Oncology Dose Finding A Case Study: Intra-patient Dose Escalation Jonas Wiedemann, Meghna Kamath Samant & Dominik Heinzmann, pRED Biostatistics, Valerie

Oncology Dose FindingA Case Study: Intra-patient Dose EscalationJonas Wiedemann, Meghna Kamath Samant & Dominik Heinzmann, pRED Biostatistics, Valerie Cosson & Sylvie Retout, pRED TRSF. Hoffmann-La Roche

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Oncology Dose Finding

- Intra-patient Dose Escalation – Pros & Cons

Why is This of Interest?

Imaging Study

Statistical Methodology

Lessons Learned & Further Development

Outline

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Imaging Study



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Oncology Dose FindingOverview

Several different approaches are more or less commonly seen:

• Conventional rule based “3+3”

• Continual Reassessment Methodology (CRM)

• More advanced methods combining toxicity and efficacy

• Intra-patient Dose Escalation

Commonly acknowledged that more advanced and innovative methods are needed using accumulated information – such as Bayesian methodologies

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FDA point of viewA need for innovative designs

• Increasing spending of biomedical research does not reflect an increase of the success rate of pharmaceutical development.

• Many drug products were recalled due to safety issues after regulatory approval.

• Critical path initiative

– In its 2004 Critical Path Report, the FDA presented its diagnosis of the scientific challenges underlying the medical product pipeline problems.

• Advancing innovative trial designs: Use of prior experience or accumulated information in trial design

• Insufficient exploration of the dose-response curve is often a key shortcoming of clinical drug development

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Accelerated Titration DesignsA direct comparison to “3+3”

• In 2008 Penel et. al. compared the performance of ATD and “3+3” in 270 (1997–2008) published phase I trials

– ATD had been used in only 10% of the these studies

• ATD had permitted to explore significantly more dose levels (seven vs. five)

• ATD reduced the rate of patients treated at doses below phase-2 recommended dose (46% vs. 56%,)

• Nevertheless, ATD did not allow a reduction in the number of enrolled patients, shorten the accrual time nor increase the efficacy

However, still support ATD as an effective clinical trial design over a standard “3+3”

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Intra-patient Dose EscalationPros & cons

Pros

• Intra-patient dose escalation designs are generally used in ethical grounds, i.e. to address the fact that in cancer research it may be unethical to only provide sub therapeutic doses to cohorts of patients

• Fewer patients needed, i.e. lower costs, faster study conduct

• Meaningful if no toxicity is expected

• If analyzed properly, they can provide information about inter-patient variability in dose–response effects

• The succession of dose levels is not necessarily determined completely by choices made before the onset of the trial

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Intra-patient Dose EscalationPros & cons

Cons

• However, though appealing these designs are not commonly applied due to some theoretical and practical objections

• Successive observations in a single patient are correlated. Hence, difficult to know if toxicity is due to current dose or cumulative exposure (same potential issue for PD markers)

• May not be feasible due to the fact that most patients in phase 1 studies would only stay on drug for 2 to 3 cycles of therapy due to rapidly progressive disease

• Could potentially create some selection bias (prognostics, characteristics, etc.)

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Imaging Study



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Why is This of Interest?Project overview

• Anti-body, angiogenesis inhibitor (inhibits growth of new blood vessels, especially by inhibiting vascular permeability)

• Tested in first-in-man multiple dose ascending study with a dose of up to 3 mg/kg, no observed toxicity, and a ½ life of ~ 9 days

– Dose schedule simulated and a q2w approach chosen

• DCE-MRI* as angiogenic PD marker – values (Ktrans, Kep, AUC90, Ve) directly related to:

* Dynamic Contrast Enhanced-Magnetic Resonance Imaging

Blood volume Blood flow Extracellular Extra-vascular Space - ESS Rate of extravasation

In addition, low within-patient variability

112 paired pre-treatment scans (Ktrans: wSD ~ 0.10-0.11)

ml/m

l/m

inDCE-MRI methodology – Excellent reproducibility

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Why is This of Interest?Decision to go for intra-patient dose escalation• Angiogenesis inhibition confirmed and DCE-MRI as angiogenic PD

marker – low within-patient variability

• No observed toxicity and tentative dose found in first-in-man study – However, still uncertainty about actual therapeutic dose −> alternative approach needed

• Modeling and simulation methods explored and tools in place, i.e. Bayesian, WinBugs, EDC, etc. −> practical feasible

• By introducing large dose-escalating steps / relatively short half life −> faith in observed Toxicity/PD dose-response

Phase I intra-patient dose escalation imaging study to establish PD dose-relationship measured as DCE-MRI

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Imaging Study

Statistical methodology


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Establish exposure – PD relationship for single agent

Identify the minimal PD effective dose

Confirm MoA

Confirm feasibility of DCE-MRI

Dose - DCE-MRI inhibition

0

20

40

60

80

100

120

0.01 0.1 1 10 100 1000

Dose (mg/kg)

Inh

ibit

ion

of

Ktr

ans

(%)

- by applying intra-patient dose escalation with 3 initial dose steps

- by applying a Bayesian approach

Dose (mg)

100 250 750 2500 3000

Imaging StudyOverall target

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Study Overview Initial Test Cohort

6-10 subjects

Terminate study

DCE-MRI signal DCE-MRI signal

First intra-patient Dose Escalation

Cohort

6-10 subjects

Parallel Fixed Dose Cohorts

6-10 subjects pr cohort

non-interpretable DCE-MRI signal

Tumor Biopsy Evaluation

Cohort

10 subjects on lowest efficacious

dose

Adapted Intra-patient Dose

Escalation Cohorts


Adapted Confirmatory Parallel Fixed Dose

Cohorts


Allows Further adjustment of timing and no of assessments

Allows timing of PD/BM adjustment dose scheme adjustment

Up to 50 subjects will be evaluated in total

Highest dose

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Why This Interest?

Imaging Study



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Primary PK/PD ModelingBayesian approach – Primary model

• A direct* inhibitory Imax model

• Two unknown parameters to be estimated, i.e. Imax and IC50 (both assumed to be Gaussian distributed with mean and precision)

With

• E the DCE-MRI parameter, i.e. Ktrans, Kep, Ve, Vp and iAUC,

• E0 the DCE-MRI parameter at baseline,

• Cp the drug concentration at the time of DCE-MRI assessment,

• Imax the maximum decrease of the DCE-MRI parameter (0<Imax<1),

• IC50 the drug concentration at which 50% of max inhibition is reached.

CpIC

CpIEE

50

max10

* If possible, an exploratory indirect model to investigate time delay in DCE-MRI

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Primary PK/PD ModelingBayesian approach – General principles

50IC ),( 1150 ICICN ~

+

Observed PD data

Bayesian estimation

Prior distribution on IC50 (and Imax)

A posterior mean value and precision

- unknown parameters are interpreted in terms of probability

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Bayesian Method• Advantages

– Combines a priori knowledge, including uncertainty, with new data

– Allows an increase of that knowledge, even with a low number of subjects

– Basis for formal approach to incremental model building, parameter estimation and other statistical inference as knowledge and data are accumulated

– Implemented in Winbugs 1.4.3

• Issues

– Construction of prior distributions is a somewhat subjective process

– Apparently very sensitive to the choice of the priors

– Bayesian inference is based on Monte Carlo Markov Chain• Iterative process which eventually converges to the posterior distribution• Requires high number of samples (5000 – 10000) => time consuming

koutP chains 1:2

iteration

4001 4500 5000 5500 6000

0.0

0.02

0.04

0.06

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Why This Interest?

Imaging Study



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Lessons Learned - so far

• Regulatory feedback (EU)– Study approved in 3 EU countries without major issues:

• Validation of analytical methods required for future studies• Concern about high dose for Initial Test Cohort

• Feedback from clinicians/operational– Internal

• Open minded lead clinician – could have been an issue!!!• Some opposition from operational

– External• Investigators very open and helpful in setting up study

• Status: Study still ongoing – 4 patients enrolled in Initial Test Cohort

• Status: Good feedback on DCE-MRI data quality– However, some issues with too large tumors since DCE-MRI here is less

sensitive

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Further DevelopmentCurrent dilemmas?

Phase Ib/IIa combination study planed in recurrent Glioblastoma (GBM)

– Target: to estimate the treatment benefit of combined treatment (with launched anti-angiogenic agent)

• Endpoint: Progression-free-survival• DCE-MRI as PD and clinical marker?

– Future dose when moving into a combination treatment• Should be based on a toxicity/efficacy trade off?• Possibility to adjust the dose of the launched agent?

– Phase 3 gating?

• Further disease areas? – difficulties in generalizing

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References

• Simon, R. Accelerated Titration Designs for Phase I Clinical Trials in Oncology, JNCI, 1997

• Orloff, J. The future of drug development: advancing clinical trial design, NATURE, 2009

• Whitehead, J. Easy-to-implement Bayesian methods for dose-escalation studies in healthy volunteers, Biostatistics, 2001

• Thall, P. F., Dose-Finding Based on Efficacy-Toxicity Trade-Offs, Biometrics, 2004

• Chang, M. A Hybrid Bayesian Adaptive Design for Dose Response Trials, Journal of Biopharmaceutical Statistics, 2005

• Penel, N., “Classical 3+3 design” versus “accelerated titration designs”: analysis of 270 phase 1 trials investigating anti-cancer agents, Invest New Drugs, 2009

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Thanks!

Contact info: [email protected]

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Oncology Dose Finding A Case Study: Intra-patient Dose Escalation Jonas Wiedemann, Meghna Kamath Samant & Dominik Heinzmann, pRED Biostatistics, Valerie