1. University of North Carolina
Drug Induced Liver Injury: Implications in drug discovery and development
Paul B. Watkins
University of North Carolina
Chapel Hill, N.C.

2. Why clinical drug development programs were terminated in 1991
% of total terminations
Nature Reviews: Drug Discovery, Aug, 2004

3. Why clinical drug development programs were terminated in 2000
% of total terminations
1991
2000
Nature Reviews: Drug Discovery, Aug, 2004

4. Industry SAE Priorities 2006 Rank Order [1 highest to 5 lowest]
Overall Priority
Variance
Your Company's Priority
Hepatotoxicity
1.1
low
1.2
QT Prolongation
2.6
moderate
2.5
high
Rhabdomyolosis
3.3
3.5
mod
Serious Skin Rashes [SJS]
3.4
Edema
4.4
4.5
SAE Consortium Survey – courtesy of Arthur Holden

5. Drug Induced Liver Injury (DILI) is Hot
FDA / Pharma steering committee
Several Critical Path Initiatives
$ millions spend in industry
New Network (DILIN)
SAE Consortium

6. Regulatory actions due to DILI (1995-2007)
Withdrawals
bromfenac
troglitazone
pemoline
Second Line
felbamate
tolcapone
trovafloxacin
Warnings
acetaminophen
leflunomide
nefazodone
nevirapine
pyrazinamide/rifampin
terbinafine
valproic acid
zifirlukast
atomoxetine
interferon 1b –1b and 1a
saquinavir
infliximab
bosentan
telithromycin
(kava, lipokinex)

7. “Hepatotoxicity has been the most common single adverse effect causing major drug problems, including withdrawals and refusals to approve”
Bob Temple, M.D.
FDA
2/15/01

8. New Hepatotox Initiatives
Liver Toxicity Biomarker Study – BG Medicine
Biomarker Consortium – Hepatoxicity group
The SAE consortium

9. Safe pathways
Drug
elimination
Reactive
Metabolite
Necrosis
Serum ALT

10. 2007 State of the Art How to avoid hepatotoxicity in drug development
1). Avoid certain molecular structures

11. Compound Pair Ibuprofen Ibufenac “Clean” Compound “Toxic” Compound*
*withdrawn from the market in the 1960’s because of clinical liver toxicity

12. 2007 State of the Art How to avoid hepatotoxicity in drug development
1). Avoid certain molecular structures
2). Target daily dose to < 10 mg/day

13. 2007 State of the Art How to avoid hepatotoxicity in drug development
1). Avoid certain molecular structures
2). Target daily dose to < 10 mg/day
3). Low covalent binding in liver microsomes
4). Low production of glutathione conjugates

14. 2007 State of the Art How to avoid hepatotoxicity in drug development
1). Avoid certain molecular structures
2). Target daily dose to < 10 mg/day
3). Low covalent binding in liver microsomes
4). Low production of glutathione conjugates
5). Wide exposure margin in preclinical species.

15. 2007 State of the Art How to avoid hepatotoxicity in drug development
1). Avoid certain molecular structures
2). Target daily dose to < 10 mg/day
3). Low covalent binding in liver microsomes
4). Low production of glutathione conjugates
5). Wide exposure margin in preclinical species.
6). Low incidence (<5%) of ALT > 3 X ULN in clinical trials.

16. Acetaminophen fails every criteria
1). Avoid certain molecular structures - No
2). Target daily dose to < 10 mg/day – 4 Gm/day
3). Low covalent binding in liver microsomes - No
4). Low production of glutathione conjugates - No
5). Wide exposure margin in preclinical species – No
6). Low incidence (<5%) of ALT > 3 X ULN in clinical trials. No

18. JAMA, 392:87,2006

19. Tylenol kills pain, may hurt liver, is harmless to oxen
Written by Frank Cotolo
                                                                   
Bad cells in the liver
attacking good cells.
Dr. Paul "Bennies" Watkins … lead author of the study, said … "This Tylenol thing is nothing new. The liver is an important organ. That, also, is nothing new. The liver is a strong organ. That is nothing new. Tylenol is not strong enough to destroy a liver. That is debatable. Debates do not prove anything. That is nothing new. Debates about drugs and studies about drugs cost money because none of us researchers like to work for nothing. That is nothing new.

20. Drug Induced Liver Injury (DILI)
1). Thorn in the side of drug development.
2). High priority to design out of drugs.
3). Little progress made to date.

21. Why is human hepatotoxicity so difficult to predict from preclinical studies?

22. A potential mechanism of DILI not related to reactive metabolite
Bile
canaliculus
BSEP
Bile acids
Hepatocyte
Hepatocyte

23. Drug Induced Liver Injury (DILI) can mimic every known liver disease
Cholestasis (&vanishing bile duct syndrome)
Steatosis (micro and macrovesicular)
Phospholipidosis
Veno-occlusive disease
Occult fibrosis/ cirrhosis
Liver cancer
Acute hepatocellular injury – High ALT/AST

24. Regulatory actions due to DILI (1995-2007)
Withdrawals
bromfenac
troglitazone
pemoline
Second Line
felbamate
tolcapone
trovafloxacin
Warnings
acetaminophen
leflunomide
nefazodone
nevirapine
pyrazinamide/rifampin
terbinafine
valproic acid
zifirlukast
atomoxetine
interferon 1b –1b and 1a
saquinavir
infliximab
bosentan
telithromycin
(kava, lipokinex)

25. Of the 23 drugs/CAM that have undergone withdrawal, restriction or warnings
19/23 (82%) were associated with acute idiosyncratic hepatocellular injury

26. “idiosyncracy” (Hippocrates, ~400 B.C.) John Senior - FDA
(idios) - one’s own, self
(syn) - together
(crasis) - a mixing, mixture
therefore
a person’s own mixture of characteristics, factors, nature and nurture, uniquely
John Senior - FDA

27. SAFE Liver injury ( ALT) safe Concept of idiosyncratic
hepatocellular injury

28. death jaundice enceph Days on drug
1). Orient to axis – note log scale – credit John Senior
2). Normal values until 3 months, then AST/ALT, next symptoms, then jaundice, then death
3). Fall in AST/ALT due to loss of liver not improvement – drug stopped too late.
4). Pattern more or less consistent across drugs, but signature features exist.
5). Rare to see this in a clinical trial

29. Challenges in identifying factors underlying susceptibility to DILI
1). How to identify susceptible individuals.
2). What to do with them once you have them.

30. Selection of patients based on serial ALT values in a clinical trial
C.V.
Non-susceptible
susceptible
ULN

31. A genetic test that predicts ALT elevations:
1). Would obviate need for ALT monitoring.
2). Would be useful in developing next in
class drugs.
3). May provide only limited insight into
mechanisms of idiosyncratic severe DILI.

32. Problem with ALT elevation as the endpoint
1). Occurs with drugs that do not have clinically important liver toxicity
2). Usually reverse with continued
treatment even with drugs that can
cause acute liver failure.

33. Incidence of ALT elevations (>3X ULN) and clinical hepatitis
troglitazone 2% <0.1
INH 15% <1%
diclofenac 3% <0.01%

34. Treatment with tacrine through ALT elevations
unpublished

35. Reversed on treatment Treatment stopped
unpublished

36. Reversal of rat liver necrosis with continued exposure to BDCM
1 week
3 weeks
Toxicol. Sci. 64:268 (2001)

37. Possible explanations for reversibility of ALT elevations
1). ALT elevations that reverse on treatment have no relationship to those that can progress to liver failure.
2). A subset of those with ALT elevations
can progress on to liver failure (i.e. those
who can not adapt).

38. X Adaptation Reactive Metabolite Safe pathways Drug elimination
Progressive injury X
ALT elevations
Adaptation

39. SAFE liver failure Increased ALT safe
jaundice
SAFE
liver failure
Increased ALT
safe
Concept of idiosyncratic hepatocellular injury

40. NAPQI safe elimination APAP Covalent binding/oxidative stress
resolution
progression

41. Effect of 8 days APAP pretreatment (---)
on single dose toxicity in mice
Hepatology 29:436, 1999.

42. 3-Cys-APAP adducts (brown) 2 hours after single toxic APAP dose
Saline pretreatment
APAP pretreatment

43. Changes in APAP metabolism
that reduce toxicity
APAP
elimination
ROS (Nrf-2)
Regeneration
CYP2E1
CYP1A2
CYP2B
GST
GSH
Acute phase (IL-6)
NAPQI

44. Transporters during recovery from APAP hepatotoxicity
TNFa X X

45. Transporters during recovery from APAP hepatotoxicity

46. Ntcp and Mrp4 expression 48 hours after APAP
Alkunes and Manatou, unpublished observations

47. MDR1 (P-glycoprotein) expression In submassive necrosis (human)
Normal liver
necrosis
J Pathol 200:553, 2003

48. submassive necrosis (human)
MRP3
MRP3 expression in
submassive necrosis (human)
Normal liver
necrosis
J Pathol 200:553, 2003

49. Conclusion Adaptation to liver toxicity can involve:
a). Down regulation of CYPs and
uptake transporters
b). Upregulation of glutathione and
efflux transporters

50. Serial ALT in healthy woman receiving APAP 1 g qid X 7 days
Unpublished data

51. NAPQI safe elimination APAP Covalent binding/oxidative stress
resolution
progression
innate immune
system

52. Balance Between Pro and Anti-inflammatory Cytokines
Kaplowitz, 2005, Nature Review Drug Discovery

53. Balance Between Pro and Anti-inflammatory Cytokines
Kaplowitz, 2005, Nature Review Drug Discovery

54. Conclusions
Adaptation is probably most important issue in idiosyncrasy.
a). Determines whether patient gets sick
b). Implications for monitoring
b). Susceptibilities may not be drug specific
Current concepts do not account for the “memory”.

55. Where do we go from here?
The most appropriate model for studying idiosyncratic hepatotoxicity are the people who actually experienced severe toxicity (i.e. they lacked the ability to adapt to the toxicity).

56. Selection of cases and controls from
serial ALT values in a clinical trial
C.V.
Non-susceptible
susceptible
ULN

57. A cooperative agreement funded by the
Division of Digestive Diseases and Nutrition,
National Institute of Diabetes and Digestive and Kidney Diseases

58. Sphere of Influence
12.8 million lives

59. Resources Created by DILIN
1). Genomic DNA bank.
2). Immortalized lymphocyte bank.
3). Registry of subjects.

60. Final take home points
1). The DILIN network represents the best opportunity to date to identify mechanisms underlying severe idiosyncratic DILI.
2). Research utilizing the resulting resources will be challenging.

61. Idiosyncratic hepatocellular injury
due to drugs is a model for all environmental disease
1). Large population with known “exposure” to a defined xenobiotic (the drug).
2). Biomarkers that are cheap, safe, and sensitive.