Netherton Syndrome (NS) is a rare autosomal recessive skin disorder caused by mutations in SPINK5. It is a debilitating condition with notable mortality in the early years of life. There is no curative treatment. We undertook a non-randomized, open-label, feasibility and safety study using autologous keratinocytes transduced with a lentiviral vector encoding SPINK5 under the control of the human involucrin promoter. Six NS subjects were recruited and gene-modified epithelial sheets were successfully generated in three out of five subjects. The sheets exhibited expression of correctly sized LEKTI protein after modification. One subject was grafted with a 20cm2 gene-modified graft on the left anterior thigh without any adverse complications and was monitored by serial sampling for 12 months. Recovery within the graft area were compared against an area outside by morphology, pro-viral copy number and expression of the SPINK5 encoded protein, LEKTI, and its down-stream target kallikrein 5, which exhibited transient functional correction.
The study confirmed the feasibility of generating lentiviral gene-modified epidermal sheets for inherited skin diseases such as NS, but sustained LEKTI expression is likely to require the identification, targeting and engraftment of long-lived keratinocyte stem cell populations for durable therapeutic effects. Important learning points for the application of gene modified epidermal sheets are discussed.

Generation and clinical application of gene modified autologous epidermal sheets in Netherton syndrome – lessons learned from a phase 1 trial