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Article ; Online: Structural and functional pharmacokinetic analogs for physiologically based pharmacokinetic (PBPK) model evaluation.

Ellison, Corie A

Regulatory toxicology and pharmacology : RTP

2018 Volume 99, Page(s) 61–77

Abstract: Physiologically based pharmacokinetic (PBPK) models enable simulations of absorption, distribution, metabolism, and elimination of chemicals from the body. Model evaluation is a key step in the PBPK model development processes whereby model predictions ... ...

Abstract	Physiologically based pharmacokinetic (PBPK) models enable simulations of absorption, distribution, metabolism, and elimination of chemicals from the body. Model evaluation is a key step in the PBPK model development processes whereby model predictions are compared to pharmacokinetic (PK) data. A prerequisite for PBPK model evaluation has always been the availability of PK data for the modeled compound, a requirement which has limited the use and acceptance of PBPK models since PK data is often limited or not available. The current work tests the hypothesis that an adequately developed PBPK model for a target chemical (chemical with no PK data) can be evaluated using PK data from a source chemical (chemical with existing PK data). Two different approaches for identifying the source chemical, a structural PK analog and functional PK analog technique, are used to evaluate a series of oral human PBPK models. Results show that both analog approaches can identify PK analogs which display similar PK as the target chemical and can be used as alternative ways for evaluating PBPK models. As animal free safety assessment strategies continue to develop, it's important to develop alternative approaches for PBPK model evaluation which does not rely on generating new PK data.
MeSH term(s)	Animals ; Humans ; Models, Biological ; Pharmaceutical Preparations/chemistry ; Pharmaceutical Preparations/metabolism ; Pharmacokinetics ; Risk Assessment ; Structure-Activity Relationship
Chemical Substances	Pharmaceutical Preparations
Language	English
Publishing date	2018-09-08
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	604672-1
ISSN	1096-0295 ; 0273-2300
ISSN (online)	1096-0295
ISSN	0273-2300
DOI	10.1016/j.yrtph.2018.09.008
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Article ; Online: Application of structural and functional pharmacokinetic analogs for physiologically based pharmacokinetic model development and evaluation.

Ellison, Corie A / Wu, Shengde

Regulatory toxicology and pharmacology : RTP

2020 Volume 114, Page(s) 104667

Abstract: This work provides case studies for the pharmacokinetic (PK) analog approach, where a physiologically based pharmacokinetic (PBPK) model for a target chemical (has no PK data) is evaluated using PK data from a source chemical (has existing PK data). A ... ...

Abstract	This work provides case studies for the pharmacokinetic (PK) analog approach, where a physiologically based pharmacokinetic (PBPK) model for a target chemical (has no PK data) is evaluated using PK data from a source chemical (has existing PK data). A bottom up PBPK modeling approach (using in vitro and in silico inputs) is used to develop human oral PBPK models for caffeine and diphenhydramine. Models are evaluated using in vivo data from structural and functional PK analogs. At the end of the case studies, in vivo PK data for caffeine and diphenhydramine is introduced and both models were able to simulate plasma concentrations which agreed with the in vivo PK data. To further demonstrate that structural analogs can serve as PK analogs, in vitro metabolism and plasma protein binding was compared for a subset of structurally similar ToxCast chemicals and shown to be similar. Next steps for the PK analog approach should focus on evaluating this concept for a broader set of compounds. Using PK analogs for evaluating and establishing confidence in a PBPK model will ensure that PBPK modeling remains a viable option in animal alternative safety assessments.
MeSH term(s)	Animal Testing Alternatives ; Animals ; Caffeine/chemistry ; Caffeine/pharmacokinetics ; Diphenhydramine/chemistry ; Diphenhydramine/pharmacokinetics ; Humans ; Models, Biological ; Molecular Structure
Chemical Substances	Caffeine (3G6A5W338E) ; Diphenhydramine (8GTS82S83M)
Language	English
Publishing date	2020-05-05
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	604672-1
ISSN	1096-0295 ; 0273-2300
ISSN (online)	1096-0295
ISSN	0273-2300
DOI	10.1016/j.yrtph.2020.104667
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Article ; Online: Practical application of the interim internal threshold of toxicological concern (iTTC): a case study based on clinical data [Correction: Jan. 2023, 97(1), p. 311]

Najjar, Abdulkarim / Ellison, Corie A. / Gregoire, Sebastien / Hewitt, Nicola J.

Arch Toxicol 2023 Jan., v. 97, no. 1, p. 155-164

2023 , Page(s) 155–164

Abstract: We present a case study that provides a practical step-by-step example of how the internal Threshold of Toxicological Concern (iTTC) can be used as a tool to refine a TTC-based assessment for dermal exposures to consumer products. The case study uses a ... ...

Abstract	We present a case study that provides a practical step-by-step example of how the internal Threshold of Toxicological Concern (iTTC) can be used as a tool to refine a TTC-based assessment for dermal exposures to consumer products. The case study uses a theoretical scenario where there are no systemic toxicity data for the case study chemicals (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, octinoxate, and ecamsule). Human dermal pharmacokinetic data following single and repeat dermal exposure to products containing the case study chemicals were obtained from data published by the US FDA. The clinical studies utilized an application procedure that followed maximal use conditions (product applied as 2 mg/cm² to 75% of the body surface area, 4 times a day). The case study chemicals were first reviewed to determine if they were in the applicability domain of the iTTC, and then, the human plasma concentrations were compared to an iTTC limit of 1 µM. When assessed under maximum usage, the external exposure of all chemicals exceeded the external dose TTC limits. By contrast, the internal exposure to all chemicals, except oxybenzone, was an order of magnitude lower than the 1 µM interim iTTC threshold. This work highlights the importance of understanding internal exposure relative to external dose and how the iTTC can be a valuable tool for assessing low-level internal exposures; additionally, the work demonstrates how to use an iTTC, and highlights considerations and refinement opportunities for the approach.
Keywords	Food and Drug Administration ; case studies ; dermal exposure ; humans ; pharmacokinetics ; surface area ; toxicity ; toxicology
Language	English
Dates of publication	2023-01
Size	p. 155-164
Publishing place	Springer Berlin Heidelberg
Document type	Article ; Online
Note	Use and reproduction
ZDB-ID	124992-7
ISSN	1432-0738 ; 0340-5761
ISSN (online)	1432-0738
ISSN	0340-5761
DOI	10.1007/s00204-022-03371-6
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Practical application of the interim internal threshold of toxicological concern (iTTC): a case study based on clinical data.

Najjar, Abdulkarim / Ellison, Corie A / Gregoire, Sebastien / Hewitt, Nicola J

Archives of toxicology

2022

Abstract	We present a case study that provides a practical step-by-step example of how the internal Threshold of Toxicological Concern (iTTC) can be used as a tool to refine a TTC-based assessment for dermal exposures to consumer products. The case study uses a theoretical scenario where there are no systemic toxicity data for the case study chemicals (avobenzone, oxybenzone, octocrylene, homosalate, octisalate, octinoxate, and ecamsule). Human dermal pharmacokinetic data following single and repeat dermal exposure to products containing the case study chemicals were obtained from data published by the US FDA. The clinical studies utilized an application procedure that followed maximal use conditions (product applied as 2 mg/cm
Language	English
Publishing date	2022-09-23
Publishing country	Germany
Document type	Journal Article
ZDB-ID	124992-7
ISSN	1432-0738 ; 0340-5761
ISSN (online)	1432-0738
ISSN	0340-5761
DOI	10.1007/s00204-022-03371-6
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Article ; Online: Correction to: Practical application of the interim internal threshold of toxicological concern (iTTC): a case study based on clinical data.

Najjar, Abdulkarim / Ellison, Corie A / Gregoire, Sebastien / Hewitt, Nicola J

Archives of toxicology

2022

Language	English
Publishing date	2022-11-27
Publishing country	Germany
Document type	Published Erratum
ZDB-ID	124992-7
ISSN	1432-0738 ; 0340-5761
ISSN (online)	1432-0738
ISSN	0340-5761
DOI	10.1007/s00204-022-03398-9
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Article ; Online: Comparison between endocrine activity assessed using ToxCast/Tox21 database and human plasma concentration of sunscreen active ingredients/UV filters.

Onyango, David O / Selman, Bastian G / Rose, Jane L / Ellison, Corie A / Nash, J F

Toxicological sciences : an official journal of the Society of Toxicology

2023 Volume 196, Issue 1, Page(s) 25–37

Abstract: Sunscreen products are composed of ultraviolet (UV) filters and formulated to reduce exposure to sunlight thereby lessening skin damage. Concerns have been raised regarding the toxicity and potential endocrine disrupting (ED) effects of UV filters. The ... ...

Abstract	Sunscreen products are composed of ultraviolet (UV) filters and formulated to reduce exposure to sunlight thereby lessening skin damage. Concerns have been raised regarding the toxicity and potential endocrine disrupting (ED) effects of UV filters. The ToxCast/Tox21 program, that is, CompTox, is a high-throughput in vitro screening database of chemicals that identify adverse outcome pathways, key events, and ED potential of chemicals. Using the ToxCast/Tox21 database, octisalate, homosalate, octocrylene, oxybenzone, octinoxate, and avobenzone, 6 commonly used organic UV filters, were found to have been evaluated. These UV filters showed low potency in these bioassays with most activity detected above the range of the cytotoxic burst. The pathways that were most affected were the cell cycle and the nuclear receptor pathways. Most activity was observed in liver and kidney-based bioassays. These organic filters and their metabolites showed relatively weak ED activity when tested in bioassays measuring estrogen receptor (ER), androgen receptor (AR), thyroid receptor, and steroidogenesis activity. Except for oxybenzone, all activity in the endocrine assays occurred at concentrations greater than the cytotoxic burst. Moreover, except for oxybenzone, plasma concentrations (Cmax) measured in humans were at least 100× lower than bioactive (AC50/ACC) concentrations that produced a response in ToxCast/Tox21 assays. These data are consistent with in vivo animal/human studies showing weak or negligible endocrine activity. In sum, when considered as part of a weight-of-evidence assessment and compared with measured plasma concentrations, the results show these organic UV filters have low intrinsic biological activity and risk of toxicity including endocrine disruption in humans.
MeSH term(s)	Animals ; Humans ; Sunscreening Agents/toxicity ; Benzophenones/toxicity ; Receptors, Estrogen
Chemical Substances	Sunscreening Agents ; oxybenzone (95OOS7VE0Y) ; Benzophenones ; Receptors, Estrogen
Language	English
Publishing date	2023-08-09
Publishing country	United States
Document type	Journal Article
ZDB-ID	1420885-4
ISSN	1096-0929 ; 1096-6080
ISSN (online)	1096-0929
ISSN	1096-6080
DOI	10.1093/toxsci/kfad082
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Article ; Online: Impact of chemical structure on the in vitro hydrolysis of fatty esters of 2-ethylhexanoic acid or 2-ethylhexanol and extrapolation to the in vivo situation.

Obringer, Cindy / Lester, Cathy / Karb, Michael / Smith, Alex / Ellison, Corie A

Regulatory toxicology and pharmacology : RTP

2022 , Page(s) 105315

Abstract: Fatty esters of 2-ethylhexanoic acid (EHA) and 2-ethylhexanol (EH) are commonly used in cosmetics. Human liver and skin S9 and human plasma were used to determine the in vitro rates of clearance ( ... ...

Abstract	Fatty esters of 2-ethylhexanoic acid (EHA) and 2-ethylhexanol (EH) are commonly used in cosmetics. Human liver and skin S9 and human plasma were used to determine the in vitro rates of clearance (CL
Language	English
Publishing date	2022-12-06
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	604672-1
ISSN	1096-0295 ; 0273-2300
ISSN (online)	1096-0295
ISSN	0273-2300
DOI	10.1016/j.yrtph.2022.105315
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Article ; Online: Letter to the editor regarding recent publication titled "Developing an internal threshold of toxicological concern (iTTC)" by Arnot et al. (2022).

Ellison, Corie A / Arnot, Jon A / Felter, Susan P / Daston, George P / Becker, Richard A / Toose, Liisa / Armitage, James M / Sangion, Alessandro / Looky, Alexandra / Brown, Trevor N / Li, Li

Journal of exposure science & environmental epidemiology

2023 Volume 33, Issue 5, Page(s) 840–841

Language	English
Publishing date	2023-07-14
Publishing country	United States
Document type	Letter ; Comment
ZDB-ID	2218551-3
ISSN	1559-064X ; 1559-0631
ISSN (online)	1559-064X
ISSN	1559-0631
DOI	10.1038/s41370-023-00571-9
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Article ; Online: Internal Threshold of Toxicological Concern (iTTC): Where We Are Today and What Is Possible in the Near Future.

Ellison, Corie A / Api, Anne Marie / Becker, Richard A / Efremenko, Alina Y / Gadhia, Sanket / Hack, C Eric / Hewitt, Nicola J / Varcin, Mustafa / Schepky, Andreas

Frontiers in toxicology

2021 Volume 2, Page(s) 621541

Abstract: The Threshold of Toxicological Concern (TTC) is a risk assessment tool for evaluating low-level exposure to chemicals with limited toxicological data. A next step in the ongoing development of TTC is to extend this concept further so that it can be ... ...

Abstract	The Threshold of Toxicological Concern (TTC) is a risk assessment tool for evaluating low-level exposure to chemicals with limited toxicological data. A next step in the ongoing development of TTC is to extend this concept further so that it can be applied to internal exposures. This refinement of TTC based on plasma concentrations, referred to as internal TTC (iTTC), attempts to convert the chemical-specific external NOAELs (in mg/kg/day) in the TTC database to an estimated internal exposure. A multi-stakeholder collaboration formed, with the aim of establishing an iTTC suitable for human safety risk assessment. Here, we discuss the advances and future directions for the iTTC project, including: (1) results from the systematic literature search for metabolism and pharmacokinetic data for the 1,251 chemicals in the iTTC database; (2) selection of ~350 chemicals that will be included in the final iTTC; (3) an overview of the
Language	English
Publishing date	2021-01-15
Publishing country	Switzerland
Document type	Journal Article
ISSN	2673-3080
ISSN (online)	2673-3080
DOI	10.3389/ftox.2020.621541
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Article ; Online: Pharmacokinetics and pharmacodynamics of chlorpyrifos in adult male Long-Evans rats following repeated subcutaneous exposure to chlorpyrifos.

Ellison, Corie A / Smith, Jordan Ned / Lein, Pamela J / Olson, James R

Toxicology

2011 Volume 287, Issue 1-3, Page(s) 137–144

Abstract: Chlorpyrifos (CPF) is a commonly used organophosphorus pesticide. Several pharmacokinetic and pharmacodynamic studies have been conducted in rats in which CPF was administered as a single bolus dose. However, there is limited data regarding the ... ...

Abstract	Chlorpyrifos (CPF) is a commonly used organophosphorus pesticide. Several pharmacokinetic and pharmacodynamic studies have been conducted in rats in which CPF was administered as a single bolus dose. However, there is limited data regarding the pharmacokinetics and pharmacodynamics following daily exposure. Since occupational exposures often consist of repeated, daily exposures, there is a need to evaluate the pharmacokinetics and pharmacodynamics of CPF under exposure conditions which more accurately reflect real world human exposures. In this study, the pharmacokinetics and pharmacodynamics of CPF were assessed in male Long-Evans rats exposed daily to CPF (0, 3 or 10mg/kg/day, s.c. in peanut oil) over a 10 day study period. Throughout the study, multiple pharmacokinetic (urinary TCPy levels and tissue CPF and metabolite levels) and pharmacodynamic (blood and brain AChE activity) determinants were measured. Average blood AChE activity on day 10 was 54% and 33% of baseline among animals in the 3 and 10mg/kg/day CPF treatment groups, respectively, while average brain AChE activity was 67% and 28% of baseline. Comparable dose-response relationships between brain AChE inhibition and blood AChE inhibition, suggests that blood AChE activity is a valid biomarker of brain AChE activity. The pharmacokinetic and pharmacodynamic measures collected in this study were also used to optimize a rat physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model for multiple s.c. exposures to CPF based on a previously published rat PBPK/PD model for CPF following a single bolus injection. This optimized model will be useful for determining pharmacokinetic and pharmacodynamic responses over a wide range of doses and durations of exposure, which will improve extrapolation of results between rats and humans.
MeSH term(s)	Acetylcholinesterase/metabolism ; Animals ; Brain/enzymology ; Chlorpyrifos/administration & dosage ; Chlorpyrifos/pharmacokinetics ; Chlorpyrifos/pharmacology ; Injections, Subcutaneous ; Insecticides/pharmacokinetics ; Liver/metabolism ; Male ; Models, Biological ; Rats ; Rats, Long-Evans
Chemical Substances	Insecticides ; Acetylcholinesterase (EC 3.1.1.7) ; Chlorpyrifos (JCS58I644W)
Language	English
Publishing date	2011-06-17
Publishing country	Ireland
Document type	Journal Article ; Research Support, N.I.H., Extramural
ZDB-ID	184557-3
ISSN	1879-3185 ; 0300-483X
ISSN (online)	1879-3185
ISSN	0300-483X
DOI	10.1016/j.tox.2011.06.010
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