# Presentation: 527195

## 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

**Lack of Efficacy**

**46.0%**

**Commercial**
**   ****Reasons**

**7.0%**

**ADRs in Man**

**16.0%**

**PK**

**7.0%**

**Animal Toxicity**

**17.0%**

**Misc**

**7.0%**

**Lack of Efficacy**

**30.0%**

**Commercial Reasons**

**5.0%**

**ADRs in Man**

**10.0%**

**PK**

**39.0%**

**Animal Toxicity**

**11.0%**

**Misc**

**5.0%**

**J. Ormerod  (1994)**

**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 C****P**** 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 C****P MAX****	****	****	****	****Neurotoxicity**
**	****	****C****P**** < ****Threshold****	****	****	****	**_**No**_** Neurotoxicity**
**Isis 5320:****	****High C****P MAX**** ****	****	****	****	****BP********, APTT********, Bb******
***	******	****** *****C****P**** < ****Threshold**** ****	****	****	****	**_**No**_** Toxic Effects**
**Halofuginone:****	****Tissue AUC ****	****	****	****	****Efficacy (?) **
**	****	****>> Plasma AUC**

- KEY _PHARMACOLOGY_ CONTRIBUTIONS TO DRUG DEVELOPMENT

## 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**

## PYRROLOBENZODIAZEPINE  (NSC-694501)

**view down axis**

**view into minor groove**

**Energy-minimised SJG-136 cross-linked DNA adduct**

## PYRROLOBENZODIAZEPINE  (NSC-694501): MEASUREMENT OF CROSSLINKING IN EX VIVO HUMAN LYMPHOCYTES USING COMET ASSAY

**Percentage decrease in tail moment**

**NSC 694501 Conc. (nM)**

**Comet Assay**

**HUMAN LYMPHOCYTES**

## 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

**IC****90****:****	****Murine = 2640 pM, Human = 826 pM**
**MED:****	****Murine =   240 ********g/m****2****  (TD, Dx5)**
**MTD:****	****Murine = 1800 ********g/m****2****  (TD, Dx5)**
**MTD:****	****Dog ~ 200 ********g/m****2****  (TD, Dx5)**
**Proj Hu MTD = Hu IC****90****/MS IC****90**** x Ms MTD**
**0.31 x 1800 = 563 ********g/m****2****  (TD, Dx5)**** **

## 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

- 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):_MYELOSUPPRESSION_

## 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

- 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

- PYRROLOBENZODIAZEPINE * *(NSC-694501):_CURRENT DEVELOPMENT PLANS_

## 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.](mailto:tpb@fcrdc.nci.nih.gov)__[nci](mailto:tpb@fcrdc.nci.nih.gov)__[fcrf](mailto:tpb@fcrdc.nci.nih.gov)_**.gov**
**Web Address: **_[http://dtp.nci.nih.gov/branches/tpb/index.html](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***