Immunotherapies show benefits in hormone-refractory prostate cancer

Two novel, investigational forms of immunotherapy showed positive outcomes in separate studies reported at the recent Genitourinary Cancers Symposium in San Francisco.

Increasing the potency of the active cellular immunotherapy sipuleucel-T (Provenge) appears to increase survival in patients with hormone-refractory prostate cancer, according to a study by researchers from Dendreon Corp. The correlation appeared to be independent of other important baseline prognostic factors.

In two phase III trials, researchers evaluated cumulative product release parameters of sipuleucel-T, including CD54 upregulation and the number of total nucleated cells (TNCs) among patients treated with sipuleucel-T. CD54 is a costimulatory molecule that serves as a marker for androgen presenting cells. Its expression increases when these cells become activated. This upregulation of CD54 serves as a potency release assay for sipuleucel-T.

Results of the trials showed that sipuleucel-T patients experienced improved survival if they received more cells across three doses (p=.019) or higher cumulative CD54 upregulation values (p=.009).

In a second study, the GVAX immunotherapy increased patient survival in a phase II trial in patients with metastatic hormone-refractory prostate cancer. More than 400 patient-specific GVAX-induced antibody responses were identified in the sera of the treated patients by three different biochemical techniques, confirming that GVAX treatment results in a broad, multi-antigen immune response, researchers from Cell Genesys, Inc. reported.

Ongoing analysis of these GVAX-induced antibody responses has shown that at least two of the antibody responses are associated with patient survival, independent of the dose and number of treatments administered, researchers said.