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Why, how, and when to think about safety assessment during drug

development

Donna Lee, PhD, DABT Safety Assessment UCSC April 29th, 2014

© 2008, Genentech

•  Why we care about toxicology: A brief history and the origin of our current approaches

•  Key drivers of the nonclinical toxicology evaluation strategy

•  Differences between small and large molecules that impact toxicology evaluations

•  How toxicity data is used in decision-making at all stages of drug discovery and development

Today’s Agenda

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Applications of Toxicology

           

Environmental:  impact    of  pollutants  on  environment/

ecosystems  

Food:  safety  of  addi5ves,  freedom  from  contaminants  

Clinical:  treatment  of  poisoning  in  humans  

Occupa4onal:  Workplace  exposure  hazards  

Agricultural:  effects  of  pes5cides,  fer5lizers  on  

workers  

Forensic:  legal  applica5ons  eg.  iden5fica5on  of  chemical  causing  death/injury  or  property  damage  

Pharmaceu4cal:  effects  of  drugs  on  

pa5ents  

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How History Has Influenced Toxicology

•  How do xenobiotics interact with living systems and impact normal function?

•  What exposure levels are safe?

Science of Toxicology: the study of the adverse effects of xenobiotics (chemicals, drugs, poisons, etc.)

“All things are poison and nothing is without poison, only the dose permits something not to be poisonous”

Paracelsus (1493-1541)

Or, there is no such thing as a totally safe drug

Understanding this “Dose-Effect Relationship” forms the philosophical basis for all toxicity evaluations

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§  Current US regulatory framework for pharmaceutical drug evaluation is based on 1938 and 1962 laws; ~70 years old:

–  Pre-marketing demonstration of safety

–  Substantial evidence required of drug efficacy

§  We have a responsibility to patients and to global regulatory agencies to ensure that the drugs we intend for human use are safe

§  Toxicology evaluations can also help to advance our understanding of the biology of the molecule

How History Has Influenced Toxicology

Elixir Sulfanilamide

Poisoning in 1938

Thalidomide Birth Defects In 1962

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What is the End Game for Toxicology Evaluations?

What Are Examples of Major “Focus Areas” for Nonclinical Toxicology? " Do Not Want to Treat for One Disease and Cause Another

§  i.e. severe or irreversible changes to normal organ function of a non-intended target

" Do Not Want to Cause Cancer

" Do Not Want to Cause Birth Defects, Fetal Deaths or alter Ability to have Children

Our Goal:

•  Identify a drug with an acceptable safety profile in humans that is appropriate for the intended population (e.g. therapeutic indication)

How Does Nonclinical Toxicology Enable this Goal? •  Identify hazards → Characterize potential risks to humans (translation of nonclinical studies) •  Guide clinical trial design

§  Starting Dose §  Dosing Duration §  Monitoring §  Use in Special Populations (WOCBP and Pediatrics) §  Inform the Label

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“On-Target” aka ‘exaggerated pharmacology’ = the undesired effect is due to pharmacological engagement of the intended molecular target “Off-Target” = the undesired effect is due to pharmacological engagement of an unintended molecular target Off-Target toxicity of large molecules is due largely to:

–  Cross-reactivity with non-target proteins (generally rare!) –  Occasional concerns over excipients in formulation

Off-Target toxicity of small molecules is due largely to: –  Physical attributes: molecular weight, pH, acid-ionization constant (pKa),

solubility, boiling & melting points, lipophilicity (cLogP)

–  Structural attributes: chemical interactions (e.g. thiophenes, anilines, basic amines, & acids)

–  Processing and Elimination (ADME): tissue or cellular accumulation, generation of reactive metabolites, excipients required for oral absorption

On-Target Versus Off-Target Toxicity

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Toxicology Supports the Entire Drug Development Cycle Slide 8 5/5/14

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There is Extensive Safety Testing of New Drugs before and During Clinical Trials in Humans: Timing is Important!

IND Filing

Ph I start Ph II Ph III NDA Filing Post

Approval

FIH Non-GLP Lead

Optimization of lead or BU:

On-target & Off-target effects

LSR ED GO ESR

In vitro and In vivo Investigational or exploratory studies

Non-GLP rodent and non-rodent

pilot dose ranging studiess

GLP repeat dose

(Duration & Dose to

Support Phase 1)

Genotoxicity*

GLP Safety Pharmacology assessments

(hERG IC50), in vivo telemetry, etc

Reprotox (teratogenicity, fertililty, postnatal)*

Subchronic Dosing

(eg 3 mos)*

Chronic Dosing

(eg 6+ mos)

Carcinogenicity

Impurity Qualification (as part of other studies)

Special Studies:

Immunotox

Phototoxicity

Animal Studies Must Precede Human Dosing

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How Do Safety Scientists Approach Non-Clinical Safety Assessment?

Identification of Potential Hazards

Assessment of Translatable Risk to Humans

Weighing of the Risk to Benefit

Use of Non-Clinical Surrogate Models (in silico, in vitro, in vivo)

Building Weight-of-Evidence: data, experience, knowledge

• Type of Toxicity (Severity, Monitorability, Reversibility) • Degree of Unmet Medical Need (competition) • Therapeutic Indication • Target Population • Length of Treatment

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How Do We Typically Use Our Models to Build WOE?

We interpret the data from these model to use for rational decision-making

A Great Place to Work

In vivo studies

Investigation or Characterization Using in vitro/ex vivo/ in vivo models

Verify with In vivo studies

Advance with characterized risk

Stop Inform Back Up

Develop counter screen

±

Rank Scaffolds Select Lead

In vitro In silico modeling

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Drug Development Heavily Regulated through HA Guidelines

Preclinical Models Limitations

ü All models are imperfect ü  Safety models tend to be biased toward conservatism ü  Some models predict clinical

outcomes better than others

Despite all of the caveats: §  Animal tox profiles are most physiologically relevant and required by Health Authorities (i.e. FDA, EMEA) to approve clinical programs §  Other models (in silico, in vitro) are used for internal decision-making and WOE building

*3R’s = Reduce, Refine, Replace

Regulatory guidances establish requirements for hazard identification and risk assessment

In silico

In vitro In vivo

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ICH S6 and S6(R1): Preclinical Safety Evaluation of Biotechnology-Derived Pharmaceuticals (1997, 2011)

Slide 13 5/5/14

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ICH S9: Nonclinical Evaluation for Anti-Cancer Pharmaceuticals (EU 2009, US 2010)

Slide 14 5/5/14

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Regulatory Requirements of Non-clinical Safety Assessment

Identify and evaluate potential risks to humans –  Target organs, dose-response relationship, and mechanism of toxicity

•  Related to molecular entity, mechanism of action, target expression? •  Expected and/or manageable versus unexpected or unmonitorable toxicity? •  Species specific?

Guide clinical study plans –  Safe first dose in humans: Clinical starting dose and dosing duration

•  Acute/Subchronic toxicity •  Safety Pharmacology (CNS, cardiovascular, respiratory systems) •  Identify appropriate safety margin •  A larger therapeutic index/safety margin over the clinical target dose enables

greater flexibility in the clinical development plan

–  Possible biomarkers of toxicity

–  Support later stages of clinical development to licensure •  Identify concerns with special populations (e.g. reproductive toxicity) •  Chronic toxicity, carcinogenicity if applicable

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Comparative Nonclinical Study Requirements (LT versus Non-LT)

ICH S9 (SM & LM) ICH M3 SM ICH M3 LM IND-enabling Repeat Dose Studies

~1 month supports P1 & P2

~1 month supports P1 ~1-3 mos supports P1

Chronic Repeat Dose Studies

3 mos. Supports P3 and NDA

6 mos (rodent) 9 mos (nonR) supports P3 and NDA

6 mos (1 species) supports P3 and NDA

Safety Pharmacology Studies

CV Studies; Endpts in RD studies

CV studies; endpts in RD studies; Respiratory; Neuro

No dedicated studies unless warranted

Genotoxicity Studies Needed for NDA Needed for P1 Not warranted

Carcinogenicity Studies

Not warranted 2 species for NDA May be warranted

Reproductive Toxicology Studies

Embryo-Fetal for NDA Embryo-Fetal (WOCBP, P2); Fertility; Peri-Post Natal for NDA

Embryo-Fetal (P3) Peri-Post Natal for NDA

Special Studies Impurities (limits) Phototox for P3 Local Tolerance (LM)

Impurities: (Limits and GTI) Phototox (P1)

Impurities Local Tolerance

Important differences

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How Are Tox Species Chosen?

•  Default is 1 Rodent (Rat/Mouse) and 1 Non-rodent (Dog/Monkey)

•  Major considerations for species selection:

§  Pharmacological target activity and tissue distribution similar to human (at least 1 species)

§  Metabolic Profile Similar to Humans (small molecules only)

§  Acceptable exposure to enable testing a wide safety range (e.g. exposure multiples)

•  Regulatory authorities may also require toxicity evaluation in a model of disease/activity

§  Toxicity profile can differ substantially between animal models (target expression level, pattern, strain differences)

§  In these cases, efficacy/PK studies can be utilized to help identify tox liabilities and select appropriate models for future studies

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The dose makes the poison

•  Typically, substances become more toxic with increasing dose

•  Most toxicology studies

examine effects over a range of doses: –  Is there an effect threshold,

and if so what is it? –  What does the dose-

response curve look like? –  Are different systems

impacted at different dose levels?

DE Johnson, Expert Rev. Clin. Pharmacol. 3: 231-242, 2010

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Slide 19 5/5/14 Large versus Small Molecules

Points to Consider Large Molecules Small Molecules

Species Selection 1 or 2 species 2 species

Toxicity

On- target Typically exaggerated pharmacology

On- and off-target Typically more toxicity expected; due to lack of specificity and metabolism Receptor profiling, in vitro genotoxicity screening, in vitro cardiotoxicity screening, lead optimization tox screening

Drug Product Simple Non-toxic Formulations Complex Formulations –

Excipient toxicity is of concern

Species Identification Relevant pharmacologic response, binds clinical candidate or surrogate

Metabolite Identification

Maximum Tolerated Dose Often Limited By Max Feasible Dose - formulation/volume limit

Defined by animal studies

PK/ADME

Specific antigen binding, can be target dependent, long t½

Assays for whole antibody

Less specific binding, short t½, may have one or more metabolites with or without pharmacologic activity

Assays for drug product + metabolites (if applicable)

Immunogenicity assays Yes No

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3Rs – Reduce, Replace, Refine Slide 20 5/5/14

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Repeat Dose Small Molecule Toxicity Studies: Enable Full Evaluation of Systemic Toxicity Potential

First Definitive (GLP) Toxicology Studies for IND •  Designed to support Phase 1 •  Generally 4 weeks in duration for small molecules (determined by CDP) •  Biologics 8 to 12 weeks

“Subchronic” Study - Approximately 13 weeks duration •  Continue to characterize toxicity •  Supports longer-term clinical trials up to 3 months duration and Life

Threatening disease indications •  For Small Molecules, conducted to bridge to chronic study

“Chronic” Study - 6 to 9 months duration (6 months for LMs) •  Dose selection focused on long term tolerability •  Required for non-Life Threatening indications projected to be taken chronically

Carcinogenicity - up to 2 years (actually 3 with data analysis!) •  Alternative models are considered (i.e. 6 mos transgenic mouse models) •  Driven by indication and intended clinical use - ie lifetime •  Required for non-LT disease indications of long dosing durations

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Integration of Many Data Points Slide 22 5/5/14

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Slide 23 5/5/14 Safety Pharmacology

q  Objective: Assess for Cardiovascular, CNS or Respiratory Changes q  Study design and focused evaluations specified by ICH guidance S7A

q  Cardiovascular q  In vitro - hERG

q  QT prolongation - Prolonging the cardiac action potential due to block of hERG channels increases the QT interval and can lead to arrhythmias

q  In vivo - telemetry q  QT prolongation q  Blood pressure q  ECG changes

q  CNS q  Any evidence of ataxia, decreased motor activity, behavioral changes

q  Respiratory q  Any effects on respiration rate, lung capacity

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Slide 24 5/5/14 Repeat Dose Toxicity Study

q  Conducted for Large and Small Molecules

q  Objective q  Characterize toxicity of molecule

q  Apoptosis/proliferation - bone marrow, gut, lymphoid q  Metabolic effects - pancreas, liver, thyroid, body wt, food con. q  Degeneration/atrophy - bone, gonads, CNS q  Necrosis - target organ vs. general q  Vascular system effects q  Inflammation q  And more!!!!!

q  Identify potential safety liabilities of long-term dosing q  Special evaluations of repeat dose toxicity

q  Reproductive Toxicity q  Carcinogenicity

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Slide 25 5/5/14 Repeat Dose Toxicity Studies - later stages

q  First Definitive (GLP) Toxicology Studies for IND q  Designed to support Phase 1 q  Generally 4 weeks for small molecules, 4-12 weeks for biologics

q  Subchronic to Chronic Studies – q  Subchronic ~ 13 weeks duration

q  Supports longer-term clinical trials up to 3 months duration q  Chronic ~ 6-9 months duration

q  To support lifetime administration

q  Carcinogenicity - up to 2 years q  Significant questions surrounding utility/appropriateness for biologics q  Driven by indication and intended clinical use – i.e. lifetime therapy for non-life threatening

diseases

q  Reproductive and Developmental Toxicity q  Characterize effects does the compound have on any phase of reproduction and on the

offspring q  Different stages of evaluation: from fertility through post-natal developement

Repro Label example: Pregnancy Category D IRESSA may cause fetal harm when administered to a pregnant woman. … When pregnant rats treated with 5 mg/kg from the beginning of organogenesis to the end of weaning gave birth, there was a reduction in the number of offspring born alive.

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Slide 26 5/5/14 IND-Enabling Program - Small Molecule

General Toxicity Acute toxicity study in rodent (may be possible to use pilot tolerability data) Pilot repeat dose studies in 2 species

Daily dosing - 1 month dosing/1 month recovery rodent Daily dosing - 1 month dosing/1 month recovery non-rodent

Genetic Toxicology Battery

Ames Chromosomal Aberrations (human peripheral lymphocytes) In vivo rat micronucleus study

Safety Pharmacology hERG (in vitro) Non-rodent cardiovascular safety pharmacology study (telemetry) Respiratory safety pharmacology study Mouse Irwin (neurobehavioral study)

Note: Program will vary according to molecule and clinical program (Target expression, species specificity, patient population, clinical development plans…)

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Slide 27 5/5/14 IND-Enabling Program- Large Molecule

Tissue cross-reactivity To evaluate potential for nonspecific/unexpected binding in off-target tissues Limitations of assay sometimes make this challenging to conduct and interpret General Toxicity Intermittent dosing (qw or q2w, based on clinical plan and PK) Dosing over 1 to 3 month with recovery (generally in non-human primate due to

limited species cross-reactivity)

Safety Pharmacology Non-rodent cardiovascular safety pharmacology - often included as part of

general toxicology study No hERG

q Large molecules unable to access the inner pore and bind amino acid residues to inhibit channel function; generally cannot bind external regions of channel

q Formulation components may interfere with assay

Note: Program will vary according to molecule and clinical plan

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So How is Non-Clinical Data Utilized Clinically?

NOAEL or STD10/HNSTD*

Safety Margin

Nonclinical In Vivo Data

ü Starting Dose ü Dose Escalation Range (how high to dose) ü Dosing Duration

Phase I Clinical Development Plan

* No Adverse Effect Level (non-onc) & Highest Non-Severely Toxic Dose (onc)

Identified Target Organ Toxicity Severity

Type Reversibility Monitorability Mechanism?

ü Starting Dose/Escalation ü Clinical Monitoring ü Exclusion Criteria ü Stopping Rules ü Labeling

Phase I & Beyond

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Impact of toxicology data on clinical plan

Clinical development plan considerations: –  Nature of nonclinical toxicities, including potential translatability and

monitorability in humans

–  Safety margin for starting dose

–  Dose escalation to maximum anticipated (target) dose level

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30 Repro and developmental tox – definitions

•  The goal of reproductive tox testing is to identify any effect on mammalian reproduction

Fertility (Segment I) – If exposed to drug, does it impact your normal reproductive

function and your ability to conceive? Embryonic development (Segment II)

– If exposed to drug while pregnant, what happens to the fetus? Postnatal function of offspring (Segment III)

– If exposed to drug later in pregnancy and/or during lactation, is the offspring physiologically normal?

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31 When are these studies (generally) done?

JAPAN: SEG I & II EU: SEG II US: w/ appropriate tests & monitoring

ALL: SEG I Men

1CP Women (on birth control)

EU: SEG I US: SEG I & II ALL: SEG III

Phase I Phase II Phase III Preclinical

NonCP Women

1childbearing potential

ALL: No additional studies needed

Pregnant Women (includes women not using highly effective birth control &/or of unknown status)

ALL: All reproductive toxicity studies & previous human safety data (if available) are needed prior to inclusion in clinical trials

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The Impact of Dose-Response on Safety Margins

Additional factors that influence the magnitude of the Safety Margin required:

•  Severity of the Toxicity

•  Monitorability

Eff

icac

y

Tox

icit

y

Max  

EE

Efficacious  Exposure  (EE)  

Toxicity  Exposure  (TE)  

[Drug]plasma  

TE1 TE2

TE3

Dose-Response Relationships: Slope of Change is important!

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The Concept of Monitorability of Toxicity (Safety Biomarkers)

Scenario A: No Warning that Road is Out

(no monitorability)

Scenario B: Warning Just before Road is Out

(monitorable, but steep response curve)

< Scenario C: Ample Warning before Road is Out

(monitorable & shallow response curve)

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Why do drugs fail… for safety?

•  Unacceptable risk to patients, outweighing the potential benefit §  This is especially challenging in certain indications where a clear “benefit” is difficult

to establish, especially in animal models §  High bar for safety is also due to long treatment durations required for efficacy in

some indications (e.g. CNS)

•  Poor therapeutic window or safety margin §  Safety margin required depends on nature of toxicity and patient population §  Based off of the anticipated efficacious dose prior to FIH trials

•  Steep dose-response curve for toxicity

•  Lack of predictability, reversibility and/or monitorability for concerning safety findings

•  Human variability is not reflected in animals, and power in numbers §  Currently difficult to detect rare events in early stages of development

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How Attrition Informs Safety Lead Optimization

§  Leading Causes of Toxicology-related Attrition (1960-2007)

Laverty. 2011. British J Pharmacology. 163:675.

Stevens & Baker (2009) Drug Disc. Today 14:162-167

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A Few Key Take-Aways…

§  Studies in animals are required by regulatory authorities to protect patients, prior to first human exposure and throughout clinical development

§  Differences in structure/activity between large and small molecule drugs mandate slightly different approaches, with small molecules more prone to “off-target” side effects

§  Ultimate interpretation of toxicity findings and potential tolerability in patients requires a thorough risk/benefit analysis including understanding disease, co-morbidities/co-medications, etc.

§  Safety evaluations can also provide insight into the biology of a target or pathway; assessment strategies that begin in the discovery phase can significantly improve chances for a drug’s success!

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Slide 37 5/5/14 The ICH Guidelines: Repeated Dose Toxicity Studies to Support the Conduct of Clinical Trials in all Regions

Maximum Duration of Clinical Trial

Minimum Duration of Repeat Dose Toxicity Studies to support Clinical Trials

Rodents Non-rodents Up to 2 weeks 2 weeks 2 weeks Between 2 weeks and 6 months

Same as clinical trial Same as clinical trial

> 6 months 6 months 9 months*

*6 months may be justified in certain circumstances e.g., intermittent treatment or life threatening diseases such as cancer or when immunogenicity or tolerance problems confound conduct of longer term studies. In EU, studies of 6 mo duration in non-rodents is acceptable. However, a global package would require 9 mo study. Clinical trials of longer duration than 6 mo can be initiated providing the data are available from a 3 mo rodent and a 3 mo non-rodent study, and complete data from the chronic rodent and non-rodent study are available before 3 mo of dosing is exceeded in the clinical trial (ICH M3) Biopharmaceuticals which produce immunosuppression may require longer duration studies to determine potential for emergence of virally related tumors Ref: ICH M3, July 2008

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Slide 38 5/5/14 ICH Guidelines: Marketing Authorization

Duration of Indicated Treatment

Rodent Non-rodent

Up to 2 weeks 1 month 1 month

>2 weeks to 1 month 3 months 3 months

>1 month to 3 months 6 months 6 months

>3 months 6 months 9 months*

*6 months may be justified in certain circumstances e.g., intermittent treatment or life threatening diseases such as cancer or when immunogenicity or tolerance problems confound conduct of longer term studies. Clinical trials of longer duration than 6 mo can be initiated providing the data are available from a 3 mo rodent and a 3 mo non-rodent study, and complete data from the chronic rodent and non-rodent study are available before 3 mo of dosing is exceeded in the clinical trial. Ref: ICH M3, July 2008

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Slide 39 5/5/14 The ICH Guidelines: Reproduction Toxicity*

•  Evaluation of reproductive organs performed in Repeat Dose toxicity studies prior to exposure. •  Men can be included in Phase I and II trials if the above is conducted and data is supportive. •  Women not of childbearing potential can be included in trials if evaluation of reproductive organs have been conducted. •  All female reproduction toxicity and genotoxicity studies should be conducted prior to inclusion of pregnant women or women

not using birth control or if pregnancy status is not known.

For Women Of Child Bearing Potential

US EU Japan

Segment I Fertility and early embryonic development to implantation

Ph III Ph III in exceptional cases may be conducted concurrent with Ph III

Ph III

Segment II Embryo-fetal development; teratogenicity Implantation to birth

Ph III (With the use of effective contraceptive methods) May not be required if a drug is teratogenic because of MOA e.g oncology products

Ph I Exceptions: with adequate birth control, in clinical trial of short duration or predominance of disease in women. If MOA known, type of agent, half-life etc. May not be required if a drug is teratogenic because of MOA until Ph III

Ph I Exceptions: with adequate birth control in short duration clinical trials or predominance of disease in women. If MOA known, type of agent, half-life etc

Segment III pre- & postnatal development and maternal function

MA MA MA

* Please note that the above timeline is based on draft guidance ICH M3 (July 2008) which could change. Current guideline for Japan require both Seg I & II prior to Phase I.

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Slide 40 5/5/14

q  Information on acute toxicity of pharmaceutical agents to predict the consequences of human overdose situations should be available prior to Phase III.

q Historically, acute toxicity information has been obtained from single dose tox studies in 2 mammalian species using both the clinical and parenteral route of administration

q  Information can also be obtained from dose escalation studies, short duration dose ranging studies that define a maximum tolerated dose, studies that achieve saturation of exposure, or use the maximum feasible dose.

The ICH Guidelines: Acute Toxicity for small molecules

Ref: ICH M3, July 2008

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Slide 41 5/5/14 ICH Guidelines: Carcinogenicity Studies

Study US EU Japan Carcinogenicity/Tumor Promotion e.g. required for biopharmaceutic with >6 months of continual or intermittent dosing If pt to live more than 2-3 yrs or if treatment prolongs life, or exposure is prolonged or cause for concern (e.g. growth factors, immune suppressors). Generally not required for oncology products

Marketing application or post approval in certain cases e.g. serious diseases.

Marketing application or post approval in certain cases e.g. serious diseases

Marketing application or post approval in certain cases e.g. serious diseases

Ref: ICH M3, July 2008