# Presentation: 075719

## Clinical Trial Preparation for Molecularly Based Agents

- 	Edward A. Sausville, M.D., Ph.D
- on behalf of Dr. Louise Grochow
- Chief, Investigational Drug Branch
- Cancer Therapy Evaluation Program
- National Cancer Institute

## Changing the Paradigm: Targeted Therapy Development

- Agent Selection:

- Murine tumors
- Xenograft models

- Credentialed targets
- molecular models

- Trial Design:

- Empirical

- Hypothesis driven

- Dose Endpoint:

- Toxicity

- Molecular effect
- When to measure?

- Endpoint Eval:

- H&P, clin. lab

- Complex assays

- Eligibililty:

- Any solid tumor

- Presence of target

- Priority:

- Log cell kill

- Growth inhibition

## Changing the Paradigm: Phase II

- Ph II Goal:

- Tumor shrinkage
- (cure)

- Tumor stabilization
- (eliminate progression)

- Ph II Metric:
-     When?

- Anatomic imaging
- 8 weeks

- Functional probes
- Establish time points

- Dose Finding

- More is better

- Molecular effect

- Combinations:

- Empiric

- Pathways and preclinical
- proof of principle

- Patient Selection

- Histology

- Molecular pathology

## What Experts Will You Need to Work With?

- Basic, translational, and clinical colleagues
- Preclinical experts in model design, toxicology, and activity
- Clinical trials experts
- Statisticians
- Experts in molecular target assessment
- Pathologists
- Imagers
- Interventional radiologists

## So You Have a Good Idea: Now What?

- Characterize the target
- Screen libraries against the target OR
- Synthesize based on in silico drug design
- Select lead compound based on pharmacology
- Screen for activity in engineered lines
- Validate in animal models mimicking human disease
- Develop reporters/probes to assess target effects
- Design a clinical trial

## Clinical Trial Design: Dose Finding (Phase I) Studies

- Establish disposition and safety
- Establish dose that produces target effect
- 		(_**T**_arget _**E**_ffect _**D**_ose)
- Establish relationship between dose/schedule 	and effect
- Agent may be non-toxic (endostatin)
- (Expensive) agent may have effects at doses 	that are not toxic
- Dose response relationship may not be 	monotonic (interferon)

## Possible Trial Designs

- PK/target concentration-guided
- Accelerated Titration Design:
- Minimize patients treated at inactive doses
- Incorporate biological target effect
- Other designs incorporating biological effect
- O6BG: AGT suppression
- single dose before planned tumor resection
- PS 341: proteasome inhibition
- circulating normal PBM
- EGFR inhibitors: assess target presence
- bcr/abl tyrosine kinase inhibitor: response

## O6BG: Rationale for Development

- Alkylator-resistant tumors often have increased intracellular alkylguanine-DNA alkyltransferase (AGT), DNA repair enzyme
- O6BG depletes AGT
- When AGT < 10 fmol, activity of DNA alkylating agents that form adducts at the O6 guanine position increases
- O6BG and BCNU more active *in vivo* than BCNU alone

- Friedman et al. *JCO* 16:3570, 1998

## O6-BG Phase 1 Trial Design in Malignant Glioma

- Undetectable AGT (< 10 fmol/mg protein) occurs in 20% in absence of O6-BG
- O6-BG administered 18 hrs before craniotomy
- BCNU-induces interstrand cross-links by 18 hrs
- Up to 13 patients entered at each dose
- At any time, if AGT detectable in 3 patients, dose was escalated
- Biologic endpoint: undetectable AGT in _>_ 11 of 13 patients

- Friedman et al. *JCO* 16: 3570, 1998

## Glioma AGT Activity After O6-BG

- Dose

- (mg)

- No. of

- Patients

- AGT
-  Undetectable

- 0

- 9

- 0

- 40

-  3

- 0

- 60

-  3

- 0

- 80

- 13

- 8

- 100

- 11

- 11

- Friedman et al. *JCO* 16:3570, 1998

## O6-Benzylguanine:  Phase I Trial 

- Suppression of AGT activity in peripheral blood mononuclear cells (PBMC) did *not* predict suppression of AGT activity in tumor tissue in phase I studies
- PBMC:     36 mg/m2
- Tumor :	120 mg/m2
- Immunoreactive AGT in PBMC a poor surrogate

**Spiro TP, et al.  *****Clin Cancer Res.***_** **_**7:2318, 2001**

## Clinical Trial Design WithBiologic Endpoints 

- Evaluate for target effect as active concentration is approached
- Expand cohort when any biologic effect seen
- reproducibility of effect
- importance of well defined confidence interval
- Escalate dose
- until maximal expected effect is seen
- until maximal effect occurs in maximal fraction of patients
- Additional steps to confirm
-  effect is maximal
-  rate of effect is maximal

## Support for Early Clinical Trials:Cancer Therapy Evaluation Program

- CTEP supply agent
- CTEP support for infrastructure
- Cooperative agreements (Dose finding)
- Contracts (Phase II)
- Other support for infrastructure
- Grant support
- Quick trials (R21)
- Clinical study section
- Cancer Center Core Grants
- General Clinical Research Centers

## Applying to CTEP for Agents

- Letter of intent (LOI)
- Form available on CTEP Web site http://ctep.info.nih.gov
**Review criteria**
- Strong scientific hypothesis
- Supporting preliminary data
- Adequate patient accrual
- Innovative correlative studies
- Ability to meet regulatory requirements
- Not duplicative
- Agent available
- Industry sponsor concurs

## Preparing a Protocol

- LOI approved after reviewed by CTEP’s Protocol Review Committee (+ extramural investigators if needed)
- Address critique in LOI approval letter
- Use available templates (supplied by CTEP)
- Include relevant details (or references) for correlative studies
- Submit electronically to CTEP PIO
- Review by CTEP PRC

## What Do You Need to Measure Drug Effect on Target?

- Characterized assay or probe to report effect on target relevant to therapeutic agent
- Quality assurance: calibration assays, interfering processes, sample handling
- Reproducible
- Sensitivity
- Specificity
- Economically and practically feasible
- Validate in engineered model

## Desirable Information for Design of Dose-Finding Trial

- Relevant models:
- Optimal schedule
- Optimal dose
- Concentration required for effect on target
- % change in target associated with efficacy
- Variability in dose/target and target/efficacy relationships
- Estimate of fraction of tumors that will have effect
- Normal target values, variability
- Target effect on tumor vs. other tissues (e.g., PBM)
- Does patient’s tumor have relevant target?

## Correlation Between 20S ProteasomeInhibitory Potency & Growth Inhibition for 13 Dipeptide Boronic Acids

- <date/time>

- Adams et al.,* Cancer Res. *59:2615, 1999

- Mean GI50 (nM)

- Ki (nM)

- Correlation
- r2=0.92

## Effect of PS-341on PC-3 Tumor Growth in Mice 

- Tumor Volume (% Vehicle)

- Week

- Adams et al.,* Cancer Res. *59:2615, 1999

## Effect of PS-341on 20S Proteasome Activity

- 20S Activity (% Vehicle)

- Mouse WBC

- PC-3

- Adams et al.,* Cancer Res.*59:2615, 1999

- 20S Activity (% Vehicle)

## Ex Vivo Proteasome Activity:1 Hour Post Treatment

**1.96 mg/m****2**

**PS-341 (Log dose, mg/m****2****)**

**% 20S Activity**

*Ex Vivo* Proteasome Activity:1 Hour Post Treatment

## MS-275 HDAC Inhibitor NSC 706995

-   Collaboration between NCI and Nihon Schering
-   Very “differential” activity in NCI screen
-   High oral bioavailability
-   Range finding tox suggests GI/Marrow DLT
- 	on qd x 14 schedule

## PC-3M Prostate

- Cancer Cells

- Peripheral
- Blood Lymphocytes

**A.  Control**
**B.  TSA, 0.3********M, 8hr**
**C.  MS-275, 0.3********M, 24hr**
**D.  MS-275, 1.0********M, 24hr**

**1.  Control**
**2.  MS-275, 0.3********M, 2hr**
**3.  MS-275, 1.0********M, 2hr**
**4.  MS-275, 0.3********M, 8hr**
**5.  MS-275, 1.0********M, 8hr**

**  ****6.  MS-275, 0.3********M, 24hr**
**  ****7.  MS-275, 1.0********M, 24hr**
**  ****8.  TSA, 0.3********M, 2hr**
**  ****9.  TSA, 0.3********M, 8hr**
**10.  TSA, 0.3********M, 24hr**

**Acetylated**
**H3**

**Acetylated**
**H4**

**Effect of HDACIs on Histone Acetylation**

## Cell Cycle Phase Analysisof MS-275 on Prostate Cancer Cells

- PC-3M, 24h Treatment

## MCF-7

- Breast Carcinoma

- Du145
- Prostate Carcinoma

- Control

- TSA
- 0.3 M
- 8 h

- MS-275
- 1 M
- 24 h

**Effect of HDACIs on P21waf1 Expression**

## Real-Time PCR of p21 cDNA in PC-3MAfter HDI Treatment

- Rn

- Cycle Number

## Options for Preliminary Efficacy (Phase II) Trials

- Conventional and/or molecular target eligibility?
- Standard phase 2 design targeting RR, survival, PFS, clinical benefit
- Standard with biologic endpoint
- Standard targeting non-progressor rate
- Ratio of TTP for new and previous therapy
- Tumor growth before and after treatment with each patient as her own control
- Multi-arm randomized selection designs
- Randomized discontinuation design

## Clinical Trial Design: Combination Studies

- Combinations of novel agents, novel agents with cytotoxics
- Preclinical models or plausible molecular hypothesis
- Biologic target effect designs
-  	– proof of principle
- Dose escalation schemes

## Tumor Tissue Studies in Clinical Trials

- Difficulty obtaining tumor tissue
- Difficulty obtaining multiple samples
- Which time points?
- Tumor heterogeneity: results vary depending upon % tumor vs. normal vs. necrotic cells
- Methodological issues: sample handling, sensitivity, reproducibility, complexity, availability
- For newer targets, limited information on normal ranges, variability, magnitude of desired effect

## Setting Priorities for Clinical Trials

- Credentialed target
- Evidence that agent effects target
- Evidence that target effect correlates with useful therapeutic effect
- Reliable way to measure presence of target
- Probes that permit assessment of target effect in clinical trial

## Selecting and Evaluating New Agents for Cancer Treatment

- Test strategies for selecting agents for trials
- Test hypothesis of molecular diagnosis
- Evaluate novel clinical  trial designs
- Target effect is necessary but not necessarily sufficient (pathway crosstalk, downstream events, other proliferative advantages
- If proposed target is not accurately characterized, a useful agent might be discarded
- This is much simpler if the agent is non-toxic, cheap and highly selective in its effects on a critical target
- This is much harder if the agent is promiscuous in its targets, toxic, and the molecular pathology of the disease is complex

## Acknowledgements

- O6BG:   H. Friedman, S. Gerson, H. Spiro, E. Dolan, J. Pluda
- Biopsy data: J. Haaga, A. Dowlati
- PS341: J. Adams
- MS275: J. Trepel