Replies to post #30732 on Biotech Values

[DewDiligence]

> GTCB – I guess one good question is whether the accelerated clearance of rhATH from the circulation (apparently with the liver playing a big role) was due to differential glycosylation (or some other form of post-translational modification such as phosphorylation, acetylation, oxidation, etc.), or rather due to purity (plasma-derived having additional blood factors bound or present which decrease clearance). Is plasma-derived ATH as highly purified?<

I discussed this with Dr. Meade at GTC’s 2005 annual meeting. His answer was that:

1) PK/PD differences between ATryn and plasma-derived AT are not caused by differences in purity or glycosylation but rather by differences in the proportion of the two isoforms of antithrombin;

2) The isoform differences give ATryn a stronger binding affinity for heparin than plasma-derived AT;

3) The stronger binding affinity for heparin is probably an advantage for ATryn in therapeutic applications, although there to date no conclusive evidence of this;

4) Luck rather than rational design was the cause of the above differences.

>I don't have online access to the journal that published the article you cited. If I have time, I may stop by the library because it would be good to read the discussion section. If I do I will let you know what I find.<

Thanks—I’ll be interested in your findings.

>On a related note, it might be in GTCB's interest to establish a goat cell line for smaller scale pilot production of proteins under investigation, because such proteins would be equivalent, or nearly equivalent, to the farmed proteins. Such a strategy is an advantage with CHO cells: they are easy to culture on a small scale in the lab for pilot experiments, and can then be scaled up as desired. This idea might be worth passing on to GTCB management.<

GTC may already have done this and I suggest that you contact Tom Newberry to find out. Newberry understands GTC’s technology and replies to inquiries in a timely manner:
Thomas E. Newberry
Vice President, Corporate Communications
Phone: [phone]
[e-mail]

Regards, Dew