Phase 3 trial data presented at the American Association of Cancer Research annual meeting support the mechanism of action of Provenge (sipuleucel-T), a novel investigative immunotherapy for advanced prostate cancer, according to a statement issued by Dendreon Corp., of Seattle, which is developing the treatment.

Designed to stimulate a T-cell response to prostate cancer cells, Provenge targets prostatic acid phosphatase (PAP), an antigen expressed in 95% of prostate cancer.

The data were from 237 patients who participated in the immune monitoring protocol of the IMPACT (Immunotherapy for Prostate Adenocarcinoma Treatment) trial. Provenge generated antigen-specific responses, including responses to PAP; these responses were not observed in placebo recipients. Provenge also triggered both cellular and humoral immune responses in vivo that were first observed six weeks after dosing; these responses persisted at 26 weeks. In addition, Provenge induced a T-cell response, suggesting the induction of immunologic memory.

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“These data strongly support our understanding of the proposed mechanism of action of active cellular immunotherapies,” said David Urdal, PhD, Senior Vice President and Chief Scientific Officer of Dendreon.