A phase I dose escalation trial of vaccine replicon particles (VRP) expressing prostate-specific membrane antigen (PSMA) in subjects with prostate cancer

► The alphavirus-based replicon vaccine strategy has advantages over other vaccines. ► PSMA-VRP is a propagation defective, viral replicon vector system encoding PSMA. ► A phase I first in human study of PSMA VRP in prostate cancer was safe. ► All subjects had immunologic competence noted by responses to standard mitogens. ► No cellular responses to PSMA was seen; few patients had a humoral response to PSMA.