important genotypes in drug- enzyme interactions nissa abbasi-shaffer university of washington...
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Important Genotypes in Drug-Enzyme Interactions
Important Genotypes in Drug-Enzyme Interactions
Nissa Abbasi-ShafferUniversity of Washington
School of PharmacyDoctoral Candidate, 2009
August 1, 2008
Nissa Abbasi-ShafferUniversity of Washington
School of PharmacyDoctoral Candidate, 2009
August 1, 2008
OutlineOutline
• Introduction
• Genotypes in GeneMedRx
• Additions to GeneMedRx
• Introduction
• Genotypes in GeneMedRx
• Additions to GeneMedRx
Drug-Enzyme InteractionsDrug-Enzyme Interactions
The activity an enzyme will have on a substrate is determined in part by the physical enzyme-substrate interaction
(Nonsynonymous) Mutations in genes can affect the protein product interaction: Conformational changes pH changes H-bonding changes
Patient response to drugs can be altered by their genotype
The activity an enzyme will have on a substrate is determined in part by the physical enzyme-substrate interaction
(Nonsynonymous) Mutations in genes can affect the protein product interaction: Conformational changes pH changes H-bonding changes
Patient response to drugs can be altered by their genotype
Genotypes in GeneMedRxGenotypes in GeneMedRx
Function in GeneMedRx for genotype selection
Users can select appropriate genotype and medication profile to determine if an “interaction” exists: Metabolic enzymes:
Reduced efficacy: eg. CYP2D6 UM Increased toxicity: eg. CYP2C9 PM
Target sites: Efficacy: eg. Her2/Neu Toxicity?
Function in GeneMedRx for genotype selection
Users can select appropriate genotype and medication profile to determine if an “interaction” exists: Metabolic enzymes:
Reduced efficacy: eg. CYP2D6 UM Increased toxicity: eg. CYP2C9 PM
Target sites: Efficacy: eg. Her2/Neu Toxicity?
Updated GenesUpdated Genes
CYP2D6 CYP2C9 CYP2C19 NAT2 TPMT UGT1A1
CYP2D6 CYP2C9 CYP2C19 NAT2 TPMT UGT1A1
Each phenotype was given a descriptor so that if selected, regardless of whether a known drug interaction exists, the significance of the genotype is displayed
e.g. CYP2D6 Poor Metabolizer updated note
e.g. CYP2D6 Poor Metabolizer updated note
Gene: 2D6 Poor MetabolizerCytochrome P450 2D6 Poor Metabolizers (PM) have absent or
greatly reduced CYP2D6 activity. They are identified by DNA testing and comprise up to 12% of the population. Drugs that are substrates of 2D6 will reach higher levels in 2D6 PMs and may cause toxicity. The increase is often substantial, roughly equal to adding a strong 2D6 inhibitor drug. Poor metabolizers may need to be started at 20-60% of standard doses for drugs metabolized by 2D6.
Prodrugs that require activation by CYP2D6 may be less effective in PMs, including: tamoxifen, codeine, tramadol, risperidone and encainide.
Recommendations for 2D6 genotype-based changes in dosage for many psychotropic drugs can be found at: http://www.healthanddna.com/professional/depression.html
Gene: 2D6 Poor MetabolizerCytochrome P450 2D6 Poor Metabolizers (PM) have absent or
greatly reduced CYP2D6 activity. They are identified by DNA testing and comprise up to 12% of the population. Drugs that are substrates of 2D6 will reach higher levels in 2D6 PMs and may cause toxicity. The increase is often substantial, roughly equal to adding a strong 2D6 inhibitor drug. Poor metabolizers may need to be started at 20-60% of standard doses for drugs metabolized by 2D6.
Prodrugs that require activation by CYP2D6 may be less effective in PMs, including: tamoxifen, codeine, tramadol, risperidone and encainide.
Recommendations for 2D6 genotype-based changes in dosage for many psychotropic drugs can be found at: http://www.healthanddna.com/professional/depression.html
New Genotypes AddedNew Genotypes Added
MTHFR DPYD HLA-B*5701 HER2/NEU 5HTT
MTHFR DPYD HLA-B*5701 HER2/NEU 5HTT
MTHFRMTHFR Methylene tetrahydrofolate reductase is an
important enzyme in folate metabolism Allows for methyl group transfer needed for DNA
synthesis and methylation Reduced activity is associated with homocysteine
accumulation
Folate status may be associated with malignancy (reduced -CH3)
Position C677T mutation results in loss-of-function of reductase enzyme T/T 70% reduction: seen in ~10% of North Americans C/T 40% reduction: seen in ~40% of North Americans One study reports 677T allele frequencies of:
Caucasians 0.34 Japanese 0.42 Africans 0.08
Methylene tetrahydrofolate reductase is an important enzyme in folate metabolism Allows for methyl group transfer needed for DNA
synthesis and methylation Reduced activity is associated with homocysteine
accumulation
Folate status may be associated with malignancy (reduced -CH3)
Position C677T mutation results in loss-of-function of reductase enzyme T/T 70% reduction: seen in ~10% of North Americans C/T 40% reduction: seen in ~40% of North Americans One study reports 677T allele frequencies of:
Caucasians 0.34 Japanese 0.42 Africans 0.08
Methotrexate Methotrexate
Folate analog that inhibits dihydrofolate reductase (also important in folate metabolism)
MTX used to treat many cancers, rheumatoid arthritis & psoriasis
T/T genotype associated with increased toxicity: Fever, malaise, GI, skin, pharyngeal, pulmonary mucositis & extended thrombocytopenia reported in
leukemia pts
Genotype is important in predicting response
Folate analog that inhibits dihydrofolate reductase (also important in folate metabolism)
MTX used to treat many cancers, rheumatoid arthritis & psoriasis
T/T genotype associated with increased toxicity: Fever, malaise, GI, skin, pharyngeal, pulmonary mucositis & extended thrombocytopenia reported in
leukemia pts
Genotype is important in predicting response
Folate pathwayFolate pathway
Image downloaded from http://www.pharmgkb.org
MTX
XX
DPYDDPYD Dihydropyrimidine dehydrogenase is the
initial and rate-limiting enzyme in pyrimidine (uracil & thymine) catabolism
Exon 14-skipping mutation GT to AT mutation located in the 5’-splicing
consensus sequence Causes exon 14 of DPYD to be spliced out
and not expressed in protein product, DPD 165 bp deletion = 55 amino acids absent Complete loss-of-function
Mutation found in ~1% of European-based population
Dihydropyrimidine dehydrogenase is the initial and rate-limiting enzyme in pyrimidine (uracil & thymine) catabolism
Exon 14-skipping mutation GT to AT mutation located in the 5’-splicing
consensus sequence Causes exon 14 of DPYD to be spliced out
and not expressed in protein product, DPD 165 bp deletion = 55 amino acids absent Complete loss-of-function
Mutation found in ~1% of European-based population
FluorouracilFluorouracil Analog of uracil
DPD is the initial enzyme in its metabolism Reduced DPD activity causes increase 5FU levels
5FU is widely used in cancer therapy (breast, colon, head & neck, etc.)
Toxicity from 5FU is reported to occur in those who have even 50% of DPD activity--one null allele can be enough Toxicity can be severe, including mucositis,
granulocytopenia In one study 24% of patients with WHO grade IV toxicity were
found to have the exon 14-skipping mutation PM will need dose reduction
Analog of uracil DPD is the initial enzyme in its metabolism Reduced DPD activity causes increase 5FU levels
5FU is widely used in cancer therapy (breast, colon, head & neck, etc.)
Toxicity from 5FU is reported to occur in those who have even 50% of DPD activity--one null allele can be enough Toxicity can be severe, including mucositis,
granulocytopenia In one study 24% of patients with WHO grade IV toxicity were
found to have the exon 14-skipping mutation PM will need dose reduction
HLA-B*5701HLA-B*5701 The HLA class I molecules present antigens to killer T cells
to induce immunity Some allotypes within this class have a propensity to induce
allergic-type reactions The HLA-B*5701 genotype is associated with allergic reactions to
abacavir Found in ~5% of the European-based population (less common in
African Americans)
Abacavir Hypersensitivity Syndrome (AHS) Graft vs host-like response, generally appears within 6 wks Symptoms can include rash, fever, malaise, nausea, vomiting,
diarrhea, respiratory problems, and can be fatal A reaction requires immediate discontinuation of the drug; do not
rechallenge
The HLA class I molecules present antigens to killer T cells to induce immunity Some allotypes within this class have a propensity to induce
allergic-type reactions The HLA-B*5701 genotype is associated with allergic reactions to
abacavir Found in ~5% of the European-based population (less common in
African Americans)
Abacavir Hypersensitivity Syndrome (AHS) Graft vs host-like response, generally appears within 6 wks Symptoms can include rash, fever, malaise, nausea, vomiting,
diarrhea, respiratory problems, and can be fatal A reaction requires immediate discontinuation of the drug; do not
rechallenge
FDA AlertFDA Alert
Last week (7/24/2008) the FDA issued an alert recommending all patients be genotyped before starting or restarting abacavir due to the high correlation of AHS to this drug, the potential severity of the symptoms and the ease of preventing the reaction by DNA testing.
HER2/NeuHER2/Neu HER2 belongs to the Epidermal Growth Factor Receptor
family, associated w/ cellular growth and differentiation
Overexpression of the HER2 protein found in 18-20% of breast cancer resulting in more aggressive tumors
Clinical testing (IHC and FISH) to screen overexpressors determines course of therapy: targeted or not better response to anthracyclines
Current targeted therapies: Trastuzumab (Herceptin) efficacy associated w/ overexpression—
std treatmant for early stage Her2/Neu positive breast cancer (given in combo w/ chemo)
Lapatinib is an oral TKI targeted to Her2/Neu in patients who are overexpressors who failed Herceptin therapy (given in combo with capecitabine)
HER2 belongs to the Epidermal Growth Factor Receptor family, associated w/ cellular growth and differentiation
Overexpression of the HER2 protein found in 18-20% of breast cancer resulting in more aggressive tumors
Clinical testing (IHC and FISH) to screen overexpressors determines course of therapy: targeted or not better response to anthracyclines
Current targeted therapies: Trastuzumab (Herceptin) efficacy associated w/ overexpression—
std treatmant for early stage Her2/Neu positive breast cancer (given in combo w/ chemo)
Lapatinib is an oral TKI targeted to Her2/Neu in patients who are overexpressors who failed Herceptin therapy (given in combo with capecitabine)
5HTT/SLC6A45HTT/SLC6A4 The serotonin transporter (5HTT)
reuptakes serotonin from the synaptic cleft into the presynaptic terminus
5HTT is the target of SSRIs--limiting reuptake allows for more serotonin transmission
Variability in SSRI efficacy within the general population has lead the search for a genetic explanation Discovery of 5HTTLPR polymorphism
The serotonin transporter (5HTT) reuptakes serotonin from the synaptic cleft into the presynaptic terminus
5HTT is the target of SSRIs--limiting reuptake allows for more serotonin transmission
Variability in SSRI efficacy within the general population has lead the search for a genetic explanation Discovery of 5HTTLPR polymorphism
5HTTLPR5HTTLPR The serotonin transporter-linked polymorphic
region is located in the promoter region of 5HTT 44-bp insertion/deletion produces the long (L = 16 repeat
units) and short (S = 14 repeat units) alleles S allele results in 50% of the transcriptional activity as
the L allele ~40% of North Americans carry at least one S allele
(varies from 10-70% globally) Other lengths have been discovered, but very rare in the
population: 15, 18-20, 22 repeated units
S allele is associated with reduced efficacy to SSRIs Hypothesis: if less transporter made, less target for SSRIs Carriers of the S allele often take longer to respond or do
not respond at all Genotyping can be used to identify candidates
The serotonin transporter-linked polymorphic region is located in the promoter region of 5HTT 44-bp insertion/deletion produces the long (L = 16 repeat
units) and short (S = 14 repeat units) alleles S allele results in 50% of the transcriptional activity as
the L allele ~40% of North Americans carry at least one S allele
(varies from 10-70% globally) Other lengths have been discovered, but very rare in the
population: 15, 18-20, 22 repeated units
S allele is associated with reduced efficacy to SSRIs Hypothesis: if less transporter made, less target for SSRIs Carriers of the S allele often take longer to respond or do
not respond at all Genotyping can be used to identify candidates
Thank you Genelex!
Any questions???
Thank you Genelex!
Any questions???
ReferencesReferences MTHFR:Kremer JM. Methotrexate pharmacogenomics. Ann Rheum Dis. 2006 Sep;65(9):1121-3. Hughes LB, Beasley TM, Patel H, et al.Racial or ethnic differences in allele frequencies of single-nucleotide
polymorphisms in the methylenetetrahydrofolate reductase gene and their influence on response to methotrexate in rheumatoid arthritis. Ann Rheum Dis. 2006 Sep;65(9):1213-8
Frosst P, Blom HJ, Milos R, Goyette P, Sheppard CA, Matthews RG, Boers GJ, den Heijer M, Kluijtmans LA, van den Heuvel LP, et al. A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase.Nat Genet. 1995 May;10(1):111-3
DPYP:Tomalik-Scharte D, Lazar A, Fuhr U, Kirchheiner J. The clinical role of genetic polymorphisms in drug-metabolizing
enzymes. Pharmacogenomics J. 2008 Feb;8(1):4-15Maitland ML, Vasisht K, Ratain MJ. TPMT, UGT1A1 and DPYD: genotyping to ensure safer cancer therapy? Trends
Pharmacol Sci. 2006 Aug;27(8):432-7Wei X, McLeod HL, McMurrough J, Gonzalez FJ, Fernandez-Salguero P. Molecular basis of the human dihydropyrimidine
dehydrogenase deficiency and 5-fluorouracil toxicity. J Clin Invest. 1996 Aug 1;98(3):610-5 HLA-B*5701:Saag M, Balu R, Phillips E, et al; Study of Hypersensitivity to Abacavir and Pharmacogenetic Evaluation Study Team.
High sensitivity of human leukocyte antigen-b*5701 as a marker for immunologically confirmed abacavir hypersensitivity in white and black patients. Clin Infect Dis. 2008 Apr 1;46(7):1111-8.
Mallal S, Phillips E, Carosi G, et al; PREDICT-1 Study Team. HLA-B*5701 screening for hypersensitivity to abacavir. N Engl J Med. 2008 Feb 7;358(6):568-79.
Chessman D, Kostenko L, Lethborg T, et al. Human leukocyte antigen class I-restricted activation of CD8+ T cells provides the immunogenetic basis of a systemic drug hypersensitivity. Immunity. 2008 Jun;28(6):822-32.
www.fda.gov/cder/drug/InfoSheets/HCP/abacavirHCP.htm HER2/Neu:Lin A, Rugo HS.The role of trastuzumab in early stage breast cancer: current data and treatment recommendations.
Curr Treat Options Oncol. 2007 Feb;8(1):47-60.Yamauchi H, Hayes D. HER2 and predicting response to therapy in breast cancer. Downloaded from:
www.uptodate.com [accessed 2008 July 29]. 5HTT:Lesch KP, Gutknecht L. Pharmacogenetics of the serotonin transporter. Prog Neuropsychopharmacol Biol Psychiatry.
2005 Jul;29(6):1062-73.Gelernter J, Cubells JF, Kidd JR, Pakstis AJ, Kidd KK. Population studies of polymorphisms of the serotonin transporter
protein gene. Am J Med Genet. 1999 Feb 5;88(1):61-6.Heils A, Teufel A, Petri S, Stöber G, Riederer P, Bengel D, Lesch KP. Allelic variation of human serotonin transporter
gene expression. J Neurochem. 1996 Jun;66(6):2621-4.
MTHFR:Kremer JM. Methotrexate pharmacogenomics. Ann Rheum Dis. 2006 Sep;65(9):1121-3. Hughes LB, Beasley TM, Patel H, et al.Racial or ethnic differences in allele frequencies of single-nucleotide
polymorphisms in the methylenetetrahydrofolate reductase gene and their influence on response to methotrexate in rheumatoid arthritis. Ann Rheum Dis. 2006 Sep;65(9):1213-8
Frosst P, Blom HJ, Milos R, Goyette P, Sheppard CA, Matthews RG, Boers GJ, den Heijer M, Kluijtmans LA, van den Heuvel LP, et al. A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase.Nat Genet. 1995 May;10(1):111-3
DPYP:Tomalik-Scharte D, Lazar A, Fuhr U, Kirchheiner J. The clinical role of genetic polymorphisms in drug-metabolizing
enzymes. Pharmacogenomics J. 2008 Feb;8(1):4-15Maitland ML, Vasisht K, Ratain MJ. TPMT, UGT1A1 and DPYD: genotyping to ensure safer cancer therapy? Trends
Pharmacol Sci. 2006 Aug;27(8):432-7Wei X, McLeod HL, McMurrough J, Gonzalez FJ, Fernandez-Salguero P. Molecular basis of the human dihydropyrimidine
dehydrogenase deficiency and 5-fluorouracil toxicity. J Clin Invest. 1996 Aug 1;98(3):610-5 HLA-B*5701:Saag M, Balu R, Phillips E, et al; Study of Hypersensitivity to Abacavir and Pharmacogenetic Evaluation Study Team.
High sensitivity of human leukocyte antigen-b*5701 as a marker for immunologically confirmed abacavir hypersensitivity in white and black patients. Clin Infect Dis. 2008 Apr 1;46(7):1111-8.
Mallal S, Phillips E, Carosi G, et al; PREDICT-1 Study Team. HLA-B*5701 screening for hypersensitivity to abacavir. N Engl J Med. 2008 Feb 7;358(6):568-79.
Chessman D, Kostenko L, Lethborg T, et al. Human leukocyte antigen class I-restricted activation of CD8+ T cells provides the immunogenetic basis of a systemic drug hypersensitivity. Immunity. 2008 Jun;28(6):822-32.
www.fda.gov/cder/drug/InfoSheets/HCP/abacavirHCP.htm HER2/Neu:Lin A, Rugo HS.The role of trastuzumab in early stage breast cancer: current data and treatment recommendations.
Curr Treat Options Oncol. 2007 Feb;8(1):47-60.Yamauchi H, Hayes D. HER2 and predicting response to therapy in breast cancer. Downloaded from:
www.uptodate.com [accessed 2008 July 29]. 5HTT:Lesch KP, Gutknecht L. Pharmacogenetics of the serotonin transporter. Prog Neuropsychopharmacol Biol Psychiatry.
2005 Jul;29(6):1062-73.Gelernter J, Cubells JF, Kidd JR, Pakstis AJ, Kidd KK. Population studies of polymorphisms of the serotonin transporter
protein gene. Am J Med Genet. 1999 Feb 5;88(1):61-6.Heils A, Teufel A, Petri S, Stöber G, Riederer P, Bengel D, Lesch KP. Allelic variation of human serotonin transporter
gene expression. J Neurochem. 1996 Jun;66(6):2621-4.