This document discusses drug-induced liver injury (DILI), which has been a major cause of drug withdrawals. It notes that while severe DILI is rare in phase 3 trials, mild hepatotoxicity could indicate potential for more serious cases. Close examination of individual cases is essential to determine the cause of injury and rule out other potential causes. The document also summarizes factors like inter-individual variability in drug metabolism and susceptibility that make predicting DILI challenging. Key signals of potential DILI are discussed, along with challenges in interpretation given the low prevalence of severe cases.

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2. Background
• DILI has been the single most frequent cause of safety
related drug marketing withdrawals for more than 50
years.
• Hepatotoxicity discovered after approval for marketing
has also limited the usage of other drugs.
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3. C ontext
• Severe DILI in phase 3 trials is rare.
• An increased incidence of mild hepatotoxicity reflects:
A potential for A capacity for only
OR
severe DILI. limited injury.
• Essential to detect any cases of severe injury and examine
each case closely.
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4. D rug Induced Liver Injury
• Tolerators
Most people exposed to a new drug show no injury.
• Adaptors
Some people show transient injury, but adapt.
• Susceptibles
A few fail to adapt and show serious toxicity.
BAD SUSCEPTIBLE
DRUG PATIENT
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5. D rug Induced Liver Injury
molecular variation in drug class
differing potencies of variants
therapeutic index variations
variable PK ADME among patients
variable PD responses in patients
a single dosing schedule may not suit all
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6. D rug Induced Liver Injury
A drug tolerated by all but a very
few
cannot be considered toxic
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7. D ILI cont’d
• If you don’t look for it, you won’t find it.
• Is there Injury or is there disease?
• How is it?... serious?... progressive?
• Is it DILI or something else?
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8. O ther C auses
• Mainly acute hepatitis: viral A or B, seldom C.
• Alcoholic.
• Biliary stones.
• Ischaemia.
• Autoimmune.
• Other…
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9. Bad drug vs susceptible patient
• Humans are very different to animal models.
• Genetically diverse.
• Resistant to standardisation or pigeon-holing.
• Human’s take a LOT of drugs!
• Human’s have a LOT of diseases.
• The ones treated are not the same as the ones studied.
• They don’t always report outcomes promptly.
• “…. though they are made from the same materials, no two
are like…” Hippocrates 460-377 BC.
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10. Research Required
• Which cytochrome isoforms interact with which parts of
the molecules?
• What are the toxic metabolites?
• Are therapeutic and toxic parts of the molecule the same.
• Further rules predicting DILI.
• Humans and Animals.
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11. Mechanisms of D ILI
• Drugs cause liver injuries by numerous mechanisms.
Mimicking all known liver diseases.
• When DILI is suspected, gather information.
• In many cases, there is a delay between initiation of
treatment and onset of liver injury.
• In general, early trials should involve LFTs every 2-4
weeks for at least a few months.
• For shorter trials post-treatment LFTs should be
performed.
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12. Mechanisms cont’d
• For the most part, the first evidence of a problem is
discovery of elevated AT or ALP during routine
measurements.
• If there is no sign of liver injury after a reasonable period
of exposure, the monitoring interval can increase.
• However, if clinical symptoms of DILI are noted LFTs
should be performed immediately.
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13. C onfirmation
• An increase in AT of >3X ULN, repeat test within 48 to
72 hours for ALL LFTs. Assess symptoms.
• For distanced trials, local retesting may be necessary.
• If symptoms persist, or repeat testing shows AT of >3X
ULN.
• CLOSE OBSERVATION or DISCONTINUE DRUG
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14. Signals of D ILI; H y’s Law
• Hepatocellular injury can be caused by drugs that rarely
cause severe DILI (Aspirin, tacrine, statins, and heparin) as well
as those who do.
• Hepatocellular injury is a necessary but not sufficient
signal for DILI.
• The frequency of AT elevations also not useful.
• Very high levels of ATs may be a better indicator of the
potential for severe DILI
• The most specific indicator is evidence of altered liver
function.
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15. Signals
Injury
transaminases: ALT Hepatocellular
enzymes AST
akaline phosphatase Cholestatic
gamma-gutamyl transferase
Function
bilirubin (total, direct) excretory
markers albumin synthetic
prothrombin (INR) synthetic
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16. Interpretation of Signals
• The presence of just one case of severe liver injury in a
premarketing DB signals high hepatotoxic risk.
• There may no identifable cases, but varying degrees of
serum AT abnormalities requiring interpretation.
• Slight abnormalities (<3XULN) are common in untreated
and placebo-treated subjects, so not useful in assessing
DILI.
• Greater deviations are observed >3X or 5X or 10X
ULN.
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17. Interpretation cont’d
• A significantly increase incidence of AT abnormalities >3X
ULN is a signal of potential severe DILI.
• High sensitive but not specific.
• AT is not regulated by the liver. AT are found in skeletal
and heart muscle, gut, etc.
• For low prevalence/incidence events need extremely high
specificity to avoid “finding” many false positive.
• Almost impossible to find hyper-specific test. Compound
test may be more effective.
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18. Interpretation cont’d
Serum ALT DILI none Predictive
>3X ULN i u totals Power
Yes 95 999 1,094 8.7%
“positive”
No 5 98,901 98,906 99.995%
“negative”
Incidence 100 99,900 100,000
1 per 1000
sensitivity specificity accuracy
95% 99% 99%
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19. H y’s Law
• The causes hepatocellular injury, generally shown by a
higher incidence of 3-fold of greater elevations of ALT or
AST ULN than the control.
• Among trial subjects showing such AT elevations, one or
more also show elevation of TBIL to 2XULN, without
cholestatis.
• No other reason can be found to explain the combination
of increase AT and TBIL (such as viral hepatitis, pre-
existing acute liver disease.
Hy Zimmermann 1917-1999
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20. H y’s Law
If both hepatocellular injury and jaundice occur, expect at
least 10% mortality rate!
Hy Zimmermann 1917-1999
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21. C ombined Elevations
• Experience shows that occurrence of even one or two
well documented cases in ominous.
• Absence of Hy’s Law cases allows the Rule of 3 binominal
assessment of the rate of severe DILI
• Eg. no case in 3,000, 95% confidence that true rate
≤ 1 in 1,000. Hy’s Law assumes 10%. So, suspected severe
injury rate is therefore ≤ 1 in 10,000 ?!? sorry!
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22. N ew D rug Submission
(FDA experience)
• Incidence of pooled data should include:
– 3X, 5X, 10X, and 20X ULN elevations of AST, ALT.
– Any elevations of bilirubin >2X ULN.
– Any elevations in ALP of >1.5X ULN.
– Elevation of AT accompanied by elevated bilirubin.
– Elevation of AT accompanied by clinical symptoms e.g. nausea,
vomiting, anorexia, abdominal pain, or fatigue.
– Possible liver related deaths or treatment discontinuations.
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23. C RO s and C entral Labs
• Assess risk of DILI. 
• We can interpret safety data. 
• We can generate the data. 
• We can perform the testing. 
• Sample integrity. 
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24. Preanalytical C onsiderations
Handling Shipping
Draw tube/volume
Incorrectly centrifuged
Haemolysis
EDTA contamination
Sample Stability
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25. Q uestions?
T hank you
Dr. Andrew Botham
Head of R&D
ACM Global Central Laboratory
abotham@acmgloballab.co.uk
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