pharmacogenomics and pharmacist provided patient care kathryn momary pharm.d., bcps associate...

Pharmacogenomics and Pharmacist

Provided Patient Care

Kathryn Momary Pharm.D., BCPSAssociate Professor

Mercer University

College of Pharmacy

[email protected]

Financial Disclosure

• Investigator Initiated Grant from Merck

Objectives

• Summarize and use appropriately the nomenclature associated with the area of pharmacogenomics.

• Describe the role of pharmacogenetic testing for certain medications in current clinical practice.

• Predict how genetic polymorphisms in genes encoding drug metabolism could effect drug response

Current Pharmacotherapy Approach

Poor or non-response

Intolerance

Good response

Same therapy for all patients

Population with a

given disease

↓ dose or different drug

↑ dose or different drug

Factors Influencing Drug Response

• Age

• Race/ ethnicity

• Pharmacokinetics

• Concomitant diseases

• Concomitant medications

• GENOTYPE

Toxicity

Goodresponse

Clinical Application of Pharmacogenomics

Population with disease

Different drug or alternative therapy

dose ordifferent drug

Traditional therapy

Predictedresponse

Poorresponse

TherapyGenotype

Pharmacogenomics

• Hereditary basis for inter-individual differences in drug response

• Goal: optimize drug therapy and limit drug toxicity based on a person’s DNA

How did it begin?

• Began with observations of unusual, inherited drug response

• Driven by observations variability in drug response

• Then researchers sought to find genetic causes of this variation

History of Pharmacogenomics

1950 1960 1970 1980 1990 2000

1956: Discovery of glucose-6 phosphate dehydrogenase polymorphism

1957: “Inheritance might explain many individual differences in the efficacy of drugs and in the occurrence of adverse drug reactions.” -Motulsky

1959: “Pharmacogenetics” introduced by Vogel

HumanGenomeProject

You may may not care about genes but you care about

proteins!

Transcription TranslationDrug TargetsMetabolizing

Enzymes

• Proteins and medication response:

• Drug receptors

• Drug metabolizing enzymes

• Proteins involved in disease physiology

Genetic Variability

Types of Genetic Variation

• Polymorphism – Variations occurring at a frequency of at least 1% in the human population

• Rare mutations / defects – Occur in < 1% of the population and can cause inherited diseases such as cystic fibrosis, Huntington's disease, or hemophilia

Single Nucleotide Polymorphism (SNP)

“Wild-type” allele

Codon 13 14 15 16 17 18

Nucleotides GCA CCC AAT AGA AGC CAT

Amino acid Ala Pro Asn Arg Ser His

“Variant” allele

Codon 13 14 15 16 17 18

Nucleotides GCA CCC AAT GGA AGC CAT

Amino acid Ala Pro Asn Gly Ser His

Types of SNPs

• Nonsynonymous – SNP resulting in an amino acid substitution– Arg16Gly or Arg16→Gly

• Synonymous – SNP not resulting in an amino acid substitution due to significant redundancy in the genetic code– GGA and GGC both code for glycine– A1166C or A1166→C

Nomenclature in Pharmacogenomics

CYP450 and Other Drug Metabolizing Enzymes

Star-allele Nomenclature

• *1– Designated reference sequence with

which polymorphic sites are compared

– The first sequence described

– May not be the most common allele in every ethnic population

Robarge et al. CPT. 2007;82:244-8.


• A unique number is assigned (i.e. *2,*3) when a novel variant is identified:– That leads to an amino acid substitution– Affects transcription, splicing, translation, or

post-transcriptional or post-translational modification

– If multiple variant alleles existing on the same chromosome are shown to have a functional effect on the protein, in a context where no single polymorphism has an effect



• A unique letter is assigned (*3B vs. *3A)– Nonfunctional nucleotide changes thought to

exist on the same chromosome– Inherited with a named star allele– Principle star allele is designated by A


CYP450 Allele Nomenclature Committee

• Peer-review process• Maintains allele nomenclature for 25 of 28

known human CYP genes• Function-centric focus (phenotype → genotype

data)• Developed prior to the genome explosion• May not sufficiently describe polymorphisms

beyond SNPs• Utility in a genotype → phenotype world?


Why do I care?!?!?!?

Case Study Gasche et al. NEJM 2004;351:2827-31.

• 62 yo male with a h/o chronic lymphoma• Chief complaint: 3 day h/o fatigue, dyspnea,

fever, and a cough• Objective: a/o, hypoxemic but normocapnic,

bilateral infiltrates on X-ray, yeast found on broncheoalveolar lavage

• A/P: Bilateral pneumonia with possible fungal infection– Begin ceftriaxone, clarithromycin, and voriconazole– Oral codeine to relieve cough

Case Study Gasche et al. NEJM 2004;351:2827-31.

• On hospital day 4 the patient was found unresponsive.

• In addition, the patient was dehydrated and experiencing renal dysfunction.

• Noninvasive ventilation was begun and he was transferred to the ICU.

• However, noninvasive ventilation did not improve his level of consciousness.

• Administration of naloxone (an opiod receptor antagonist) did improve responsiveness.

So…what happened?

Kidney – renal elimination

•Codeine:

•CYP3A4 – Norcodeine

•Glucuronidation – Codeine-6 glucuronide

•CYP2D6 – MORPHINE

•CYP3A4 is inhibited by clarithromycin and voriconazole

•This patient had ultra-rapid or extensive CYP2D6 activity

80%

Gasche et al. NEJM 2004;351:2827-31.

Clopidogrel as an Example

CYP2C19 Gene

• Wild Type:– CYP2C19 *1

• Variants associated with decreased activity or “loss of function”:– CYP2C19*2– CYP2C19*3

• Variant associated with increased activity or “gain of function”:– CYP2C19*17

Iverson Genetics - PlaviStat

Metabolic Capacity Type of polymorphism

Number of Copies

Extensive - EM None 0

Intermediate - IM Loss of function 1

Poor - PM Loss of function 2

Ultra-Rapid single - UMS Gain of function 1

Ultra-Rapid double - UMD Gain of function 2

http://www.iversongenetics.com/layout2009/Clopidogrel.html

Clopidogrel and CYP2C19

• Possession of a CYP2C19*2 or *3 allele is associated with:– Decreased formation clopidogrel active

metabolite– Less efficient inhibition of platelet aggregation

by clopidogrel– Increased risk of adverse cardiovascular

events and stent thrombosis with clopidogrel

Geisler et al. Pharmacogenomics. 2008;9:1251-9.Kim et al. Clin Pharmacol Ther. 2008;84:236-42.Trenk et al. J Am Coll Cardiol. 2008;51:1925-24.

CYP2C19 Genotype and Clopidogrel Response

Average RespondersAverage Responders

CYP2C19 *1/*1

HYPER RespondersHYPER Responders

CYP2C19 *1/*17

HYPORespondersHYPOResponders

CYP2C19 *1/*2

HYPORespondersHYPOResponders

CYP2C19 *2/*2

↓ Production of active metabolite

↑ Risk of Cardiovascular Events

CYP2C19 and ClopidogrelThings to keep in mind…

• Other factors effecting response, such as drug interactions

• Other causes of variability– Diabetes– Smoking– Adherence– Other genes?

CYP2C19 Genotyping Tests

• Currently available

• Test is a “send out” at most insitutions

• Turn around time is 24-72 hours

• Standard cost is $300

What do you do?

• Increase the dose?– Loading dose of 600mg, MD 150mg– The data with this is conflicting

• Therapeutic alternative?– Prasugrel – ONLY INDICATED FOR PCI– Ticagrelor – indicated for ACS

Clopidogrel Patient Case

• FD is a 57 year old male who began having crushing substernal chest pain while watching TV at home.

• In the emergency department, FD was given aspirin 325mg and sublingual nitroglycerin. Cardiac enzymes were drawn and he had an EKG done that revealed persistent ST-segment elevations, so he was rushed to the catheterization lab for treatment of his STEMI.

• Standard medications for the cath lab are given included clopidogrel 600mg po x 1.

• He had a Taxus stent (paclitaxel drug eluting stent) placed in his LCx, and blood flow was restored. His drips were discontinued after the intervention in the cath lab and he was transferred to the CICU for observation.

• A CYP2C19 genotyping test is performed for FD and the following report is provided to the medical team:– CYP2C19*2/*3

• They ask you what this means. How would you define FD?a.FD is an ultra-rapid metabolizer

b.FD is an extensive metabolizer

c.FD is an intermediate metabolizer

d.FD is a poor metabolizer

What does this CYP2C19 metabolizer status mean for FD?

• He is a VERY poor metabolizer

• Significant decrease in clopidogrel active metabolite production

• Increased risk of cardiovascular events

• They would also like a recommendation on how to address this information.a. Continue clopidogrel 75mg daily

b. Increase clopidogrel dose to 150mg daily

c. Change to prasugrel 10mg daily

d. Change to ticagrelor 90mg q12h

• Considerations:– Cost– Compliance

• How would you counsel FD on his CYP2C19 genotype?– You have a fairly common change in your

DNA that causes you to have a decrease in response to clopidogrel

– We are going to change your medication to ensure that you get the best possible therapy

• Terms to avoid:– Mutant– Dysfunction

Warfarin as an Example

Carboxylase

Reduced Vitamin K

Oxidized Vitamin K

VKORC1

R-warfarinS-warfarin

CYP1A / CYP3A4CYP2C9

ActivatedClotting Factors

HypofunctionalClotting Factors

CYP2C9 Gene• Common alleles and their frequencies

– CYP2C9*1 - Wild-type– CYP2C9*2 - Arg144Cys– CYP2C9*3 - Ile359Leu– CYP2C9*5 – Asp360Glu

• CYP2C9*2 and *3 alleles – About 35% of Caucasians, but only 3% of African

Americans and Asians, carry 1 variant allele.

• CYP2C9*5– Found only in African Americans

Decreased CYP2C9 activity

Carboxylase

Reduced Vitamin K

Oxidized Vitamin K

VKORC1





CYP2C9 Genotype and Warfarin Dose Requirement

Higashi et al. JAMA 2002;287:1690.M

edia

n do

se (m

g/da

y)

p<0.001

0

1

2

3

4

5

6

*1/*1 *1/*2 *1/*3 *2/*2 *2/*3 *3/*3

CYP2C9 Genotype and Warfarin Dose Requirement

• CYP2C9*2 and *3 alleles– Increased risk of INR above range– Longer time to achieve stable dosing– Higher risk for bleeding during initiation– Higher risk of bleeding during long term

therapy

• In a study of 368 European Americans, CYP2C9 genotype found to account for 6-10% of the variability in warfarin dose.

Higashi et al. JAMA 2002;287:1690.Limdi et al. CPT 2008;83:312.

Rieder et al. N Engl J Med 2005;352:2285.

Carboxylase

Reduced Vitamin K

Oxidized Vitamin K

VKORC1





VKORC1 Gene and Warfarin

0

1

2

3

4

5

6

7

-1639AA -1639AG -1639GG

Me

an

Do

se

(m

g/d

ay) p<0.001

• VKORC1 genotype accounted for 25% of the variability in warfarin dose.

Rieder et al. N Engl J Med 2005;352:2285.

Contribution to the Variability in Warfarin Dose Requirements

McClain et al. Genet Med. 2008;10:89-98.

•http://abcnews.go.com/Video/playerIndex?id=3492770

Updated and Expanded in 2010

http://abcnews.go.com/Video/playerIndex?id=3492770

Warfarin Dosage from the Official Prescribing Information

• The dose of COUMADIN must be individualized by monitoring the PT/INR. Not all factors causing warfarin dose variability are known. The maintenance dose needed to achieve a target PT/INR is influenced by:

– Clinical factors including age, race, body weight, sex, concomitant medications, and comorbidities and

– Genetic factors (CYP2C9 and VKORC1 genotypes).

• Select the starting dose based on the expected maintenance dose, taking into account the above factors. … If the patient’s CYP2C9 and VKORC1 genotypes are not known, the initial dose of COUMADIN is usually 2 to 5 mg per day.

• The patient’s CYP2C9 and VKORC1 genotype information, when available, can assist in selection of the starting dose. Table 5 describes the range of stable maintenance doses observed in multiple patients having different combinations of CYP2C9 and VKORC1 gene variants. Consider these ranges in choosing the initial dose.

Warfarin Prescribing Information. Bristol-Myers Squibb Company 2010

CYP2C9 and VKORC1 Genotypes and Warfarin Dose

CYP2C9 Genotype

VKORC1 genotype *1/*1 *1/*2 *1/*3 *2/*2 *2/*3 *3/*3

-1639AA 3-4 3-4 0.5-2 0.5-2 0.5-2 0.5-2

-1639AG 5-7 3-4 3-4 3-4 0.5-2 0.5-2

-1639GG 5-7 5-7 3-4 3-4 3-4 0.5-2


Warfarin Dosing Algorithms

• >7 algorithms have been published

• International Warfarin Pharmacogenomics Consortium– 4043 racially diverse subjects

– Model includes age, height, weight, VKORC1 AA and AG genotype, 5 different CYP2C9 genotype levels, race, enzyme inducer use, and amiodarone use

– Accurately predicts low and high dose requirements

– warfarindosing.org

Patient Case

• RG is a 49 yo caucasian male diagnosed with a DVT• 5’5” and 145 lbs• SH: smoked 1ppd for ~30 years, EtOH 1 drink/day• PMH: HTN, hyperlipidemia, DVT• Meds: simvastatin 40mg po daily, hydrochlorothiazide

25mg po daily• Labs: INR prior to initiating therapy was 1.1• Rapid genotyping performed: CYP2C9 *1/*3, VKORC1 -

1639 A/G• Maintenance warfarin dose:


CYP2C9 Genotype

VKORC1 genotype *1/*1 *1/*2 *1/*3 *2/*2 *2/*3 *3/*3

-1639AA 3-4 3-4 0.5-2 0.5-2 0.5-2 0.5-2

-1639AG 5-7 3-4 3-4 3-4 0.5-2 0.5-2

-1639GG 5-7 5-7 3-4 3-4 3-4 0.5-2


Clinical Decision MakingTo genotype or not to genotype

prior to starting warfarin?

• It depends…• Are they already receiving warfarin therapy?

– No

• New to therapy?– Ability to follow up in Coumadin clinic– High risk for bleed

The Future of Pharmacogenomics

• Genotyping patients before the information is necessary.

• This requires:– Consent from all patients for genetic testing– Technology to store a lot of information (potentially

entire patient genomes)– An electronic medical record that supports the

information– A system to effectively communicate the genotype

information in a straight forward manner

Vanderbilt University as an Example

• PREDICT: Pharmacogenomic Resource for Enhanced Decisions in Care and Treatment

• ALL patients undergoing cardiac catheterization at Vanderbilt University Medical Center will be genotyped for CYP2C19

• The CYP2C19 genotype will be available in the medical record in case clopidogrel is needed in the future

Toxicity

Goodresponse

Clinical Application of Pharmacogenomics

Population with disease

Different drug or alternative

therapy

dose ordifferent drug

Traditional therapy

Predictedresponse

Poorresponse

Therapy

Gen

otyp

e

Population at risk for disease

One More Case…

• JM presents to your pharmacy straight from the doctor and is waiting in the store to get his new prescription filled.

• Presents with a new prescription for warfarin 5mg PO daily

• He also has a genetic report with him today

Patient Profile:

Name: JMAge: 56 Sex: M Allergies: NKDA

Home Medication List:Omeprazole 40mg PO dailyAlbuterol 2 puffs PO q4h prnSertraline 100mg PO dailyLisinopril 20mg PO dailyAtorvastatin 40mg PO dailyMetformin ER 1000mg PO daily

Last date of fill for all medications was 1 week ago.

Which genes do you care about?

• Omeprazole – metabolized by CYP2C19

• Albuterol – stimulates the β2 receptor

• Sertraline – metabolized by CYP2D6, 3A4, 2C9, 2C19

• Lisinopril – none

• Atorvastatin – CYP3A4, SLCO1B1

• Metformin – none

• Warfarin – CYP2C9, VKORC1

Patient Profile:

Name: JMAge: 56 Sex: M Allergies: NKDA

Home Medication List:Omeprazole 40mg PO dailyAlbuterol 2 puffs PO q4h prnSertraline 100mg PO dailyLisinopril 20mg PO dailyAtorvastatin 40mg PO dailyMetformin ER 1000mg PO daily

Last date of fill for all medications was 1 week ago.

JM’s genotypes




• Lisinopril – none• Atorvastatin – CYP3A4,

SLCO1B1• Metformin – none• Warfarin – CYP2C9, VKORC1

• CYP2C19 *1/*1– Normal

• CYP2C9 *1/*3– Intermediate metabolizer

• CYP2D6 – Ultrarapid metabolizer

• SLCO1B1 – Normal

• VKORC1 -1639 A/A– Low warfarin dose

JM’s genotypes







• CYP2C9 *1/*3– Poor metabolizer




CYP2C19 normal metabolizer. No change needed.

CYP2C9 and 2D6 likely counterbalance each other. Plus, if he’s receiving benefit without side effects…leave it alone.

Do you need to change the dose?


CYP2C9 Genotype

VKORC1 genotype *1/*1 *1/*2 *1/*3 *2/*2 *2/*3 *3/*3

-1639AA 3-4 3-4 0.5-2 0.5-2 0.5-2 0.5-2

-1639AG 5-7 3-4 3-4 3-4 0.5-2 0.5-2

-1639GG 5-7 5-7 3-4 3-4 3-4 0.5-2


JM’s genotypes







• CYP2C9 *1/*3– Poor metabolizer




CYP2C19 normal metabolizer. No change needed.

CYP2C9 and 2D6 likely counterbalance each other. Plus, if he’s receiving benefit without side effects…leave it alone.

Do you need to change the dose? Yes, it needs to be decreased to 2-3mg PO daily

Clinical Genotyping

Clinical Pharmacogenetic Testing

1. FDA regulated• In vitro diagnostic device (IVD) or test kit

• Self contained package with all of the ingredients

2. “Home-brew” tests• Developed by an individual clinical lab

• Accounts for the majority of available tests

• Don’t require FDA approval, but are regulated by CLIA (Clinical Laboratory Improvement Amendment)

• No proficiency testing is currently required for pharmacogenetic tests

Shin et al. AJHP. 2009;66:625-37.

FDA Approved Pharmacogenetic Tests

Shin et al. AJHP. 2009;66:625-37.

Clinical Labs Performing Pharmacogenetic Tests

Shin et al. AJHP. 2009;66:625-37.

Genetic Non-Discrimination Act

• GINA signed into Law by President Bush May 21, 2008• Ensures that no one can be denied coverage or have their

premiums increased because of their genetic information• Genetic Information is defined as:

– an individual’s genetic tests (including genetic tests done as part of a research study);

– genetic tests of the individual’s family members (defined as dependents and up to and including 4th degree relatives);

– genetic tests of any fetus of an individual or family member who is a pregnant woman, and genetic tests of any embryo legally held by an individual or family member utilizing assisted reproductive technology;

– the manifestation of a disease or disorder in family members (family history);

– any request for, or receipt of, genetic services or participation in clinical research that includes genetic services (genetic testing, counseling, or education) by an individual or family member.

Genetic Non-Discrimination Act

• How will the law be enforced?– Corrective action and monetary penalties.– Individuals may also have the right to pursue private litigation.

• What doesn’t GINA do?– Does not extend to life insurance, disability insurance and long-

term care insurance. – Employment provisions generally do not apply to employers with

fewer than 15 employees. – Does not prohibit the health insurer from determining eligibility or

premium rates for an individual based on the manifestation of a disease or disorder in that individual.

References with Pharmacogenomic Information

• OMIM – Online Mendelian Inheritence in Man– http://www.ncbi.nlm.nih.gov/sites/entrez?db=OMIM&itool=toolbar

– Search engine associated with Pubmed

– Has information on genes

• PharmGKB – Pharmacogenomics Knowledge Base– http://www.pharmgkb.org/

– Information specifically on genes associated with drug response

• Lexi-Comp online– When search online for a drug can get info from pharmacogenomics

specific book

– Some pharmacogenomic information in standard lexi books also

• FDA website– www.fda.gov/cder/genomics

– Information from the agency perspective

– Includes educational material, table of valid genetic biomarkers, and a link to the respective drug label

http://www.ncbi.nlm.nih.gov/sites/entrez?db=OMIM&itool=toolbar

http://www.pharmgkb.org/

http://www.fda.gov/cder/genomics

http://www.shareapic.net/content.php?id=3618234&owner=kamalu

pharmacogenomics and pharmacist provided patient care kathryn momary pharm.d., bcps associate...

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