Dendritoma vaccination combined with low dose interleukin-2 in metastatic melanoma patients induced immunological and clinical responses

A pilot clinical trial using dendritomas, purified hybrids from the fusion of dendritic/tumor cells combined with a low dose of IL-2, in metastatic melanoma patients was conducted in order to determine its safety and potential immunological and clinical responses. Ten metastatic melanoma patients were enrolled into this study. Dendritoma vaccines were created by fusing dendritic cells stained with green fluorescent dye with irradiated autologous tumor cells stained with red fluorescent dye and purifying the hybrids using immediate fluorescent-activated cell sorting. Initial vaccine was given subcutaneously and followed by IL-2 in serially elevated doses from 3-9 million units/m2 for 5 days. Repeated vaccinations were administered without IL-2, at 3-month intervals for a maximum of 5 times. Immune reactions were measured by the increase of interferon-γ (IFN-γ) expressing T cells. Vaccine doses ranged from 250,000 to 1,000,000 dendritomas. There was no grade 2 or higher toxicity directly attributable to the vaccine. All patients experienced toxicity due to IL-2 administration (9-grade 2, 3-grade 3, 1-grade 4). Eight of nine evaluable patients demonstrated immunologic reactions by increased IFN-γ expressing T cells. One patient developed partial response at 12 weeks after the first vaccine. Nine months later, this patient achieved a complete response. In addition, two patients had stable disease for 9 and 4 months, respectively; one patient had a mixed response. Our findings demonstrated that dendritoma vaccines with a low dose of IL-2 can be safely administered to patients with metastatic melanoma and induce immunological and clinical responses.