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Biotech / Medical : Cell Therapeutics (CTIC)
CTIC 9.0900.0%Jun 26 5:00 PM EST
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To: quidditch who wrote (457)2/24/2005 1:52:00 PM
From: former_pgs  Read Replies (3) of 946
 
>Why is there, necessarily, an inconsistency between the theory advanced by CTIC (tumor takes up and retains xyotax) and Miljenko's theory that the xyotax in the blood is being excreted?<

So all drugs have a range of concentrations that they must reach in cells to be effective. To elicit an effect on the tumour, you need to reach a threshold concentration of the drug. If 75% of the dose of Xyotax excreted unchanged, that means that you only have 25% of the remaining dose to reach that threshold and elicit the therapeutic effect. That means having less and less margin of error insofar as where the remaining drug goes once inside the body. So for 25% of the administered dose to reach the critical concentration inside the tumour, it would have to be very exquisitely delivered to the tumour while minimizing (or almost eliminating?) uptake by any additional organ.

I find that highly unlikely. I'm not aware of any drug that is able to target so selectively (almost specifically) to one tissue simply based on a somewhat restricted diffusion mechanism. In fact, the remaining neutropenia side effects for Xyotax suggest that such extremely precise targeting may not be happening.

So with regards to #2, I agree with you that there is not a theoretical disagreement between high clearance and highly selective targeting of the remaining drug. It's just my opinion that in practice, this is highly unlikely.
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