RNA interference (RNAi) has the potential to revolutionize treatment of dominant genetic disorders. Small inhibitory RNAs (siRNAs) are highly potent and selective, demonstrating remarkable single-nucleotide specificity. Clinical trials using siRNAs are currently underway for a number of indications including skin. Facilitated by Phase 1 funding, a small one patient phase 1b clinical trial was undertaken for pachyonychia congenita (PC). This ultrarare skin disorder is caused by mutations, including single nucleotide changes, in the genes encoding keratins 6, 16, and 17. The major complaint of PC patients is the debilitating painful callusing and blistering which occurs on or near the pressure points of the feet. These defined regions on the soles of the feet were targeted for local siRNA treatment by intralesional injection of siRNA (TD101) with encouraging results. Unfortunately, the pain associated with injections into lesions (oral pain medication and regional nerve blocks were required to allow treatment), prevents widespread use of this mode of administration. This observation has led to intense efforts to identify patient-friendly (i.e., little or no pain) delivery options. This clinical trial was the first human use of siRNA in skin and also the first siRNA to target a mutated gene. In Phase 2 of this proposal, we extend the progress of Phase 1 and the Phase 1b clinical trial. We have found that unmodified or stabilized siRNAs are not taken up readily by skin keratinocytes but that modified, so-called """"""""self-delivery"""""""" (sd) siRNAs are. Additional optimization of the sd-siRNA will be undertaken in mouse and human skin models followed by synthesis of GMP material for mouse and rabbit toxicology studies and clinical trials in which the siRNA will be delivered by dissolvable microneedle arrays or a topical GeneCream"""""""" formulation, both developed and manufactured at TransDerm. GeneCream and microneedle arrays are both designed to effectively deliver sd-siRNA with little or no pain (microneedle protrusions are designed to only penetrate to the non-innervated epidermis). Although PC is a rare disease, the nature of the disorder makes it an ideal prototype skin disorder (defined mutations with expression in limited, defined areas) for first-in-man siRNA skin clinical trials, and we fully expect the lessons learned will be readily generalized to other skin disorders.

Public Health Relevance

Despite the discovery of the underlying mutations responsible for many inherited skin diseases, few effective treatments have emerged. The discovery that siRNAs can be developed to target specific disease-related mutations portends the advent of a new treatment paradigm. We have identified a potent and selective siRNA that targets a single nucleotide mutation in the keratin 6a gene that is responsible for the rare skin disorder pachyonychia congenita and blocks its expression. This siRNA (known to the FDA as TD101) was successfully tested in a Phase 1b clinical trial. Despite signs of efficacy, the painful nature of the administration route (intradermal injection of large volumes) required that we develop a more patient-friendly delivery system. Phase 2 of this proposal allows preclinical studies enabling a second clinical trial using microneedles loaded with a self-delivery version of TD101 siRNA. The lessons learned in applying siRNA technology for treatment of PC should be readily generalizable to a host of other dominant skin disorders and likely to other disorders resulting from mutated or overexpressed disease-causing genes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Small Business Innovation Research Grants (SBIR) - Phase II (R44)
Project #
5R44AR056559-03
Application #
8336922
Study Section
Special Emphasis Panel (ZRG1-MOSS-D (12))
Program Officer
Baker, Carl
Project Start
2008-09-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
3
Fiscal Year
2012
Total Cost
$973,429
Indirect Cost
Name
Transderm, Inc.
Department
Type
DUNS #
557564775
City
Santa Cruz
State
CA
Country
United States
Zip Code
95060
Hickerson, Robyn P; Speaker, Tycho J; Lara, Maria Fernanda et al. (2016) Non-Invasive Intravital Imaging of siRNA-Mediated Mutant Keratin Gene Repression in Skin. Mol Imaging Biol 18:34-42
Cao, Yu-An; Hickerson, Robyn P; Seegmiller, Brandon L et al. (2015) Gene expression profiling in pachyonychia congenita skin. J Dermatol Sci 77:156-65
van Steensel, Maurice A M; Coulombe, Pierre A; Kaspar, Roger L et al. (2014) Report of the 10th Annual International Pachyonychia Congenita Consortium Meeting. J Invest Dermatol 134:588-591
Chong, Rosalind H E; Gonzalez-Gonzalez, Emilio; Lara, Maria F et al. (2013) Gene silencing following siRNA delivery to skin via coated steel microneedles: In vitro and in vivo proof-of-concept. J Control Release 166:211-9
Hickerson, Robyn P; Gonzalez-Gonzalez, Emilio; Vlassov, Alexander V et al. (2012) Intravital fluorescence imaging of small interfering RNA-mediated gene repression in a dual reporter melanoma xenograft model. Nucleic Acid Ther 22:438-43
Geihe, Erika I; Cooley, Christina B; Simon, Jeff R et al. (2012) Designed guanidinium-rich amphipathic oligocarbonate molecular transporters complex, deliver and release siRNA in cells. Proc Natl Acad Sci U S A 109:13171-6