Phase I Study of CTL Anti-DP Infusion Post-hematopoietic Stem Cell Transplantation

For several decades, allogeneic hematopoietic stem cell trans-plantation (allo-HSCT) has remained an important strategy in the management of patients with high-risk hematological malignancies. The acceptance of umbilical cord blood (UCBT) and haploidentical grafts (Haplo) as viable alternative donors for allo-HSCT has increased the options for patients with no matched donors and now ensures that a donor can be identified for virtually all patients. Relapsed disease is a principal threat to these patients and affects 30-50% of them. The therapeutic options for these relapsing patients are diverse but remain largely ineffective in altering their long-term outcomes. Therefore, pre-emptive treatment post allo-HSCT is considered.

MHC (major histocompatibility complex) class II molecules are a family of molecules normally found only on hematopoietic cells. cell-surface proteins are responsible for the regulation of the immune system in humans and are important in disease defense.

They are the major cause of organ transplant rejections. Different HLA-DPB1 alleles exist in the general population. HLA-DPB1\*04:01 is the most frequent (70.5%) while HLA-DPB1\*02:01 represents 32% and HLA-DPB1\*03:01 20%. In allo-HSCT, the donor and the recipient may express different HLA-DPB1 molecules. HLA-DPB1 matching status has an impact on GVL (graft versus leukemia) and GVHD. In recipients of HSCT, a match for DPB1 is associated with a significantly increased risk of disease relapse, irrespective of the matching status of other HLA molecules.. Therefore, one could anticipate that a mismatched of HLA class II could induce a selective GVL reactivity without GVHD.

HLA-DP-expressing B cell and myeloid malignancies can be recognized and lysed by HLA-DP-specific T cells. The majority of leukemic cells (Acute Myeloid Leukemia, Acute Lymphoid Leukemia, Chronic Lymphoid Leukemia) express HLA-DP. A T cell clone recognizing specifically HLA-DPB1\*0401 has been developed as a permanent cell line This clone has been demonstrated to be able to kill HLA-DPB1\*0401 positive leukemic cells. In addition, this clone harbors a special suicide gene allowing the destruction of the clone in presence of a specific anti-viral drug named ganciclovir.

We hypothesize that infusion of a third party suicide gene-transduced T cell clone directed against HLA-DPB1\*401 might protect against possible relapse of hematological malignancies.

We propose to inject iv escalating dose of a third party clone recognizing HLA-DPB1\*04:01, 4 to 5 months following transplantation (when immunosuppressive drugs have been discontinued) in patients HLA-DPB1\*04:01 positive with a donor HLA-DPB1\*04:01 negative to evaluate the feasibility, toxicity, benefits of this immune intervention.