Pharmacogenetics Flashcards
4 different drug responses?
toxic + beneficial
toxic + not beneficial
non-toxic + beneficial
non-toxic + non-beneficial
3 goals for personalized medecine?
- Identify genetic differences between people that affect drug response
- Develop genetic tests that predict an individual’s response to a drug
- Tailor medical treatments to the individual
Difference between pharmacogenetics and pharmacogenomics?
genetics : evaluate how an individual’s genetic makeup corresponds to their response to a particular medication
genomics : large group of patient to evaluate how drugs interact with many different genes and their proteins
5 drugs that are ineffective in a certain percentage of people?
- ACE inhibitors - Hypertension (10-30%)
- Beta blockers - Heart Failure (15-25%)
- Anti-depressants (20-50%)
- Statins - Cholesterol (30-70%)
- B2 agonists - asthma (40-70%)
How can a change in a gene lead to toxicity/low efficacy in PK? (3)
Gene that affects ADME
Drug metabolizing enzymes
T.I.
How can a change in a gene lead to toxicity/low efficacy in PD? (1)
Slightly different target or loss of target
The two major types of drug metabolizing enzymes? What do they act on? (2)
Ultra drug metabolizer
Poor drug metabolizer
They act on drugs and pro-drugs
Effect of ultra drug and poor drug metabolizers on drugs?
UM : rapid inactivation so ineffective
PM : toxic doses
Effect of ultra drug and poor drug metabolizers on prodrugs?
UM : metabolized to active form rapidly, toxic doses
PM : Little conversion of prodrug to active form, ineffective
Three reasons why there can be NO consequences of genetic polymorphisms?
- Outside of coding and regulatory regions
- Synonymous substitution
- No signi. effect on function
4 consequences of genetic polymorphisms?
None
Decrease/loss function of protein
Increase function of protein
Change is compared to population majority
What are 4 reasons why there can be decreased function in a protein due to genetic polymorphisms?
- Less enzyme produced
- Enzyme not complete (stop codon)
- Enzyme not stable
- Less affinity for substrate
What are 3 reasons why there can an increased function in a protein due to genetic polymorphisms?
- More production
- More stable
- More affinity for substrate
3 enzymes with genetic polymorphisms that cause disease?
NAT2
TPMT
ALDH2
NAT2 involved in what disease?
Tuberculosis
Tuberculosis is an infection of which bacteria
mycobacterium tuberculosis
Tuberculosis attacks mainly what?
lungs
Which drug targets TB? It is metabolized by the _____ via which modification?
When the drug reaches toxic levels it causes what?
Isoniazid
Liver
Acetylation
Peripheral neuropathy
Which enzyme acetylates isoniazid?
NAT2 : N-acetyl-transferase
Two types of NAT2 acetylators? Which is WT and which has many AA substitutions?
Rapid: WT
Slow : many alleles
11 haplotypes of NAT2? Rapid or slow?
4 : rapid 5A : slow 5B : slow 6A : slow 7B : slow 7Bnew : unknown 10 : unknown 11 : unknown 12A : rapid 13 : rapid 14B : slow
Thiopurines treat which diseases? (4)
- Leukemia
- Inflammatory bowel disease
- Prevent organ rejection
- Other autoimmune diseases
Enzyme that acts on thiopurines? What modification does it do
Thiopurine methyltransferase
Methylation
Thiopurines are converted into __________
This gets inserted in _______ and can have toxic effects at high levels.
Reduced TPMT activity leads to ___________
Thioguanine nucleotides (TGNs)
DNA bases
Fatal toxicity
5 Haplotypes of TPMT?
1 2 3A 3B 3C
If a patient have two nonfunctional variant alleles of TPMT (homozygous), what changes with dosage?
What about heterozygous?
Homo : 6-10% of regular dose
Hetero : normal dose but monitor closely
Role of ALDH2?
Produces Acetate from Acetaldehyde
Mutation in ALDH2? What does this cause?
ALDH2*2
Accumulation of acetaldehyde, less clearance from liver
Acetaldehyde is a known _________
carcinogen
Drug that acts on ALDH2? What does it do?
Disulfiram
Blocks ALDH2 and is used for alcohol dependence
Main drug metabolizing enzyme?
CYP450
4 consequences to having no CYP2D6 enzymes? (PMs)
- Slow drug metabolism
- High drug levels
- High risk for adverse drug effects
- No response to certain prodrugs
2 consequences to having CYP2D6 duplicates?
- Too rapid metabolism
2. No drug response at ordinary dose
Example of drug that is metabolized by CYP2D6?What is i?
Nortriptyline
Antidepressant
Does nortriptyline have a low or high therapeutic index?
Narrow
If nortriptyline is metabolized by a CYP2D6 POOR drug metabolizer : what is the effect?
What about an ultra drug metabolizer?
Poor : toxic doses of the drug
Ultra : inactivation of drug rapidly, becomes ineffective
If a patient carries ultra drug metabolizer alleles of CYP2D6, should the dosage of a drug increase or decrease?
Increase
which drug is used for breast cancer?
Tamoxifen
Tamoxifen is metabolized by _______ to which metabolites?
CYP2D6
4-hydroxytamoxifen and endoxifen
Which drug is used to treat blood clots?
Plavix
Which enzyme metabolizes plavix into it’s active form?
CYP2C19
How does Plavix become inactive?
CYP2C19 alleles resulting in poor metabolizers
Inactive plavix results to clots leading to __________
MI
Drug used for anti-coagulation?
Narrow or large TI?
Warfarin
Narrow
What metabolizes warfarin? what are it’s alleles?
CYP2C9
CYP2C91
CYP2C92
CYP2C9*3
What is the target of warfarin? How many polymorphisms does it have and how does this affect dosage of warfarin?
VKORC1
2 major polymorphisms
Lower expression so less warfarin dosing required
Pharmacogenetics gives us the knowledge of what?
direct link between _____ and ______
requires small or large sample sizes?
Target genes ahead of time
SNP and phenotype
Small
Pharmacogenomics has what target?
Does identified SNP have a direct link to phenotype?
Requires small or large sample sizes?
No target known
Maybe
Large
3 types of point mutations?
Silent
Nonsense
Missense
Steps to detecting SNPs? (5)
- Isolate DNA
- Digest DNA
- Label DNA with fluorescence probe
- Hybridize onto matrix containing an array of oligonucleotides (known SNPs)
- Detect signal for each SNP spot on the array
Graph that detects SNPs associated with disease?
GWAS Manhattan plot
Which drugs treats hepatitis C?
Interferon
Hepatitis C is the leading cause of what?
liver cirrhosis
The GWAS plot revealed what region to correlate with response to interferon?
Region on chromosome 19
Which genotype is more likely to clear hepatitis C infection?
Which ancestry is more likely to have C/C? Lowest?
C/C
Highest : East Asian
Lowest : African