Episomal vector Zif-VP64 analysis as an HbF inducer for treatment of sickle cell anemia using gene therapy.

Abstract

Enabling gene therapy for sickle cell anemia (SCA) will represent a curative treatment for patients with an indication for hematopoietic cell transplantation (HCT) who do not have an HLA-identical donor. The gene therapy is based on the genetic editing of autologous hematopoietic stem cells and hematopoietic progenitors (HSCP). The main strategies used are: the addition of a non-sickle cell ²-globin gene, the correction of the sickle cell mutation or the induction of ³-globin expression. Induction of ³-globin can be done by adding an extra ³-globin gene or by inhibiting transcription factors that block ³-globin expression or by adding fusion proteins that reactivate ³-globin expression or through generation of mutations present in individuals with persistent fetal hemoglobin (HbF). Currently, 15 clinical trials registered on clinicaltrials.org are studying the efficacy and safety of the treatment. Most studies use lentiviral vectors for the delivery of transgenes followed by insertion of sequences or alteration in the cell genome. However, two recent cases of myelodysplastic syndrome followed by acute myeloid leukemia (MDS/AML), reported in clinical trial participants, strengthen the search for non-integrative approaches to cell transformation. One such strategy is episomal vectors, such as the Zif-VP64 vector. Described in 2019, Zif-VP64 is a non-integrating intranuclear vector capable of artificially activating ³-globin expression in healthy human CD34+ cells. Aiming to expand the analysis of this promising vector, this project will analyze the efficiency of Zif-VP64 in the transformation of CD34+ cells from patients with SCA, as well as the potential for engraftment and maintenance of transformed cells in-vivo, in a pre-clinical stage, using an immunodeficient murine model. The results of this study may stimulate and enable the opening of a future clinical trial using the Zif-VP64 in the treatment of patients with SCA.