Journal Article

Low-dose cyclophosphamide enhances antigen-specific CD4 super(+) T cell responses to NY-ESO-1/ISCOMATRIX(TM) vaccine in patients with advanced melanoma

Hopkins, Wendie, Parente, Phillip, McArthur, Grant A, Davis, Ian D, Stan, Rodica, Chen, Li, Haydon, Andrew, Xiao, Kun, Jackson, Heather, Klein, Oliver, Cebon, Jonathan, Dimopoulos, Nektaria, Chen, Weisan, Maraskovsky, Eugene

2015

Overview

Clinical outcomes from cancer vaccine trials in patients with advanced melanoma have so far been disappointing. This appears at least partially due to a state of immunosuppression in these patients induced by an expansion of regulatory cell populations including regulatory T cells (Tregs). We have previously demonstrated potent immunogenicity of the NY-ESO-1/ISCOMATRIX(TM) vaccine in patients with resected melanoma (study LUD99-08); however, the same vaccine induced only a few vaccine antigen-specific immune responses in patients with advanced disease (study LUD2002-013). Pre-clinical models suggest that the alkylating agent cyclophosphamide can enhance immune responses by depleting Tregs. Therefore, we have enrolled a second cohort of patients with advanced melanoma in the clinical trial LUD2002-013 to investigate whether pre-treatment with cyclophosphamide could improve the immunogenicity of the NY-ESO-1/ISCOMATRIX(TM) vaccine. The combination treatment led to a significant increase in vaccine-induced NY-ESO-1-specific CD4 super(+) T cell responses compared with the first trial cohort treated with vaccine alone. We could not detect a significant decline in regulatory T cells in peripheral blood of patients 14 days after cyclophosphamide administration, although a decline at an earlier time point cannot be excluded. Our observations support the inclusion of cyclophosphamide in combination trials with vaccines and other immune-modulatory agents.