PRECLINICAL PHARMACOLOGY

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PRECLINICAL PHARMACOLOGY TOXICOLOGY IN CANCER
DRUG DEVELOPMENT

• Joseph M. Covey, Ph.D.
• Toxicology Pharmacology Branch
• DTP, DCTD, NCI

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Preclinical Pharmacology Toxicology Why?

• Balance of
• Regulatory Issues
• Need for information
• Science
• Practical Considerations
• Preclinical Costs versus Patient Cost

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Reasons for Termination of Development of NCEs
(Excluding Anti-Infectives)
J. Ormerod (1994)
Commercial Reasons
Lack of Efficacy
5.0
46.0
Lack of Efficacy
30.0
ADRs in Man
Commercial Reasons
10.0
Misc
7.0
Misc
5.0
7.0
ADRs in Man
PK
Animal Toxicity
16.0
39.0
PK
11.0
Animal Toxicity
7.0
17.0
Data taken from 7 UK-owned
Companies (1964 - 1985)
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FDA Preclinical Pharmacology Toxicology
Requirements

• DRUGS
• Two Species - Rodent Non-rodent
• Clinical Route Schedule
• Pharmacokinetics - Optional

• BIOLOGICALS
• Most Relevant Species
• Clinical Route Schedule
• Biodistribution

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Representative Surface Area to Weight Ratios (km)
for Various Species (Freireich, et al, Cancer
Chemotherapy Reports, 1966, 50 219-244)
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TPB Drug Evaluation Philosophy

• Agent-Directed Studies
• Pharmacologically (PK/PD) - Guided
• Integrate With Preclinical Efficacy Data the
  Proposed Clinical Protocol
• Rational Evaluation of Role of Schedule
  Dependence, Pharmacodynamics, Pharmacokinetics
  Metabolism in the Development of Toxicity
• Relate Drug Levels and/or AUC (Plasma /or
  Tissue), Biomarkers to Safety and to Occurrence
  Severity of Toxicity
• Extrapolate Toxic Effects Across Species

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Advantages Of Agent-Directed Drug Development

• Greater Scientific Basis for Development
• Permits Greater Flexibility
• Data Rich IND Submission to Support Phase I
• Preclinical Potential .. Less Expensive
• Permits PK/PD-Guided Dose Escalation in Phase I
• Optimal Schedule .. Greater Chance of Success?
• Patients .. Greater Chance of Effective Therapy?

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Objectives Of Preclinical Pharmacology Studies
For Anti-Neoplastic Drugs

• Development of Sensitive Analytical Methods
• Determine In Vitro Metabolism and Protein Binding
• Analog Evaluation - Determine Optimal Development
  Candidate
• Determine Pharmacokinetics in Various Species
• Identification and Analysis of In Vivo
  Metabolites
• Define Optimal Dose Schedule
• Correlate CP and/or AUC with Efficacy, Safety
  Toxicity and PD

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Key Pharmacology Contributions to Drug
Development

• 9-AC Suspension 72 Hr civ
• 17-AAG Parent Efficacy
• Active metabolite Efficacy
• Penclomedine High CP MAX Neurotoxicity
• CP lt Threshold No Neurotoxicity
• Isis 5320 High CP MAX BP?, APTT?, Bb?
• CP lt Threshold No Toxic Effects
• Halofuginone Tissue AUC Efficacy (?)
• gtgt Plasma AUC

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Selective Retention of17-AAG in Tumors
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Objectives Of Preclinical Toxicology Studies For
Anti-Neoplastic Drugs

• DETERMINE IN APPROPRIATE ANIMAL MODELS
• The Maximum Tolerated Dose ( MTD )
• Dose Limiting Toxicities ( DLT )
• Schedule-Dependent Toxicity
• Reversibility of Adverse Effects
• A Safe Clinical Starting Dose

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Additional Agent-Directed Toxicology Study
Requirements

• Attain Efficacious Drug Levels in Plasma In Vivo
• Correlate Drug Plasma Levels and/or AUC with
  Toxicity and Safety Across Species
• Ameliorate Toxicity by Change in Route/Schedule
• Compare Toxicity with Previously Studied Clinical
  Agents as Necessary

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PYRROLOBENZODIAZEPINE (NSC 694501)
Energy-minimized SJG-136 cross-linked DNA adduct
View into minor groove
View down axis
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PYRROLOBENZODIAZEPINE (NSC 694501) MEASUREMENT
OF CROSSLINKING IN EX VIVO HUMAN LYMPHOCYTES
USING COMET ASSAY
Single Cell Gel Electrophoresis
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PYRROLOBENZODIAZEPINE (NSC 694501) Toxicity
Concerns

• Potent DNA Minor Groove Cross-Linking Alkylating
  Agent Similar to Bizelesin Myelosuppression
  with Human Sensitivity Much Greater than Mouse
• Anthramycin-Like Compound Potential for Serious
  Cardiotoxicity

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BIZELESIN (NSC 615291)In Vitro Bone Marrow
Toxicity Data
728X
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PYRROLOBENZODIAZEPINE (NSC 694501) In Vitro
Bone Marrow Toxicity Data
3X
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PYRROLOBENZODIAZEPINE (NSC 694501)Projected
Human Clinical MTD

• IC90 Murine 2640 pM, Human 826 pM
• MED Murine 240 ?g/m2 (TD, Dx5)
• MTD Murine 1800 ?g/m2 (TD, Dx5)
• MTD Dog 100 ?g/m2 (TD, Dx5)
• Proj Hu MTD Hu IC90/Ms IC90 x Ms MTD
• 0.31 x 1800 563 ?g/m2 (TD, Dx5)

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PYRROLOBENZODIAZEPINE (NSC-694501)MYELOSUPPRESS
ION

• In Vitro
• Bizelesin Human 728-fold gt Mouse
• Taxol Human 5-fold gt Mouse
• PBD Human 3-fold gt Mouse
• Human CFU-GM IC90 826 pM
• Sensitive Tumor Lines
  GI50 170 - 1222 pM
• In Vivo
• Dose Limiting in Rats Dogs ( GI)
• Based on In Vitro Bone Marrow and In Vivo MTDs,
  Projected Human MTD for PBD is within Mouse
  Efficacy Range (MED and MTD)
• PBD Has Greater Chance of Activity in Humans

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PYRROLOBENZODIAZEPINE (NSC-694501)Current
Development Plans

• Perform PK Studies at Effective Doses in Mouse
• Determine if Effective Concentrations can be
  Achieved in Rat and Dog
• Use Comet Assay for PK/PD Correlation in Mouse
  Lymphocytes Tumor
• Use Comet Assay for TK/PD Correlation in Rat and
  Dog Lymphocytes

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Approach to PK Toxicology Studies Conclusions

• Do Not Think of Tox as Simply Checking a
  Regulatory Box ?
• Develop Preclinical Plan For Each Agent Using All
  Available Data
• In Vitro and In Vivo Preclinical Data Is Useful
  in Predicting Human Sensitivity and Toxicity

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Acknowledgements

• TPB Contractors
• Pharmacology
• Mayo Foundation
• Ohio State University
• Southern Research
• Univ Alabama
• Univ Pittsburgh
• Univ Texas - MDA

• Toxicology
• Battelle
• IIT Research Inst.
• Southern Research
• SRI International
• Univ Illinois, Chicago
• Pathology Assoc.

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TPB Contact Information

• Phone [phone]
• Fax [phone]
• E-mail ncidtptpbinfo_at_mail.nih.gov
• Web Address
• http//dtp.nci.nih.gov/branches/tpb/index.html

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Our next speaker is Dr. Edward
Sausville Developmental Therapeutics Program for
Dr. Louise Grochow, Cancer Therapy Evaluation
Program