPLC/Q-TOF MS was used to identify metabolites in human plasma, urine and feces. Notably, oxidative metabolites catalyzed by CYP3A were scarcely detected in these matrixes. The amide hydrolyzed metabolite M9 and the cyano hydrolyzed metabolite M10 were recognized as the predominant metabolites, with the main excretion being through feces (19.0% and 12.7% of the administered dose, respectively). In vitro experiments indicated that M10 is primarily formed in the duodenum and jejunum, with further metabolism to M9 by microbiota in the large intestine. Overall, the co-administration of simnotrelvir with ritonavir led to predominant metabolism by intestinal enzymes or microbiota, resulting in hydrolyzed metabolites. These findings highlight the critical role of intestinal metabolism in the pharmacokinetics of simnotrelvir and emphasize the need to consider interactions with antibiotics and individual differences of intestinal microbiota.

Calculations of the conversion factor from organic carbon to organic matter for aerosol mass balance

Aerosol mass balance studies based on filter samples require a conversion factor to derive organic matter (OM) concentrations from organic carbon (OC) measurements from thermo-optical methods. This factor provides indirect insights on the molecular structure of OM needed in chemical transport models. Site- and season-specific ratios of OC to OM (fOM:OC) were calculated using data from five rural background sites in France between 2012 and 2021 by relating the unidentified chemical fraction in PM2.5 samples to thermo-optical OC concentrations. Further, multiple linear formulations were used to evaluate the impact of possible artefacts on the determination of fOM:OC. The resulting fOM:OC was then compared to other estimates derived from online aerosol mass spectrometry data, showing good agreement. The spatial and temporal variability in fOM:OC is discussed considering factors such as seasonality, meteorological conditions and the atmospheric oxidative potential. Linear-mixed effect models were formulated to quantitatively determine the drivers which influence the fOM:OC at the French rural background sites. Both ozone and relative humidity were variables with statistically significant effects on fOM:OC, indicating that differences in the contributions from both photooxidation and water content, explain the variability in fOM:OC observed at the French rural background sites. Site-specific fOM:OC yielded more accurate PM2.5 mass closure and are therefore recommended in mass-balance exercises. Accurate fOM:OC are critical to maintain consistency in OM time series, especially in cases where filter-based time series may be replaced by state-of-the-art online instrumentation.

Mass Balance of Maritime Glaciers in the Southeastern Tibetan Plateau during Recent Decades

Maritime glaciers in the southeastern Tibetan Plateau (SETP) are particularly sensitive to changes in climate, and their changes directly and severely affect regional water security and glacier-related hazards. Given their large societal importance, a better understanding of the mass balance of maritime glaciers in the SETP, a key variable for characterizing the state of glacier health, is of great scientific interest. In this review, we synthesize in situ, satellite-based observations and simulations that present an overall accelerating negative mass balance of maritime glaciers in the SETP in recent decades. We hereby highlight a significant spatiotemporal difference in the mass balance of maritime glaciers across the SETP and investigate the drivers of the accelerated mass loss of these glaciers in recent years. We find that accelerated glacier mass loss agrees with the variabilities in temperatures rising and precipitation decreasing at regional scales, as well as the spatial patterns of widespread melt hotspots (e.g., thin debris, ice cliffs, supraglacial ponds, and surface streams), the expansion of glacial lakes, enlarged ice crevasses, and frequent ice avalanches. Finally, the challenges of the mass balance study of maritime glaciers and future perspectives are proposed. Our review confirms the urgent need to improve the existing glacier inventory and establish comprehensive monitoring networks in data-scarce glacierized catchments, and it suggests paying particular attention to the development of glacier mass-balance models that coupe multiple physical processes at different interfaces to predict the status of maritime glaciers and their responses to climate change. This study can inform the sustainable management of water resources and the assessment of socio-economic vulnerability due to glacier-related hazards in the SETP and its surroundings in the context of marked atmospheric warming.

Mass balance and economic study of a treatment chain for nickel, cobalt and rare earth elements recovery from Ni-MH batteries

ABSTRACT The aim of this project is to develop and evaluate the economic performance of a complete process for recovering nickel, cobalt, and rare earths (REEs) from nickel metal hydride (Ni-MH) battery waste. The main elements contained in the battery powder are Ni (523 g/kg), La (58 g/kg), Co (39 g/kg), Zn (21 g/kg), Nd (19 g/kg), Sm (19 g/kg) and Ce (14 g/kg). Metal leaching was carried out with 2 M sulfuric acid, solubilising 100% of Ni, 93% of Co and 94% of REEs. Rare earths were precipitated with NaOH, then purified after resolubilization in nitric acid. Solvent extraction with bis(2-ethylhexyl) phosphoric acid (D2EHPA) followed by bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) was used to separate Ni and Co. At the end of the process, REEs, nickel, and cobalt were recovered as oxides after precipitation as oxalates. The REE, nickel and cobalt oxides obtained have purities of 97.6%, 97.2% and 93.2% respectively. A techno-economic study was carried out using SuperPro Designer software. In this scenario, plant capacity was set at 1.0 t of used battery powder per hour for an operating period of 8 h/d and 250 days per year. The total investment was estimated at $26.9 million, with a payback period of 1.58 years. For a 15-year life, the net present value of this project is estimated at $95.9 million, with an interest rate of 7%. The internal rate of return is estimated at 46.1%, which is considered acceptable and economically viable.

New stability indicating RP-HPLC methods for the determination of related substances and assay of trametinib acetic acid: a mass balance approach.

New stability indicating related substances and assay methods for trametinib acetic acid by RP-HPLC have been developed and validated through forced degradation and mass balance studies for the first time. In related substances (RS) method, trametinib acetic acid was successfully separated from its six related substances namely, cyclopropanamide impurity, desiodo trametinib, desacetyl trametinib, trione acetamide intermediate, trione intermediate, and trione PTSA intermediate using YMC-Triart C18 (150 × 4.6mm, 3µm) column. Orthophosphoric acid (0.15%) in water was used as buffer. Gradient elution was programmed using mobile phase-A (buffer and acetonitrile mixture in 80:20 v/v ratio) and mobile phase-B (buffer and acetonitrile mixture in 20:80 v/v ratio). Acetonitrile and methanol mixture (1:1 v/v) was used as diluent. Flow rate, injection volume, column temperature, and wavelengths were kept as 0.8mL/min, 10µL, 55°C, and 240nm, respectively. Desacetyl trametinib and cyclopropanamide impurity were identified as potential degradation impurities in acid and base degradation conditions, respectively. Assay method specific to above six related substances was also developed. Assay of forced degradation samples was also determined, and the mass balance was established by adding total impurities formed in RS method to assay of trametinib acetic acid.

The enduring world forest carbon sink.

The uptake of carbon dioxide (CO2) by terrestrial ecosystems is critical for moderating climate change1. To provide a ground-based long-term assessment of the contribution of forests to terrestrial CO2 uptake, we synthesized in situ forest data from boreal, temperate and tropical biomes spanning three decades. We found that the carbon sink in global forests was steady, at 3.6 ± 0.4 Pg C yr-1 in the 1990s and 2000s, and 3.5 ± 0.4 Pg C yr-1 in the 2010s. Despite this global stability, our analysis revealed some major biome-level changes. Carbon sinks have increased in temperate (+30 ± 5%) and tropical regrowth (+29 ± 8%) forests owing to increases in forest area, but they decreased in boreal (-36 ± 6%) and tropical intact (-31 ± 7%) forests, as a result of intensified disturbances and losses in intact forest area, respectively. Mass-balance studies indicate that the global land carbon sink has increased2, implying an increase in the non-forest-land carbon sink. The global forest sink is equivalent to almost half of fossil-fuel emissions (7.8 ± 0.4 Pg C yr-1 in 1990-2019). However, two-thirds of the benefit from the sink has been negated by tropical deforestation (2.2 ± 0.5 Pg C yr-1 in 1990-2019). Although the global forest sink has endured undiminished for three decades, despite regional variations, it could be weakened by ageing forests, continuing deforestation and further intensification of disturbance regimes1. To protect the carbon sink, land management policies are needed to limit deforestation, promote forest restoration and improve timber-harvesting practices1,3.

Mass balance and economic study of a treatment chain for rare earths, base metals and precious metals recovery from used smartphones

In the present study, a comprehensive hydrometallurgical process was developed for the recovery of several types of metals from used cell phone printed circuit board assemblies. The overall process is divided into four stages of selective leaching of rare earth elements (REE), copper, nickel, silver and finally gold. After solubilization, the metals were purified using precipitation, solvent extraction, electrodeposition, and cementation techniques. Laboratory pilot-scale tests of the complete smart phone printed circuit board processing line showed REE, copper, nickel, silver, and gold recovery efficiencies of 78.0 %, 98.8 %, 81.8 %, 100 % and 96.1 %, respectively. The purity of the products obtained is evaluated at 94.8 % for rare earth oxides (70.0 % Nd2O3, 18.5 % Pr2O3, 2.8 % Dy2O3 and 2.4 % Sm2O3), 99.8 % for elemental copper, 94.3 % for nickel oxide, 93.8 % for silver and 89.3 % for gold. A scenario involving the installation of a plant processing 1 t/h of waste was evaluated using SuperPro Designer software. For a total investment of $53.22 million and an operating cost of $18.23 million per year, the main revenue is $65.77 million per year, with a return on investment of 91.6 % and a payback period of 1.1 years.

A comparative study of mass balance in the Lambert Glacier and Amery Ice Shelf along the Chinese inland traverse during 2019–2023 using altimetry, gravity, and in-situ observations

Abstract. The new photon-counting laser altimetry satellite ICESat-2 was successfully launched on September 15, 2018 with an unprecedented ice surface elevation measurement accuracy of 2–4 cm. It is meaningful for accurately estimating volumetric changes in the Antarctic Ice Sheet. Cross-validation of different types of data, especially comparison with in-situ data, is important for the ice sheet mass balance results of a new satellite. This paper proposes an elevation-difference method of grid elevation change rate model, based on ICESat-2 ATL11 elevation time series data, to distinguish the linear change trend of ice sheet surface elevation from the elevation change resulting from periodic precipitation. In order to compare the estimated elevation-change rate with the flux computed from in-situ snow stake velocity measurements and GRACE-FO gravity survey data, we made corrections for firn air content, elastic, and glacier isostatic adjustment. Based on the ATL11 data from 2019 to 2023, our results show that the ice sheet change in Basin 11 along the CHINARE traverse is from ~0.019 m yr−1 to ~0.121 m yr−1, and the mass balance in the upstream of the traverse in Basin 11 is ~1.9±0.2 Gt yr−1. It is comparable to ~2.4±1.2 Gt yr−1 from GRACE-FO during the same time period. Furthermore, the flux across traverse-11.9±1.1 Gt yr−1 is comparable to that of ~-9.7±0.9 Gt yr−1 across the same flux gate during 1997–2009 which is calculated based on GNSS-derived ice velocity observations, considering the time period difference and uncertainties.

Evaluation of in vitro bioaccessibility of Cu, Fe, Mn, and Zn from cooked Uruguayan pink shrimp by microwave induced plasma atomic emission spectrometry

Microwave induced plasma atomic emission spectrometry (MP-AES) was evaluated as a strategy for the analysis of simulated gastrointestinal solutions to estimate the in vitro bioaccessibility of essential elements in cooked pink shrimp. Operational conditions such as pump speed, nitrogen flow, and viewing position were thoroughly optimized for each element. Afterwards the validation of the analytical method was performed. Limits of quantification ranged from 0.005 mg kg−1 (Mn) to 0.106 mg kg−1 (Zn). Accuracy was evaluated by using a certified reference material and performing a mass-balance study. Suitable mass balances within the range 95–105% were obtained. In vitro bioaccessibility in cooked shrimp samples ranged from 14.7% (Fe) to 48.1% (Zn), in agreement with previous data from other shrimp species. The proposed procedure proved to be an outstanding sequential analytical strategy for elemental bioaccessibility studies, providing simplicity and high sample throughput compared to conventional approaches. Furthermore, this work constitutes the first work regarding the optimization of an elemental bioaccessibility study on animal protein employing MP-AES.

The practical impact of the FDA draft guidance on human mass balance studies – a year of client discussions

The practical impact of the FDA draft guidance on human mass balance studies – a year of client discussions

A Phase I, Open-Label, Mass Balance Study of [14C]-Iberdomide in Healthy Subjects.

Iberdomide is a novel potent cereblon modulator (CELMoD®) agent, which is currently under clinical development for hematological malignancies. A human mass balance study was conducted to characterize the biotransformation and excretion pathways of iberdomide. After a single dose of radiolabelled [14C]-iberdomide (1 mg) in six healthy subjects. Blood, urine, and fecal samples were collected for pharmacokinetics, mass balance, and clinical laboratory assessments. Results showed that a single oral dose of 1 mg iberdomide was generally well tolerated in healthy subjects. The recovery of [14C]-iberdomide-derived radioactivity in humans was 45.9% in urine and 42.6% in feces. Based on exposure (area under the concentration-time curve [AUC0-24]), iberdomide and M12 (metabolites) accounted for approximately 59% and 14% of circulating total radioactivity (TRA) exposure, respectively. Of the 88.5% TRA excreted, approximately 27% was excreted as unchanged iberdomide and 62% as metabolites, with similar amounts of excreted metabolites in the urine (16%) and feces (11%). Biotransformation of iberdomide in humans included multiple oxidations of the morpholino moiety as well as glutarimide ring hydrolysis of parent and oxidized metabolites and a combination of these pathways. Iberdomide was the predominant component in human plasma, with metabolite M12 being the most prominent circulating metabolite. In excreta, similar iberdomide-derived radioactivity was found in urine and feces. NCT03294603.

Pharmacokinetics, mass balance, and metabolism of [14C]envonalkib (TQ-B3139), a novel ALK tyrosine kinase inhibitor, in healthy Chinese subjects.

Envonalkib (TQ-B3139) is a novel, potent anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor used to treat ALK-positive non-small cell lung cancer. This phase I mass balance study investigated the pharmacokinetics, metabolism, and excretion of 14C-radiolabeled envonalkib in healthy Chinese male subjects. A single oral dose of 600mg (150µCi) [14C]envonalkib was administered to healthy male subjects under fasted state. Samples of blood, urine and feces were collected for quantitative determination of total radioactivity and unchanged envonalkib, and the metabolites identification. After dosing, the median Tmax of radioactivity was 4h and the mean t1/2 was 65.2h in plasma. The exposure of total radioactivity was much higher than that of unchanged envonalkib in plasma. The mean total recovery of the radiolabeled dose was 93.93% over 504h post-dose, with 15.23% in urine and 78.71% in feces. Envonalkib underwent extensive metabolism and a total of 15 metabolites were identified in plasma, urine, and feces. Unchanged envonalkib and its major metabolite M315 were the main components in plasma, accounting for 20.37% and 33.33% of total plasma radioactivity. In urine, O-dealkylation metabolite M315 was the major component accounted for 7.98% of dose. In feces, 16.01% of dose was excreted as cysteine conjugate M434-1. Envonalkib was well tolerated and there were no serious adverse events observed in the study. Envonalkib was extensively metabolized prior to excretion and eliminated primarily as metabolites via feces.

Pharmacokinetic Study of Ultrasmall Superparamagnetic Iron Oxide Nanoparticles HY-088 in Rats.

HY-088 injection is an ultrasmall superparamagnetic iron oxide nanoparticle (USPIOs) composed of iron oxide crystals coated with polyacrylic acid (PAA) on the surface. The purpose of this study was to investigate the pharmacokinetics, tissue distribution, and mass balance of HY-088 injection. The pharmacokinetics of [55Fe]-HY-088 and [14C]-HY-088 were investigated in 48 SD rats by intravenous injection of 8.5 (low-dose group), 25.5 (medium-dose group), and 85 (high-dose group) mg/100 μCi/kg. Tissue distribution was studied by intravenous injection of 35 mg/100 μCi/kg in 48 SD rats, and its tissue distribution in vivo was obtained by ex vivo tissue assay. At the same time, [14C]-HY-088 was injected intravenously at a dose of 25.5 mg/100 μCi/kg into 16 SD rats, and its tissue distribution in vivo was studied by quantitative whole-body autoradiography. [14C]-HY-088 and [55Fe]-HY-088 were injected intravenously into 24 SD rats at a dose of 35 mg/100 μCi/kg, and their metabolism was observed. In the pharmacokinetic study, [55Fe]-HY-088 reached the maximum observed concentration (Cmax) at 0.08 h in the low- and medium-dose groups of SD rats. [14C]-HY-088 reached Cmax at 0.08 h in the three groups of SD rats. The area under the concentration-time curve (AUC) of [55Fe]-HY-088 and [14C]-HY-088 increased with increasing dose. In the tissue distribution study, [55Fe]-HY-088 and [14C]-HY-088 were primarily distributed in the liver, spleen, and lymph nodes of both female and male rats. In the mass balance study conducted over 57 days, the radioactive content of 55Fe from [55Fe]-HY-088 was primarily found in the carcass, accounting for 86.42±4.18% in females and 95.46±6.42% in males. The radioactive recovery rates of [14C]-HY-088 in the urine of female and male rats were 52.99±5.48% and 60.66±2.23%, respectively. Following single intravenous administration of [55Fe]-HY-088 and [14C]-HY-088 in SD rats, rapid absorption was observed. Both [55Fe]-HY-088 and [14C]-HY-088 were primarily distributed in the liver, spleen, and lymph nodes. During metabolism, the radioactivity of [55Fe]-HY-088 is mainly present in the carcass, whereas the 14C-labeled [14C]-HY-088 shell PAA is eliminated from the body mainly through the urine.

Radiolabel Uncovers Nonintuitive Metabolites of BIIB104: Novel Release of [14C]Cyanide from 2-Cyanothiophene and Subsequent Formation of [14C]Thiocyanate.

BIIB104 (formerly PF-04958242), N-((3S,4S)-4-(4-(5-cyanothiophen-2-yl)phenoxy)tetrahydrofuran-3-yl)propane-2-sulfonamide, is an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor potentiator investigated for the treatment of cognitive impairment associated with schizophrenia. Preliminary in vitro metabolism studies with non-radiolabeled BIIB104 in rat, dog, and human liver microsomes (RLM, DLM, and HLM) showed O-dealkylation in all three species, tetrahydrofuran hydroxylation dominating in DLM and HLM, and thiophene hydroxylation prevalent in RLM. However, a subsequent rat mass balance study with [nitrile-14C]BIIB104 showed incomplete recovery of administered radioactivity (∼80%) from urine and feces over 7 days following an oral dose, and an exceptionally long plasma total radioactivity half-life. Radiochromatographic metabolite profiling and identification, including chemical derivation, revealed that [14C]cyanide was a major metabolite of [nitrile-14C]BIIB104 in RLM, but a minor and trace metabolite in DLM and HLM, respectively. Correspondingly in bile duct-cannulated rats, [14C]thiocyanate accounted for ∼53% of total radioactivity excreted over 48 hours postdose and it, as an endogenous substance, explained the exceptionally long plasma radioactivity half-life. The release of [14C]cyanide from the 2-cyanothiophene moiety is postulated to follow an epoxidation-initiated thiophene-opening based on the detection of non-radiolabeled counterpart metabolites in RLM. This unusual biotransformation serves as a lesson regarding placement of the radioactive label on an aryl nitrile when material will be used for evaluating the metabolism of a new drug candidate. Additionally, the potential cyanide metabolite of nitrile-containing drug molecules may be detected in liver microsomes with liquid chromatography-mass spectrometry following a chemical derivatization. SIGNIFICANCE STATEMENT: Using [nitrile-14C]BIIB104, non-intuitive metabolites of BIIB104 were discovered involving a novel cyanide release from the 2-cyanothiophene motif via a postulated epoxidation-initiated thiophene-opening. This unusual biotransformation serves as a lesson regarding placement of the radioactive label on an aryl nitrile when material will be used for evaluating the metabolism of a new drug candidate.

Where the White Continent Is Blue: Deep Learning Locates Bare Ice in Antarctica

AbstractIn some areas of Antarctica, blue‐colored bare ice is exposed at the surface. These blue ice areas (BIAs) can trap meteorites or old ice and are vital for understanding the climatic history. By combining multi‐sensor remote sensing data (MODIS, RADARSAT‐2, and TanDEM‐X) in a deep learning framework, we map blue ice across the continent at 200‐m resolution. We use a novel methodology for image segmentation with “noisy” labels to learn an underlying “clean” pattern with a neural network. In total, BIAs cover ca. 140,000 km2 (∼1%) of Antarctica, of which nearly 50% located within 20 km of the grounding line. There, the low albedo of blue ice enhances melt‐water production and its mapping is crucial for mass balance studies that determine the stability of the ice sheet. Moreover, the map provides input for fieldwork missions and can act as constraint for other geophysical mapping efforts.

Pharmacokinetics, Disposition, and Biotransformation of [14C]Lenacapavir, a Novel, First-in-Class, Selective Inhibitor of HIV-1 Capsid Function, in Healthy Participants Following a Single Intravenous Infusion.

Lenacapavir (LEN) is a novel, first-in-class, multistage, selective inhibitor of human immunodeficiency virus type 1 (HIV-1) capsid function recently approved for the treatment of HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 infection. The purpose of this multicohort study was to evaluate the pharmacokinetics, metabolism, excretion, safety, and tolerability of LEN following a single intravenous (IV) infusion of 10 mg LEN or 20 mg [14C]LEN in healthy participants. Twenty-one healthy adult participants were enrolled into the study and received either a single IV dose of 10 mg LEN (n = 8 active, n = 3 placebo; cohort 1) or a single IV dose of 20 mg [14C]LEN containing 200 µCi (n = 10; cohort 2). Blood, urine, and feces samples (when applicable) were collected after dosing, and radioactivity (cohort 2) was assessed using liquid scintillation counting in both plasma and excreta. LEN in plasma was quantified by liquid chromatography (LC) tandem mass spectroscopy (MS/MS) method bioanalysis. Metabolite profiling in plasma and excreta were performed using LC-fraction collect (FC)-high-resolution MS and LC-FC-accelerator mass spectrometry in plasma. Between the 10 mg and 20 mg doses of LEN, the observed plasma exposure of LEN doubled, while the elimination half-life was similar. Following administration of 20 mg [14C]LEN (200 µCi), the mean cumulative recovery of [14C] radioactivity was 75.9% and 0.24% from feces and urine, respectively. The mean whole [14C] blood-to-plasma concentration ratio was 0.5-0.7, which showed a low distribution of LEN to red blood cells. Intact LEN was the predominant circulating species in plasma (representing 68.8% of circulating radioactivity), and no single metabolite contributed to >10% of total radioactivity exposure through 1176 h postdose. Similarly, intact LEN was the most abundant component (32.9% of administered dose; 75.9% of recovered dose) measured in feces, with metabolites accounting for trace amounts. These results suggest metabolism of LEN is not a primary pathway of elimination. Of the metabolites observed in the feces, the three most abundant metabolites were direct phase 2 conjugates (glucuronide, hexose, and pentose conjugates), with additional metabolites formed to a lesser extent via other pathways. The administered LEN IV doses were generally safe and well-tolerated across participants in this study. The results of this mass balance study indicated that LEN was majorly eliminated as intact LEN via the feces. The renal pathway played a minor role in LEN elimination (0.24%). In addition, no major circulating metabolites in plasma or feces were found, indicating minimal metabolism of LEN.

Recommendations on the Use of Multiple Labels in Human Mass Balance Studies.

The administration of radiolabeled drug candidates is considered the gold standard in absorption, distribution, metabolism, and excretion studies for small-molecule drugs since it allows facile and accurate quantification of parent drug, metabolites, and total drug-related material independent of the compound structure. The choice of the position of the radiolabel, typically 14C or 3H, is critical to obtain relevant information. Sometimes, a biotransformation reaction may lead to cleavage of a part of the molecule. As a result, only the radiolabeled portion can be followed, and information on the fate of the nonlabeled metabolite may be lost. Synthesis and administration of two or more radiolabeled versions of the parent drug as a mixture or in separate studies may resolve this issue but comes with additional challenges. In this paper, we address the questions that may be considered to help make the right choice whether to use a single or multiple radiolabel approach and discuss the pros and cons of different multiple-labeling strategies that can be taken as well as alternative methods that allow the nonlabeled part of the molecule to be followed. SIGNIFICANCE STATEMENT: Radiolabeled studies are the gold standard in drug metabolism research, but molecules can undergo cleavage with loss of the label. This often results in discussions around potential use of multiple labels, which seem to be occurring with increased frequency since an increasing proportion of the small-molecule drugs are tending towards larger molecular weights. This review provides insight and decision criteria in considering a multiple-label approach as well as pros and cons of different strategies that can be followed.

Pharmacokinetics of asundexian with combined CYP3A and P-gp inhibitors and an inducer: Target in vitro and in vivo studies.

Asundexian is an oral, direct and reversible inhibitor of activated factor XI (FXIa) in development for the treatment of thromboembolic events. This article summarizes results from preclinical and clinical studies, including identification of enzymes involved in asundexian pharmacokinetics, and evaluation of potential target drug-drug interactions. In vitro studies investigated the substrate characteristics of asundexian towards several cytochrome P450 (CYP) isoforms, hydrolytic enzymes and drug transporters. Inhibition of the amide hydrolysis of asundexian was investigated in vitro for several relevant drugs. Phase 1 studies in healthy male participants investigated the pharmacokinetics (PK) of asundexian upon co-administration of combined inhibitors or an inducer of P-gp and CYP3A4 (itraconazole, verapamil or carbamazepine, respectively, or the moderate CYP3A4 inhibitor fluconazole). The pharmacodynamic (PD) markers are activated partial thromboplastin time and FXIa inhibition. Asundexian was predominantly metabolized via carboxylesterase 1 and, to a lesser extent, via CYP3A4 and is a substrate of P-gp. The asundexian area under the plasma concentration-time curve (AUC) increased by 103% and 75.6% upon combined inhibition of P-gp and strong or moderate inhibition of CYP3A4, respectively, but was unaffected by moderate CYP3A4 inhibition. Combined P-gp and CYP3A4 induction by carbamazepine decreased asundexian AUC by 44.4%. PD is concentration-dependent, thus no differences in maximum responses and recovery commensurate with PK effect(s) were observed. Adverse events were mild and asundexian was well tolerated. The presented studies confirmed that CYP3A4 and P-gp contribute to asundexian metabolism and excretion. Observed effects were in line with data from a previous mass balance study.

Pharmacokinetics, metabolism, excretion and safety of iruplinalkib (WX-0593), a novel ALK inhibitor, in healthy subjects: a phase I human radiolabeled mass balance study

ABSTRACT Background Iruplinalkib is a novel anaplastic lymphoma kinase (ALK) inhibitor for the treatment of ALK-positive crizotinib-resistant NSCLC. Research design and methods A single oral dose of 120 mg/3.7 MBq [14C]iruplinalkib was administered to healthy subjects. Blood, urine and fecal samples were collected and analyzed for iruplinalkib and its metabolites. The safety of iruplinalkib was also assessed. Results Iruplinalkib was absorbed quickly and eliminated slowly from plasma, with a Tmax of 1.5 h and t1/2 of 28.6 h. About 88.85% of iruplinalkib was excreted at 312 h, including 20.23% in urine and 68.63% in feces. Seventeen metabolites of iruplinalkib were identified, and M3b (demethylation), M7 (cysteine conjugation), M11 (oxidative dehydrogenation and cysteine conjugation of M3b) and M12 (oxidative dehydrogenation and cysteine conjugation) were considered the prominent metabolites in humans. Iruplinalkib-related compounds were found to be covalently bound to proteins, accounting for 7.70% in plasma and 17.96% in feces, which suggested chemically reactive metabolites were formed. There were no serious adverse events observed in the study. Conclusions Iruplinalkib was widely metabolized and excreted mainly through feces in humans. Unchanged iruplinalkib, cysteine conjugates and covalent protein binding products were the main drug-related compounds in circulation. Iruplinalkib was well tolerated at the study dose. Trial registration The trial is registered at ClinicalTrials.gov (Identifier: Anonymized).