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Vaccine therapy: review of results of
"Dendreon" trial in patients with metastatic disease. (December 2002)
The Dendreon Corporation is in our back
yard (located on 1st Avenue) and they have made a good start on prostate
vaccines. They have recently reported results of a 127 subject trial
(D9901) of their "Provenge" product addressing men with hormone refractory
PC (HRPC) who had metastatic disease. Provenge is a fusion of prostatic
acid phosphatase (PAP), a ubiquitous PC cell surface antigen, with
Granulocyte/Macrophage Colony Stimulating Factor (GMCSF), an adjuvant that
stimulates the dendritic cell's uptake of Provenge. Their vaccine
manufacturing process involves harvesting subjects' white blood cells,
selecting out the T lymphocytes and pre-dendritic cells, then incubating
these cells with Provenge. During incubation the dendritic cells take up
and process the Provenge and the product is then reinfused into the
subject with the expectation that the educated dendritic cells will home
to lymph nodes and in that nurturing setting present snippets of PAP to
cadres of T cells. The instruction is to go forth and battle PC. Half of
the men received Provenge and half a placebo infusion.
The overall trial showed a trend toward effectiveness for the vaccine. The
outcome was best seen in men with Gleason sums of 7 or less (60% of the
127). In this group of men, by evaluating only that subset that showed no
PSA progression over 12 weeks, the time to disease progression (TTP) was
l6 weeks for the Provenge subjects and 9 weeks for men receiving the
placebo. Dendreon has now initiated a second trial for HRPC patients with
metastases concentrating on men with Gleason 7 or less.
Another trial, P11, continues to be open for enrollment. This trial is
targeted at HRPC men at an earlier point in the disease process - hormone
sensitive men (no metastatic sites) showing PSA rise following radical
prostatectomy. [I encourage offering participation in P11 to appropriate
patients. The study is available at the Swedish Cancer Institute (call
Jane Arthur 206-386-6921), Virginia Mason Hospital, and at the University
of Washington.
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