Drug Metabolism and Disposition最新文献

{"title":"Pharmacokinetics of repeated, high-dose fentanyl administration in rats.","authors":"David P Obert, Autumn McKnite, Gwi H Park, Kevin M Watt, Christopher A Reilly, Kathleen F Vincent, Joseph E Rower, Ken Solt","doi":"10.1016/j.dmd.2026.100390","DOIUrl":"10.1016/j.dmd.2026.100390","url":null,"abstract":"<p><p>Fentanyl is a potent synthetic opioid widely used as a recreational drug. It is primarily metabolized in the liver to the inactive compound norfentanyl, with only a small fraction excreted unchanged via the kidneys. However, it remains unclear whether repeated high-dose exposure alters its pharmacokinetics (PK) over time. This study evaluated the effects of repeated high-dose fentanyl administration on PK and assessed sex-related differences in metabolism. Male and female Sprague-Dawley rats (n = 19) received intravenous boluses of 100 μg/kg fentanyl twice weekly for 5 weeks. After the 1st, 5th, and 10th doses, plasma concentrations of fentanyl and norfentanyl were measured using ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. PK data were analyzed using noncompartmental methods, followed by covariate analysis within a population PK model and a physiologically based PK model to identify underlying physiological factors. Noncompartmental analysis showed significantly lower C_max and longer t_1/2 of norfentanyl in females than males. Population PK analysis using a two-compartment model confirmed slower fentanyl clearance and reduced norfentanyl formation in females. Repeated dosing led to decreased fentanyl clearance after the 10th exposure. In males, higher muscle volume was inversely correlated with total body clearance, whereas in females, fat volume correlated positively with total fentanyl exposure. Repeated high-dose fentanyl administration had only modest effects on PK, limited to reduced fentanyl clearance after the final exposure. Pronounced sex differences in fentanyl metabolism were observed with female animals clearing both fentanyl and norfentanyl more slowly and producing less norfentanyl than males. SIGNIFICANT STATEMENT: In a rat model of repeated fentanyl exposure mimicking illicit use, PK changes over time were minimal, suggesting limited accumulation with intermittent dosing. In contrast, marked sex differences were observed, with female rats showing slower fentanyl clearance and reduced metabolite formation, highlighting sex-specific determinants of opioid metabolism with potential implications for interpreting toxicology findings and overdose risk.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100390"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13670244/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148891186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Liver transcriptomics reveals dysregulated hepatic absorption, distribution, metabolism, and excretion signatures in a mouse model of erythropoietic protoporphyria.","authors":"Ze-Yu Sun, Ruizhi Gu, Fu-Ying Qin, Yifan Bao, Jie Lu, Min Zhang, Da Yang, Xiao-Bo Zhong, Junjie Zhu, Xiaochao Ma","doi":"10.1016/j.dmd.2026.100367","DOIUrl":"10.1016/j.dmd.2026.100367","url":null,"abstract":"<p><p>Erythropoietic protoporphyria (EPP) is an inherited disorder caused by loss-of-function mutations in the ferrochelatase (FECH) gene. FECH deficiency leads to the accumulation of its substrate protoporphyrin IX (PPIX), resulting in cholestatic liver injury in patients with EPP. Because the liver is the primary organ responsible for drug metabolism and disposition, liver injury can alter these processes and compromise drug safety. However, safety-oriented precision medicine strategies for EPP remain poorly defined. Moreover, marked interindividual variability in EPP-associated liver injury has been observed, but the underlying risk factors remain unclear. To address these gaps, we performed RNA sequencing of liver tissue from an EPP mouse model carrying a Fech mutation. Compared with wild-type mice, more than 1700 genes were upregulated and more than 900 genes were downregulated in the liver of EPP mice. Pathway enrichment analysis revealed that upregulated pathways include immune activation, inflammatory responses, and extracellular matrix remodeling, whereas downregulated pathways include cholesterol biosynthesis, fatty acid β-oxidation, bile acid biosynthesis, and xenobiotic metabolism. Focusing on drug metabolism and disposition, we found broad downregulation of genes encoding phase I and phase II drug-metabolizing enzymes and drug transporters. Mechanistically, suppression of xenobiotic metabolism-related genes was associated with PPIX-induced liver injury and activation of inflammatory responses. Together, these findings demonstrate that PPIX-induced liver injury broadly disrupts hepatic signaling pathways, particularly those governing liver pathophysiology and xenobiotic metabolism. SIGNIFICANCE STATEMENT: Erythropoietic protoporphyria (EPP) can cause cholestatic liver injury with poorly defined implications for drug safety. Using an EPP mouse model, the study demonstrated that EPP-associated liver damage broadly suppresses hepatic drug-metabolizing enzymes and transporters while activating inflammatory signaling pathways. These findings can potentially be used to guide absorption, distribution, metabolism, and excretion-based precision medicine in patients with EPP to improve therapeutic safety.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100367"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148721744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cell line-dependent metabolic fate of curcumin analogs assessed by liquid chromatography with quadrupole time-of-flight mass spectrometry and subcellular microscopy.","authors":"Julie De Munck, Yannick Verheust, Charlotte Grootaert, Maximiliaan De Wolf, Katarina Magdalenic, Katleen Raes, Matthias D'hooghe, John Van Camp","doi":"10.1016/j.dmd.2026.100376","DOIUrl":"10.1016/j.dmd.2026.100376","url":null,"abstract":"<p><p>Curcumin exhibits broad biological activity, including anticancer effects, but its therapeutic potential is limited because of poor stability, rapid metabolism, and nonspecific activity, prompting the development of structurally modified analogs with improved drug-like properties. However, how such modifications influence intracellular metabolism and subcellular behavior remains insufficiently understood. In this study, the intracellular fate of the reference molecule curcumin and 3 promising curcumin-based benzothiazepine analogs with enhanced selective anticancer activity was investigated in cancerous (HCT-116) and noncancerous (IPEC-J2) intestinal cell lines. An untargeted liquid chromatography with quadrupole time-of-flight mass spectrometry approach was applied to characterize degradation and metabolic products in cell lysates and extracellular medium, complemented by fluorescence-based imaging to explore their subcellular distribution. Interestingly, all compounds were detected intracellularly in both cell lines but displayed distinct structure- and cell-dependent metabolic patterns. Sulfation was predominant in HCT-116 cells, whereas methylation was more abundant in IPEC-J2 cells. In addition, phase II modifications-methylation and sulfation-occurred preferentially at phenolic moieties. Fluorescence imaging revealed mainly cytosolic, nuclear-excluded distribution for all compounds, with limited evidence for selective organelle accumulation. These findings demonstrate that curcumin-based benzothiazepine analogs undergo distinct cell-dependent metabolic processing, highlighting intracellular metabolism as a potential contributor to their previously reported selective anticancer activity. SIGNIFICANCE STATEMENT: By combining liquid chromatography with quadrupole time-of-flight mass spectrometry and subcellular fluorescence microscopy, this study provides insight into the intracellular fate of curcumin and 3 analogs, which differed both between compounds and between cancerous HCT-116 and noncancerous IPEC-J2 cells. These findings highlight the importance of structural modifications and cell-dependent metabolic processing when evaluating bioactive compounds because such mechanisms may substantially influence biological activity and selectivity.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100376"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148896473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Virtual special section: Gut microbiota in drug metabolism.","authors":"Hyunyoung Jeong","doi":"10.1016/j.dmd.2026.100364","DOIUrl":"10.1016/j.dmd.2026.100364","url":null,"abstract":"","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100364"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148705842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discovery of novel plasma biomarkers for OATP1B1 activity using nontargeted metabolomics.","authors":"Jun Negami, Yosuke Suzuki, Teruhide Koyama, Ayako Oda, Koudai Iino, Sakura Suzuki, Nao Yamagishi, Natsuki Kamio, Etsuko Ozaki, Yasuyuki Yamamoto, Masahiro Nakatochi, Yukihide Momozawa, Ryota Tanaka, Hiroyuki Ono, Takahiro Sumimoto, Ryosuke Tatsuta, Hiroki Itoh, Naoyuki Takashima, Keitaro Matsuo, Keiko Ohno","doi":"10.1016/j.dmd.2026.100366","DOIUrl":"10.1016/j.dmd.2026.100366","url":null,"abstract":"<p><p>Organic anion transporting polypeptide (OATP) 1B1 is an influx transporter mediating the hepatic uptake of many compounds through the cell membrane. OATP1B1 activity fluctuates due to various factors; hence, evaluating OATP1B1 activity is important for pharmacokinetic studies and precision dosing of substrate drugs. This study aimed to discover novel biomarker candidates using nontargeted metabolomics. Blood samples of 432 individuals selected from the Japanese general population and 264 patients were analyzed. The samples were pretreated by more vigorous extraction methods than those conventionally used in metabolomics, and metabolites were measured comprehensively using ultraperformance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry. These participants were classified by a major OATP1B1 polymorphism, the c.521T>C variant, into the OATP1B1 normal function group (c.521TT) and the decreased function group (c.521TC and c.521CC). Specific biomarker candidates were extracted from metabolome profiles by multivariate analyses in the general population and patients separately. Four novel candidate compounds were identified to be probably 13'-hydroxy-gamma-tocopherol, 6-deoxodolichosterone, (20R or 20S)-24-hydroxygeminivitamin D3, and glycochenodeoxycholate-3-O-glucuronide (GCDCA-3G). The intensities of the 4 compounds were compared between the OATP1B1 normal function group and the decreased function group and among 3 groups classified by OATP1B1 c.521T>C polymorphism. GCDCA-3G, 13'-hydroxy-gamma-tocopherol, and (20R or 20S)-24-hydroxygeminivitamin D3 clearly discriminated against differences among 3 c.521T>C genotype groups, whereas 6-deoxodolichosterone discriminated between the OATP1B1 normal function group and the decreased function group. These results confirm the robustness and specificity of GCDCA-3G as an OATP1B1 biomarker and propose 13'-hydroxy-gamma-tocopherol, 6-deoxodolichosterone, and (20R or 20S)-24-hydroxygeminivitamin D3 as potentially useful novel OATP1B1 functional biomarkers. SIGNIFICANCE STATEMENT: Endogenous biomarkers for drug transporters are valuable tools for predicting adverse events caused by substrate drugs. This study aimed to explore novel biomarker candidates for organic anion transporting polypeptide (OATP) 1B1 activity using the nontargeted metabolomics approach with more vigorous pretreatment using solid-phase extraction and liquid-liquid extraction. Three novel and one conventional OATP1B1 biomarker candidates were detected by our nontargeted metabolomics. These findings contribute to the advancement of biomarker research for OATP1B1 and support further exploration of novel biomarkers.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100366"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148705850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of simulated exogenous and endogenous lipid microenvironments on cannabidiol disposition and cytochrome P450 2C19-mediated drug interactions: New mechanistic insights.","authors":"Aiden-Hung P Nguyen, Fridah C Rotich, Nadja B Cech, Mary F Paine","doi":"10.1016/j.dmd.2026.100375","DOIUrl":"10.1016/j.dmd.2026.100375","url":null,"abstract":"<p><p>Cannabidiol (CBD) is an in vitro inhibitor of multiple cytochrome P450 (P450) enzymes, which has been confirmed in healthy adults. Whether these observations translate to different patient populations, including those with hepatic steatosis, is not known. Accordingly, the effects of simulated exogenous and endogenous lipid microenvironments on the P450 inhibition potential and disposition of CBD were evaluated using human liver microsomes (HLMs). Consistent with clinical observations, CYP2C19 was most sensitive to inhibition by CBD as both a component of a mixture containing triglycerides (CBD_m) and in purified form (CBD_p), with a K_i of 0.22 ± 0.03 and 0.16 ± 0.03 μM, respectively. CYP2C19 activity (S-mephenytoin 4'-hydroxylation) decreased by 25% ± 3.5% and 68% ± 0.4%, respectively, upon exposure to triglycerides and fatty acids under simulated hepatic steatotic conditions. Triglycerides and fatty acids enhanced the CYP2C19 inhibitory effects of CBD_p by 1.3- to 3-fold, respectively. The IC₅₀ for CBD_p against CYP2C19 activity in HLMs from donors with and without metabolic dysfunction-associated steatohepatitis (MASH) was 1.28 ± 0.25 and 1.12 ± 0.23 μM, respectively. Intrinsic clearance of CBD_p via P450 and UDP-glucuronosyltransferase pathways in MASH HLMs (0.33 ± 0.02 and 0.15 ± 0.02 mL/min per mg, respectively) was lower compared with non-MASH HLMs (0.73 ± 0.03 and 0.18 ± 0.04 mL/min per mg, respectively). Results from this collection of in vitro experiments provide foundational knowledge that informs future research regarding the effects of a high-fat diet and steatotic liver disease on CBD disposition and CYP2C19-mediated drug interactions. SIGNIFICANCE STATEMENT: Exposure of human liver microsomes to simulated exogenous and endogenous lipid microenvironments provided new mechanistic insight into the direct effects of triglycerides and fatty acids on cannabidiol disposition and CYP2C19-mediated cannabidiol-drug interactions. Modified in vitro hepatic models, including human liver microsomes and human hepatocytes, under hepatic steatotic and metabolic dysfunction-associated steatohepatitis conditions could be applied to future studies aimed at evaluating the disposition and drug interaction potential of other drugs in these specific populations.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100375"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148873428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Idelalisib 8-oxidation as an enzyme-selective catalytic marker of human aldehyde oxidase in HepG2 cells: Application to the investigation of enzyme inactivation.","authors":"Nicholas Kai Ming Ng, Sian Wen Chan, Andres Kai Zhi Lim, Min Hao Eng, Vijaya Saradhi Mettu, Aik Jiang Lau","doi":"10.1016/j.dmd.2026.100397","DOIUrl":"https://doi.org/10.1016/j.dmd.2026.100397","url":null,"abstract":"<p><p>Aldehyde oxidase 1 (AOX1) is a cytosolic drug-metabolizing enzyme. Idelalisib is a phosphoinositide-3-kinase-delta inhibitor that undergoes extensive biotransformation, mainly via 8-oxidation, which is catalyzed predominantly by human AOX1 and, to a lesser extent, cytochromes P450. In the present study, the primary objective was to test the hypothesis that idelalisib 8-oxidation is an enzyme-selective catalytic marker of AOX1 in HepG2 human hepatocellular carcinoma cells that express AOX1 but has little or no CYP3A functionality, and this approach is effective in identifying AOX1 inactivators. Enzyme kinetic analysis indicated comparable values of k_cat, K_m, and ratio of k_cat/K_m (catalytic efficiency) for idelalisib 8-oxidation catalyzed by HepG2 cells and human liver cytosol, whereas V_max was greater for liver cytosol-catalyzed idelalisib 8-oxidation. Human recombinant AOX1, CYP3A4, and CYP3A5 were major catalysts of idelalisib 8-oxidation. However, experiments with a panel of enzyme-selective chemical inhibitors indicated that AOX1, but not cytochrome P450 or xanthine oxidase, was responsible for idelalisib 8-oxidation in HepG2 cells and human liver cytosol. The HepG2 cell-catalyzed idelalisib 8-oxidation assay correctly identified time-dependent AOX1 inactivators (erlotinib, O-desmethylerlotinib, O-didesmethylerlotinib, and hydralazine) and noninactivators (gefitinib, O-desmethylgefitinib, O-desmorpholinopropylgefitinib, and raloxifene). The data from the experiment to address our secondary objective indicated that erlotinib dosing increased the accumulation of idelalisib and 8-oxo-idelalisib in mouse plasma, liver, and kidney. In conclusion, (1) idelalisib 8-oxidation is an AOX1-selective catalytic marker in HepG2 cells that can be used to study AOX1 catalytic function; and (2) the in vivo mouse pharmacokinetic approach is not effective in identifying erlotinib as an inhibitor of idelalisib 8-oxidation. SIGNIFICANCE STATEMENT: Idelalisib 8-oxidation as an aldehyde oxidase 1 (AOX1)-selective catalytic marker in HepG2 cells provides a convenient experimental platform to study AOX1 catalytic function, eg, time-dependent inactivation. The experimental tools for AOX1 research can now include a dual AOX1-CYP3A substrate to be used as an AOX1-selective catalytic marker in a cellular system (eg, HepG2 cells) that expresses AOX1 but lacks CYP3A functionality.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 10","pages":"100397"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149147638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The impact of the DiI fluorescent probe on the in vivo fate of paclitaxel-loaded methoxy polyethylene glycol-block-poly (d,l-lactide) micelles.","authors":"Jiayi Yao, Jiaqi Wang, Peipei Bu, Kexin Liu, Mingyang Zhao, Jingkai Gu, Xiangjun Meng","doi":"10.1016/j.dmd.2026.100372","DOIUrl":"10.1016/j.dmd.2026.100372","url":null,"abstract":"<p><p>Fluorescent probes are extensively used for tracking the in vivo behavior of nanocarriers. However, the impact of fluorescent probes on the in vivo fate of nanomedicines remains uncertain. Potential interference from the probes may lead to misleading conclusions. This study investigated the influence of a commonly used fluorescent probe, DiI, on the in vivo fate of paclitaxel (PTX)-loaded polymeric micelles (PMs) in rats. The drug release kinetics of PTX-loaded PMs (PTX-PM) with DiI/PTX coloaded PMs (DiI/PTX-PM) in rat plasma was quantitatively compared. The results indicate that coencapsulation with DiI significantly exacerbated drug release and altered the protein binding of PTX through competitive binding, resulting in an increased proportion of free PTX. DiI enhanced diffusion-driven drug leakage without affecting the micelle dissociation kinetics. Notably, DiI inhibited elimination and increased the systemic exposure of both the free micelle material and the nanocarrier. This study provides evidence that DiI can potentially interfere with the in vivo fate of both the therapeutic payload and the nanocarrier, highlighting the necessity for rigorous validation when using it for nanocarrier tracking. SIGNIFICANCE STATEMENT: This study reveals that the common fluorescent probe DiI significantly alters the in vivo fate of paclitaxel-loaded polymeric micelles by accelerating drug release, competing for plasma protein binding, and inhibiting carrier elimination. These findings highlight the critical need for rigorous validation when using fluorescent probes to track nanomedicines.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100372"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148789345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breaking the 1% unbound threshold: an IQ consortium whitepaper on the evaluation of plasma protein binding of highly bound compounds.","authors":"Faraz Kazmi, Ulrike Gradhand, Eric T Gangl, Robert Fricke, Tanya Aldinger, Rob Chambers, Massimiliano Donzelli, Douglas Ferguson, Bernard G Francq, Paul J Harradine, Rémi Kazma, Saro Mardirosian, Jean-Marie Nicolas, Raku Shinkyo, Sandrine Simon, Michael Sinz, Patricia Stuart, Kanaka Tatikola, Matthias Beat Wittwer, Gloria Vendrell-Navarro, Zhengyin Yan, John C Kalvass","doi":"10.1016/j.dmd.2026.100358","DOIUrl":"10.1016/j.dmd.2026.100358","url":null,"abstract":"<p><p>The reliable measurement of plasma protein binding (PPB) is crucial for understanding drug pharmacokinetics and predicting drug-drug interactions (DDIs). Historically, regulatory guidelines had imposed a cutoff of 1% for the unbound fraction (f_u) of highly bound drugs, leading to concerns about overestimating DDI risks and triggering unnecessary clinical DDI trials. In this study, an IQ working group comprising 11 member companies evaluated the interlab accuracy and precision of the PPB determination of 20 compounds highly bound to plasma proteins with f_u values <1%. Utilizing equilibrium dialysis and 2 alternative methodologies-flux dialysis and plasma P450 IC₅₀ shift method-this collaborative effort aimed to rigorously assess the limits and reproducibility of f_u measurement. Results demonstrated that f_u values as low as ∼0.003% can potentially under optimized conditions be reliably quantified, challenging the necessity of a fixed cutoff. The findings suggest that the bioanalytical sensitivity, qualification of the PPB assays in the appropriate unbound fraction range, and compound properties dictate the lower limit for f_u, rather than an arbitrary threshold. In addition to advancing scientific knowledge of PPB, this work provides robust scientific justification to revise f_u criteria during the elaboration of international harmonized guidelines, allowing the use of f_u values <1% in DDI risk assessments when appropriate qualified methods are being used. Ultimately, increased confidence in low f_u values supports more efficient development of safe and efficacious drugs by improving understanding of drug pharmacological and toxicological profiles and by reducing the number of false positive DDI studies. SIGNIFICANCE STATEMENT: This study demonstrates that plasma protein binding of drugs with <1% unbound fraction can be accurately and reliably measured using qualified methodologies. By challenging the traditional 1% cutoff, our findings ultimately allow for more accurate predictions of drug pharmacological and toxicological profiles (eg, drug-drug interactions and safety margins).</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100358"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148789352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimizing ¹⁴C-radiochemical doses for absorption, distribution, metabolism, and excretion studies: A predictive approach.","authors":"Alfin D N Vaz, Katia E Vaz, Cenalo T A Vaz, Justine L Lam, Loren Berry, Tim F Ryder","doi":"10.1016/j.dmd.2026.100370","DOIUrl":"10.1016/j.dmd.2026.100370","url":null,"abstract":"<p><p>A simple method is described that uses pharmacokinetic parameters for an unlabeled drug to predict for a ¹⁴C-absorption, distribution, metabolism, and excretion study, the radiochemical dose consistent with the analytical instrument for quantitative profiling of circulating metabolites by scintillation counting. Analysis of mass balance studies for 19 drugs verified the predictive method and shows that many mass balance studies are conducted with radiochemical doses either substantially higher than required and inconsistent with the as low as reasonably achievable principle or inadequate to conduct profiling of plasma with the intended instrumentation. SIGNIFICANCE STATEMENT: The method to predict the radiochemical doses for ¹⁴C-absorption distribution, metabolism, and elimination (¹⁴C-ADME) studies enables research teams to select the radiochemical dose at which to conduct an ADME study consistent with the analytical instrument for plasma profiling and with the as low as reasonably achievable principle. Furthermore, it can also be used to assess whether a microdose or macrodose study is more appropriate.</p>","PeriodicalId":11309,"journal":{"name":"Drug Metabolism and Disposition","volume":"54 9","pages":"100370"},"PeriodicalIF":3.6,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148944489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}