Biotech Values

[urche]

No, it's not GERN that worries me.

Though I don't know much about it.

Rather, the collaboration between Cytogen and Progenics, The PSMA Development Company, is what makes me wonder if, in retrospect, we DNDN investors were barking up the wrong tree so loud we couldn't see the evidence around us.

First, to get back to an earlier question posed by Bio (#8583), PSA is indeed a poor marker for prostate cancer in some respects. PSA elevation says something about chances of prostate cancer when used as a screening test; and PSA doubling time has even more important significance and acceptance as a measure of tumor load and pathogenicity. But, the fact remains that something like half of men who have an elevated PSA do not have prostate cancer---but need to go thru needless worry, risk (from further testing), and expense once the test is done. Also, as we have seen, PSA rises do not correlate well with survival. So, PSA has its limitations, for sure.

PSMA (prostate specific membrane antigen) has a lot of theoretical and practical reasons to consider it a potentially better target both diagnostically and therapeutically.
Here is a link to the Cytogen website with a few paragraphs on the complicated story behind PSMA:
http://www.cytogen.com/pipeline/index.php#psma

Here is my take on what PSMA has going for it, based largely on some research I did on the topic last year.

It is a cell surface glycoprotein with much smaller “sink” effect caused by large secreted pool of antigen. This apt description comes from a Cathi email (from another discussion group:
PSMA sounds like an ideal target.....cell surface, rapidly internalizing antigen present in high density in all prostate cancer, increasing in density (two cell lines have 1 million receptor sites per cell) as cancer progresses, highly specific to prostate tissue and other solid tumor vasculature....low normal expression and poor access for antibody to that normal expression, NON SECRETORY, and prostate cancer mets are typically small volume and predominately involve bone marrow and lymph nodes which recieve high levels of circulating antibody....in other words, good access and better penetration for the drug to the typical mets

PSMA holds promise both diagnostically and therapeutically in prostate cancer research, but has not gained widespread acceptance yet.

Commercially, PSMA appears to be controlled by an alliance of Cytogen and Progenics, or, to be more precise, the PSMA Development Company, LLC, equally owned by Progenics and Cytogen. Antibody to PSMA, it should be noted, is also the strategy chosen by Medarex in developing MDX-070, a non-vaccine therapeutic agent in phase II study.

The intellectual property behind PSMA is so convoluted that it's unfathomable to me and a major reason to doubt the Cytogen-Progenics collaboration will succeed, IMO.

Even though I feel like I am obscuring, not clarifying the issues, that's enough for now.

Urche