Developing a programmable siRNA-based therapeutic platform for gene silencing in the skin

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PROJECT SUMMARY Skin diseases affect nearly one-third of the global population. Current dermatological drugs are inadequate for many of these diseases, and some have few or no treatments available. There is an urgent need to develop new dermatological therapies. RNA interference (RNAi)-based therapeutics—e.g., small interfering RNA (siRNA)— represent a third class of therapeutic modalities, in addition to small molecules and biologics, that enable specific and sustained mRNA silencing to prevent production of proteins driving disease. With recent advances in nucleic acid chemistries, five siRNA drugs have been approved by the FDA for treatment of liver-associated diseases. Key benefits of siRNA drugs include: (a) ease of sequence-based design; (b) high specificity; (c) a well-defined mechanism of action; and (d) long durability (up to 3-6 months from one dose). These properties of siRNAs allow rapid drug discovery and durable modulation of disease targets previously considered “undruggable”. The goal of this proposal is to expand the clinical utility of therapeutic siRNAs for the treatment of skin diseases. An siRNA that silences expression of the immune mediator, JAK1 (human and mouse), and supports functional inhibition of JAK1 in vivo, has been identified. Aim 1 (K99 phase) will systematically evaluate the safety and efficacy of selective JAK1 silencing by therapeutic siRNA in mouse models of autoimmune and inflammatory skin diseases (i.e., vitiligo, cutaneous lupus erythematosus, and skin fibrosis). Gene silencing in skin requires efficient delivery of chemically-engineered siRNA to skin cell types expressing the target gene. Aim 2 (K99 phase) will dissect the skin biodistribution and efficacy profiles of hydrophobically conjugated siRNAs targeting JAK1 following local and systemic delivery. The R00 phase will expand the scope of the siRNA delivery platform by determining skin cell biodistribution and efficacy of new siRNA conjugates and scaffolds, and siRNAs targeting immune mediators in the IFN-γ (i.e., IFNGR1, JAK2, STAT1, and CXCL9/10/11) and IL15 (i.e., IL15 and IL15RA) pathways, for which lead compounds have already been identified. Preliminary work has developed a dual-targeting siRNA scaffold supporting simultaneous silencing of two genes in vivo. Aim 3 (K99 phase) will test the efficacy of modulating two inflammatory targets in the mouse models mentioned in Aim 1. In the R00 phase, biocompatible click chemistry and nanostructure engineering strategies will be used to construct programmable unimolecular multi-targeting siRNA scaffolds to potentiate combinatorial modulation of 3 or more inflammatory targets, a crucial goal for treating skin diseases with complex pathology. This project will establish an siRNA-based platform for modulating gene expression in the skin, and foster the PI’s continued scientific and professional training. Research in the mentored K99 phase will be carried out under the guidance of an esteemed mentor committee, whose expertise range from basic RNA biology to clinical dermatology. By the R00 phase, the PI will be ready to establish an independent lab focused on developing novel siRNA therapeutic programs for complex skin diseases.