Defining Success in Oncology Drug Development

Richard Pazdur, MDCDER, FDA

The views expressed are the results of independent work and do not necessarily represent the views or

findings of the United States Food and Drug Administration or the United States

Basis for NDA Approval• Demonstration of efficacy with acceptable

safety in adequate and well-controlled studies

• Ability to generate product labeling that– Defines an appropriate patient population – Provides adequate information to enable safe

and effective use – Approval for an indication, not drug

Regulatory Terms• Accelerated Approval--serious or life-threatening

disease, benefit over available therapy. Use of surrogate; mandated phase IV trials

• Fast Track--life-threatening disease, potential to address unmet medical need. Rolling NDA, meetings

• Priority review--drug would be a significant improvement compared to available drugs. Review of NDA in 6 months

Activity vs. Benefit

• Biologic Activity--screening of a compound, phase II trial endpoint, an indication for further study

• Clinical benefit--what is meaningful to a patient

• The approval process is not a screening process for drug activity

Should Oncology Drug Regulation Be Different?

• Life-threatening nature of diseases--patient access vs necessary data for approval

• Drugs multiple action modes; combinations• Risk/benefit ratio--different perspective on

serious adverse events; highly trained specialists using drugs rather than GP

• Product label and off-label uses

Should Oncology Drug Regulation Be Different?

• Investigational nature of discipline--Cancer Centers, Cooperative Groups, NCI

• Wide variety of products used by oncologists--chemotherapy, biotherapy, devices, supportive care, diagnostics

• Multidisciplinary approaches• Represents over 100 diseases/indications

Risks in Developing Oncology Drugs

• Indication--lack of predictive models• “Creative Indications”--progressively more

refractory patient, market share• Two trials versus one trial• Dose ranging studies--moving away from

MTD

Oncology Trial Concerns

• Minimize bias– Blinding trials (few)– Endpoints that minimize bias– Internal consistency of subgroups, endpoints

• Magnitude of change of endpoint– Clinical significance– Underpowered trials--guessing treatment effect

• Isolating effect of drug

Endpoints for traditional approval: Survival

• Defined as the time from randomization to death

• Unambiguous endpoint that is not subject to investigator interpretation or bias from unblinded studies

• Assessed daily

Traditional Endpoints: Survival

• Drawbacks– Requires large sample size and long follow-up– Confounder--Cross-over therapy may “wash

out” a survival effect

Traditional Endpoints: Survival

• Non-inferior or improved survival constitutes “patient benefit” after consideration of toxicity and the magnitude of the benefit

• Non-inferior outcome ensures that a survival advantage associated with an approved drug will not be lost with a new agent

Time to Progression--Advantages

• Could use a smaller sample size and shorter follow-up than trials that require a survival endpoint

• Differences will not be obscured by secondary therapy if cross-over effect exists

• “Time to symptomatic progression”

TTP: Problems

• Unblinded trials introduce bias• Must evaluate all patients on a regular basis

– Must evaluate all sites of possible disease – Complete ascertainment of all sites at baseline

and follow-up (i.e., look for new sites) – Same type of assessment tool at each follow-up – Should use same evaluation schedule

TTP: Problems

• How much improvement constitutes benefit?

Response Rate

• Unique endpoint--treatment is “entirely” responsible for tumor reduction

• In contrast, survival and TTP have an effect of the natural history PLUS treatment effect

• Must consider duration of response• Does not include stable disease• Pick your criteria and stick with it

Complicated Picture of RR

• Number of CRs vs PRs?• Duration of responses?• Location of responses (e.g., liver vs skin)?• Association with symptom improvement?• Extent or bulk of metastatic disease?

Palliation and Patient Reported Outcomes

• Blinding and associated antitumor effects (response rates) lend credibility– Use simple instruments– Hypothesis-driven– Avoid multiple endpoints– Example: Photofrin PDT and dysphagia

scale

Potential palliative endpoint: Health-related quality of life

• Pro: Patient’s perspective on treatment• Con:

– Blinding is essential, but difficult to do– Careful serial assessments

• Missing data makes interpretation problematic• Multiple endpoints and comparisons to baseline must be

adjusted for in the statistical analysis plan– Clinical significance of score changes may be unclear– Is additional information gained, compared to a careful

recording of toxicity/symptom data?

Accelerated Approval- Subpart H (21CFR 314)

• For serious or life-threatening diseases• Where the drug appears to provide benefit

over available therapy• Approval based on a surrogate that is

reasonably likely to predict clinical benefit

21CFR314 (continued)

• Subject to the requirement that the applicant verify and describe benefit

• Post-marketing studies would usually be underway

• The applicant shall carry out such studies with due diligence

Accelerated Approval• Docetaxel (Taxotere)• Irinotecan (Camptosar)• Doxorubicin HCl liposome (Doxil--2 indications)• Capecitabine (Xeloda)• Cytarabine liposomal injection (Depocyt)• Temozolomide (Temodar)• Amifostine (Ethyol)--sNDA• Celecoxib (Celebrex)• Gemtuzumab (Mylotarg)• Gleevec (imatinib mesylate) (STI 1571)

Issues Related to the AA Program As a Whole

• The importance of confirmatory trials being underway at the time of AA

• The approach of studying slightly different populations in the confirmatory setting than the AA population

• Relative merits of different trial designs – single arm in refractory populations– randomized trials in less refractory patients

Challenges for Oncology Drug Regulations

• New “targeted therapies”– Re-define definitions of diseases– Greater efficacy in selected population may

result in smaller patient populations– Novel surrogates to be validated– Dosing aimed at target rather than MTD– Dose studies, chronic administration

Challenges

• Greater number of candidate drugs– Careful selection of agents to demonstrate clinical

benefit by oncology community– Patient accrual to trials need to be increased– Patients entering trials should reflect the patient

population which will eventually use the drug– International studies, international agreement of

endpoints and study design and approval criteria