Antigen-presenting cells 8015 (Provenge®) in patients with androgen-dependent, biochemically relapsed prostate cancer

Background: Antigen-presenting cells 8015 (APC8015; Provenge®) is an immunotherapeutic product designed to initiate a T-cell-mediated immune response against prostatic acid phosphatase, an antigen overexpressed in 95% of prostate cancer cells. In phase I/II trials, APC8015 has shown immunologic and clinical responses in patients with androgen-independent prostate cancer. This phase II trial was conducted to assess the prostate-specific antigen (PSA)-modulating effects of APC8015 in patients with androgen-dependent prostate cancer (ADPC) with biochemical progression. Patients and Methods: Patients with nonmetastatic recurrent disease as manifested by increasing PSA levels (0.4-6.0 ng/mL) and who had undergone previous definitive surgical or radiation therapy were enrolled. Therapy consisted of APC8015 infusion on weeks 0, 2, and 4 (ie, 3 infusions). Prostate-specific antigen was measured at baseline and monthly until disease progression, defined as a doubling of the baseline or nadir PSA value (whichever was lower) to ≥ 4 ng/mL or development of distant metastases. Results: Thirteen of 18 patients demonstrated an increase in PSA doubling time (PSADT), with a median increase of 62% (4.9 months before treatment vs. 7.9 months after treatment; P = 0.09; signed-rank test). Conclusion: Therapy was well tolerated. APC8015 as single-agent immunotherapy for patients with ADPC and biochemical progression did not result in ≥ 50% decrease in PSA from baseline levels but did appear to modulate PSADT in some patients. Further manipulations of host immunity may be required to achieve a significant antitumor effect.