Replies to post #138525 on Biotech Values

[exwannabe]

Background: Futility limits at interims are done in an inherently odd and confusing fashion

It does not seam odd to me. Rephrase it as "What is the present power of the trial, under the original assumptions but inserting the known events. Is this power now less than X?"

I am stunned that some Futility Thresholds are this high though.

[p3analyze]

Clark, assuming the futility boundary was completely decoupled with the OBF upper efficacy boundary, then I agree with your calculation with a futility HR of 1.04 and 0.92 for IA1 and IA2, respectively.

However, it's not clear to me whether the conditional power futility approach was used, and whether the OBF boundary was modified to compensate for the power loss. The reverse engineering seems to suggest OBF was left intact.