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

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

Industry SAE Priorities 2006 Rank Order [1 highest to 5 lowest] Overall Priority Variance Your Company's Priority Variance Hepatotoxicity1.1low1.2low QT Prolongation2.6moderate2.5high Rhabdomyolosis3.3moderate3.5mod Serious Skin Rashes [SJS]3.5high3.4high Edema4.4high4.5high SAE Consortium Survey – courtesy of Arthur Holden

Troglitazone (Rezulin®) 1). PPAR  agonist 2). Treats type 2 diabetes 3). Caused liver failure

Presentation by Dr. Mark Pierce (Parke-Davis Pharmaceutical Research) March 26th Troglitazone - FDA Advisory Panel Overall Post-Marketing Reporting Death/Transplant Rate March March in 1.58 million = 1 in 45,098 Background incidence of liver failure with no known cause ~ 1 in 1 million

Troglitazone (Rezulin®) 1). Acute liver failure reports continued despite warnings and monitoring recommendations 2). Second in class (2) came on the market and appeared to be safer 3). Withdrawn from the market

Troglitazone (Rezulin®) The Rise and Fall of the Killer Drug Rezulin Los Angeles Times, June 4, 2000, p.1A. The Rise and Fall of the Killer Drug Rezulin Los Angeles Times, June 4, 2000, p.1A. “…a disparate collection of physicians inside the U.S. Food and Drug Administration waged a remarkable revolt that … combined meticulous research and bluntly worded messages to upbraid their government superiors for contributing to the needless deaths of patients.” for contributing to the needless deaths of patients.”

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

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

“Hepatotoxicity has been the most common single adverse effect causing major drug problems, including withdrawals and refusals to approve” Bob Temple, M.D. FDA2/15/01

2006 State of the Art How to avoid hepatotoxicity in drug development 1). Avoid certain molecular structures

Compound Pair Ibuprofen “Clean” Compound Ibufenac “Toxic” Compound* *withdrawn from the market in the 1960’s because of clinical liver toxicity

2006 State of the Art How to avoid hepatotoxicity in drug development 1). Avoid certain molecular structures 2). Target daily dose to < 10 mg/day

2006 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

2006 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). Low incidence ( 3 X ULN in clinical trials.

1). Avoid certain molecular structures - NO 2). Target daily dose to < 10 mg/day – 4 grams/day 3). Low covalent binding in liver microsomes – NO 4). Low production of glutathione conjugates – NO 5). Low incidence (<5%) of ALT - NO Example: Acetaminophen

JAMA, 392:87,2006

1). Avoid certain molecular structures - NO 2). Target daily dose to < 10 mg/day – 4 grams/day 3). Low covalent binding in liver microsomes – NO 4). Low production of glutathione conjugates – NO 5). Low incidence (<5%) of ALT - NO Example: Acetaminophen

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

Drug Induced Liver Injury (DILI) can mimick 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

Regulatory actions due to DILI ( ) Second Line felbamatetolcaponetrovafloxacinWithdrawalsbromfenactroglitazonepemoline Warningsacetaminophenleflunomidenefazodonenevirapinepyrazinamide/rifampinterbinafine valproic acid zifirlukastatomoxetine interferon 1  –1b and 1a saquinavirinfliximabbosentantelithromycin (kava, lipokinex)

Regulatory actions due to DILI ( ) Second Line felbamatetolcaponetrovafloxacinWithdrawalsbromfenactroglitazonepemoline Warningsacetaminophenleflunomidenefazodonenevirapinepyrazinamide/rifampinterbinafine valproic acid zifirlukastatomoxetine interferon 1  –1b and 1a saquinavirinfliximabbosentantelithromycin (kava, lipokinex)

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

“idiosyncracy” “idiosyncracy” (Hippocrates, ~400 B.C.) (idios) - one’s own, self (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

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

death jaundice enceph Days on drug

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

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

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

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.

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.

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

Treatment with tacrine through ALT elevations unpublished

unpublished Reversed on treatmentTreatment stopped

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

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).

Drugelimination ReactiveMetabolite ALT elevations Safe pathways Adaptation Progressive injury X

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

APAP safeelimination NAPQI Covalent binding/oxidative stress resolutionprogression

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

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

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

X Transporters during recovery from APAP hepatotoxicity X TNF 

Transporters during recovery from APAP hepatotoxicity

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

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

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

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

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

Conclusions It is adapation to toxicity.It is adapation to toxicity. Arguably the most important issue in idiosyncrasy.Arguably the 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”.Current concepts do not account for the “memory”.

Where do we go from here? The most appropriate model for studying idiosyncratic hepatotoxicity are the people who actually experienced this.

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

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

Sphere of Influence Sphere of Influence 12.8 million lives

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

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.

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.