European Journal of Drug Metabolism and Pharmacokinetics

03/11/2024

The Loss-of-Function ATP Binding Cassette Subfamily G Member 2 Polymorphism ABCG2 c.421C>A Reduces Lamotrigine Trough Concentrations in Adults with Epilepsy
Authors: Nada Božina, Iva Klarica Domjanović, Ivana Šušak Sporiš, Lana Ganoci, Mila Lovrić & Vladimir Trkulja
Full-text, read-only, sharable link https://rdcu.be/dY1bb

Abstract
Background and Objectives
The commonly used antiseizure medication lamotrigine is a substrate to ATP binding cassette subfamily G member 2 (ABCG2) transporter. The objective of this study was to evaluate the effect of the common loss-of-function polymorphism ABCG2 c.421C>A (rs2231142) on the lamotrigine trough concentrations at steady state in adults with epilepsy.

Methods
In two consecutive studies (Study 1, Study 2) in patients on lamotrigine monotherapy, carriers of the variant ABCG2 c.421C>A allele (CA/AA) were considered exposed, and wild-type homozygotes (CC) were considered controls. They were mutually balanced on covariates (age, s*x, body weight, several polymorphisms in genes encoding other transporter proteins and lamotrigine-metabolizing enzymes that have been suggested to affect exposure to lamotrigine) to estimate the exposure effect (geometric means ratios, GMRs) in each study separately and overall (individual patient data meta-analysis). The overall estimate was evaluated for sensitivity to residual confounding.

Results
In both studies (exposed n = 28 vs. controls n = 103; exposed n = 44 vs. controls n = 153, in Study 1 and Study 2, respectively) and overall (exposed n = 72 vs. controls n = 256), dose-corrected lamotrigine trough concentrations were moderately lower in the exposed patients: frequentist GMR [95% CI] = 0.82 [0.63–1.08]; GMR = 0.69 [0.60–0.81] and GMR = 0.72 [0.63–0.83] in Study 1, Study 2 and overall, respectively; Bayes GMR [95% CrI] = 0.83 [0.68–1.00]; GMR = 0.69 [0.58–0.83] and GMR = 0.75 [0.65–0.86] in Study 1, Study 2 and overall, respectively. Estimates appeared resistant to unmeasured confounding—the E-values for the pooled point estimates were high, and estimates corrected for a strong hypothetical bias were GMR = 0.78 [0.68–0.90] frequentist and GMR = 0.81 [0.70–0.93] Bayes.

Conclusion
Polymorphism ABCG2 c.421C>A moderately reduces lamotrigine concentrations in adults with epilepsy.

https://link.springer.com/article/10.1007/s13318-024-00925-0

Background and Objectives The commonly used antiseizure medication lamotrigine is a substrate to ATP binding cassette subfamily G member 2 (ABCG2) transporter. The objective of this study was to evaluate the effect of the common loss-of-function polymorphism ABCG2 c.421C>A (rs2231142) on the lamotri...

28/10/2024

Assessment of Abuse Liability and Ni****ne Pharmacokinetics of glo Heated To***co Products in a Randomized, Crossover Study
Authors: Milly N. Kanobe, Patrudu Makena, Kristen Prevette & Sarah A. Baxter
Full-text, read-only, sharable link https://rdcu.be/dYpZH
Abstract
Background and Objective
Heated to***co products (HTPs) are a class of non-combustible, inhaled to***co products with the potential to reduce the harm associated with cigarette smoking due to reduced cigarette smoke toxicant exposure. Subjective and ni****ne pharmacokinetics measures taken over the course of product use provide a framework for abuse liability (AL) assessment of to***co and ni****ne products as well as information on adoption potential for a new to***co product, which are important aspects for premarket to***co product authorization by the US Food and Drug Administration. This study aimed to assess the AL of glo HTPs, operated in either Standard or Boost Modes, compared with high- and low-AL comparators (subjects’ usual brand ci******es and ni****ne gum, respectively).

Methods
Ni****ne uptake and pharmacodynamics measures (including subjective and physiological measures) were assessed in a clinical study of 75 healthy adult non-menthol or menthol smokers using an open-label, randomized crossover study design. Comparisons were made between glo HTPs (Standard or Boost Modes) and each of usual brand (UB) ci******es and ni****ne gum to evaluate ni****ne exposure and subjective effects measures.

Results
Ni****ne uptake, as reflected in the area under the curve (AUC) at 15 and 240 min after product use (AUC0-15 and AUC0-240, respectively) and maximum ni****ne concentration (Cmax) were significantly lower for all glo HTPs compared to UB ci******es, regardless of the glo device mode. AUC0-15 values for glo HTPs ranged from 41.26 to 75.71 ng × min/mL, versus 158.04 to 165.53 ng × min/mL for UB ci******es. Similarly, AUC0-240 values for glo HTPs ranged from 379 to 596 ng × min/mL, compared to 1123.73 and 1283.37 ng × min/mL for UB ci******es. The Cmax for glo HTPs ranged from 5.46 to 9.00 ng/mL, whereas UB ci******es had Cmax values of 16.29 to 16.76 ng/mL. The time to reach maximum ni****ne concentration (Tmax) was significantly shorter for glo HTPs (4–5 min) compared to UB ci******es (6–7 min), except for one variant of glo HTP in Standard Mode. Ni****ne gum exhibited a slower ni****ne absorption profile, with a Tmax of 45 min and Cmax of 4.60 ng/mL. AUC0-15 and AUC0-240 values for ni****ne gum were 6.18 and 5.22 ng × min/mL, and 647.80 and 687.68 ng × min/mL for non-menthol and menthol groups, respectively. Subjective measures indicated that glo HTPs were rated significantly lower than UB ci******es in terms of product liking, smoking urge reduction, product effects, and intent to use again, but were comparable to ni****ne gum.

Conclusion
glo HTPs demonstrated lower AL than combustible ci******es while delivering sufficient ni****ne to support product adoption among current smokers. This positions glo HTPs as a potential tool in to***co harm reduction, offering a less harmful alternative to traditional ci******es.

https://link.springer.com/article/10.1007/s13318-024-00921-4

Background and Objective Heated to***co products (HTPs) are a class of non-combustible, inhaled to***co products with the potential to reduce the harm associated with cigarette smoking due to reduced cigarette smoke toxicant exposure. Subjective and ni****ne pharmacokinetics measures taken over the....

23/10/2024

Comparison of Vancomycin AUC24 Calculation Methods for Neonates and Infants
Authors: Tuomas Laitila, Ulla Sankilampi, Marjo Renko, Merja Kokki & Veli-Pekka Ranta

Full-text, read-only, sharable link https://rdcu.be/dXRMH

Abstract
Background and Objective
For neonates and infants receiving intermittent vancomycin infusions, the area under the concentration-time curve during 24 h (AUC24) is often estimated with Bayesian forecasting using one or more measured vancomycin concentrations. When practical peak and trough concentrations are measured at steady state, AUC24 can also be calculated with first-order steady-state equations for a one-compartment model (Sawchuk–Zaske method), but previously this method has been applied only for adults. The objective of this study was to compare AUC24 values obtained with the Sawchuk–Zaske method and two Bayesian models.

Methods
AUC24 values were estimated retrospectively for 18 neonates and infants with steady-state peak and trough concentrations using traditional compartmental analysis with a one-compartment model (reference method), the Sawchuk–Zaske method, and Bayesian forecasting with two previously published models. In Bayesian forecasting, both original and modified residual error models were used. In the modified models, the residual error was reduced by setting the additive residual error to zero and the proportional error to 15%.

Results
AUC24 estimates obtained with the Sawchuk–Zaske method differed − 2.7 to 0.9% from the reference method. When both peak and trough concentrations were used in Bayesian forecasting, 61% and 33% of AUC24 estimates obtained with two original models differed less than 15% from the reference method, and these fractions increased to 83% and 72% with the modified models, respectively.

Conclusion
When practical peak and trough concentrations are measured at steady state, the simple Sawchuk–Zaske method is very useful for AUC24 estimation in neonates and infants. In Bayesian forecasting, the reduced residual error model can be used to improve the model fit.

https://link.springer.com/article/10.1007/s13318-024-00920-5

Background and Objective For neonates and infants receiving intermittent vancomycin infusions, the area under the concentration-time curve during 24 h (AUC24) is often estimated with Bayesian forecasting using one or more measured vancomycin concentrations. When practical peak and trough concentrati...

24/09/2024

Pharmacokinetic Model of Drug Interaction of Tacrolimus with Combined Administration of CYP3A4 Inhibitors Voriconazole and Clarithromycin After Bone Marrow Transplantation

Authors: Toshinori Hirai, Takahiko Aoyama, Yasuhiro Tsuji, Kazuko Ino, Makoto Ikejiri, Isao Tawara & Takuya Iwamoto

Abstract
Background and Objectives
A pharmacokinetic model has been developed to quantify the drug–drug interactions of tacrolimus with concentration-dependent inhibition of cytochrome P450 (CYP) 3A4 from voriconazole and clarithromycin based on the CYP3A5 and CYP2C19 genotypes.

Methods
This retrospective study recruited unrelated bone marrow transplant recipients receiving oral tacrolimus concomitantly with voriconazole and clarithromycin. The published population pharmacokinetic model that implemented genotypes of CYP3A5 (tacrolimus) and CYP2C19 (voriconazole) was integrated. The tested CYP3A4 inhibition models (Sigmoid efficacy maximum [Emax], Emax, log-linear, and linear) were a function of competitive inhibition of voriconazole and mechanism-based inhibition of clarithromycin in a virtual enzyme compartment.

Results
The total tacrolimus trough concentrations were 119 points, with a median of 4.3 (range: 2.0–9.9) ng/mL (n = 3). The final model comprised the Sigmoid Emax model for voriconazole and clarithromycin, which depicted time-course alterations in tacrolimus concentration and clearance when given voriconazole and clarithromycin.

Conclusions
These findings could facilitate the model-informed precision dosing of tacrolimus after unrelated bone marrow transplant.

Background and Objectives A pharmacokinetic model has been developed to quantify the drug–drug interactions of tacrolimus with concentration-dependent inhibition of cytochrome P450 (CYP) 3A4 from voriconazole and clarithromycin based on the CYP3A5 and CYP2C19 genotypes. Methods This retrospective ...

23/09/2024

Pharmacokinetic and Pharmacodynamic Interaction of Finerenone with Diltiazem, Fluconazole, and Ritonavir in Rats

Authors: Tham Thi Bui, So-Hyeon Kim, Woojin Jung, Sung-yoon Yang, Quyen Thi Tran, Hyunjung Lee, Seongwon Park, Lien Thi Ngo, Hwi-yeol Yun & Jung-woo CHAE

Full-text, read-only, sharable link: https://rdcu.be/dURql

Abstract
Background and Objectives
Finerenone, a novel selective non-steroidal mineralocorticoid receptor antagonist, has been indicated in chronic kidney disease associated with type 2 diabetes mellitus. Considering the potential complications of diabetes, finerenone can be co-administered with various drugs, including fluconazole, diltiazem, and ritonavir. Given that finerenone is a substrate of cytochrome P450 (CYP) 3A4, the concurrent administration of finerenone with CYP3A4 inhibitors (diltiazem or fluconazole or ritonavir) could potentially lead to drug interactions, which may cause adverse events such as hyperkalemia. No studies have investigated interactions between finerenone and diltiazem or fluconazole or ritonavir. Therefore, this study aims to investigate the pharmacokinetic interaction of finerenone with diltiazem or fluconazole or ritonavir and to evaluate the impact of fluconazole on the pharmacodynamics of finerenone.

Methods
The pharmacokinetic study included four rat groups (n = 8 rats/group), including a control group (finerenone alone) and test groups (finerenone pretreated with diltiazem or fluconazole or ritonavir) using both non-compartment analysis (NCA) and population pharmacokinetic (pop-PK) modeling. The pop-PK model was developed using non-linear mixed-effects modeling in NONMEM® (version 7.5.0). In the pharmacodynamic study, serum potassium (K+) levels were measured to assess the effects of fluconazole on finerenone-induced hyperkalemia.

Results
The NCA results indicated that the area under the plasma concentration-time curve (AUC) of finerenone increased by 1.86- and 1.95-fold when coadministered with fluconazole and ritonavir, respectively. In contrast, diltiazem did not affect the pharmacokinetics of finerenone. The pharmacokinetic profiles of finerenone were best described by a one-compartment disposition with first-order elimination and dual first-order absorption kinetics. The pop-PK modeling results demonstrated that the apparent clearance of finerenone decreased by 50.3% and 49.2% owing to the effects of fluconazole and ritonavir, respectively. Additionally, the slow absorption rate, which represents the absorption in the distal intestinal tract of finerenone, increased by 55.7% due to the effect of ritonavir. Simultaneously, a pharmacodynamic study revealed that finerenone in the presence of fluconazole caused a significant increase in K+ levels compared with finerenone alone.

Conclusions
Coadministration of finerenone with fluconazole or ritonavir increased finerenone exposure in rats. Additionally, the administration of finerenone in the presence of fluconazole resulted in elevated K+ levels in rats. Further clinical studies are required to validate these findings.

https://link.springer.com/article/10.1007/s13318-024-00917-0

Background and Objectives Finerenone, a novel selective non-steroidal mineralocorticoid receptor antagonist, has been indicated in chronic kidney disease associated with type 2 diabetes mellitus. Considering the potential complications of diabetes, finerenone can be co-administered with various drug...

22/09/2024

Prediction of First-in-Human Dose of Chimeric Antigen Receptor-T (CAR-T) Cells from Mice

Author: Iftekhar Mahmood

Full-text, read-only, sharable link: https://rdcu.be/dUKIp

Abstract
Background and Objective
Currently, there is no available method for the prediction of first-in-human (FIH) dose for chimeric antigen receptor-T (CAR-T) cells. The objective of this work was to predict the FIH dose of CAR-T cells from different doses given to mice.

Methods
In this study, six scaling methods were evaluated for the prediction of FIH dose for CAR-T cells. The methods were body weight-based fixed exponents such as 1.0 and 0.75, human equivalent dose (HED) using exponents 0.33, two modified HED methods such as using total animal dose (in place of per kg basis) and body surface area in place of body weight using total animal dose with exponent 0.33 and a physiological factor derived from physiological parameters. The FIH doses of six CAR-T cells were predicted in this study. The predicted human doses were compared with the recommended human dose by the US-FDA for four CAR-T cell products, and the literature data were used for the remaining two CAR-T cells.

Results
The results indicated that the two modified HED methods and physiological factor are the best and reliable methods for the prediction of FIH dose for CAR-T cells.

Conclusions
The proposed methods are simple and accurate in their predictive power and can be used on a spreadsheet.
https://link.springer.com/article/10.1007/s13318-024-00918-z

18/09/2024

Vancomycin in Pediatric Patients with Cystic Fibrosis: Dose Optimization Using Population Pharmacokinetic Approach

Authors: Aysenur Yaliniz, Mathieu Blouin, Marie-Élaine Métras, Marie-Christine Boulanger, Karine Cloutier, Marie-Hélène Dubé, Julie Autmizguine & Amélie Marsot

Full-text, read-only, sharable link: https://rdcu.be/dUnqi

Abstract
Background
An increase in Staphylococcus aureus infections has been reported in pediatric patients with cystic fibrosis (CF) over the last few years. This pathogen is commonly treated with vancomycin, an antibiotic for which therapeutic drug monitoring (TDM) is recommended. Updated guidelines were recently published regarding new targets of exposure for the TDM of vancomycin through a Bayesian approach, using population pharmacokinetic (popPK) models.

Objectives
This study aims to assess the predictive performance of vancomycin popPK models in pediatric patients with CF and to recommend optimal initial dosing regimens based on simulations.

Methods
Patient data were collected from two centers in Canada, and a literature review was conducted to identify all published vancomycin popPK models for pediatric CF patients. External evaluation and simulations were performed according to patient and occasion of treatment.

Results
A total of 53 vancomycin concentrations were collected from six pediatric CF patients. Only two popPK models of vancomycin for pediatric CF patients were identified through the literature review. The external evaluation results for both centers combined revealed a population bias of 28.1% and an imprecision of 33.7%. A re-estimation of parameters was performed to improve predictive performance. The optimal initial dosing regimen was 15 mg/kg/dose administered every 6 hours according to the per occasion remodel.

Conclusion
The predictive performance and identified optimal initial dosing regimens associated with the model were different depending on the data used, showing external evaluation’s importance before implementing a model in clinical practice.

https://link.springer.com/article/10.1007/s13318-024-00913-4

Background An increase in Staphylococcus aureus infections has been reported in pediatric patients with cystic fibrosis (CF) over the last few years. This pathogen is commonly treated with vancomycin, an antibiotic for which therapeutic drug monitoring (TDM) is recommended. Updated guidelines were r...

18/09/2024

Whole Body Physiologically Based Pharmacokinetic Model to Explain A Patient With Drug–Drug Interaction Between Voriconazole and Flucloxacillin

Authors: Heshu Abdullah-Koolmees, Julia F. van den Nieuwendijk, Simone M. K. ten Hoope, David C. de Leeuw, Linda G. W. Franken, Medhat M. Said, Maarten R. Seefat, Eleonora L. Swart, N. Harry Hendrikse & Imke H. Bartelink

Full-text, read-only, sharable link: https://rdcu.be/dUnp3

Abstract
Background and Objectives
Voriconazole administered concomitantly with flucloxacillin may result in subtherapeutic plasma concentrations as shown in a patient with Staphylococcus aureus sepsis and a probable pulmonary aspergillosis. After switching our patient to posaconazole, therapeutic concentrations were reached. The aim of this study was to first test our hypothesis that flucloxacillin competes with voriconazole not posaconazole for binding to albumin ex vivo, leading to lower total concentrations in plasma.

Methods
A physiologically based pharmacokinetic (PBPK) model was then applied to predict the mechanism of action of the drug–drug interaction (DDI). The model included non-linear hepatic metabolism and the effect of a severe infectious disease on cytochrome P450 (CYP) enzymes activity.

Results
The unbound voriconazole concentration remained unchanged in plasma after adding flucloxacillin, thereby rejecting our hypothesis of albumin-binding site competition. The PBPK model was able to adequately predict the plasma concentration of both voriconazole and posaconazole over time in healthy volunteers. Upregulation of CYP3A4, CYP2C9, and CYP2C19 through the pregnane X receptor (PXR) gene by flucloxacillin resulted in decreased voriconazole plasma concentrations, reflecting the DDI observations in our patient. Posaconazole metabolism was not affected, or was only limitedly affected, by the changes through the PXR gene, which agrees with the observed plasma concentrations within the target range in our patient.

Conclusions
Ex vivo experiments reported that the unbound voriconazole plasma concentration remained unchanged after adding flucloxacillin. The PBPK model describes the potential mechanism driving the drug–drug and drug–disease interaction of voriconazole and flucloxacillin, highlighting the large substantial influence of flucloxacillin on the PXR gene and the influence of infection on voriconazole plasma concentrations, and suggests a more limited effect on other triazoles.

https://link.springer.com/article/10.1007/s13318-024-00916-1

Background and Objectives Voriconazole administered concomitantly with flucloxacillin may result in subtherapeutic plasma concentrations as shown in a patient with Staphylococcus aureus sepsis and a probable pulmonary aspergillosis. After switching our patient to posaconazole, therapeutic concentrat...

18/09/2024

Personalized Medicine Approach to Proteomics and Metabolomics of Cytochrome P450 Enzymes: A Narrative Review

Authors: John Fetse, Emmanuel Oladayo Olawode & Subrata Deb

Full-text, read-only, sharable link: https://rdcu.be/dUnpE

Abstract
Cytochrome P450 enzymes (CYPs) represent a diverse family of heme-thiolate proteins involved in the metabolism of a wide range of endogenous compounds and xenobiotics. In recent years, proteomics and metabolomics have been used to obtain a comprehensive insight into the role of CYPs in health and disease aspects. The objective of the present work is to better understand the status of proteomics and metabolomics in CYP research in optimizing therapeutics and patient safety from a personalized medicine approach. The literature used in this narrative review was procured by electronic search of PubMed, Medline, Embase, and Google Scholar databases. The following keywords were used in combination to identify related literature: “proteomics,” “metabolomics,” “cytochrome P450,” “drug metabolism,” “disease conditions,” “proteome,” “liquid chromatography-mass spectrometry,” “integration,” “metabolites,” “pathological conditions.” We reviewed studies that utilized proteomics and metabolomics approaches to explore the multifaceted roles of CYPs in identifying disease markers and determining the contribution of CYP enzymes in developing treatment strategies. The applications of various cutting-edge analytical techniques, including liquid chromatography-mass spectrometry, nuclear magnetic resonance, and bioinformatics analyses in CYP proteomics and metabolomics studies, have been highlighted. The identification of CYP enzymes through metabolomics and/or proteomics in various disease conditions provides key information in the diagnostic and therapeutic landscape. Leveraging both proteomics and metabolomics presents a powerful approach for an exhaustive exploration of the multifaceted roles played by CYP enzymes in personalized medicine. Proteomics and metabolomics have enabled researchers to unravel the complex connection between CYP enzymes and metabolic markers associated with specific diseases. As technology and methodologies evolve, an integrated approach promises to further elucidate the role of CYPs in human health and disease, potentially ushering in a new era of personalized medicine.
https://link.springer.com/article/10.1007/s13318-024-00912-5

Cytochrome P450 enzymes (CYPs) represent a diverse family of heme-thiolate proteins involved in the metabolism of a wide range of endogenous compounds and xenobiotics. In recent years, proteomics and metabolomics have been used to obtain a comprehensive insight into the role of CYPs in health and di...

01/09/2024

Does Age Influence Immunosuppressant Drug Pharmacokinetics in Kidney Transplant Recipients?
Authors: Amelia R. Cossart, Nicole M. Isbel, Scott B. Campbell, Brett McWhinney & Christine E. Staatz
Full-text, read-only, sharable link https://rdcu.be/dSD6S
Abstract
Background
The pharmacokinetics of immunosuppressant drugs may change with advancing age, potentially affecting patient outcomes.

Objective
To characterise the effects of age on the pharmacokinetic and exposure parameters of tacrolimus, mycophenolate, and prednisolone.

Methods
Pharmacokinetic profiling, involving whole blood tacrolimus, total and free plasma mycophenolic acid (MPA), total plasma mycophenolic acid glucuronide (MPAG), and total and free plasma prednisolone, was performed in an older and younger adult cohort. Thirteen samples were drawn on a single occasion, pre-oral dose and then at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4, 6, 9, and 12 h post-dose. Non-compartmental analysis was conducted using the PKNCA package, and pharmacokinetic and exposure parameters were compared between age groups using a Mann–Whitney test. A regression analysis was conducted for free MPA and MPAG using significant variables of interest.

Results
This exploratory study included 21 older and 18 younger adults. Dose-adjusted tacrolimus, total MPA and free prednisolone pharmacokinetic parameters were not different between age groups; however, for free MPA and MPAG, older recipients had significantly greater minimum and maximum concentrations, trough concentrations, and half-life. There was a two-fold increase in free MPA exposure in older adults (median dose-adjusted AUC0–12: 1284 vs. 684 μg h/L, p < 0.0001); MPAG exposure similarly increased. Age was significantly associated with free MPA and MPAG exposure, and free MPA exposure was associated with haematocrit (p < 0.05).

Conclusion
Differences in MPA were found with advancing age and may be due to altered kidney function, haematocrit, plasma protein binding and/or drug absorption. Future research should explore specific covariate contributions to this further.
https://link.springer.com/article/10.1007/s13318-024-00914-3

Background The pharmacokinetics of immunosuppressant drugs may change with advancing age, potentially affecting patient outcomes. Objective To characterise the effects of age on the pharmacokinetic and exposure parameters of tacrolimus, mycophenolate, and prednisolone. Methods Pharmacokinetic profil...

20/08/2024

Pharmacokinetics and Bioavailability Study of a Novel Smoothened Inhibitor TPB15 for Treatment of Triple-Negative Breast Cancer in Rats by High Performance Liquid Chromatography-Mass Spectrometry

Authors: Bo-yu Chen, Jia-huan Xu, Qian-qing Chen, Huan-xian Wu, Bao-fang Ou, Zhiwei Zhou, Fei Xu, Shao-yu Wu, Shui-lin Xie & Ding-sheng Wen

Abstract
Background and Objectives
Smoothened (SMO), a key component of the hedgehog signaling pathway, represents a therapeutic target for triple negative breast cancer (TNBC), yet the chemotherapy response rate in TNBC patients is only 40–50%, underscoring the urgent need for the development of novel drugs to effectively treat this condition. The novel compound TPB15, an SMO inhibitor derived from [1,2,4] triazolo [4,3-α] pyridines, demonstrated superior anti-TNBC activity and lower toxicity compared to the first SMO inhibitor vismodegib in both in vitro and in vivo. However, the compound's pharmacokinetic properties remain unclear. The present work aims to develop a simple HPLC-MS/MS method to profile the pharmacokinetics and bioavailability of TPB15 in rats as a ground work for further clinical research.

Methods
Separation was performed on an Agilent ZORBAX StableBond C18 column by gradient elution using acetonitrile and 0.1% formic acid as mobile phase at a flow rate of 0.3 mL/min. Multiple reaction monitoring(MRM) in positive mode with the transitions of m/z 454.2 → 100.0, 248.1 → 121.1 was employed to determine TPB15 and internal standard tinidazole, respectively. The specificity, intra- and inter- day precision and accuracy, extraction recovery, stability, matrix effect, dilution integrity and carryover of the method was validated. The pharmacokinetics and bioavailability study of TPB15 were carried out on rats through intravenous injection at the dose of 5 mg/kg and oral gavage at the dose of 25 mg/kg, and the pharmacokinetics parameters were calculated by the non-compartment analysis using the pharmacokinetics software DAS 2.1.1.

Results
The values of specificity, intra- and inter- day precision and accuracy, extraction recovery, stability, matrix effect, dilution integrity and carryover satisfied the acceptable limits. The lower limit of quantification of this method was 10 ng/mL with a linear range of 10–2000 ng/mL. The validated method was then applied to pharmacokinetics and bioavailability studies in rat by dosing with gavage (25 mg/kg) and intravenous injection(5 mg/kg), and the oral bioavailability of TBP15 in rat was calculated as 16.4 ± 3.5%. The pharmacokinetic parameters were calculated as following: maximum of plasma concentration (Cmax) (PO: 2787.17 ± 279.45 µg/L), Time to maximum plasma concentration (Tmax) (PO: 4.20 ± 0.90 h), the area under the concentration-time curve 0 to time (AUC0–t) (PO: 17,373.03 ± 2585.18 ng/mL·h, IV: 21,129.79 ± 3360.84 ng/mL·h), the area under the concentration-time curve 0 to infinity (AUC0–∞) (PO: 17,443.85 ± 2597.63 ng/mL·h, IV: 17,443.85 ± 2597.63 ng/mL·h), terminal elimination half-life (t1/2) (PO: 7.26 ± 2.16 h, IV: 4.78 ± 1.09 h).

Conclusions
TPB15, a promising candidate for treating TNBC, has demonstrated outstanding efficacy and safety in vitro and in vivo. This study established a simple, sensitive, and rapid HPLC-MS/MS bioanalytical method, developed and validated in accordance with FDA and EMA guidelines, for conducting pharmacokinetic and bioavailability studies of TPB15. The results revealed a favorable pharmacokinetic profile owing to its long t1/2. Nevertheless, the next phase of research should include formulation screening to enhance bioavailability, as well as clinical trials, metabolism pathway analysis, and assessment of potential drug-drug interactions.

https://link.springer.com/article/10.1007/s13318-024-00911-6