Immunotherapy of malignant melanoma using a dendritic cell-amplified tumor RNA vaccine: A phase I study

Abstract

2597 Background: We prepared a dendritic cell (DC) vaccine specific for malignant melanoma and tested its safety in a phase 1 clinical trial of immunotherapy of stage IV malignant melanoma. Methods: Immature DCs were prepared from immunomagnetically isolated patients’ CD14+ cells. Messenger RNA was isolated from fresh tumor tissue obtained at surgery and was reversely transcribed, amplified, and in vitro transcribed. Amplified RNA was tested for the presence of melanoma-associated antigens gp100, tyrosinase and Mart1 and introduced into immature DCs by electroporation. Then the DCs were matured and cryopreserved. Five million cells were injected at three-week intervals for up to four injections. Results: We studied six patients (median age 52, range 40–66) suffering from predominantly non-visceral disease (four patients). After surgery, the tumor was measurable in three patients, evaluable in two and non-evaluable (completely resected) in one patient. Prior to DC therapy, two patients were treated by radiation, one by hormonal therapy and three by interleukin-2. The mRNA isolate from one patient did not contain any gp100, tyrosinase or Mart1, one isolate contained tyrosinase and four contained all three transcripts, with the presence of these transcripts maintained after amplification. Electroporation and transfection did not affect viability and phenotype of fresh mature DCs, but post-thaw viability was lower in comparison to non-electroporated cells (69 v. 82%; p<0.03). DC injections were tolerated well. We tested the efficiency of vaccination by measuring in vitro reactivity of patients’ T cells before and after DC injections. Both pre- and post-vaccination T cells from one patient secreted IFN-γ upon DC stimulation in vitro while post-vaccination T cells from another patient proliferated upon such stimulation. Conclusions: We demonstrated the feasibility of preparation of viable clinical-grade DCs transfected with tumor-derived mRNA. The vaccine was tolerated well indicating that it can be used in future clinical trials. No significant financial relationships to disclose.