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Evaluation of phase I/II clinical trials in prostate cancer with dendritic cells and PSMA peptides
B A Tjoa1, S J Simmons, V A Bowes
1Cancer Research Division, Pacific Northwest Cancer Foundation, Northwest Hospital, Seattle, Washington 98125, USA.
Background:
A phase I trial involving patients with advanced prostate cancer was conducted to assess the safe administration of dendritic cells (DC) and HLA-A0201-specific prostate-specific membrane antigen (PSMA) peptides (PSM-P1 or -P2). Thirty-three of the phase I participants were subsequently enrolled in a phase II trial, which involved six infusions of DC pulsed with PSM-P1 and -P2 peptides.
Methods:
Clinical monitoring was conducted up to 770 days from the start of the phase I study. Data collected included: complete blood count, bone and total alkaline phosphatase, prostate markers, physical examination, performance status, bone scan, ProstaScint scan, and chest X-ray, as well as assays to monitor cellular immune responses.
Results:
Nine partial responders were identified in the phase II study based on National Prostate Cancer Project (NPCP) criteria, plus 50% reduction of prostate-specific antigen. Four of the partial responders were also responders in the phase I study, with an average response duration of 225 days. Their combined average total response period was over 370 days. Five other responders were nonresponders in the phase I study. Their average partial response period was 196 days.
Conclusions:
The responses observed in the phase I and II clinical trials were significant and of long duration. The partial-responder group included patients who continued to respond from phase I, as well as those who started to respond during the phase II trial.