Pharmacokinetics, Pharmacodynamics, & Drug Metabolism Community

In in vivo studies, CYP induction-mediated drug-drug interactions can be evaluated by comparing the ratio of the area under the plasma concentration-time curve (AUC) of the substrates with and without adding inducers. On the other hand, in vitro assays are also available using different types of cells or cell models by comparing the mRNA fold change or the concentration (or peak area ratio) of metabolites from substrates in culture medium between the absence and presence of the inducer. Here, I would like to dive deep into the mechanisms of CYP induction.

1. The first question that I would like to discuss is: are there any approaches that can be used to investigate the molecular mechanisms of enzyme induction? For example, the AhR, PXR, CAR, PPAR, FXR, LXR, and other different types of receptors.

2. How can we modify the Michaelis-Menten equation to describe CYP induction?

3. What are the pros and cons of different cell types and assays to perform the CYP induction assay (e.g., 2D cell culture, 3D cell culture, or coculture model)? Are they translatable?

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Yi-Hua Chiang
Ph.D. Student
University of Florida
Gainesville FL
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
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Thank you for starting this discussion thread!

I am tagging @Chukwunonso Nwabufo and @Pankajini Mallick into the discussion.

Thank you, all!

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Stacey Axler
Community Manager
AAPS
Arlington VA
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
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Original Message:
Sent: 05-14-2024 16:48
From: Yi-Hua Chiang
Subject: Cytochrome P450 Induction

In in vivo studies, CYP induction-mediated drug-drug interactions can be evaluated by comparing the ratio of the area under the plasma concentration-time curve (AUC) of the substrates with and without adding inducers. On the other hand, in vitro assays are also available using different types of cells or cell models by comparing the mRNA fold change or the concentration (or peak area ratio) of metabolites from substrates in culture medium between the absence and presence of the inducer. Here, I would like to dive deep into the mechanisms of CYP induction.

1. The first question that I would like to discuss is: are there any approaches that can be used to investigate the molecular mechanisms of enzyme induction? For example, the AhR, PXR, CAR, PPAR, FXR, LXR, and other different types of receptors.

2. How can we modify the Michaelis-Menten equation to describe CYP induction?

3. What are the pros and cons of different cell types and assays to perform the CYP induction assay (e.g., 2D cell culture, 3D cell culture, or coculture model)? Are they translatable?

------------------------------
Yi-Hua Chiang
Ph.D. Student
University of Florida
Gainesville FL
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
------------------------------

Hi Yi-Hua,

Thanks for bringing these questions in this forum. To your question-

1. YES, we can assess transcriptional regulatory mechanism behind CYP-inductions. It is well-known that all of them (AhR, PXR, CAR, PPAR, FXR, LXR) play significant role in CYP-expression. To extend, these days not only mRNA, people also check for protein-level (immune assay or omics-based approaches) and functions in a row to see a better IVIVE capacity.
2. I didn't get that in greater detail. Usually, Vmax (intercept) can explain higher activity (when a particular enzyme induced).
3. There are few things we often face in different in vitro system such as 2D models are not similar to physiological as compared to 3D model. Additionally, there are recent advancement showing by groups that co-culture model can generate a better data for special cases (i.e., low cleared compound). On the other hand, things to be considered that time-consuming, complexity of in vitro system and the cost. Co-culture and 3D models are not high-throughput, contrary primary hepatocytes could be used in early stage.

[these statement reflect my own perspective, independent of my employer's practice or perspective].

Thanks,

Masud

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Md Masud Parvez,
Research Associate, WSU.
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Original Message:
Sent: 05-14-2024 16:48
From: Yi-Hua Chiang
Subject: Cytochrome P450 Induction

In in vivo studies, CYP induction-mediated drug-drug interactions can be evaluated by comparing the ratio of the area under the plasma concentration-time curve (AUC) of the substrates with and without adding inducers. On the other hand, in vitro assays are also available using different types of cells or cell models by comparing the mRNA fold change or the concentration (or peak area ratio) of metabolites from substrates in culture medium between the absence and presence of the inducer. Here, I would like to dive deep into the mechanisms of CYP induction.

1. The first question that I would like to discuss is: are there any approaches that can be used to investigate the molecular mechanisms of enzyme induction? For example, the AhR, PXR, CAR, PPAR, FXR, LXR, and other different types of receptors.

2. How can we modify the Michaelis-Menten equation to describe CYP induction?

3. What are the pros and cons of different cell types and assays to perform the CYP induction assay (e.g., 2D cell culture, 3D cell culture, or coculture model)? Are they translatable?

------------------------------
Yi-Hua Chiang
Ph.D. Student
University of Florida
Gainesville FL
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
------------------------------

Thank you so much Yi-Hua for this very important discussion.

1. Yes, using your in vitro system, you can assess the relationship between the potential inducer and xenosensing regulators, as well as your CYP450 enzyme of interest.  You can identify core xenosensing regulators for your specific CYP450 by measuring changes in mRNA (or protein) expression of both the investigated CYP450 and xenosensing regulatory proteins over a range of inducer concentrations (depending on the viability of your in vitro cell system for this particular inducer and the clinically relevant inducer concentration). If the potential inducer shows a direct proportional relationship with the gene (or protein) expression of both specific xenosensing regulators and CYP450, then it is an inducer for your CYP450 of interest.
2. Yes, I agree with Masud, the Vmax does increase leading to reduced exposure of the parent drug with a concomitant increased exposure of its corresponding metabolite(s).
3. In addition to the excellent points that Masud already made, It is important to think carefully about the exact cell system that one may plan to use for such studies, for example, do they express the CYP450 and xenosensing regulators abundantly relative to the actual clinical scenario?  Are there other cell-system-specific variables that may confound outcome measurements, i.e. diseased cell system, or culture cocktail mixture? Opinions are mine! 

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Chukwunonso Nwabufo
Senior Research Associate I,
Analytical Operations,
Gilead Sciences Alberta Canada
Edmonton AB
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
------------------------------

Original Message:
Sent: 05-14-2024 16:48
From: Yi-Hua Chiang
Subject: Cytochrome P450 Induction

In in vivo studies, CYP induction-mediated drug-drug interactions can be evaluated by comparing the ratio of the area under the plasma concentration-time curve (AUC) of the substrates with and without adding inducers. On the other hand, in vitro assays are also available using different types of cells or cell models by comparing the mRNA fold change or the concentration (or peak area ratio) of metabolites from substrates in culture medium between the absence and presence of the inducer. Here, I would like to dive deep into the mechanisms of CYP induction.

1. The first question that I would like to discuss is: are there any approaches that can be used to investigate the molecular mechanisms of enzyme induction? For example, the AhR, PXR, CAR, PPAR, FXR, LXR, and other different types of receptors.

2. How can we modify the Michaelis-Menten equation to describe CYP induction?

3. What are the pros and cons of different cell types and assays to perform the CYP induction assay (e.g., 2D cell culture, 3D cell culture, or coculture model)? Are they translatable?

------------------------------
Yi-Hua Chiang
Ph.D. Student
University of Florida
Gainesville FL
[email protected]

Disclaimer: Opinions expressed are solely my own and do not express the views or opinions of my employer.
------------------------------