RHAMM/CD168-R3 Peptide Vaccination of HLA-A2+ Patients with Acute Myeloid Leukemia (AML), Myelodysplastic Syndrome (MDS) and Multiple Myeloma (MM).

The receptor for hyaluronic acid mediated motility (RHAMM/CD168) has been described as a leukemia-associated antigen (LAA) eliciting both humoral and cellular immune responses in patients with hematological malignancies. RHAMM/CD168 is expressed in more than 80% of patients with acute myeloid leukemia (AML) or multiple myeloma (MM). Recently, we characterized the RHAMM/CD168-derived peptide R3 (ILSLELMKL) as a CD8+ T cell epitope. R3-primed CD8+ T lymphocytes were able to lyse autologous RHAMM/CD168+ AML blasts in a MHC class I-restricted and epitope-specific manner. Therefore, we initiated a phase I/II R3 peptide vaccination trial for patients with AML, MDS or MM overexpressing RHAMM/CD168. Patients were included with positive RHAMM/CD168 expression but with a limited tumor load. 300 mcg RHAMM R3 peptide emulsified with the incomplete Freund’s adjuvant (ISA-51, Montanide; day 3) and GM-CSF (Leukine, days 1–5) was administrated four times subcutaneously at a biweekly interval. The primary aim of the study is safety and feasibility of this peptide vaccination, secondary aims the evaluation of a specific T cell immune response to RHAMM/CD168 R3 peptide and the assessment of the influence of the R3 peptide vaccination on the remission status. Since January 2005, ten patients were enrolled in this study. The first eight patients (2 AML, 3 MDS, 3 MM) have completed the course of four vaccinations and four patients have been evaluated. The only side effects observed under R3-peptide vaccination were erythema and induration of the skin at the site of injection (CTC I°). In 2/4 patients, we found in the peripheral blood a significant increase of specific CD8+ T cells (from 0.01% to 0.8%) recognizing the R3 peptide in ELISPOT analysis and tetramer staining, one patient showed already initially a high number of HLA-A2/R3 tetramer+CCR7-CD27-CD45RA+ effector T cells and maintained this level of T cell response. Clinical responses have been assessed by the examination of peripheral blood and bone-marrow samples before and after vaccination. Patients showed a reduction of the tumor-specific expressed antigen RHAMM/CD168 in real-time RT-PCR analysis after vaccination. 2/4 patients with myeloid disorders (1 AML, 1 MDS RAEB1) showed a reduction of CD33+ cells in FACS analysis of the bone-marrow after 4 vaccinations from 10 and 7 % to 1–2 and <1%, respectively. One patient with MM showed a reduction of plasma cells in bone-marrow and a stable quantity of light chains in peripheral blood, one patient with AML showed a progressive disease. In summary, RHAMM/CD168 is a promising target antigen for immunotherapies in patients with hematological malignancies.