.. GM-CSF-Modified Tumor Cell Vaccines GM-CSF stimulates myeloid progenitor cells and induces antitumor immunity and has been demonstrated to have biologic activity in metastatic CRPC as well as biochemical hormonenaive disease.22 An increase in the number of circulating monocytes and DCs was observed after 14 days of GM-CSF treatment. Patients on long-term GM-CSF tended to have lower initial T stage, Gleason score,
and pretreatment PSA, suggesting that lower stage and more indolent disease may optimally benefit from immunotherapy. Although irradiated autologous tumor cell vaccines transfected with the GM-CSF gene have exhibited immunogenicity and antitumor Inhibitors,research,lifescience,medical activity in small trials, the need for harvesting an adequate number of autologous tumor cells followed by Inhibitors,research,lifescience,medical ex vivo manipulation is onerous. The GM-CSF-secreting vaccine GVAX (Cell GeneSys, Inc., South San Francisco, CA; now part of BioSante Pharmaceuticals) was a mixture of the PCa cell lines PC-3 and LNCaP transduced with a replication-defective retrovirus containing cDNA for GM-CSF and then irradiated. In an earlier trial, GVAX platform-based
Inhibitors,research,lifescience,medical click this immunotherapy was administered to 34 patients with metastatic chemonaive CRPC.23 This trial demonstrated a complete PSA response (PSA level dropped to 0.1 ng/mL) in 1 patient, a reduced PSA velocity in 73% of patients, stabilized or decreased levels of a biomarker of osteolytic activity in 69% of patients, and produced median survival times of 34.9 and 24 months with the high and low doses of immunotherapy,
respectively. The agent was subsequently modified to increase GM-CSF Inhibitors,research,lifescience,medical production. A phase I–II, multicenter, open-label study was designed to characterize the selleck Tofacitinib safety and activity of this modified product in patients with metastatic CRPC.24 Eighty men with progressive asymptomatic, chemotherapy-naive PCa with castration-resistant disease were Inhibitors,research,lifescience,medical treated with different dose levels of the vaccine product. The most common adverse effect was injection-site erythema and a maximal tolerated dose was not established. The median survival time was 35 months in the high-dose group, 20 months in the mid-dose, group, and 23.1 months in the low-dose Brefeldin_A group. However, data on administration of postvaccine docetaxel were unavailable and may have affected outcomes and there was no control arm that did not receive GVAX. PSA stabilization occurred in 15 patients (19%), and a > 50% decline in PSA was seen in 1 patient. The proportion of patients who generated an antibody response to 1 or both cell lines increased with dose and included 10 of 23 (43%) in the low-dose group, 13 of 18 (72%) in the mid-dose group, and 16 of 18 (89%) in the high-dose group.