March 20, 2017 | Author: Iqha HoNeysweet | Category: N/A
Molecular Toxicology: Roles in Drug Disposition and Drug Safety August 8 and 9, 2009, Yogyakarta
Prof. Dr. Nico P.E. Vermeulen and Dr. Jan N.M. Commandeur npe.
[email protected] [email protected] and
[email protected] www. nl/far/ www.chem.vu. chem.vu.nl/far/
Molecular Toxicology: Roles in Drug Disposition and Drug Safety Projected Time Schedule: Course part I, Introduction, Course part II, ADME-PK, Course part III, ADME-Met,
Friday August 8th, 9.00 - 11.00 hrs Friday August 8th, 11.00 - 15.00 hrs Friday August 8th, 15.00 - 17.00 hrs Saturday August 9th, 9.00 - 10.00 hrs Course part IV, ADME-Tox, Saturday August 9th, 10.00 - 14.00 hrs Course part V, Case and Discussion, Saturday August 9th, 14.00 - 15.30 hrs
Objectives: 1) 2) 3)
To obain knowledge of the molecular aspects of ADME To learn about the roles of ADME in PK To learn about the roles of ADME in Tox
LACDR-Division of Molecular Toxicology
Research theme: Key feature: dr. Jan Commandeur dr. Chris Oostenbrink dr. Chris Vos prof.dr. Peter Grootenhuis
Drug disposition and safety: From molecular structures to molecular mechanisms and effects integration of experimental and computational approaches (experimental; molecular toxicology) (computational; chem-/bioinformatics > November 2004) (experimental; molecular biology, > July 2006) (extraord. chair: computational ADME, > June 2005) ADMET (npev & jnmc) 3
Pharmaco-/Toxicokinetics and ADME-Tox Adverse side effects
Absorption Distribution
Cmax
Therapeutic window Minimal effective concentration
Metabolism Excretion
AUC
Half life duration
Toxicology
ADMET (npev & jnmc)
• bioavailability • efficacy • duration of action • frequency of dosing • safety (~ Cmax) 4
Biologically available
Orally
Uptake Urine
ADMET (npev & jnmc)
Faeces
5 Excretion
Reasons why 80-90% of candidate drugs fail in the ‘clinical development’ phase
ADMET (npev & jnmc)
6
“Pharmacokinetic defects of drugs” • Low bioavailability:
limited human intestinal absorption (HIA) first-pass metabolism
• Too fast or too slow systemic elimination • Compound does not reach site of action (e.g. blood-brain barrier) • High plasma binding • Enzyme induction
Drug-drug interactions (DDI)
• Enzyme inhibitor • Pharmacokinetics dose-dependent ‘non-linear / saturation pharmacokinetics’ • Large inter-individual difference in pharmacokinetics
ADME
Volume of distribution Blood brain barrier Transporters Plasma Protein binding
ADME
ADME
Hepatic excretion to bile metabolism Renal excretion to urine metabolism Plasma
Intestinal metabolism efflux Hepatic metabolism excretion to bile
ADMET (npev & jnmc)
ADME
Physicochemical Properties MW pKa Log P Solubility Dissolution Etc.
8
Drug-drug interactions (DDI)
ADMET (npev & jnmc)
9
LARGE INTERINDIVIDUAL DIFFERENCES IN PHARMACOKINETICS tolterodine
PM’s
EM’s
16 Patients; each given a single dose of 4 mg tolterodine Brynne et al. Clin.Phar.Ther 63, 529 (1998)
Linear pharmacokinetics
Non-linear pharmacokinetics
‘Steady-state’ : Uptake (mg/hr) = Elimination (CL*Cpl)
ADMET (npev & jnmc)
11
Reasons why 80-90% of candidate drugs fail in the ‘clinical development’ phase
ADMET (npev & jnmc)
12
JAMA 279, 1200 (1998)
ADMET (npev & jnmc)
13
ADMET (npev & jnmc)
15
CLASSIFICATION ADVERSE DRUG REACTIONS
Type A Pharmacological activity A1: intrinsic to drug target A2: not related to drug target
Too high plasmaconcentration of parent compound Or: ACTIVE METABOLITES
Type B Idiosyncratic drug reactions rare, unpredictable
Type C Predictable toxicity compounds containing ‘toxicophores’ Type D Delayed toxicity (carcinogen, teratogen)
REACTIVE METABOLITES (often INTERMEDIATES)
IDIOSYNCRATIC DRUG REACTIONS • low incidence: 1 : 1.000 to 100.000 • escapes discovery in clinical trial, so unpredictable • delayed onset (14 days to months after onset of therapy) • often fatal • most frequent target organs: blood (agranulocytosis, aplastic anemia) liver (fulminant hepatitis) skin (lupus) • toxicity mediated by (auto)immune response formation of reactive metabolite (ADME-Tox) (combination of) genetic factors (enzymes, MHC,..?) • no animal models available ADMET (npev & jnmc)
Drug Acetaminophen Aldipenem Amineptine Amodiaquine Bromfenac Carbamazepine Clozapine Cyproterone Diclofenac Dideoxinosine Dihydralazine Ebrotidine Enalapril Felbamate Flutamide Halothane Isoniazide Ketokonazole MDMA Methoxyflurane Minocycline Nefazodone Phenobarbital Phenprocoumon Phenytoin Procainamide Pyrazinamide Rifampicin Salicilate Sulfasalazine Tacrine Tienilic acid Troglitazone Valproate
Indication Daily dose Analgesic 500 mg Anxiolytic 225 mg Antidepressant 200 mg Malaria 200-1000 mg Analgesic 25-100 mg Anticonvulsant 200 mg Antidepressant 500-600 mg Androgen antagonist 50 mg NSAID 50 mg HIV 750 mg Hypertension 100-200 mg H2-antagonist 150-800 mg Hypertension 10-40 mg Antiepileptic 400-600 mg Nonsteroid antiandrogen 750 mg Anesthesia 0.5-3% Anticonvulsant 300 mg Antifungal 200 mg Euphoria 500 mg (est.) Anesthesia 0.5-3% Acne 200 mg Antidepressant 200 mg Anticonvulsant 60-200 mg Anticoagulant 1 -4 mg Antiepileptic 300 mg Antiarrhytmic 3500 mg Antibacterial 1500 mg Antimicrobial 600 mg Analgesic 3900 mg Crohn’s disease 50-250 mg Alzheimer 40 mg Diuretic 250 mg Diabetis 400 mg ADMET (npev & jnmc) Anticonvulsant 250 mg
17
Risk factor: Dose > 10 mg/day ?
N C
H2 N
CH3
O
N N Cl
N N H
COOH Cl
H N Cl O
CH3 H3 C
O
CH3
O
S NH O
HO CH3
18 Case-studies
Case(s): drugs causing idiosyncratic drug reactions
Aim of case-study/studies: Get familiar with various experimental approaches used in: ADME;
metabolite - identification active metabolite formation (iso)enzyme - identification
Safety/Tox:
interindividual variability enzyme inhibition/induction bioactivation to reactive intermediates drug-drug interactions drug toxicities
Emphasis on molecular aspects ADMET ADMET (npev & jnmc)
19
ADME-Tox: Drug metabolism studies AIMS: • assessment of enzyme kinetical parameters (Km, Vmax) of drug Prediction metabolic (in)stability (in)stability,, pharmacokinetics Low Km: saturable, saturable, enzyme inhibitor • identification enzymes determining pharmacokinetics of drug Genetically determined or inducible enzymes involved ? Prediction effect enzyme-inhibiting drugs (DDI) • inhibitory or inducing properties of the drug Prediction drug-drug interactions by drug (DDI) • identification metabolites Potential toxic metabolites ? Pharmacologically active metabolites ? Selection of animal model for toxicity studies
I.
II.
BIOTRANSFORMATION OF DRUG
IDENTIFICATION OF (ISO)ENZYMES RESPONSIBLE FOR PHARMACOKINETICS OF THE DRUG
compound
Fig # approach 1: effect of specific enzyme inhibitors on human enzyme fractions
major metabolites (vivo/slices/hepatocytes)
approach 2: correlation analysis with individual human enzyme fractions
enzyme-classes to be considered ? yes
no
cytochrome P450 (CYP) flavin-containing monooxygenase (FMO) epoxide hydrolase (mEH, sEH)
approach 3: recombinant human enzymes: KM , Vmax, Vmax/Km
UDP-glucuronosyltransferase (UGT) Sulfotransferase (ST) N-acetyltransferase (NAT)
approach 4: Effect of model inducers (cells, vivo)
Glutathione transferase (GST) Quinone reductase / DT diaphorase Catechol methyltransferase (COMT) Others
approach 5: Genotyped/phenotyped individuals / Knock-out animals
(vivo/vitro)
Enzyme kinetics of drug (human liver microsomes / cytosol) Michaelis-Menten kinetics ? yes
Km
Enzyme class
Vmax
Fig #
no
one-enzyme
Conclusion: two enzymes
non-Michaelis-Menten kinetics ? yes
Fig #
Enzyme class
no
substrate inhibition / negative cooperativity 1) what enzyme(s) are mainly responsible for pharmacokinetics in vivo ? 2) are genetically polymorphic enzymes involved and what may be consequence of deficiency.
autoactivation / positive cooperativity
III.
ABILITY TO CAUSE DRUG-DRUG INTERACTIONS Fig #
PHYSIOLOGICAL CONCENTRATION (PLASMA, LIVER)
IV.
PREDICTION OF SAFETY AND INTERINDIVIDUAL DIFFERENCES IN SUSCEPTIBILITY Fig #
TOXICITY IN IN VITRO MODELS ?
REVERSIBLE INHIBITOR OF ENZYME-SPECIFIC REACTIONS ? HIGH-AFFINITY SUBSTRATE FOR ENZYME ? WHICH (ISO)ENZYMES ?
COVALENT BINDING TO PROTEINS ? which enzyme ?
type inhibition; IC50; Ki ?
MECHANISM-BASED INHIBITOR OF ENZYME-SPECIFIC REACTIONS ?
WHICH (ISO)ENZYMES ?
which enzyme ?
Ki, ki, half-life ?
GLUTATHION (GSH)-CONJUGATES ? (vivo or vitro experiments) N-ACETYLCYSTEINE (NAC)-CONJUGATES ? METHYLTHIO-CONJUGATES ?
DOES THE COMPOUND CAUSES ENZYME INDUCTION ? (PRIMARY CULTURE, IN VIVO)
MECHANISM-BASED ENZYME INHIBITION ? what class of induction ?
DOES THE COMPOUND INHIBITS DRUG TRANSPORTERS ?
WHICH (ISO)ENZYMES ?
LIVER, BILE, KIDNEY, BRAINS, INTESTINES
BSEP, OAT, OCT, MDR, MRP
CONCLUSIONS
CONCLUSIONS
physiological relevance ?
1) is the drug bioactivated to toxic/reactive metabolites 2) are genetically polymorphic enzymes involved ? 3) what may be consequence of enzyme deficiency ?
PRESENTATION AND DISCUSSION OF CASE STUDY Groups of participants give summary/overview - of enzymes involved in the metabolism of the particular drug - factors which may have caused increased sensitivities of individuals - the best and the worst case scenario’s for individuals
Identify the (combination) of factors which may have determined the increased sensitivity of specific individuals for the idiosyncratic drug reactions. What would be the ‘worst case scenario’ ?
Make use of: - database provided - guidelines/forms provided Prepare a presentation of 15 minutes
Part II: (ADME-PK) Phamaco-/Toxicokinetics, incl Absorption, Distribution and Elimination
Molecular Toxicology: Roles in Drug Disposition and Drug Safety August 8 and 9, 2009, Yogyakarta Prof. Dr. Dr. Nico P.E. Vermeulen and Dr. Dr. Jan N.M. Commandeur
