Dendritic Cell Vaccination in Patients With Advanced Melanoma

This is a single arm open label trial that will assess the safety and tolerability of mature dendritic cell (mDC3/8) vaccine (primer and booster) in subjects with stage III and stage IV melanoma, followed by treatment with pembrolizumab (anti-PD-1 therapy). Eligible patients that provide written informed consent will undergo apheresis to collect blood mononuclear cells for vaccine production approximately 1 week prior to vaccine infusion. Each study subject will receive cyclophosphamide 300mg/m\^2 intravenously or by mouth 3 to 4 days prior to the vaccine dose, to deplete regulatory T cells. For each vaccine dose, all subjects will receive autologous dendritic cells pulsed with melanoma tumor-specific peptides. On Day 1, the subject will receive the primer vaccine dose; this will be followed by two booster vaccine doses at 6 weeks apart. Peripheral blood will be taken weekly to monitor the immune response to each peptide by tetramer assay. Re-staging will occur after the 3rd vaccine dose, along with tumor biopsy and second apheresis. Anti PD-1 therapy (standard of care) will commence 7-8 weeks after the subject's last dendritic cell vaccine.