Genetic polymorphisms can profoundly influence drug metabolism, impacting how medications are processed in the body. Variations in genes encoding drug-metabolizing enzymes, like cytochrome P450 (CYP) enzymes, can lead to differences in drug efficacy and safety among individuals. This presentation provides a concise overview of how polymorphisms affect drug metabolism.

1. POLYMORPHISM
affecting
Drug Metabolism
AnaghaR Anil
MPharm Pharmacology

2. CONTENTS
Drug Metabolism
Types of Drug Metabolism
Polymorphism
Types of Polymorphism
How Polymorphism affects Drug Metabolism?
Research Article
Reference

3. DRUG METABOLISM
• Drug metabolism (biotransformation) is the processby which the bodybreaks down and transforms drugs
into different chemical forms.
MAJOR FUNCTIONS
1. Activation of Prodrugs
Enalapril
𝑚𝑒𝑡𝑎𝑏𝑜𝑙𝑖𝑠𝑒𝑑 𝑡𝑜 𝑎𝑐𝑡𝑖𝑣𝑒 𝑓𝑜𝑟𝑚
Enalaprilat
2. Inactivation of Drugs
Losartan
𝐶𝑦𝑡𝑜𝑐ℎ𝑟𝑜𝑚𝑒 𝑃450
E-3174
𝐺𝑙𝑢𝑐𝑢𝑟𝑜𝑛𝑖𝑑𝑎𝑡𝑖𝑜𝑛/𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛
excretedout
3. Excretion of Drugs
Caffeine
𝐶𝑦𝑡𝑜𝑐ℎ𝑟𝑜𝑚𝑒 𝑃450 1𝐴2
Paraxanthine
4. Detoxification
Paracetamol
𝐶𝑌𝑃2𝐸1
N-acetyl-p-benzoquinoneimine (NAPQI) 𝑡𝑜𝑥𝑖𝑐
𝐺𝑙𝑢𝑡𝑎𝑡ℎ𝑖𝑜𝑛𝑒 𝑆−𝑡𝑟𝑎𝑛𝑠𝑓𝑒𝑟𝑎𝑠𝑒
excretedout
5. First-pass Metabolism
Ethinylestradiol
𝐶𝑌𝑃3𝐴4
Less potent metabolitewith controlled and sustained releaseof estrogen

4. TYPES OF DRUG METABOLISM
PHASE I
Hydroxylation
Oxidation
Dealkylation
Deamination
Reduction
PHASE II
1.Glucuronidation
1.Sulfation
1.Methylation
1.Acetylation
1.Conjugation with Glutathione
1.Conjugation with Amino Acids
PHASE III
ATP-binding cassette (ABC)
Solute carrier (SLC) transporters

5. Phase I Metabolism
• Phase I metabolism is the initial step in the biotransformation of drugs in the body.
• Involves a series of enzymatic reactions that aim to modify the chemical structure of these
substances, usually by introducing or exposing functional groups.
• The primary purpose of Phase I metabolism is to increase the water solubility of the
compounds, facilitating their elimination from the body.
PHASE I REACTIONS
Hydroxylation Addition of a hydroxyl group to the drug molecule.
Oxidation Introduction of oxygen into the drug molecule.
Dealkylation Removal of alkylgroups from the drug molecule.
Deamination Removal of amino groups from the drug molecule.
Reduction Addition of electrons to the drug molecule.

6. Phase I Metabolism
ENZYMES INVOLVED (“oxygenases”)
• Cytochrome P450 (CYP) Enzymes
 CYP3A4
 CYP2D6
 CYP2C9
 CYP1A2
 CYP2E1
 CYP2C19
• Flavin-Containing Monooxygenases(FMOs)
• Monoamine Oxidases (MAOs)
• Alcohol Dehydrogenase(ADH)
• AldehydeDehydrogenase(ALDH)
• Xanthine Oxidase
• Esterases
• Epoxide Hydrolases
CYP3A4 is the most abundant isoenzyme in
the human liver and accounts for about
50% of all CYP450 activity.

7. Phase I Metabolism
Cytochrome P450 (CYP) Enzymes
 most prominent enzymesinvolvedin Phase I metabolism
 Heme-containing monooxygenases(donate–OHgroup)
 Found in liver, intestines, lungs,kidneys,and the brain.
Fe3+
CYP450
Drug +
Drug
Fe3+
CYP450
NADPH
Drug
Fe2+
CYP450 𝑶𝟐
+
Fe3+
𝑶𝟐
−
Drug
CYP450
NADPH
Fe3+
𝑶𝟐
𝟐−
Drug
CYP450
2H+
𝑯𝟐𝑶
Fe3+
CYP450
DRUG
METABOLITE +

8. Phase II Metabolism
• Drugs that already have -OH, -NH2, or COOH groups bypassesPhase I and enter Phase II directly to become
conjugated.
• Addition of hydrophilic groups to the original molecule,a toxic intermediate or a nontoxic metabolite
formed in phase I, that requiresfurther transformation to increase its polarity.
• The ultimate goal of phase II reactions is to form water-solubleproducts that can be excreted by the body.
PHASE II REACTIONS
Glucuronidation X + glucuronicacid → X-glucuronide(catalyzed by UGTs)
Sulfation X + sulfate→ X-sulfate(catalyzed by sulfotransferaseenzymes)
Acetylation X + acetyl-CoA→ X-acetate(catalyzed by acetyltransferaseenzymes)
Methylation X + S-adenosylmethionine→ X-methyl(catalyzed by methyltransferaseenzymes)
GlutathioneConjugation X + glutathione → X-SG (catalyzed by glutathioneS-transferaseenzymes)
Amino Acid Conjugation X + amino acid → X-amino acid (conjugation with glycine or taurine)

9. Phase II Metabolism
ENZYMES INVOLVED (“transferases”)
• Glucuronidation: UDP-glucuronosyltransferases(UGTs)(e.g.,UGT1A1)
• Sulfation: Sulfotransferase enzymes(e.g.,SULT1A1 )
• Acetylation: Acetyltransferase enzymes (e.g.,N-acetyltransferase)
• Methylation: Methyltransferase enzymes (e.g.,catechol-O-methyltransferase)
• Glutathione Conjugation: Glutathione S-transferase (GST) enzymes(e.g.,GSTP1 )
• Amino Acid Conjugation: Enzymesvary depending on the specific amino acid involved (e.g.,glycine
conjugation is catalyzed by glycine N-acyltransferase).
Glucuronidation, the most common phase II reaction.

10. Phase III Metabolism
• Phase III drug metabolism involvesthe transport of drug metabolites (formedduring Phase I and Phase II
metabolism) across cell membranes for eventual excretion.
• This step is crucial for the elimination of drugs and their metabolites from the body.
TRANSPORTER SUPERFAMILIES
ATP-binding Cassette (ABC) Transporters Solute Carrier (SLC) Transporters
Function
ABC transporters are involved in the active
transport of various substrates, including
drugs and their metabolites, across cell
membranes.
SLC transporters facilitate the passive or
facilitated transport of substances, including
drugs, across cell membranes.
Examples
P-glycoprotein (ABCB1), multidrug resistance-
associated proteins (MRPs), breast cancer
resistance protein (BCRP).
SLC22 family (organic cation transporters, OCTs;
organic anion transporters, OATs), SLC47 family
(multidrug and toxin extrusion proteins, MATEs).
Role in Drug Metabolism
These transporters contribute to the efflux of
drugs and metabolites from cells, impacting
their bioavailability and distribution.
SLC transporters are involved in the uptake of
drugs from the blood into cells, influencing
drug distribution and elimination.

11. POLYMORPHISM
• Polymorphism,as related to genomics, refers to the presence of two or more variant forms of a specific
DNA sequence that can occur among different individuals or populations.
• These variations can be observedin the form of single nucleotide changes, insertions, deletions,or
rearrangements in the DNA sequence.
• DNA polymorphismsare producedby changes in the nucleotide sequence or length. These result from:
(i) Variations in the fragment length pattern producedafter digesting DNA with restriction enzymes
(ii) Variations in the size of a DNA fragment after PCR amplification
(iii) Variations in the DNA sequenceitself.

12. Types of Polymorphism
• RFLP – restriction fragment length polymorphism
Eg: Debrisoquine – poor metabolisers of this drug have RFLP in
CYP2D6 gene (decreasedmetabolism )
• VNTR – variable number of tandem repeats
Eg : Codeine – poor metabolisers of this drug have VNTR in CYP2D6
gene (ultrafast metabolism metabolism )
• SSR – simple sequencerepeats or STR – simple tandem repeat, i.e.
microsatellites
Eg: Thiopurine – SSR cause decreased enzyme activity
• SNP – single nucleotide polymorphism
Eg: Warfarin – SNP in CYP2C9 gene cause variation in anticoagulant
action

13. Types of Polymorphism
POLYMORPHISM NATURE DETECTION METHOD RESULT
RFLP(Restriction
Fragment Length
Polymorphism)
Biallelicpolymorphismsresulting
from point mutations affecting a single
restriction enzyme recognition site
(E*).
Southern blot analysis using a
DNA probe or PCR amplification
of the specific region.
Two fragment sizes (largeor
small)dependingon the
presence or absence of the
polymorphic restriction
fragment site (*).
VNTR (Variable Number
TandemRepeat)
Multiallelicpolymorphisms with
changes in the restriction fragment
brought about by the insertion of a
variable number of repeat units at the
polymorphic site.
Southern analysis after
restriction enzyme digests.
More polymorphic DNA
fragments, increasing the
chances of detecting
heterozygous patterns.
SSR(Simple Sequence
Repeat)
Microsatellites with polymorphism
due to repeats of simple sequences,
e.g., (CA)n.
PCR amplification.
Fragments of variable size
based on the number of repeats.
SNP (SingleNucleotide
Polymorphism)
Singlebase changes.
DNA sequencingor other
methods.
Biallelicor multiallelic
polymorphisms,frequently
found throughout the genome,
offering effective discrimination
of alleles.

14. Polymorphism affecting Drug Metabolism
• Enzymes responsiblefor drug metabolism (mostlythe CYP450 group) are potentially affected by genetic
polymorphisms.
• Any clinical implications of changes in drug metabolism depend on
 Whether the affected enzyme is crucial for the activation or elimination of the drug or its metabolites.
 The importance of the affected pathway in the overallactivation or elimination of the drug.
 Whether there is any overlappingsubstrate specificity of CYP450groups of enzymes.

15. Polymorphism affecting Drug Metabolism
• Scenario 1: Route 1 is the major pathway for drug
elimination and it is affected by a polymorphismthat
results in less active enzyme.
• Scenario 2: Routes 2 and 3 are the major pathways for
drug elimination and they are affected by
polymorphismsthat result in lessactive enzymes.
• Scenario 3: Route 1 is the minor pathway for drug
metabolism and it is affected by a polymorphismthat
results in a less active enzyme.
• Scenario 4: Route 1 is the minor pathway and route 3 is
the major pathway for drug elimination. Route 3
enzymesare affected by polymorphismsthat result in
poor metabolism.

16. Polymorphism affecting Drug Metabolism
• Poor Metabolizers:
 reducedor absent activity of CYP450 enzymes.
 As a result,the metabolismof drugs that rely on theseenzymesmay be significantly slower, leading to higher drug
concentrations in the body.
 Poor metabolizersmay be at an increased risk of adverse effects from certain drugs.
• Normal Metabolizers:
 Normal metabolizershave the typical or most common geneticvariants for CYP450 enzymes.
 Their drug metabolismis considered to be within the normal range.
• Ultrafast Metabolizers:
 increased activity of CYP450 enzymes.
 enzymes are processed more rapidly, leading to lower drug concentrations
in the body.
• Intermediate Metabolizers:
 CYP450 enzyme activityis betweennormal and poor metabolizers.
 The metabolism of drugs not as slow as in poor metabolizers.

17. Polymorphism affecting Drug Metabolism
ULTRAFAST METABOLIZERS:
• Codeine is metabolizedby CYP2D6. Ultrafastmetabolizerswith
multiplecopies of active CYP2D6 genes may rapidly convert codeine
to its active form, morphine, resulting in higher and potentiallytoxic
levels.
INTERMEDIATE METABOLIZERS:
• Tamoxifen is metabolizedby CYP2D6 to its active form. Intermediatemetabolizerswith reduced CYP2D6 activitymay have
slower conversion to the active metabolite,potentiallyimpacting the efficacyof tamoxifenin breast cancer treatment.
POORMETABOLIZERS:
• Clopidogrel is a prodrug activatedby CYP2C19. Poor metabolizerswith reducedor absent CYP2C19 activitymay have impaired
activation of clopidogrel, leading to a decreasedantiplateleteffectand potentially an increased risk of cardiovascular events.
NORMALMETABOLIZERS:
• Warfarin, an anticoagulant, is metabolizedby multipleCYP450 enzymes, including CYP2C9. Normal metabolizersefficiently
process warfarin, and their stable metabolismis crucial for maintaining the desired anticoagulant effect.

18. Summary
• Genetic polymorphismsin drug-metabolizing enzymes,particularly those in the cytochrome P450 family,
can significantly impact therapeutic outcomes.
• Individuals with different drug metabolism genotypesmay respond variably to the same dose of a drug,
leading to diverseclinical effects.
• The high polymorphismin drug-metabolizing enzymesemphasizes the need for an individualizedapproach
to prescribing rather than relying solelyon evidence-basedguidelines.
• Clinical trials often incorporate genetic tests for variations in CYP450genes to screen participants,
acknowledging the importance of genetic factors in drug response.
• Transitioning from a one-size-fits-allapproach to personalizedmedicine considers genetic diversity and
enhances the precision of drug therapy.
• The goal is to optimize drug efficacy, minimize adverseeffects,and improveoverall patient outcomes
through a more individual-based approach to prescribing medications.

19. Article
• Frontiers in Pharmacology
• Impact Factor: 5.6
• Publishedon: 18 March 2022
Enzymes involved in the metabolismof SLE Regimens
• CytochromeP450 (CYP)
• Glutathione S-Transferase (GST)
• ArylamineN-Acetyltransferase (NAT)
• UDP-Glucuronosyltransferase (UGT)
• Thiopurine S-Methyltransferase (TPMT)
• NAD (P) H Quinone Dehydrogenase(NQO)
PharmacodynamicMechanisms Involved
• Fc Gamma Receptor (FCGR)
• Interferon Gamma (IFNG) and Interleukin (IL)
• Toll-likeReceptor (TLR), Toll/Interleukin-1Receptor
Domain-ContainingAdapter Protein (TIRAP), Tumor
Necrosis Factor (TNF), and B-cellActivating Factor (BAFF)
• Innate ImmunityActivator (INAVA/C1orf106)
• AutoimmuneRegulator(AIRE)
• TMEM 245 (C9orf5) (Transmembrane Protein - 245)
• Glucocorticoid Receptor (GR), Heat Shock Protein (HSP),
and TNF Receptor-AssociatedProtein (TRAP)
The review emphasizes the need for considering
genetic profilesin SLE treatment for more effectiveand
personalizedapproaches.

20. References
• Molecular Pharmacology from DNA to Drug Discovery;John Dickenson et al
• Molecular Diagnostics, Fundamentals, Methods & Clinical Application; Lela Buckingham
• The Pharmacological basis of Therapeutics; Goodman and Gilman’s
• Elsevier
• PubMed
• Science Direct
• DNA Polymorphism - an overview | ScienceDirect
• Genetic Polymorphismsand the Clinical Responseto Systemic Lupus Erythematosus Treatment Towards
PersonalizedMedicine | Article

21. THANK
YOU