Table 1.

Technologies for HSCT Gene Therapy	Advantages	Disadvantages
γ-Retroviral Vectors	Ability to target many cell types Long-term expression due to integration Increased safety due to SIN development	Requirement of cellular division Necessity of cytokine cocktails to stimulate HSC cycling Insertional mutagenesis potential Complex manufacturing
Lentiviral Vectors	Wide range of cell targets Long-term expression due to integration Increased safety due to SIN development	Require multiple plasmids/elements provided in trans for production Risk of insertional mutagenesis Complex manufacturing
Sleeping Beauty Transposon Systems (SBTS)	Low complexity Simple manufacturing (plasmid DNA only) Potentially reduced immunogenic response	Lower-level expression of the transgene product Random insertion pattern Potential for secondary or tertiary transposition events
Zinc Finger Nucleases (ZFNs)	Targeted gene correction or addition Potential to utilize endogenous genetic control elements Long-term expression through chromosomal integration	Safety remains undetermined Risk of off-target mutagenesis Require additional means of cellular entry Limited sequence targeting potential
Peptide Nucleic Acids (PNAs)	Site-specific modification Useful in gene silencing In vivo delivery and functionality possible	Limited research to date Risk of off-target sites of genetic modification Low efficiency