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Biotech / Medical : Cell Therapeutics (CTIC) -- Ignore unavailable to you. Want to Upgrade?

To: quidditch who wrote (457)	2/24/2005 1:06:59 PM
From: Ian@SI	Respond to of 946

Couldn't the public results to date also be consistent with excellent efficacy? i.e. Xyotax is selectively absorbed by the tumour, kills it, causing the excess drug to be removed from the bloodstream by the kidneys simply because there's a shortage of tumour? ======================================================== From CTIC's last 10-K (Filed 2004 03 12): We are also developing a new way to deliver cancer drugs more selectively to tumor tissue to reduce the toxic side effects to normal organs and tissues and to improve the anti-tumor activity of existing chemotherapy agents. Our technology links, or conjugates, chemotherapy drugs to biodegradable polymers, including polyglutamate. Two of our product candidates, XYOTAX and CT-2106, utilize a unique biodegradable protein polymer to deliver a taxane and a camptothecin, respectively, more selectively to tumor tissue. Because tumor blood vessels are more porous than those in normal tissue, polymers within a specific size range circulate in the bloodstream and get trapped in tumor tissue and accumulate preferentially within the tumor. In the tumor tissue, the polymer drug is taken up by cells. The polymer bound drugs are inactive while circulating in the bloodstream, which may also lower toxicity compared to the active drug substance alone. Once within a cell, naturally occurring enzymes digest the polymer releasing the chemotherapy drug. Preclinical animal studies and human clinical data to date indicate that our polygulatamate technology may allow more drug to reach the tumor, provide increased efficacy using the same amount of chemotherapy drug and less toxicity at the same or higher equivalent doses of drug, as compared to unlinked cancer drugs. Our first application of the polymer technology is XYOTAX ™ , or CT-2103, which is paclitaxel linked to polyglutamate. Paclitaxel is the active ingredient in Taxol ® , one of the world’s best selling cancer drugs. In animal studies, XYOTAX demonstrated fewer side effects and improved tumor killing-activity when compared to paclitaxel alone. Eight phase I clinical trials, three phase II clinical trials and three phase III clinical trials are currently underway. We also anticipate that the Gynecologic Oncology Group, or GOG, will submit a phase III trial protocol through a Special Protocol Assessment, or SPA, to the FDA to compare XYOTAX as maintenance therapy, administered monthly for 12 months, to no maintenance treatment for ovarian cancer patients who have achieved a complete remission, or CR, following front-line treatment with carboplatin and paclitaxel. The trial is expected to begin in the first half of 2004. We also initiated development of a novel polyglutamate-camptothecin molecule, or CT-2106, and filed a U.S. investigational new drug application, or IND, in December 2001. We initiated a phase I clinical trial with CT-2106 in the first quarter of 2002, and plan to initiate phase II trials in 2004.

To: quidditch who wrote (457)	2/24/2005 1:52:00 PM
From: former_pgs	Read Replies (3) \| Respond to 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.