Hormone-Refractory Prostate Cancer
or Castrate-Resistant Prostate Cancer
Treating Maintaining Quality of Life
VACCINES FOR PROSTATE CANCER
The FDA has approved Dendreon's Provenge vaccine and it is an available, proven treatment. The other vaccines currently in development are GVAX and Prostvac-VF. These two are briefly discussed here. Provenge is on its own page.
May 3, 2010. Originally
developed by Cell Genesys, it was bought out by BioSante last
October. BioSante plans new prostate cancer drug testing (or
re-start testing almost two years after research was stopped -- it
was put on hold in August 2008 because of a high number of deaths
among patients taking the drug..) This is expected by YE2010,
subject to regulatory approval. BioSante said it has started
manufacturing new GVAX Prostate and is working to get the Food and
Drug Administration to allow it to resume testing. It hopes to begin
treating patients in a midstage clinical study in the beginning of
the fourth quarter. This Vaccine was in phase III development.
The most recent clinical trial results for
this vaccine is a phase II trial whose purpose was to evaluate
PROSTVAC-VF for safety and for prolongation of progression-free
survival (PFS) and overall survival (OS). The trial was a
randomized, controlled, and blinded phase II study. Details follow.
No. of patients: 125 randomly assigned. Patients had minimally symptomatic HRPC (mCRPC). Eighty-two patients received PROSTVAC-VF and 40 received control vectors (essentially a placebo). Patients were limited to those believed to have favorable risk features. Patients with visceral metastases or pain requiring opioid analgesics were excluded and they were required to have ECOG performance status of 0 or 1 as well as a Gleason score of ≤ 7 (2).
vaccine: "PROSTVAC-VF comprises two recombinant viral vectors, each
encoding transgenes for PSA, and three immune costimulatory
molecules (B7.1, ICAM-1, and LFA-3). Vaccinia-based vector was used
for priming followed by six planned fowlpox-based vector boosts.
Patients were allocated (2:1) to PROSTVAC-VF plus
granulocyte-macrophage colony-stimulating factor or to control empty
vectors plus saline injections." Note that the viruses are the same cowpox virus that
forms the basis of the smallpox vaccine and a bird virus called fowlpox. They are genetically engineered to carry prostate specific
antigen or PSA, which is made only by prostate cells.
Overall Survival (OS) (evaluated 3 years post study),
Conclusion: PROSTVAC-VF immunotherapy was well tolerated and associated with a 44% reduction in the death rate and an 8.5-month improvement in median OS in men with mCRPC. A larger phase III trial is needed.
Note: PROSTVAC-VF is being developed by BN ImmunoTherapeutics, a division of Danish biotech firm Bavarian Nordic (BAVA.CO).
References - Prostvac-VF
1. Philip W. Kantoff, Thomas J. Schuetz, Brent A. Blumenstein, L. Michael Glode, David L. Bilhartz, Michael Wyand, Kelledy Manson, Dennis L. Panicali, Reiner Laus, Jeffrey Schlom, William L. Dahut, Philip M. Arlen, James L. Gulley, Wayne R. Godfrey, Overall Survival Analysis of a Phase II Randomized Controlled Trial of a Poxviral-Based PSA-Targeted Immunotherapy in Metastatic Castration-Resistant Prostate Cancer, J. Clinical Oncology Jan 25 2010: doi:10.1200/JCO.2009.25.0597.
2. EJ Small et al, Developing Immunotherapy As Legitimate Therapy for Patients with Prostate Cancer, J. Clin Oncology, vol 28, 2010, editorial.
Author: Howard Hansen, last update 28 July 2010
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