Safety Pharmacology Society Webinar Series:
Safety Pharmacology Endpoints: Integration into Toxicology Studies
Integrating functional CNS observations
into toxicology studies: the CONS!
Will Redfern, PhD
Safety Assessment UK
Alderley Park
Cheshire
United Kingdom
September 20, 2012
Reasons for attrition of candidate drugs
Meanwhile, ADME failures
have been reduced by a
‘frontloading’ approach
Kola & Landis (2004) Nature Reviews: Drug Discovery 3: 711-715.
Attrition due to inadequate safety – why?
Shortcoming
Impact
Solution?
1. Lack of early
detection of safety
signals
‘Doomed’ compounds enter in
vivo tox phase
Improve frontloaded screening: in
silico and in vitro
2. Lack of detection of
safety hazards
preclinically
‘Doomed’ compounds enter
clinical development
Improve quality and increase
information content of safety
pharmacology and toxicology
studies
3. Lack of
confidence/knowledge/
precision in preclinicalclinical translation
Defective risk assessment:
‘Doomed’ compounds may be
let through, anticipating a large
safety margin; ‘safe’
compounds may be stopped,
anticipating an inadequate
safety margin.
Improve risk assessment and
decision-making by better
understanding of the translation of
the preclinical signals to humans.
3
Attrition due to inadequate safety – why?
Shortcoming
Impact
Solution?
1. Lack of early
detection of safety
signals
‘Doomed’ compounds enter in
vivo tox phase
Improve frontloaded screening: in
silico and in vitro
2. Lack of detection of
safety hazards
preclinically
‘Doomed’ compounds enter
clinical development
Improve quality and increase
information content of safety
pharmacology and toxicology
studies
3. Lack of
confidence/knowledge/
precision in preclinicalclinical translation
Defective risk assessment:
‘Doomed’ compounds may be
let through, anticipating a large
safety margin; ‘safe’
compounds may be stopped,
anticipating an inadequate
safety margin.
Improve risk assessment and
decision-making by better
understanding of the translation of
the preclinical signals to humans.
4
Impact of adverse effects of drugs by organ function throughout the pharmaceutical life cycle
 
‘Nonclinical’
Phase I
Phase I-III
Phase III/
Marketing
PostMarketing
PostMarketing
Information:
Causes of
attrition
Serious ADRs
Causes of
attrition
ADRs on label
Serious ADRs
Withdrawal from
sale
Source:
Car (2006)
Sibille et al.
(1998)
Olson et al.
(2000)
BioPrint® (2006)
Budnitz et al.
(2006)
Stevens & Baker
(2008)
88 CDs stopped
1,015 subjects
82 CDs stopped
1,138 drugs
21,298 patients
47 drugs
Cardiovascular:
27%
9%
21%
36%
15%
45%
Hepatotoxicity:
8%
7%
21%
13%
0%
32%
Haematology/BM:
7%
2%
4%
16%
10%
9%
NERVOUS SYSTEM:
14%
28%
21%
67%
39%
2%
Immunotox; photosensitivity:
7%
16%
11%
25%
34%
2%
Gastrointestinal:
3%
23%
5%
67%
14%
2%
13%
0%
1%
10%
0%
2%
2010 Update:
4%
0%
1%
28%
3%
2%
Phase
Sample size:
Reprotox:
Musculoskeletal:
Respiratory:
2%
0%
0%
32%
8%
2%
Renal:
2%
0%
9%
19%
2%
0%
Genetic tox:
5%
0%
No change
0%in 10 years!
0%
0%Increased contribution
0%
Carcinogenicity:
3%
0%
0%
1%
0%
Other:
0%
0%
4%
16%
2%
from Nervous System
AEs in 2010
0%
The various toxicity domains have been ranked first by contribution to products withdrawn from sale, then by attrition during clinical development.
0%
Adapted from Redfern WS et al. SOT 2010; 2011
1-9%
10-19%
>20%
2%
Impact of functional adverse effects on the nervous
system on drug development during 2010:
Drug
Therapeutic target
Adverse effect
Taspoglutide
Type II diabetes
Nausea and vomiting
Robitussin (contains dextromethorphan)
Cough
etc.suppression
Abuse liability in adolescents
Benlysta (belimumab)
Lupus
Increase in deaths; cancer, serious infections, and three suicides.
Pandremix (Influenza vaccine)
H1N1
Narcolepsy in children
Ezogabine
Epilepsy
Urinary retention, which may cause infections or permanent bladder and kidney damage
Rekinla (sodium oxybate)
Fibromyalgia
Abuse liability and accidental overdose concerns
Girosa (flibanserin)
Female hypoactive sexual desire disorder Depression, anxiety, fatigue
Daxas (roflumilast)
COPD
Suicidality, weight loss and cancer
Qnexa (phentermine/topiramate)
Obesity
Tachycardia, birth defects, psychiatric problems (suicidal thinking, impaired memory & concentration), kidney stones
Dopamine agonists
Parkinson's disease
Increase in impulse control disorders
Viagra (sildenafil) etc.
Erectile dysfunction
Hearing loss
Zinc nasal sprays
Common cold
Anosmia
Chantix (varenicline)
Smoking-cessation
Unprovoked acts and thoughts of aggression and violence
Presciption drugs (various)
Various
Impaired driving ability - contribution to road traffic accidents
Tramadol
Pain
Suicide risk in addiction-prone patients, as well as those taking antidepressants or tranquilizers
Valganciclovir (Valcyte)
Paediatric transplantation
Abdominal pain, vomiting, diarrhoea, tremor, seizure.
Influenza vaccine
Seasonal flu
Increased incidence of febrile convulsions in infants
Qualaquin (quinine)
Nocturnal leg cramps (off-label)
Thrombocytopenia, electrolyte imbalance, hearing loss, cardiovascular problems, and hemolytic uremic syndrome
Zyflo CR (zileuton)
Asthma
Liver toxicity, sleep disorders and behavioral changes
Geodon (ziprasidone)
Bipolar disorder
Dyskinesia during paediatric clinical trial
Benadryl (diphenhydramine) - gel Pruritis (topical gel)
Unconsciousness, hallucinations, and confusion if swallowed
Exelon (rivastigmine)
Dementia
Nausea, hypertension, slowed heart rate or death
Neurontin (gabapentin)
Epilepsy
Suicidality
Pandremix (Influenza vaccine)
H1N1
Narcolepsy in children
Massive bleeding; severe high blood pressure; blood clots, heart attack; kidney damage, headache, confusion,
Avastin (bevacizumab)
Breast cancer
seizures, and vision loss.
Outcome
Clinical trial halted/delayed
Regulatory scrutiny/review of data
Regulatory scrutiny/review of data
Regulatory scrutiny/review of data
Non-approval
Non-approval
Non-approval
Non-approval
Non-approval
Publication
Publication
Publication
Publication
Publication
Labelling
Labelling
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Litigation
Withdrawn from sale
Withdrawn from sale
Source: DIA Daily
January to December 2010
Impact of functional adverse effects on the nervous
system on drug development during 2010:
Drug
Therapeutic target
Adverse effect
Taspoglutide
Type II diabetes
Nausea and vomiting
Robitussin (contains dextromethorphan)
Cough
etc.suppression
Abuse liability in adolescents
Benlysta (belimumab)
Lupus
Increase in deaths; cancer, serious infections, and three suicides.
Pandremix (Influenza vaccine)
H1N1
Narcolepsy in children
Ezogabine
Epilepsy
Urinary retention, which may cause infections or permanent bladder and kidney damage
Rekinla (sodium oxybate)
Fibromyalgia
Abuse liability and accidental overdose concerns
Girosa (flibanserin)
Female hypoactive sexual desire disorder Depression, anxiety, fatigue
Daxas (roflumilast)
COPD
Suicidality, weight loss and cancer
Qnexa (phentermine/topiramate)
Obesity
Tachycardia, birth defects, psychiatric problems (suicidal thinking, impaired memory & concentration), kidney stones
Dopamine agonists
Parkinson's disease
Increase in impulse control disorders
Viagra (sildenafil) etc.
Erectile dysfunction
Hearing loss
Zinc nasal sprays
Common cold
Anosmia
Chantix (varenicline)
Smoking-cessation
Unprovoked acts and thoughts of aggression and violence
Presciption drugs (various)
Various
Impaired driving ability - contribution to road traffic accidents
Tramadol
Pain
Suicide risk in addiction-prone patients, as well as those taking antidepressants or tranquilizers
Valganciclovir (Valcyte)
Paediatric transplantation
Abdominal pain, vomiting, diarrhoea, tremor, seizure.
Influenza vaccine
Seasonal flu
Increased incidence of febrile convulsions in infants
Qualaquin (quinine)
Nocturnal leg cramps (off-label)
Thrombocytopenia, electrolyte imbalance, hearing loss, cardiovascular problems, and hemolytic uremic syndrome
Zyflo CR (zileuton)
Asthma
Liver toxicity, sleep disorders and behavioral changes
Geodon (ziprasidone)
Bipolar disorder
Dyskinesia during paediatric clinical trial
Benadryl (diphenhydramine) - gel Pruritis (topical gel)
Unconsciousness, hallucinations, and confusion if swallowed
Exelon (rivastigmine)
Dementia
Nausea, hypertension, slowed heart rate or death
Neurontin (gabapentin)
Epilepsy
Suicidality
Pandremix (Influenza vaccine)
H1N1
Narcolepsy in children
Massive bleeding; severe high blood pressure; blood clots, heart attack; kidney damage, headache, confusion,
Avastin (bevacizumab)
Breast cancer
seizures, and vision loss.
Outcome
Clinical trial halted/delayed
Regulatory scrutiny/review of data
Regulatory scrutiny/review of data
Regulatory scrutiny/review of data
Non-approval
Non-approval
Non-approval
Non-approval
Non-approval
Publication
Publication
Publication
Publication
Publication
Labelling
Labelling
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Litigation
Withdrawn from sale
Withdrawn from sale
Impact of QT/TdP issues on drug development during 2010 by comparison:
Drug
Therapeutic target
Bydureon
Type II diabetes
Invirase; Norvir (in combination)
HIV
Saquinavir-ritonavir (in combination) HIV
Anzemet (dolasetron mesylate injectable)
Anti-emetic
Darvon (propoxyphene)
Analgesia
Darvocet (propoxyphene + acetaminophen) Analgesia
Adverse effect
QT prolongation
QT prolongation
QT prolongation, torsade de pointes
Torsade de pointes
Torsade de pointes
Torsade de pointes
Outcome
Regulatory scrutiny/review of data
Regulatory scrutiny/review of data
Prescribing restrictions/warning letter
Prescribing restrictions/warning letter
Withdrawn from sale
Withdrawn from sale
Source: DIA Daily
January to December 2010
Functional measurements in repeat-dose toxicity studies
Scientific drivers
Doing it in addition to
standalone safety
pharmacology studies
Regulatory drivers
Doing it instead of
standalone safety
pharmacology studies
Rationale:
Rationale:
•To provide early warning flags well ahead
of the regulatory GLP SP core battery
studies (by incorporating into early tox/MTD studies).
•To assess whether findings in acute SP
studies persist, intensify, or diminish after
repeated dosing, and to demonstrate
recovery after cessation of dosing.
•To provide functional correlates of
histopathological findings in previous tox
studies.
•To assess potential effects that may only
develop after prolonged exposure.
To opt for the minimum regulatory requirement
for FTIM:
ICHS6 (Biologics)
I’m OK with this. Let’s have more of it!
ICHS9 (Oncology Products)
FDA Guidance on Exploratory IND Studies
by incorporating SP core battery assessments
into the 1-month regulatory tox studies.
I have reservations about this. This will be
what I’m focusing on today.
Starting point...
• Clearly, adverse effects on the nervous system make
a significant contribution to attrition of candidate
drugs during clinical development.
• Therefore, the last thing we should do is reduce the
quality of the preclinical CNS safety pharmacology
assessment.
• So, do more ‘as well as’, and reduce the temptation
to go for ‘instead of’*.
*In other words, do include CNS safety pharmacology endpoints in
repeat-dose toxicity studies as well as standalone single-dose safety
pharmacology studies, rather than instead of.
Why not replace standalone CNS safety
pharmacology studies with assessments in
repeat-dose toxicity studies – what’s the big deal?
1. The laboratory conditions in toxicology holding
rooms/procedure rooms are not optimal for obtaining high
quality behavioural data (due to noise; disturbance etc.).
2. The phenomenon of tolerance means that the responses
measured on Day X may be diminished compared to Day 1 (ie,
first administration).
3. By Day X, what you may be measuring is not the
pharmacological response to the compound, but the effects of
overt toxicity (inappetance; weight loss; general malaise).
4. Circumventing ‘2’ and ‘3’ above by doing the assessments on
Day 1 of dosing causes logistical difficulties.
Limitations of SP endpoints in tox studies
• The primary aim of a repeat-dose toxicity study is to expose
animals to different levels of a test compound over a prolonged
period, and to assess a standard list of in-life parameters (incl.
clinical chemistry; body weights, food & water consumption;
routine clinical observations; ophthalmoscopy; ECG, etc.),
toxicokinetics, and post-mortem histological changes.
• Any additional functional measurements MUST NOT interfere
with these aims or affect their outcome.
• The study design and laboratory conditions may be sub-optimal
for obtaining high-quality functional data.
Differences in in-life environments (etc.)
Safety pharmacology studies
General toxicology studies
Dosing staggered to accommodate functional
measurements
Animals dosed all in one session (usually a.m.)
TK sample taken after key functional
measurements
TK sampling takes priority
No necropsy to consider
Scheduled to accommodate necropsy slots
Studies powered to detect the functional effect
Studies adequate to detect histopathological
effects
Behavioural studies usually require young rats
Sexually mature animals used
Usually restricted to male animals
Equal numbers of both sexes used
May require non-standard strains (e.g.
pigmented rats)
Restricted to standard strains
Functional measurements may require pretraining of animals
Rarely required
Functional measurements require a quiet room
Sometimes anything but!
Equipment/software may not be fully GLPcompliant
GLP sacrosanct
Should be run by experienced safety
pharmacologists and technicians fully au fait
with safety pharmacology measurements and
data interpretation
Toxicology facilities may be geographically
remote from available safety pharmacology
expertise, or such expertise may not be
available within the company.
Example of a custom-designed, fit-for-purpose in vivo safety pharmacology suite
CNS
evaluations
done here
Features:
•Testing labs located remote from corridor noise (e.g., trundling of cage racks; loud conversations).
•Primary access to suite via single entry door, with warning to limit entry to essential visits and to minimise noise level.
•Staff requiring access to the other animals on the study can do so without disturbing the safety pharmacology
observations/measurements.
•Entry to the testing labs restricted to staff involved in the observations/measurements.
•Designed to accommodate bulky test equipment, ergonomically.
•Lighting control with local (manual) override.
Example of toxicology study holding rooms with ante room
CNS
evaluations
done here
Drawbacks (for CNS safety pharmacology observations/measurements):
•Testing area adjacent to corridor noise (e.g., trundling of cage racks; loud conversations).
•Access from corridor directly into testing area.
•Staff requiring access to the other animals on the study disturb the safety pharmacology observations/measurements.
•Entry to the testing area unrestricted.
•Bulky test equipment may be difficult to accommodate ergonomically.
•Automated lighting control with no manual override.
Development of tolerance with repeat-dosing
A DECREASE in response/clinical efficacy with repeat-dosing
Drug
Therapeutic
target
Effects
Opiate analgesics
Pain
Rapid tolerance to most effects develops on
repeat-dosing
Baclofen
Spasticity
Tolerance develops to muscle relaxant effects
due to down-regulation of GABA-B receptors
Benzodiazepines
Anxiety
Tolerance develops to initial sedative effect
L-DOPA; bromocriptine
Parkinson’s
Reduced efficacy
SSRI’s
Depression
Reduced efficacy
Haloperidol;
chlorpromazine
Schizophrenia
Reduced efficacy
Anticonvulsants
Epilepsy
Reduced efficacy
‘‘Some form of adaptive
syndrome is the inevitable
consequence of the reciprocal
interaction between most or
all classes of drugs and the
organism’’.
W Haefely (1986)
Pupillary light reflex in a repeat-dose toxicology study in rats:
tolerance developing to a mydriatic effect
**
**
(slow)
Drug X
µmol/kg po
(n = 6 each)
**
(slow)
Vehicle
AZD400
AZD500
AZD750
AZD1500
1.0
** **
**
1.5
*
Pupil diameter (mm)
2.0
(slow)
**
(slow)
2.5
(No further dosing
at high dose level)
0.5
0.0
Day -1
Day 1
4h
Day 2
pre
Day 3
4h
Day 4
pre
Day 7
4h
Day 8
pre
Redfern WS et al. (2007) A simple method for estimating pupil diameter in conscious rats
and dogs during repeat-dose toxicity studies. J Pharmacol Toxicol Methods 56: e50.
Saliva production in a repeat-dose toxicology study in dogs:
tolerance developing to a salivatory effect
0.5
Saliva weight (g)
**
0.4
vehicle (n = 12)
high dose (n = 12)
0.3
0.2
0.1
0.0
7
14
21
Day of dosing
Salivation quantified by placing a pre-weighed gauze swab
inside a jowl for 20 s; removed and re-weighed.
First measurement was on Day 3 of study. (AZ in-house data)
28
Example of tolerance, increased response, and no change
in response in the same study with the same compound!
Effects of once-daily dosing with baclofen (10 mg/kg po) in the Irwin test in rats (3M; 3F)
Day 1
Day 2 Day 3 Effect
Abnormal
respiration
6/6
3/6
2/6
Diminishing
Decreased
activity
6/6
6/6
6/6
Stable
Increased
scratching
0/6
0/6
3/6
Delayed onset
Conclusion:
Change in magnitude of effect over repeated dosing is both pharmacologyand parameter-specific – and can’t be predicted in advance.
AZ in-house data: courtesy of Lorna Ewart
Logistics for rodent studies…
If you choose to go down this route (replacing the standalone safety pharmacology study), it is
preferable to conduct functional measurements on Day 1 of the repeat-dose toxicity
studies for the reasons outlined earlier (ie, you may miss an acute response that diminishes with repeatdosing).
But Day 1 of a tox study is usually mayhem, with timed TK bleeds etc.
So, you could do the measurements on Day 2 of the repeat-dose study.
However, you won’t get through all the Irwin tests (multiple time points) and whole-body
plethysmography (WBP) measurements (4 hours’ recordings) on the vehicle and 3 dose
levels (Irwin: 24 rats; WBP: 32 rats) in one day!
So you could do (say) the Irwin tests on Day 2 and the WBP measurements on Day 3.
Even then, you still won’t complete either of these evaluations in a single day. So you may
have to stagger the start of the rodent 1-month study, e.g.:
MON
TUE
WED
THU
Day 1 Start cohort 1
Day 2 cohort 1: Irwin
Day 1 Start cohort 2
Day 3 cohort 1: WBP
Day 2 cohort 2: Irwin
Day 4 cohort 1
Day 3 cohort 2: WBP
And you’ll have to reduce the standard number of time points in the Irwin test.
Do you have enough quiet space to run Irwin and WBP simultaneously, close to the tox
holding room…?
Conclusions
• Replacement of the ‘standalone’ CNS safety
pharmacology study with ‘CNS safety pharmacology
assessments’ in a repeat-dose tox study represents a
dumbing-down of the preclinical CNS risk
assessment.
• This would be like replacing the dog telemetry
cardiovascular assessment with a ‘snapshot ECG’ in
a tox study to assess QT risk.
• You wouldn’t do that, would you...?
Acknowledgements
Colleagues at AstraZeneca Alderley Park:
Sharon Storey; Helen Prior; Claire Grant; Louise Marks; Lorna
Ewart; Kat Greenwood; Claire Barnard; Dave Simpson; Sally
Robinson; Jean-Pierre Valentin.