Introduction: Pediatric patients with refractory/relapsed acute myeloid leukemia (AML) have only one treatment option: hematopoietic cell transplantation (HCT). Using cord blood (CB)-derived stem cells, instead of cells from bone marrow cells or peripheral blood, results in less relapses (increased anti-tumor reactivity) and less graft-versus-host disease (increased safety). Although this treatment is potentially curative, still more than half of the children die from relapses. We therefore aim to develop additional powerful and safe CB-derived immunotherapies for pediatric AML.
Methods: We have successfully translated our pre-clinical protocol for generations of a dendritic cell (DC) vaccine from CD34+ CB stem cells into GMP production. This production process enables us to generate sufficient CBDC for at least 4 vaccinations when using the 20% fraction of the CB unit. After CliniMACS isolation the CD34+ cells are expanded in culture bags using medium containing FLT3L, SCF, IL-3 and IL-6. When sufficient expansion is reached the cells are differentiated into DCs using medium containing FLT3L, SCF, GM-CSF and IL-4. The CBDCs are then matured using proinflammatory cytokines and electroporated with Wilms' Tumor 1 (WT1) mRNA as tumor antigen. After 4 hours recovery, cells are cryopreserved until time of validation or intradermal vaccination
Results: CD34+ CB stem cells were expanded and differentiated into DCs. CBDCs upregulated co-stimulatory molecules after maturation and showed enhanced CCR7-dependent migration towards CCL19 in a trans-well migrations assay. In addition, CBDCs expressed the tumor antigen Wilms' Tumor 1 (WT1) protein after electroporation with WT1-mRNA. These WT1 expressing CBDCs were not only able to stimulate T cells in a mixed lymphocyte reaction but in an antigen-specific setting as well.
Conclusions: We are able to produce a GMP CBDC vaccine with the goal to stimulate the anti-tumor reactivity of the newly developing immune system in AML patients after CB-HCT in a Phase 2 clinical trial starting early 2016.
Citation Format: Colin de Haar, Ester Dunnebach, Niek van Til, Maud C. Plantinga, Nina JG Blokland, Stefan Nierkens, Jaap Jan Boelens. GMP production of cord blood-derived dendritic cell-based vaccine to prevent relapses after hematopoietic cell transplantation in children with AML. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B038.
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