Protoxin trial for recurrent prostate cancer

November 11, 2006

Protoxin, also called PRX302, is a drug being tested on men with
localized recurrent prostate cancer in Phase I clinical trials in Texas
and Vermont.

Patients considering this trial must have experienced recurrence after
completing a full course of definitive external beam radiation or
definitive brachytherapy (but not both) as primary therapy for diagnosed
prostate cancer at least one year prior to enrollment

Our main news about Protoxin is here:
PSA-activated protoxin that kills prostate cancer: phase I clinical
trial is underway
http://www.psa-rising.com/prostateca...otoxin1106.htm

Background:

In Texas, one trial enrolled the first patients in May this year and is
hoping to recruit 36 men with localized recurrent prostate cancer.
Patients must have recurred after EBR or brachytherapy, have PSA level
less than 20 ng/mL and PSA doubling time longer than 3 months. They must
NOT be taking hormone drugs. Also, they must NOT have signs of
metastatic disease including no bone metastases on bone scan, or any
lymph node, lung, liver or soft tissue.
A link to info about that trial is here:
http://clinicaltrials.gov/ct/gui/sho...379561?order=2

The 3 cancer centers so far are
1) Scott and White Cancer Center, Temple, Texas:
http://www.sw.org/sw/portal/_pagr/105/_pa.105/161
2) M. D. Anderson Cancer Center
3) University of Vermont (contact Dr. Mark Plante).

If you think you would want to be in this trial take this info to your
doctor.
This Phase I trial aims to find out:
1) whether the drug is safe
2) whether it has side effects
3) whether it beats back the cancer.

So far they have reached the third "dose level" in testing the drug in
the Temple, TX trial, which began in May and are moving forward to
recruit more patients there and at the 2 other centers.
What they know so far is that PRX302 is activated (switched on) by PSA.
It reduces the size of a prostate cancer tumor by destroying cancer
cells. It does this by making a hole (or pore) in the cell membrane (the
surface covering each prostate cancer cell).

PRX302 is injected into the prostate under ultrasound guidance.

PRX302 is expected to have fewer side effects than traditional or
current systemic treatments because it is injected directly into the
prostate.

The high level of PSA being produced by prostate cancer cells switches
on the drug, the drug forms pores on the cell´s surface, and the
cancer cells die.
This is the plan. Whether it will really work on men with localized
recurrent prostate cancer, and whether it will keep working permanently
or for a long time, no one will know for sure till the trial is further
along and/or completed.

If it works reasonably well they will take it to a Phase II and then a
Phase III clinical trial. Ultimately this might create a whole new
treatment for men with early stage localized prostate cancer.

Another Phase I trial testing Protoxin for BPH (benign overgrowth of the
prostate) is under way in Vancouver, Canada.

knowledge is power - growing old is mandatory - growing wise is optional
"Many more men die with prostate cancer than of it. Growing old is
invariably fatal. Prostate cancer is only sometimes so."
http://community.webtv.net/PALMER_ENT/doc

Trials like this make me think that early ADT after treatment
failure may be a Good Thing. This drug, like Tookad and
some other experimental drugs, appears to be best used
to attack known, localized tumors, not systemic cancer that's
all over the body. If a patient has failed treatment but there
is evidence that his disease is still localized, then if ADT can
keep the cancer contained for a few years there might be
time for one of these new therapies to develop. If the
patient waits for ADT until known metastasis, then his
only options are whatever new systemic therapies may
be available.

We often think that patients who have recurrent PSA after
treatment must have metastases, and some do. But I don't
think they all necessarily do. Failed radiation patients may
have tumor cells in the prostate that survived the xrays.
Failed surgery patients may have bits of prostate tissue
remaining, or bits of tumor in the immediate surroundings
of the prostate that might still be accessible to local
therapies. Maybe even the guys who had both surgery
and radiation still have "localized" disease.

A real specialist could say whether or not that's possible,
but it seems reasonable to my non-expert mind that it
could happen.

Alan

Alan, the premise - that rising PSA after primary Tx does not
necessarilly mean systemic disease - is far more than reasonable; I
think it is prevalent. Although detectable PSA post-Tx is a major
downer, it is not by any means a death sentence, especially if you did
acheive undetectability.

Bill Denton
RP 2/12/02
PSA 1.10
Memphis