A new gene therapy study in New England Journal of Medicine reports positively on the use of a self-inactivated lentivirus (i.e. a lentivirus deleted of long terminal repeat (LTR) sequences containing potential viral transcriptional elements) supplemented by an insulator and a codon-optimised human common γ chain (γc) gene (also known as IL2RG or Interleukin 2 receptor subunit gamma) to treat X-linked severe combined immunodeficiency (SCID-X1) or “bubble boy” disease.
After around 16 months of follow-up, results from eight treated patients show reconstitution of functional T cells and B cells, and normalization of NK-cell counts.
Vector site integration data generally showed polyclonal pattern, but long term follow-up will be needed to show absence of vector-induced leukaemia to complement the promising data.