1

Statistical Review

Dr. Shan Sun-Mitchell

2

ENT 00-02

Primary endpoint: Time to treatment failure by day 50

Placebo BDP Patients randomized 67 62 Number of treatment failures 30(45%) 18 (29%)Adjusted hazard ratio (95% CI) 0.63 (0.35, 1.13) Stratified log rank test P = 0.1177

3

Multiplicity

• Multiple analyses on multiple pre-specified and non-specified endpoints for study ENT 00-02, study 875 and both studies combined were conducted.

• Once the study failed on the primary endpoint, any further analyses are exploratory and statistical significance cannot be determined.

4

Post-Hoc Endpoints• Survival at Day 200 Post-Transplant

– Based on the timing of the transplant, not on randomization date or study drug administration

– Not a valid endpoint for comparison

• Survival at One Year Post-Randomization– Not pre-specified for either trial– Sponsor’s p=0.04 in ENT 00-02 can not be compared with

the 0.05 level

---primary failed, no α left

---multiple analyses on multiple endpoints • Overall Survival Post-Randomization

– Not pre-specified for either trial– No planned uniform follow-up

5

Problems with Post-Hoc Analyses

• Study ENT 00-02 failed to demonstrate efficacy based on the primary endpoint

• There was no uniform follow-up for patients post study treatment and any post study treatment or other conditions that may influence survival were not captured---potential bias in the analyses.

• All subsequent analyses are considered exploratory since there is no type I error rate left for further testing. Any subsequent analyses can only inflate type I error rate. All the p-values in the subsequent analyses are not interpretable.

6

Problems with Pooling / Meta Analyses

7

Problems with Pooling

• The two trials are not concurrent—10 years apart

• Two different study designs

• Primary objective and study endpoints were different

• The stratification factors were different

• Different study therapy and follow-up durations

• Different enrolled populations

• Follow-up on all patients for survival not planned

8

Guidelines on Meta Analyses

• ICH Guidance E9: “Under exceptional circumstances a meta analytic approach may also be most appropriate way, or the only way, of providing sufficient overall evidence of efficacy via an overall hypothesis test. When used for this purpose the meta-analysis should have its own prospectively written protocol”

9

Guidelines for Meta Analyses

• EMEA 2001 Points to consider on applications with 1. Meta analyses; 2. One pivotal study, Section 11.1.3 Regulatory prerequisites of retrospective meta-analysis: “prerequisites for a retrospective meta-analysis to provide sufficient evidence for a claim include:--Some studies clearly positive”… “A retrospective meta-analysis of only two studies originally intended to stand on their own is not expected to add any useful information”

10

Post-Hoc Exploratory Analyses:Overall survival post-randomization

for studies 875 and ENT 00-02

875 00-02

Placebo BDP Placebo BDP

Subjects randomized 29 31 67 62

Survival status (dead ) 17(59%) 10(32%) 32(48%) 27(44%)

Hazard ratio (95% CI) 0.47 (0.22, 1.04) 0.71(0.42, 1.20)

Stratified logrank test* p=0.06 p=0.20

* p-value can not be compared to 0.05

11

• No pooling / Meta analyses can be conducted (ICHE9 and EMEA 2001) as neither of the studies demonstrated efficacy with respect to survival

12

Summary• Failed primary endpoint

• Further analyses of pre-specified /unspecified endpoints increases the false positive error rate

• Multiple analyses of multiple endpoints have been conducted

• Survival at day 200 post-transplant—not valid efficacy endpoint

• Pooling /Meta analysis not acceptable

13

Safety

• Clinically significant safety issue is HPA axis suppression

• ACTH stimulation tests done at baseline and, also day 51, if normal baseline and no treatment failure by day 50, ENT 00-02

• Abnormal HPA axis function day 51 in 86% of BDP patients vs. 58% of control group (77% vs. 57% in a second analysis)

14

Registration Study

• Failed primary efficacy endpoint

• Abnormal HPA axis function at day 51 was identified as a safety issue

15

Conclusion

• Additional studies are necessary to demonstrate efficacy and safety