Phase I study in melanoma patients of a vaccine with peptide-pulsed dendritic cells generated in vitro from CD34⁺ hematopoietic progenitor cells

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that can be used for vaccination purposes, to induce a specific T-cell response in vivo against melanoma- associated antigens. We have shown that the sequential use of early-acting hematopoietic growth factors, stem cell factor, IL-3 and IL-6, followed by differentiation with IL-4 and granulocyte- macrophage colony-stimulating factor allows the in vitro generation of large numbers of immature DCs from CD34⁺ peripheral blood progenitor cells. Maturation to interdigitating DCs could specifically be induced within 24 hr by addition of TNF-α. Here, we report on a phase I clinical vaccination trial in melanoma patients using peptide-pulsed DCs. Fourteen HLA-AI⁺ or HLA-A2⁺ patients received at least 4 i.v. infusions of 5 x 10⁶ to 5 x 10⁷ DCs pulsed with a pool of peptides including either MAGE-1, MAGE-3 (HLA- A1) or Melan-A, gp 100, tyrosinase (HLA-A2), depending on the HLA haplotype. A total of 83 vaccinations were performed. Clinical side effects were mild and consisted of low- grade fever (WHO grade I-II)-Clinical and immunological responses consisted of anti-tumor responses in 2 patients, increased melanoma peptide-specific delayed-type hypersensitivity reactions in 4 patients, significant expansion of Melan-A- and gp 100-specific cytotoxic T lymphocytes in the peripheral blood lymphocytes of I patient after vaccination and development of vitiligo in another HLA-A2⁺ patient. Our data indicate that the vaccination of peptide-pulsed DCs is capable of inducing clinical and systemic tumor-specific immune responses without provoking major side effects. (C) 2000 Wiley-Liss, Inc.