Download Cytochrome P450 Inhibition

Cytochrome P450 Inhibition
2014-02-21 손한표
Index
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Overview
Introduction
CYP Inhibition Fundamentals
Effects of CYP Inhibition
CYP Inhibition Case Studies
Structure Modification Strategies to Reduce CYP
Inhibition
Reversible and Irreversible CYP Inhibition
Other DDI Issues
Methods
Problems
Overview
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Drug-drug interactions can occur when two drugs are
coadministered and compete for the same enzyme.
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In cytochrome P450(CYP) inhibition, one drug(“perpetrator”)
binds to the isozyme and the other drug(“victim”) is excluded
from metabolism, thus increasing to a toxic concentration
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Irreversible binding inactivates CYP and is termed mechanismbased inhibition
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CYP inhibition can cause withdrawal from clinical use or
restrictive labeling for a drug
Introduction
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Many patients receive more than one drug at a time;
physicians must be careful to avoid drug-drug interaction.
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A major DDI concern is cytochrome P450 (CYP)
inhibition.
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Because of CYP inhibition effects on clearance and halftime, it has become an important concern with the FDA
and at pharmaceutical companies.
CYP Inhibition Fundamentals
Cl = Clearance rate
Clint(i) ≈ Clint/[1+(I+Ki)]
CYP Inhibition Fundamentals
CYP3A4
CYP2D6
CYP Inhibition Fundamentals
Effects of CYP Inhibition
Terfeneadine
Erythromycin
Effects of CYP Inhibition
In vitro
In vivo
Coincubation
method
Cmax & Ki
Guidelines
Plasma protein
binding of
inhibitor
Effects of CYP Inhibition
Effects of CYP Inhibition
Effects of CYP Inhibition
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CYP3A4 vs CYP2C19
Plasma protein binding
Cmax & Ki
CYP Inhibition Case Studies
CYP Inhibition Case Studies
CYP Inhibition Case Studies
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Consequences of Chirality on CYP Inhibition
(+)-isomer :
CYP2C9 more
inhibition!
Quinidine :
CYP2D6 Inhibition
Quinine : NOT
inhibtion
Structure Modification Strategies to Reduce
CYP Inhibition
Structure Modification Strategies to Reduce
CYP Inhibition
Structure Modification Strategies to Reduce
CYP Inhibition
Structure Modification Strategies to Reduce
CYP Inhibition
Reversible and Irreversible CYP Inhibition
Inhibition
Reversible
Irreversible mechanism-dependant
Formation
covalent bond
Tight
quasiirreversible
binding
Reversible and Irreversible CYP Inhibition
Other DDI Issues
DDI
Issues
Candidate as Victim to a mechanism
Inhibition Perpetrator
Multiple pathway
Candidate as a Victim or Perpetrator at a
Transporter
Using DDI
Candidate as a Victim or Perpetrator of
Metabolic Enzyme Induction
Induce the metabolizing enzyme
Method
Fluorescent Assay
for CYP Inhibition
In Silico
Single Substrate
HLM Assay for CYP
Inhibition
Method
In Vitro
CYP Inhibition
assessment strategy
Cocktail Substrate
HLM Assay for
CYP Inhibition
Double Cocktail
Assay for CYP
Inhibition
Method
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In Silico
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Two software companies offer tools for predicting CYP
Inhibition.
Name
Company
Web site
KnowItAll
Biorad
www.biorad.com
ADMENSA
Inpharmatica
www.inpharmatica.com
Method
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In vitro CYP Inhibition Methods
Assays can be distinguished by four method elements
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CYP material – rhCYP, HLM
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Substrate compounds – Fluorogenic , Drug substrate.
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Detection method – Fluoroscence, LC/MS/MS, Radioactivity,
Luminescence
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Strategy of analysis
Method
Method
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Strategy of analysis
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1.Fluorescent Assay for CYP Inhibition
Individual rhCYP isoenzymes, individual fluorescent substrate,
fluoroescent detection.
Method
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Strategy of analysis
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2.Single Substrate HLM Assay for CYP Inhibition
HLM, individual specific drug substrates, LC/MS/MS detection
Method
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Strategy of analysis
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3.Cocktail Substrate HLM Assay for CYP Inhibition
HLM, cocktail of specific drug substrates, LC/MS/MS
detection
Three problems exist.
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1.The native abundance of each of the CYP isozymes varies widely in
HLM.
2.Many test compounds are highly metabolized by the HLM.
3.Nonspecific protein binding to the HLM material.
Method
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Strategy of analysis
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4.Double Cocktail Assay for CYP Inhibition
Cocktail of rhCYP isozymes, cocktail of drug substrates, LC/
MS/MS detection.
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Double Cocktail name comes from using two kinds of cocktail;
cocktail of rhCYP isozymes plus specific drug substrates.
Problems
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1.For initial CYP inhibition screening, a useful goal is an
IC50 greater than what concentration?
10𝜇M
2.For human studies, Ki should be what? At what
concentration is there likely to be CYP inhibition?
greater than 10times than Cmax. When concentration
greater than Ki
3.Why was Saldane removed from the market?
because its metabolism at CYP3A4 was inhibited by
3A4 inhibitor. Such as erythromycin.
Problems
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4.what is difference between reversible and mechanismbased CYP inhibition? How can you distinguish these
mechanism?
Reversible : inhibitor binds and releases from the
enzyme.
Irreversible : inhibitor binds to enzyme by covalent
interaction or strong complexation interatction.
Time dependacy of inhibition.
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5. How might you modify the following structure to
reduce CYP inhibition?

Problems
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6.What is the risk associated with CYP inhibition?
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A. a coadministered drug is metabolized too quickly,
B. a compound is not stable,
C. a coadministered drug is not metabolized quickly enough,
D. an isozyme may be induced.
7. Should CYP inhibition be used to estimate metabolic
stability?
NO