GTC Biotherapeutics (fka GTCB)

[DewDiligence]

Re: Handicapping the US Atryn trial

>What was your opinion on the possibility of top-lines results being negative?<

Negative results are a possibility in any clinical trial; seasoned biotech investors know that there are many ways for a clinical trial to be undone by poor execution or bad luck.

Nonetheless, I see several reasons to be confident of the outcome of the US ATryn trial:

1. The primary efficacy endpoint is symptomatic DVT—not merely DVT observable with a ultrasound scan. Thus, the US trial has a more favorable endpoint for GTC than the “any DVT” endpoint used in the trial that supported EU approval. (There were two cases of DVT seen in the EU trial, but they were asymptomatic.)

2. The comparator arm in the US trial is plasma-derived antithrombin as determined by analysis of historical cases (#msg-5609005). There is no scientific reason to believe that ATryn will work less well than plasma-derived AT.

3. Forty-five percent (14/31) of the patients in the ATryn arm of the U.S. phase-3 trial are already known to have been treated successfully because they are the same 14 patients who comprised the data set that led to ATryn approval in the EU. This is like a baseball player stepping up to home plate with a count of two balls and no strikes!