Clinical relivance of pk interaction with anti epleptic drugs
Williams Oncology Study Fin
1. Mechanisms
of
unpredictable toxicities
Dominic Williams
MRC Centre for Drug Safety Science
The University of Liverpool
dom@liv.ac.uk
2. Overview
MRC CDSS strategy for adverse drug reaction (ADR) research
Classification of ADRs
Role of drug metabolism
Focus on Drug-Induced Liver Injury (DILI)
Mechanisms
Polymorphisms in drug metabolising enzymes
Pharmacogenetics in the treatment of cancer
Neoadjuvant chemotherapy & DILI
3. Centre Strategy for Investigating ADRs
DRUG
Define
structural Characterize
Investigation basis of ADR Investigation
of the liability of the
chemical “Closing the loop” patient
on adverse drug
reactions
Identify Characterize
causal patient
biochemical phenotype/
variable genotype
4. Integrated Mechanistic Drug Safety: Patient
SAR
Drug
SMR
Class
STR
Animal
Chemistry
Clinical Research Man
Bioanalysis
Mechanism Outcomes
Problem Question
Biomarkers
In vitro
Clinical
Samples
5. Integrated Mechanistic Drug Safety: Chemical
SAR
SMR
STR
In vitro
Drug / Chemical Man Chemical Biological
Bioanalysis
Compound Studies Validation Validation
Animal
Clinical
Validation
&
Application
6. Lessons for the future
Inform mechanism and pathogenesis
Inform the Medicinal Chemist
Inform the Clinician
Inform the Regulator
Inform the Public – what is feasible
Develop biomarkers for integrated
patient, in vitro & animal studies
7. Classification of Adverse Drug Reactions
ON TARGET
• Predictable from the known primary or secondary
pharmacology of the drug
• Exaggeration of the pharmacological effect of the drug
• Clear dose-dependent relationship
OFF TARGET
• These are not predictable from a knowledge of the basic
pharmacology of the drug
• Exhibit marked inter-individual susceptibility (idiosyncratic)
• Complex dose dependence
8. Drug Metabolism: Pharmacology
Cellular
DRUG RESPONSE
accumulation
Concentration
in
Phase I/II Plasma
Drug
Stable
Disposition
metabolites
Metabolism
Absorption
Excretion Drug plasma level
Excretion Pharmacological exposure
9. Drug Metabolism: Toxicology
Cellular
DRUG RESPONSE
accumulation
Concentrations
in
organs
Phase I/II
Drug
Stable
Disposition
metabolites
Metabolism
Absorption
Excretion Drug & metabolites
Excretion Pharmacological &
Toxicological exposure
15. Hepatotoxic drugs in man:
Withdrawn or with warning label
Drugs with black warnings for hepatotoxicity*
Drugs withdrawn for hepatotoxicity
drug dose (mg/day) reactive products
drug date dose reactive
acitretin 25-50 no (mg/day) products
bosentan 125-250 no cincopher 1930 300 no
dacarbazine 140-315 yes iproniazid 1959 25-150 yes
dantrolene 300-400 yes pipamazinc 1969 15 no
felbamate 1200 yes fenclozic acid 1970 300 yes
flutamide 750 yes oxyphenisatin 1973 50 no
2011; 10: 1-15
gemtuzumab 9 mg.m-3 yes (?) nialamide 1974 200 yes
isoniazid 300 yes tienilic acid 1980 250-500 yes
ketoconazole 200 yes benoxaprofen 1982 300-600 yes
naltrexone 50 no nomifensine 1986 125 yes
nevirapine 200 yes chlomezanone 1996 600 no
tolcapone 300 yes bromfenac 1998 25-50 yes
trovafloxacin 100-500 no troglitazone 2000 400 yes
valproic acid 1000-2400 Yes (10/14 = 71%) nefazodone 2004 200 yes
*Definition: a black box warning is the strongest type of warning that the pemoline 2005 38-110 no
FDA can require for a drug and is generally reserved for warning
prescribers about adverse drug reactions that can cause serious injury or
death. An issue here is the benefit/risk ratio.
16. Focus on Drug-Induced Liver Injury
SM
EC
CLEARANCE
phospholipidosis
DRUG bioaccumulation mitochondria microvesicular steatosis
METABOLITE organelle impairment lysosome hepatocyte apoptosis
REACTIVE METABOLITE hepatocyte necrosis
inhibition of biliary efflux
CLEARANCE
hypersensitivity
Intrahepatic
cholestasis
immunoallergic toxicity
17. DILI – a consequence of multiple steps
Drug
Patient-specificfactors
Drug-specific factors
1.
2. 3. Biological response in 4. Biological response in
Chemical Insult in liver
Drug absorption & disposition target cell tissue
e.g. reactive metabolite-
e.g. hepatic uptake e.g. cell toxicity, stress e.g. cytokine release,
mediated
response immune cell response
Screening opportunity
Outcome:
pre-clinical species vs man
Amplification
vs Innate & adaptive
Protection immunity
e.g. stress response
Tolerance & adaptation
Toxicity
18. Clinicopathological presentation of DILI
CLEARANCE
Acute fatty liver with lactic acidosis
Acute hepatic necrosis
DRUG
Acute liver failure
Acute viral hepatitis-like liver injury
Autoimmune-like hepatitis
DRUG Bland cholestasis
+ Cholestatic hepatitis
METABOLITE Cirrhosis
Immuno-allergic hepatitis
Nodular regeneration
Nonalcoholic fatty liver
Sinusoidal obstruction syndrome
Vanishing bile duct syndrome
Multi-cellular and multifunctional organ
Multiple and variable forms of disease
Multi step pathologies
Tujios and Fontana Nature 2011
19. Hepatotoxin Accumulation
Mit DNA Energy Depletion
Fialuridine
OXPHOS ROS Generation
Fatty acid synthesis Apoptosis
HepatocellularTargets Toxic Consequences hENT1 Steatosis
Toxicity Mechanisms
Inhibits DNA polymerase-γ of Reactive
Independent
Oxidative Stress
Transporters Metabolites
Protein Oxidation Decreases MtDNA Perhexiline
Apoptosis Fialuridine
Necrosis Disrupts electron transportAplovirac
chain
Tacrine
Mitochondria Steatosis
ROS generation Valproic Acid
Amiodarone
Troglitazone
Mitochondrial Dysfunction/Cell Death
Accumulation Ritonavir
• Physicochemical Rifampin
• Biochemical NRTIs eg Stavudine
• Transport
20. Hepatotoxin Accumulation
Mit DNA Energy Depletion
Fialuridine
OXPHOS ROS Generation
Fatty acid synthesis Apoptosis
HepatocellularTargets Toxic Consequences Steatosis
Toxicity Mechanisms
Independent of Reactive
Oxidative Stress
Transporters Metabolites
Protein Oxidation Perhexiline
Apoptosis Fialuridine
Necrosis Aplovirac
Tacrine
Mitochondria Steatosis
Valproic Acid
Amiodarone
Troglitazone
Accumulation Ritonavir
• Physicochemical Rifampin
• Biochemical NRTIs eg Stavudine
• Transport McKenzie et al, 1995
Lai et al, 2004
21. Mechanisms of Drug Induced Liver Injury
Hepatic Injury Biological stratification
Drug
• accumulation • Plasma / liver level
• bioactivation • GSH/mercapturate
• covalent binding • Protein binding
• chemical stress • chemical stress
DRUG
METABOLITE • mitochondrial dysfunction • glutamate dehydrogenase
REACTIVE METABOLITE • apoptosis • cytochrome C
• hepatocyte hypertrophy
• hepatocyte hyperplasia • ALT, AST, SDH, LDH, GST
• hepatocyte integrity • ALP, GT, 5’nucleotidase
• hepatobiliary integrity Biology • Bilirubin, bile acids,
• innate immune activation
• hepatic function • prothrombin, metabolism /
• fibrosis secretion
22. Variation in Drug Metabolism - Toxicity
Cellular
DRUG accumulation
Toxicity
VariationH
N
Phase I/II/III In
drug metabolism
Stable Perhexiline &
metabolites Genetic Variation
In
genetics
Cytochrome P450
enzyme induction
enzyme inhibition
Excretion disease
Shah et al 1982; Davies et al 2007
23. Perhexiline Maleate and CYP2D6
H
Indications - prevention of angina pectoris N
- prevention of ventricular systoles
Toxicity - peripheral neuropathy
- hepatotoxicity
HO
H
N
Pharmacokinetics:
T1/2 Metabolic ratio (%D/%M)
- ADR patients 2-6 0.3 ± 0.4
+ ADR patients 9-22 2.82 ± 0.4
- related to CYP2D6 phenotype
(Singlas et al, 1978; Shah et al, 1982; Cooper et al, 1984)
24. Lipidosis Induced by Amphiphilic Cationic Drugs
N
H PHOSPHOLIPIDS
PHOSPHOLIPIDS
N
N N H
H H
Extracellular Cytosol
pH 7.4 pH 7.2 Lysosome
pH 4.5
25. Prediction of Variation in Drug Metabolism
• Human liver banks
• Expression systems
• Cell lines
• In silico techniques / models
• Transgenic animals
• Volunteer & Patient studies
• Genotype
• Phenotype
Transfer of knowledge
Development of
to clinical practice
pre-clinical screens
26. Drug Safety Science and DILI
CLEARANCE
20 / safety pharmacology targets
1st effects 2nd effects 3rd effects
Ca2+
Occurrence,DRUG
Frequency
= f1 + f2
DRUG Chemistry Biology of
& Severity of
+ DNA
of drug individual
Drug Hepatotoxicity
METABOLITE
phospholipid
specific
TARGET proteins
BIOMARKERS
PHARMACOLOGICAL ADVERSE
EFFECT EFFECT
Dose
CHEMICAL STRUCTURE
f (chemistry) f (biology)
SPECIES and INDIVIDUAL VARIATION
27. Drug Safety Science and DILI
Occurrence, Frequency
& Severity of
Drug Hepatotoxicity
= f1 Chemistry
of drug + f2 Biology of
individual
N
H
Amphiphilic 2D6 genotype /
Cation phenotype
Rationale for
Safe clinical use
28. Genetic Polymorphisms known to affect
response to anti-cancer drugs
Relling & Dervieux, 2001; Nature Reviews Cancer
29. Pharmacogenetics in the Treatment of Cancer
thiopurine methyl transferase
6-mercaptopurine TPMT
inactive metabolites
Azathioprine
Active Incorporation into DNA
thioguanine Anti-leukemic effect
nucleotides Myelosuppression
1 in 300 have TPMT deficiency
Several polymorphisms including G238C, G460A and A719G
TPMT deficiency predicts severe neutropenia following
treatment with 6-mercaptopurine or azathioprine
Krynetski & Evans, 1998
30. Thiopurine Methyl Transferase (TPMT)
and Treatment of Childhood Leukaemia
Myelotoxicity
↑ Risk of 2o cancer
Narrow therapeutic index Therapy
↓ toxicity
1:300 have TPMT deficiency
Risk of relapse
0.3% mut/mut
10% wt/mut
90% wt/wt
Associated with severe Dose adjustment
haemopoietic toxicity
6-Mercaptopurine dosage
500
(mg/m2/week)
REDUCTION OF DOSE TO 10% CAN
LEAD TO SUCCESSFUL TREATMENT 25 0
WITHOUT TOXICITY
25
m /m w t/m w t/w t
Krynetski & Evans, 1998
31. Neoadjuvant chemotherapy improves
progression free survival
Neoadjuvant chemotherapy in
colorectal liver metastases:
5-fluorouracil
Leucovorin
Oxaliplatin
} FOLFOX
5-fluorouracil
Leucovorin
Irinotecan
} FOLFIRI
EORT study: 9.2% improvement
3 year disease-free survival (FOLFOX)
Pre-operative chemotherapy can cause problems
Nordlinger, Lancet 2008
32. Irinotecan Metabolism & Toxicity
Irinotecan (Campostar®) is a topoisomerase-I inhibitor pro-drug widely used for
treatment of metastatic and recurrent colorectal cancer
The most common dose-limiting adverse effects of irinotecan are neutropenia &
diarrhoea
UGT normally conjugates to & increases hydrophilicity of bilirubin, drugs &
xenobiotics
Variations in uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene may
help predict which patients develop adverse effects
Frequency of the inactive allele varies:
African (43%), European (39%) Asian(16%)
33. Irinotecan Metabolism
N
CH2CH3
N O O
Irinotecan N
Cyp 3A4/5 Oxidised
O
N Irinotecan
O
Carboxyl H3CH2C
OH O
esterase
CH2CH3
HO O
SN38
N
(active) N
Anti-tumour
O activity
H3CH2C
OH O
UGT 1A1 / 7 / 9
CH2CH3
GLUCURONIDE O O
N
N
O
Intestinal SN38
H3CH2C SN38-G -glucuronidase
SN38-G OH O (active)
34. Irinotecan Metabolism & Toxicity
CH2CH3
X
HO O
N
CH2CH3
N UGT 1A1 / 7 / 9
O GLUCURONIDE O O
H3CH2C N
SN38 OH O Intestinal -glucuronidase N
O
H3CH2C
OH O
Detoxification
Intestine Diarrhoea
Bone Marrow Leukopenia
Thrombocytopenia
Adverse Reaction Anaemia
Other metabolic determinants:
Carboxylesterase activity
CYP 3A4 inhibition
Gut transporters
Enzyme activity in tumour
35. Systemic chemotherapy causes hepatotoxicity
Normal Steatohepatitis (Irinotecan)
• 19-79% incidence of sinusiodal injury with oxaliplatin
vs 5FU alone
• steatosis 30-47% patients treated with 5FU
• Irinotecan ~20% incidence of steatohepatitis vs 4.4%
• ~15% increase in 90 day mortality with SOS (Oxaliplatin)
steatohepatitis
36. Chemotherapy-induced liver damage
Oxaliplatin Irinotecan
Sinusoidal obstruction syndrome causes Steatohepatitis causes an increase in 90
increased operative bleeding but no day operative mortality
increase in operative mortality
‘Blue’ liver ‘Yellow’ liver
37. Systemic chemotherapy causes hepatotoxicity
Steatohepatitis (Irinotecan)
Steatosis
• Impaired hepatic defence
• Enhanced oxidative stress
• BMI is an independent risk factor in steatohepatitis
38. Systemic chemotherapy causes hepatotoxicity
SOS (Oxaliplatin) • Drug kills endothelial cells
• Leads to sinusoidal disruption
• Activation of hepatic stellate cells
• Matrix deposition
• Sloughing of erythrocytes & blebbing
of cytoplasmic processes
39. Conclusions
Understanding the complex mechanisms of DILI requires an integrated bioanalytical
approach – DMPK, genomics, metabolomics & proteomics
Understanding mechanisms of DILI will assist with
Identifying biochemical risk factors
Developing biomarkers of efficacy & toxicity
Using potentially toxic drugs more safely
Off-target idiosyncratic drug toxicity cannot be predicted from the chemistry of the
drug and/or its metabolite because such reactions are by definition (largely) a function
of the biology of the individual.
Occurrence, Frequency
& Severity of
Drug Hepatotoxicity
= f1 Chemistry
of drug + f2 Biology of
individual
Different chemical classesAnd different therapeutic areas
Major consequence of bioactivation is in fact bioinactivation
Mjajorr consequence of bioactivation is in fact bioinactivation
Most common consequence of bioactivation is in fact bioinactivation
The physiological role of the liver is hepatic clearance.Interference with this process, can itself be a cause of DILIDawson et al quantified the inhibition of BSEP ABCB 11 by 85 pharmaceuticals using taurochalate uptake in inverted plasma membrane vesicles from Sf 21 cells which express these proteins.Overall they found that inhibition of both human BSEP and the rat ortholog (rBsep) correlates with the propensitiyOf numerous pharmaceuticals to cause to cause cholestatic DILI
What are we trying to predict?
We believe that neoadjuvant chemotherapy is beneficial for patients undergoing resection of colorectal liver metastases. These data are from the EORTC study, where 364 patients with resectable colorectal hepatic metastases were randomized to six cycles of neoadjuvant FOLFOX, followed by surgery and six further cycles of chemotherapy, or surgery alone. Those who received perioperative chemotherapy and were resected had a 9.2% improvement in 3-year disease-free survival.
However, there is growing recognition that preoperative systemic chemotherapy can adversely affect normal hepatic parenchyma. Patients who receive systemic oxaliplatin are more likely to develop sinusoidal obstructive syndrome, whilst those treated with Irinotecan are more likely to developed steatosis and steatohepatitis. Sinusoidal obstructive syndrome is associated with increased intraoperative bleeding, but no increase in morbidity and mortality. Steatohepatitis is associated with increased post-operative morbidty, and Vauthey at el demonstrated a strong correlation between steatohepatitis and 90-day mortality after resection.