Study Using Vaccination With Heat Shock Protein 70 (HSP70) for the Treatment of CML in Chronic Phase

Rational for immunotherapy of CML

Conceptually,CML in chronic phase is the best model for immunological intervention. It is a disease as a result of chromosomal translocation, which generates a true tumor-specific antigen. Patients in chronic phase have relatively preserved immune function for a prolonged period of time. Studies have indeed shown that peptides spanning the junctional region of both the bcr/abl and abl/bcr fusion proteins can bind to major histocompatibility complex (MHC) class I molecules (Berke et al. 2000). Vaccination of patients with bcr/abl breakpoint fusion peptides generates specific immune responses (Pinilla-Ibarz et al. 2000). In addition, for patients relapsed after bone marrow or stem cell transplant, donor lymphocyte infusion is effective in inducing a majority of them into remission. The role of donor lymphocyte infusion has proven the original concept of graft versus leukemia effect and the effectiveness of immunotherapy, in practice, towards CML (Dazzi et al. 1999). More recently, it was found that the presence of cytotoxic T lymphocytes (CTL) against HLA-A2-restricted myeloid-specific antigen proteinase 3 correlates significantly with cytogenetic remission of CML treated either with IFN or stem cell transplant (Molldrem et al. 2000), which provides strong evidence for a role of T cell immunity in clearing malignant cells.

Current proposal and hypothesis:

Based on the established roles of HSPs in T cell immunity and a large body of preclinical and clinical safety data, we propose to initiate a pilot study to test the feasibility of immunization with autologous tumor-derived HSP70 in the treatment of CML in chronic phase. This study will facilitate more clinical trials in the future, testing the ultimate hypothesis that the combination of the cytostatic therapy such as IFN and STI571, with specific immunomodulator such as HSP70 offers the best chance of eradication of CML. A total of 10 eligible patients will be enrolled in the study. All eligible patients will undergo aphaeresis to collect peripheral blood mononuclear cells. The autologous HSP70 is then purified using the standard protocol. After passing the established sterility testing, the patients are immunized intradermally with 50 micrograms HSP70 for a total of 8 injections in 2 months. They may receive their standard therapy during this time. In addition to collecting the feasibility and toxicity data, the development of anti-tumor immunity will be measured by,

1. an increase in peripheral blood of IFN-gamma producing CD8+ T-lymphocytes which are reactive to the autologous bcr/abl positive peripheral mononuclear cells
2. an increase of PR-1 specific CTLs by PR1-HLA-A2 tetramer techniques in patients who are HLA-A2 positive
3. the change of immunophenotype of peripheral lymphocytes
4. the cytogenetic remission of Philadelphia chromosome from the bone marrow