ORLANDO, FL, USA (UroToday.com) - In this study, as of September 14, 2012, 7 patients received an infusion of sipuleucel-T. These patients had progressed to mCRPC and had been previously treated with at least one infusion of sipuleucel-T on the PROTECT trial. The median interval since the last infusion had been 8.6 years. This is the first study to demonstrate an immunological memory response of several years after initial treatment in patients being retreated with sipuleucel-T. The retreatment was well tolerated and the antigen-specific cellular responses were boosted after retreatment.
A conversation with Michael Glode, MD
“This study was initially done by giving patients a single injection of GnRH analog to suppress testosterone, and then giving them the sipuleucel-T vaccine (or not) and finding out what would happen to PSA and time to recurrence. The main point of the (original) study (Beer T. et al. Clin Can Res, 2011) was that there was some prolongation of the rate of rise of PSA. These patients were then being followed for longer-term effects -- as well as including survival. As part of that, when these patients began to have biochemical relapse, they could receive a booster of the sipuleucel-T product.
“And the purpose of the current study, presented here at the GU Cancers Symposium, was to look at the immune response. The main take-home points of this study were to look at activation of antigen-presenting cells, which is measured by CD54 up-regulation, as well as the response on ELISPOT assays to either PA2024 or prostate-acid phosphatase. PA2014 is the fusion protein used as the vaccine, specifically the fusion between prostate-acid phosphatase in GMC-SF. There is a very nice correlation between the ELISPOT assays, between the prostate-acid phosphatase, and the fusion protein, indicating a nice immune response as measured by either of those tests.
"In conclusion, the key point in this poster is that in these initial responses (where an up-regulation of the CD54 goes from the 5 range to the 20 range, 15 or 20 range) the average time was 8.6 years. This immune response persists; before the first booster infusion, the immune response was still in the 20 range and stayed there through the next three infusions. There is a prolonged, activated cell-immune response to the initial infusion, and whether or not the booster makes any difference was indeterminate from this study, which, with seven patients, was relatively small."
Presented by Tomasz M. Beer,1 L. Michael Glode,2 Raymond Lance,3 Richard Greengold,4 Robert Sims,5 Yang Wang,5 Nadeem Sheikh,5 John Corman6 at the 2013 Genitourinary Cancers Symposium - February 14 - 16, 2013 - Rosen Shingle Creek - Orlando, Florida USA
1Oregon Health & Science University Knight Cancer Institute, Portland, OR; 2University of Colorado, Denver, CO; 3Eastern Virginia Medical School, Norfolk, VA, 4South Orange County Medical Research Center, Laguna Hills, CA; 5Dendreon Corp. Seattle, WA; 6Virginia Mason Medical Center, Seattle, WA
Written by Karen Roberts, medical writer for UroToday.com