Development of Novel Efficient SIN Vectors with Improved Safety Features for Wiskott–Aldrich Syndrome Stem Cell Based Gene Therapy

Abstract

Gene therapy is a promising therapeutic approach to treat primary immunodeficiencies. Indeed, the clinical trial for the Wiskott-Aldrich Syndrome (WAS) that is currently ongoing at the Hannover Medical School (Germany) has recently reported the correction of all affected cell lineages of the hematopoietic system in the first treated patients. However, an extensive study of the clonal inventory of those patients reveals that LMO2, CCND2 and MDS1/EVI1 were preferentially prevalent. Moreover, a first leukemia case was observed in this study, thus reinforcing the need of developing safer vectors for gene transfer into HSC in general. Here we present a novel self-inactivating (SIN) vector for the gene therapy of WAS that combines improved safety features. We used the elongation factor 1 alpha (EFS) promoter, which has been extensively evaluated in terms of safety profile, to drive a codon-optimized human WASP cDNA. To test vector performance in a more clinically relevant setting, we transduced murine HSPC as well as human CD34+ cells and also analyzed vector efficacy in their differentiated myeloid progeny. Our results show that our novel vector generates comparable WAS protein levels and is as effective as the clinically used LTR-driven vector. Therefore, the described SIN vectors appear to be good candidates for potential use in a safer new gene therapy protocol for WAS, with decreased risk of insertional mutagenesis.

Preclinical Safety and Efficacy of Human CD34+ Cells Transduced With Lentiviral Vector for the Treatment of Wiskott-Aldrich Syndrome

“…19,20 On the other hand, the occurrence of leukemia associated to an insertion near the LMO2 gene 21 in this trial reinforces the need for a potentially safer vector platform to deliver the WAS transgene.…”

“…21 In this regard, the implementation of a LV platform in combination with a moderately active internal promoter should confer a substantially improved safety profile 9,38 over the MLV approach.…”

Bioluminescence imaging as a tool to evaluate germ cells in vitro and transplantation in vivo as fertility preservation of prepubertal male mice

“…However, a great deal of interesting research is being done on other monkeys (18) and in Drosophila (19). Several studies have raised the possibility of using gene therapy to correct lethal genetic diseases or genetic causes of life-threatening metabolic failure in middle age or later (20,21). The use of SSCs is a promising and feasible approach, although there are considerable ethical concerns (17).…”

BET-independent MLV-based Vectors Target Away From Promoters and Regulatory Elements

“…Gene transfer vectors based on retroviruses have been used successfully in several gene transfer trials to treat genetic disorders, 1,2,3,4,5 with clear signs of efficacy for more than 90% of the patients in clinical trials for primary immunodeficiencies. 6 However, in 10% of the patients, insertional mutagenesis resulted in uncontrolled clonal proliferation.…”