Domain-substituted IGF2 tag modulates targeting of lentiviral gene therapy for Hunter syndrome.

We present the SWAP design, a novel, structurally cohesive IGF2-based tag for modular receptor targeting during gene therapy for lysosomal storage disorders (LSDs). We found that IGF2's central loop is critical for high-affinity binding to the insulin receptor (IR) and IGF1 receptor (IGF1R)-both involved in glucose homeostasis-but is not required for interaction with the cation independent mannose 6-phosphate/IGF2 receptor (CI-M6P/IGF2R)-a key target for lysosomal delivery. This formed the basis for designing the Substitution of the central-loop With Augmenting Peptides (SWAP) tag. By replacing the central loop with alternative epitopes, SWAP ensures high-affinity multimodal receptor targeting while maintaining structural integrity. In vivo, lentiviral gene therapy employing IDS fused to SWAP variants containing ApoE and RAP12x2 inserts corrected Hunter disease pathology across multiple tissues, including liver, spleen, heart, bone, and brain, matching the efficacy of the traditional IGF2 tag. These findings position SWAP as a novel and effective tag design for IGF2-based therapeutics with a more favourable ligand-receptor interaction.