Replies to post #30703 on Biotech Values

[aslan2772]

re: GTCB equivalency. Dew, thanks for the great find.

I would have to agree that the philosophy makes sense, at least for the example you provided (Human plasma-derived vs. recombinant production in Goats). But in comparing GTCB's technology to a CHO bioreactor (Chinease Hamster Ovary), both producing a Human protein, the line is really more blurry, is it not? In the cell biological and biochemical senses, CHO bioreactors also produce "transgenic" proteins, they just do it in vitro. Thus, my main point is that since glycosylation patterns are specific to the host cell species, they can be expected to differ between all three species: human, goat and hamster. But for us humans, goat and hamster are more similar to each other (and thus likely more interchangable) in that they both have non-human glycosylation patterns.

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 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.

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.

[DewDiligence]

Reposted from the GTCB board on iHub (msg #65):

>DEW, could you explain the significance in the difference in rhAT and pAT from the article you posted. I gathered that the pAT stayed active longer in the bloodstream than the rhAT. Please also explain how this could impact approval and prescribing choice by MD's<

For those who haven’t seen the reference, here’s it is: #msg-11801772.

ATryn evidently does have a shorter half-life than plasma-derived antithrombin due to a different proportion of the two AT isoforms. When I asked GTC about this, the answer was that the shorter half-life is immaterial in most clinical settings. They felt that, if anything, the shorter half-life is a modest benefit in that it makes it easier to avert an overdose.