Comparative route of administration studies using therapeutic siRNAs show widespread gene modulation in Dorset sheep.

Chantal M Ferguson,Dimas Echeverria,Emily G Knox,Reka A Haraszti,Neil Aronin,James W Gilbert,Heather Gray-Edwards,Robert M King,Julia F Alterman,Anastasia Khvorova,Bruno M.D.C Godinho,Toloo Taghian,Andrew H Coles,Matthew J Gounis,Ajit Puri,Richard P Moser,Jillian Caiazzi,Matthew Hassler

doi:10.1172/jci.insight.152203

Abstract

siRNAs comprise a class of drugs that can be programmed to silence any target gene. Chemical engineering efforts resulted in development of divalent siRNAs (di-siRNAs), which support robust and long-term efficacy in rodent and nonhuman primate brains upon direct cerebrospinal fluid (CSF) administration. Oligonucleotide distribution in the CNS is nonuniform, limiting clinical applications. The contribution of CSF infusion placement and dosing regimen on relative accumulation, specifically in the context of large animals, is not well characterized. To our knowledge, we report the first systemic, comparative study investigating the effects of 3 routes of administration — intrastriatal (i.s.), i.c.v., and intrathecal catheter to the cisterna magna (ITC) — and 2 dosing regimens — single and repetitive via an implanted reservoir device — on di-siRNA distribution and accumulation in the CNS of Dorset sheep. CSF injections (i.c.v. and ITC) resulted in similar distribution and accumulation across brain regions. Repeated dosing increased homogeneity, with greater relative deep brain accumulation. Conversely, i.s. administration supported region-specific delivery. These results suggest that dosing regimen, not CSF infusion placement, may equalize siRNA accumulation and efficacy throughout the brain. These findings inform the planning and execution of preclinical and clinical studies using siRNA therapeutics in the CNS.

Highlights

SiRNAs and antisense oligonucleotide (ASO) drugs can be chemically engineered to silence almost any disease-linked gene and hold great potential for the treatment of neurological disorders
We previously demonstrated that i.c.v. administration of di-siRNA in mice resulted in broad distribution throughout the entire brain and spinal cord, including deeper brain regions such as striatum and hippocampus [11]
The impact of cerebrospinal fluid (CSF) infusion placement on di-siRNAs, which are much larger in size compared with ASOs, has not been reported

Summary

Introduction

SiRNAs and antisense oligonucleotide (ASO) drugs can be chemically engineered to silence almost any disease-linked gene and hold great potential for the treatment of neurological disorders. Therapeutic oligonucleotides cannot cross the blood brain barrier [1, 2] and, require direct administration into the CNS to achieve potent and sustained gene silencing. Depending on the therapeutic strategy, siRNAs and ASOs can be administered directly into brain tissue via intraparenchymal injection or directly into cerebrospinal fluid (CSF) [1, 3, 4]. There has been extensive investigation on the clearance and distribution of ASOs that are currently in clinical development but minimal evaluation of other oligonucleotide classes

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