Evaluating the effects of aging on distribution and gene silencing activity of lipid-siRNA conjugates delivered into cerebrospinal fluid

Aging is the primary risk factor for chronic neurodegenerative diseases and is associated with alterations to cerebrospinal fluid (CSF) flow and clearance. CSF delivery is currently the most clinically advanced route of administration for oligonucleotide therapeutics, but it remains poorly understood how aging, which is rarely incorporated into clinical trials, impacts biodistribution, gene silencing activity, and potential toxicity of these compounds. Here, we evaluated a lipid-siRNA conjugate (L2-siRNA) for potential age-related changes to CSF-mediated delivery, mRNA silencing, and safety. In the context of aging, we also studied how conjugate chemistry and siRNA structure impact delivery and activity by comparing L2-siRNA to an alternative lipid-siRNA conjugate design. We determined that age had minimal impact on the performance of L2-siRNA and that conjugates exhibit better activity when each lipid is paired with the siRNA structure and chemistry for which it was initially optimized. Collectively, these results provide valuable insight into siRNA conjugate biodistribution and activity in the central nervous system in the context of aging and further establish the performance of L2-siRNA under conditions relevant to the treatment of neurodegenerative diseases.