PRECLINICAL PHARMACOLOGY & TOXICOLOGY IN CANCER DRUG DEVELOPMENT

PRECLINICAL PHARMACOLOGY & TOXICOLOGY IN CANCER DRUG DEVELOPMENT Adaline C. Smith, Ph.D., D.A.B.T. Toxicology & Pharmacology Branch DTP, DCTD, NCI

PRECLINICAL PHARMACOLOGY & TOXICOLOGY: WHY? • Balance of: • Regulatory Issues • Need for information • Science • Practical Considerations • Preclinical Costs versus Patient Cost

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)

FDA PRECLINICAL PHARMACOLOGY & TOXICOLOGY REQUIREMENTS • DRUGS • Two Species - Rodent & Non-rodent • Clinical Route & Schedule • Pharmacokinetics - Optional • BIOLOGICALS • Most Relevant Species • Clinical Route & Schedule

REPRESENTATIVE SURFACE AREA TO WEIGHT RATIOS (km) FOR VARIOUS SPECIES(Freireich, et al, Cancer Chemotherapy Reports, 1966, 50: 219-244)

T&PB 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

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?

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

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 < ThresholdNo Neurotoxicity • Isis 5320: High CP MAX BP, APTT, Bb • CP < ThresholdNo Toxic Effects • Halofuginone: Tissue AUC Efficacy (?) >> Plasma AUC

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

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 Accepted Clinical Agents as Necessary

5'-CICGATCICG GCICTAGCIC-5' Interstrand G–G cross-link PYRROLOBENZODIAZEPINE (NSC-694501) Energy-minimised SJG-136 cross-linked DNA adduct view into minor groove view down axis

100 75 50 25 0 0 25 50 75 100 PYRROLOBENZODIAZEPINE (NSC-694501):MEASUREMENT OF CROSSLINKING IN EX VIVO HUMAN LYMPHOCYTES USING COMET ASSAY Comet Assay Percentage decrease in tail moment HUMAN LYMPHOCYTES NSC 694501 Conc. (nM)

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

BIZELESIN (NSC-615291):IN VITRO BONE MARROW TOXICITY DATA 728X

PYRROLOBENZODIAZEPINE (NSC-694501):IN VITRO BONE MARROW TOXICITY DATA 3X

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 ~ 200 g/m2 (TD, Dx5) • Proj Hu MTD = Hu IC90/MS IC90 x Ms MTD 0.31 x 1800 = 563 g/m2 (TD, Dx5)

PYRROLOBENZODIAZEPINE (NSC-694501):MYELOSUPPRESSION • In Vitro: • Bizelesin: Human 728-fold > Mouse • Taxol: Human 5-fold > Mouse • PBD: Human 3-fold > Mouse (IC90 826 nM) • HTCFA: PBD IC90 20-30 nM • 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

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 Lymph & Tumor • Use Comet Assay for TK/PD Correlation in Rat and Dog Lymph

APPROACH TO 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

ACKNOWLEDGEMENTS • T&PB Contractors • Pharmacology • Mayo Foundation • Ohio State University • Southern Research • Univ Alabama • Univ Pittsburgh • Univ Texas - MDA • Toxicology • Battelle • IIT Research • Southern Research • SRI International • Univ Illinois, Chicago • Pathology Assoc.

T&P CONTACT INFORMATION • Phone No: 301-496-8777 • Fax No: 301-480-4836 • E-mail: tpb@dtax2.ncifcrf.gov • Web Address: http://dtp.nci.nih.gov/branches/tpb/index.html

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

PRECLINICAL PHARMACOLOGY & TOXICOLOGY IN CANCER DRUG DEVELOPMENT