Vaccination with synthetic analog peptides derived from WT1 oncoprotein induces T-cell responses in patients with complete remission from acute myeloid leukemia

A pilot study was undertaken to assess the safety, activity, and immunogenicity of a polyvalent Wilms tumor gene 1 (WT1) peptide vaccine in patients with acute myeloid leukemia in complete remission but with molecular evidence of WT1 transcript. Patients received 6 vaccinations with 4WT1 peptides (200 mu g each) plus immune adjuvants over 12 weeks. Immune responses were evaluated by delayed-type hypersensitivity, CD4(+) T-cell proliferation, CD3(+) T-cell interferon-gamma release, and WT1 peptide tetramer staining. Of the 9 evaluable patients, 7 completed 6 vaccinations and WT1-specific T-cell responses were noted in 7 of 8 patients. Three patients who were HLA-A0201-positive showed significant increase in interferon-gamma-secreting cells and frequency of WT1 tetramer-positive CD8(+) T cells. Three patients developed a delayed hypersensitivity reaction after vaccination. Definite related toxicities were minimal. With a mean follow-up of 30 plus or minus 8 months after diagnosis, median disease-free survival has not been reached. These preliminary data suggest that this poly valent WT1 peptide vaccine can be administered safely to patients with a resulting immune response. Further studies are needed to establish the role of vaccination as viable postremission therapy for acute myeloid leukemia. This study was registered at www.clinicaltrials.gov as #NCT00398138. (Blood. 2010; 116(2): 171-179)