Replies to post #6831 on GTC Biotherapeutics (fka GTCB)

[croumagnon]

"There is no SPA."

I suppose that can be good or bad depending on the results!

If the results are superb, say for instance 0 DVTs for ATryn while the historical cases of Plasma derived AT had a 4% occurence of DVTs, then it does not really matter whether or not there was an SPA, although most would feel more confortable knowing that there was a contractual obligation from the FDA to approve (although the FDA is free to break that contractual agreement!)... If the results are horrible, then again it does not matter as ATryn would be failed in either case...

It is when the results are borderline that an SPA could matter. For instance if the results are just slightly as good or better than what an SPA requirement would have been, then an SPA would bode well for approval while a lack of an SPA would give us pause as to what the FDA may do. However, if the results are slightly inferior to such an SPA agreement, then not having an SPA may bode better for the chance of approval because the hard nosed statisticians at the FDA usually like to stick to the number previously agreed upon. Without an SPA, there is no such agreement so anything could happen...

[exwannabe]

Re: 2 points.. Point 1

In any non-inferiority trial of A vs B the goal is to show that A is better than "half" of the B "treatment effect". How that exact value is defined seams to be very open.

So in ANY NI trial, we must pre-determine what the "half" value is. To do this, we MUST look at historical B vs placebo (or SOC). This sets the NI target for the trial to beat relative to B.

In this trial, it's somewhat confusing because the control arm itself is semi-historical, but this matters nadda.

The comparison in this trial is between rAT vs (AT arm + NIDelta), where the NI delta is something like historical (placebo-AT)/2.

Given that I assume the comparison arm will come out at near 0, the biggest variable in the goal will be the NI Delta, which will be based on the historical rate of symptomatic DVT.

WRT the lack of a SPA, I have a serious question.

Would GTCB have discussed the NI delta with the FDA before hand?

If not, then a "close call" trial result would be a serious issue.

[I assume the efficacy data will come in very sound, and this is all irrelavent]