Pharmacogenomics: Clinical Application and Effects on Drug Metabolism Rodney J. Hunter, Pharm.D. Assistant Professor Texas Southern University College

Pharmacogenomics: Pharmacogenomics: Clinical Application and Clinical Application and

Effects on Drug Effects on Drug

MetabolismMetabolism Rodney J. Hunter, Pharm.D.Rodney J. Hunter, Pharm.D.

Assistant ProfessorAssistant ProfessorTexas Southern University College of Pharmacy and Texas Southern University College of Pharmacy and

Health SciencesHealth SciencesSNPhA Regional Conference District III, IV, & VSNPhA Regional Conference District III, IV, & V

February 19February 19thth, 2011, 2011

Financial DisclosureFinancial Disclosure

I have no conflicts of interest in I have no conflicts of interest in regards to this program regards to this program

“Why genetic polymorphisms? Why pharmacogenomics and oncology? Why so much excitement in this field?”

ObjectivesObjectives

Describe pharmacogenomics and the clinical Describe pharmacogenomics and the clinical relevance of this field of study in relation to relevance of this field of study in relation to oncologyoncology

Outline the drug metabolism pathways Outline the drug metabolism pathways affected by pharmacogenomic abnormalities affected by pharmacogenomic abnormalities in the oncology patient populationin the oncology patient population

Identify the different drug classes and Identify the different drug classes and significant adverse drug effects associated significant adverse drug effects associated with pharmacogenomic changes in the with pharmacogenomic changes in the oncology patient populationoncology patient population

Human Genome ProjectHuman Genome Project

Begun in 1990 with an expected Begun in 1990 with an expected completion date of 2005, it was completion date of 2005, it was completed in 2003 due to advances in completed in 2003 due to advances in technologytechnology

Set out to map the 20,000-25,000 Set out to map the 20,000-25,000 human geneshuman genes

3 billion DNA bases3 billion DNA bases

Introns and Exons

http://www.emc.maricopa.edu

.

Genetic PolymorphismsGenetic Polymorphisms

Single Nucleotide Polymorphism Single Nucleotide Polymorphism (SNPs)(SNPs) 1/1000 base pairs 1/1000 base pairs

Types of SNPsTypes of SNPs Insertion-DeletionInsertion-Deletion Tandem repeatsTandem repeats Frameshift mutationFrameshift mutation Defective splicingDefective splicing Aberrant splice siteAberrant splice site Premature stop codonPremature stop codon

Dipiro JT, Talbert RL, et al. Pharmacotherapy 7th ed. 2008;6:31-45.

Rationale for Rationale for PharmacogenomicsPharmacogenomics

Meta-analysis estimated ~2 Meta-analysis estimated ~2 million ADR/yr in the USmillion ADR/yr in the US

ADR accounting for 100,000 ADR accounting for 100,000 deathsdeaths

Cost in 2000 ~$177.4 billionCost in 2000 ~$177.4 billion

Lazarou, J et al JAMA. 1998;279:1200-05.

Goals of Goals of PharmacogenomicsPharmacogenomics

Prevent and predict adverse drug Prevent and predict adverse drug reactionsreactions

Optimize drug therapyOptimize drug therapy

Lead to novel approaches to drug Lead to novel approaches to drug discoverydiscovery

Goals of Goals of PharmacogenomicsPharmacogenomics

Evans WE and Johnson JA. Annu Rev Genomics Hum Genet. 2001;2:9-39.

Other Pharmacogenomic Other Pharmacogenomic ImplicationsImplications

Evans, WE and McLeod HL. N Engl J Med. 2003;6:538-49.

Pharmacogenomics in Pharmacogenomics in OncologyOncology

Drug effectsDrug effects Drug metabolismDrug metabolism Drug TargetsDrug Targets Drug Transporters Drug Transporters

Somatic mutations in malignant tissueSomatic mutations in malignant tissue

Narrow therapeutic indexNarrow therapeutic index

Metabolism and GeneticsMetabolism and Genetics


WT/WT = homozygous wild-type allele, Wt/V = heterozygous for one wild-type and one variant allele, V/V = homozygous for variant allele, AUC = area under the curve

Efficacy and GeneticsEfficacy and Genetics


WT/WT = homozygous wild-type allele, Wt/V = heterozygous for one wild-type and one variant allele, V/V = homozygous for variant allele, AUC = area under the curve

Polygenic Drug ResponsePolygenic Drug Response


Thiopurine-S-Thiopurine-S-methyltransferase (TPMT)methyltransferase (TPMT)

Mechanism of ActionMechanism of Action

Azathiopurine 6-mercaptopurine

6-thioguanine

6-methylmercaptopurine

Thiouric Acid

TPMT

Xanthine Oxidase


TPMT deficiencyTPMT deficiency Autosomal codominant genetic Autosomal codominant genetic

polymorphismpolymorphism High TPMT activity is most commonHigh TPMT activity is most common

TMPT*3A and TMPT*3CTMPT*3A and TMPT*3C

Heterozygous phenotypeHeterozygous phenotype Intermediate toleranceIntermediate tolerance

Evans WE, Hon YY, et al. J Clin Oncol. 2001;2293-301.

Patient populationPatient population Patient referred due to excessive Patient referred due to excessive

toxicity secondary to 6-MP or AZAtoxicity secondary to 6-MP or AZA Twenty-three patients evaluatedTwenty-three patients evaluated Hospitalizations, platelet transfusions, Hospitalizations, platelet transfusions,

and missed chemotherapy dosesand missed chemotherapy doses

Genetic TestingGenetic Testing TMPT genotype determined by PCRTMPT genotype determined by PCR





90%

SummarySummary A dosage reduction of A dosage reduction of 90%90% has benefited has benefited

patients with homozygous TPMT patients with homozygous TPMT deficiencydeficiency

Homozygous TPMT deficient patients Homozygous TPMT deficient patients have a high incidence of hematopoetic have a high incidence of hematopoetic toxicity induced by thiopurinestoxicity induced by thiopurines

Heterozygous patients can tolerate full Heterozygous patients can tolerate full doses in most casesdoses in most cases


“JP has a homozygous TPMT deficiency, JP’s full dose of 6-MP is 500 mg/m2/week. What dose should JP receive?”

UGT1A1UGT1A1


UGT1A1UGT1A1 UGT1A1*28UGT1A1*28

Extra TA dinucleotide promotor Extra TA dinucleotide promotor regionregion

Decreased expression of UGT1A1 Decreased expression of UGT1A1 proteinprotein

Increased risk of irinotecan toxicityIncreased risk of irinotecan toxicity Mainly in homozygous patientsMainly in homozygous patients

UGT1A1UGT1A1

Cote JH, Kirzin S, et al. Clin Cancer Res. 2007;3269-75.

Patient populationPatient population 400 patients with high-risk stage III colon 400 patients with high-risk stage III colon

cancercancer Patients randomizedPatients randomized

5-fluorouracil/Leucovorin (Arm A) or FOLFIRI 5-fluorouracil/Leucovorin (Arm A) or FOLFIRI (Arm B)(Arm B)

Genetic TestingGenetic Testing DNA from 184 patients was evaluatedDNA from 184 patients was evaluated

UGT1A1, ABCB1, and CYP3A5UGT1A1, ABCB1, and CYP3A5

UGT1A1UGT1A1


UGT1A1UGT1A1


Results Results

UGT1A1UGT1A1

SummarySummary Homozygous patients usually require at Homozygous patients usually require at

least one level dosing reductionleast one level dosing reduction

Heterozygous patients can tolerate normal Heterozygous patients can tolerate normal dosesdoses

Irinotecan screeningIrinotecan screening FDA-approved genotype test (Invader® FDA-approved genotype test (Invader®

Molecular Assay)Molecular Assay)


Dihydropyrimidine dehydrogenase Dihydropyrimidine dehydrogenase

(DPD)(DPD)

Watters JW, McLeod HL. Biochimica et Biophysica Acta 2003 1603; 99–111

Dihydropyrimidine dehydrogenase Dihydropyrimidine dehydrogenase

(DPD)(DPD) DPD deficiencyDPD deficiency

AG to C single nucleotide change on AG to C single nucleotide change on exon 14exon 14

Decreased activity of DPD responsible Decreased activity of DPD responsible for 5-FU breakdownfor 5-FU breakdown

Major SymptomsMajor Symptoms Diarrhea, neutropenia, and neurotoxicityDiarrhea, neutropenia, and neurotoxicity

Thymidylate synthase (TS)Thymidylate synthase (TS)

Watters JW, McLeod HL. Biochimica et Biophysica Acta 2003 1603; 99–111

5’-promotor enhancer region (TSER) 5’-promotor enhancer region (TSER) genegene


Methylenetetrahydrofolate Methylenetetrahydrofolate

Reductase (MTHFR)Reductase (MTHFR) Mechanism of action in relation to Mechanism of action in relation to

fluoropyrimidines and antifolatesfluoropyrimidines and antifolates

AntifolatesAntifolates MethotrexateMethotrexate and and pemetrexedpemetrexed

FluoropyrimidinesFluoropyrimidines 5-fluorouracil 5-fluorouracil

Methylenetetrahydrofolate Methylenetetrahydrofolate Reductase (MTHFR)Reductase (MTHFR)

C677T and A1298CC677T and A1298C Caucasian and Asian PopulationCaucasian and Asian Population Possible increase susceptibilityPossible increase susceptibility 5-FU increased activity5-FU increased activity Other implicationsOther implications

Further study mandatedFurther study mandated Folate status and geographic originFolate status and geographic origin

Dezemtje VO, Guchelaar HJ, et al. Annu Rev Clin Cancer Res 2009;15:15-21.


Patient populationPatient population 76 patients initiated on 5-FU therapy76 patients initiated on 5-FU therapy TS, DPD, and MTHFR analyzedTS, DPD, and MTHFR analyzed

Patient Genetic CharacteristicsPatient Genetic Characteristics TS 2R/2R – TS 2R/2R – 18%18%; 2R/3R – ; 2R/3R – 50%50%; 3R/3R - ; 3R/3R -

30%30% MTHFR polymorphisms evenly spreadMTHFR polymorphisms evenly spread DPD deficiency in DPD deficiency in 1.6%1.6%

Capitain O et al. Pharmacogenomics J 2008;6:256-67.

5-FU, Genetics, and Outcome

Advanced colorectal cancer patients Receiving 5-FU (n = 76)

Efficacy TS 3R/3R genotype (log-rank test p =

0.0065)

Toxicity DPD (p = 0.031) MTHFR 1298 A > T (p = 0.0018)

Capitain O et al. Pharmacogenomics J 2008;6:256-67.

SummarySummary Patients with verified homozygous Patients with verified homozygous DPD DPD

deficiencydeficiency should be changed to another should be changed to another treatment regimentreatment regimen

Patients with DPD deficiency develop Patients with DPD deficiency develop significantly earlier than patients with normal significantly earlier than patients with normal DPD activityDPD activity

Increased TS activity linked to poor outcomes Increased TS activity linked to poor outcomes in patients treated with 5-FU and its derivativesin patients treated with 5-FU and its derivatives

5-Fluorouracil (5FU)5-Fluorouracil (5FU)

“Should RS, a patient with homozygous DPD deficiency be treated with 5-fluorouracil?

Tamoxifen Tamoxifen PharmacogeneticsPharmacogenetics

Marsh S and McLeod HL. Expert Opin. Pharmacother. 2007;8:119-27.

CYP 2D6 polymorphismCYP 2D6 polymorphism


Dezemtje VO, Guchelaar HJ, et al. Annu Rev Clin Cancer Res. 2009;15:15-21.


Patient enzyme activity identified by Patient enzyme activity identified by probeprobe

Patients separated in to four groupsPatients separated in to four groups Poor, intermediate, extensive, or ultra-Poor, intermediate, extensive, or ultra-

rapid metabolizersrapid metabolizers

Higher rates of recurrence in poor Higher rates of recurrence in poor metabolizersmetabolizers

Dezemtje VO, Guchelaar HJ, et al. Annu Rev Clin Cancer Res. 2009;15:15-21.

SummarySummary Majority of studies conducted failed to account Majority of studies conducted failed to account

for tumor grade and prognostic factorsfor tumor grade and prognostic factors

Only one of the major studies accounts for the Only one of the major studies accounts for the use of other CYP2D6 inhibitorsuse of other CYP2D6 inhibitors

Recent studies showing some “negative data” Recent studies showing some “negative data” publishedpublished

AmpliChip CYP450 test is an FDA approved testAmpliChip CYP450 test is an FDA approved test


Food and Drug Food and Drug Administration Administration

Endocrinology and Metabolic Drugs FDA Endocrinology and Metabolic Drugs FDA Advisory Committee Advisory Committee

October 16October 16thth, 2006, 2006

Package insert updated for tamoxifenPackage insert updated for tamoxifen

““Increased risk of breast cancer recurrence Increased risk of breast cancer recurrence in postmenopausal estrogen receptor positive in postmenopausal estrogen receptor positive patients who are CYP2D6 poor metabolizers”patients who are CYP2D6 poor metabolizers”

Epidermal Growth Factor Epidermal Growth Factor Receptor (EGFR)Receptor (EGFR)

Small Molecule InhibitorsSmall Molecule Inhibitors Gefitinib and ErlotinibGefitinib and Erlotinib

Monoclonal AntibodiesMonoclonal Antibodies Cetuximab and Cetuximab and Panitumumab

EGFR prognostic or predictive EGFR prognostic or predictive


Tyrosine Kinase Domain MutationsTyrosine Kinase Domain Mutations Cluster around the ATP-binding sitesCluster around the ATP-binding sites

Exons 18, 19, and 21Exons 18, 19, and 21

Most common mutationsMost common mutations L858RA (exon 21)L858RA (exon 21) E19delE19del

Yong WO et al. Br J Pharmacol. 2006;62:35-46.


Major focuses of new research Major focuses of new research Somatic mutations tyrosine kinase Somatic mutations tyrosine kinase

domaindomain Erlotinib and GefitinibErlotinib and Gefitinib

Development of skin rashDevelopment of skin rash

Transcriptional activity and expression Transcriptional activity and expression of EGFRof EGFR

Yong WO et al. Br J Pharmacol. 2006;62:35-46.


GefitinibGefitinib ISELISEL

Efficacy associated with nationalityEfficacy associated with nationality Japanese vs. CaucasianJapanese vs. Caucasian

High gene copy numberHigh gene copy number

ErlotinibErlotinib BR.21BR.21

Gene status had no significant Gene status had no significant contributions to activitycontributions to activity

Patient populationPatient population Prospective clinical study Prospective clinical study NSCLC, Head and neck CA, and NSCLC, Head and neck CA, and

Ovarian CAOvarian CA ErlotinibErlotinib

Pharmacokinetics, toxicity, and Pharmacokinetics, toxicity, and polymorphic changespolymorphic changes ABCG2 levelsABCG2 levels

Rudin CM et al. J Clin Oncol 2008;26:1119-27.


Phase II studies using EGFR Phase II studies using EGFR TKIs in EGFR mutation (+) TKIs in EGFR mutation (+)

patientspatientsStudy N Treatment RR median PFS median

Asahina et al

16 Gefitinib 75% 8.9 mo

Yoshida et al


Inoue et al 16 Gefitinib 75% 9.7 mo

Tamura et al


Sequist et al


Paz-Ares et al

37 Erlotinib 82% 13.3 mo

Heist RS et al. Pharmacogenomics. 2009;10:59-68.

Kristen-rat Sarcoma (Kristen-rat Sarcoma (K-K-RasRas) Gene) Gene

Mechanism of Action Mechanism of Action

Khambata-Ford S et al. J Clin Oncol. 2007;25:3230-7.

K-RasK-Ras

K-RasK-Ras mutation mutation Codon 12 or 13 mutationsCodon 12 or 13 mutations

G-protein coupled receptor signalingG-protein coupled receptor signaling Cell proliferation and survivalCell proliferation and survival

Adenocarcinomas in North AmericaAdenocarcinomas in North America

Progression free survival and overall Progression free survival and overall survival implications?survival implications?

K-RasK-Ras Testing and Testing and Economic ImplicationsEconomic Implications

Annual incidence of 29,762 mCRC casesAnnual incidence of 29,762 mCRC cases Cetuximab Cost $4,032 loading dose, Cetuximab Cost $4,032 loading dose,

$2,880/weekly$2,880/weekly $753 million annually$753 million annually

K-RasK-Ras testing testing PCR-based = $452/patientPCR-based = $452/patient $13 million annually$13 million annually

Theoretical cost savings of $740 millionTheoretical cost savings of $740 million

Shankaran V et al. ASCO GI Cancer Symposium. 2009; abstract 298.

SummarySummary Standardized Standardized K-RasK-Ras mutation testing mutation testing

Substantial Cost savingsSubstantial Cost savings

Patients can benefit from Patients can benefit from preemptive testingpreemptive testing ASCO & NCCN endorsement for ASCO & NCCN endorsement for K-RasK-Ras testing testing

K-RasK-Ras Testing and Testing and Economic ImplicationsEconomic Implications

BRAF and K-RasBRAF and K-Ras

Nicolantonio FD et al. J Clin Oncol 26:5705-5712

Study Conclusions Demonstrated a 30% frequency of the K-

Ras mutation in the patients analyzed

The BRAF V600E is has negative implications on EGFR monoclonal antibody therapy, progression free survival, and overall survival

Sorafenib restored sensitivity to the EGFR monoclonal antibody therapies

BRAF BRAF and and K-RasK-Ras

“So what exactly do we want to take away from the information presented this morning?”

ConclusionsConclusions

Pharmacogenomic sampling Pharmacogenomic sampling continues to be focus of researchcontinues to be focus of research TPMT, UGT1A1, DPD, TS, TPMT, UGT1A1, DPD, TS, K-RasK-Ras, and , and

most recently most recently BRAF BRAF impact drug impact drug efficacy and toxicityefficacy and toxicity

Drug dosing guidelines based upon Drug dosing guidelines based upon pharmacogenetics will continue to pharmacogenetics will continue to emergeemerge

Pharmacogenomics: Pharmacogenomics: Clinical Application and Clinical Application and

Effects on Drug Effects on Drug

MetabolismMetabolism Rodney J. Hunter, Pharm.D.Rodney J. Hunter, Pharm.D.

Assistant ProfessorAssistant ProfessorTexas Southern University College of Pharmacy and Texas Southern University College of Pharmacy and

Health SciencesHealth SciencesSNPhA Regional Conference District III, IV, & VSNPhA Regional Conference District III, IV, & V

February 19February 19thth, 2011, 2011

Documents

Pharmacogenomics: Clinical Application and Effects on Drug Metabolism Rodney J. Hunter, Pharm.D. Assistant Professor Texas Southern University College