Spherical Nucleic Acids Show Increased Distribution and Longer Persistence than Linear Oligonucleotides in Rat Brain Following Intrathecal Administration (P1.6-032)

Objective: We characterized and compared the CNS distribution of intrathecally (IT) administered nusinersen in the spherical nucleic acid (SNA) or unformulated (linear) format in rats.

Background: SNAs are densely packed, radial arrangements of oligonucleotides around a nanoparticle core. As a consequence of their structure, SNAs have increased cellular uptake, nuclease stability, and affinity to targets compared with linear oligonucleotides. Our previous studies showed that nusinersen-SNAs substantially increased the median survival of spinal muscular atrophy (SMA) mice versus nusinersen following intracerebroventricular injection. We hypothesized that the increased survival was due, at least in part, to improved retention of SNAs in the CNS tissues.

Design/Methods: ¹²⁵I-labeled nusinersen-SNA and nusinersen were IT injected into wild-type rats. The nusinersen-SNA and nusinersen distribution in the spinal cord, brain, and peripheral tissues were profiled by single-photon emission computed tomography combined with computed tomography (SPECT/CT) imaging over 7 days.

Results: The SPECT/CT imaging analyses revealed the presence of nusinersen-SNA and nusinersen throughout the spinal cord and brain tissues as early as 0.25 to 0.5 hr after dosing, and accumulation in all CNS tissues by 6 hr. Integration of the signal revealed that by 24 hours after dosing, the levels of nusinersen-SNA were greater than nusinersen in the brain and spinal cord tissues. At 7 days after dosing, the concentration of nusinersen-SNA in the spinal cord and brain was 50% to 100% higher than nusinersen.

Conclusions: These data demonstrate that nusinersen-SNA delivered by IT injection to rats widely distributes throughout the CNS and persists to a greater extent than nusinersen, and explain, at least in part, our previous observations of improved survival duration of SMA mice. These data also support the therapeutic potential of SNAs for treating CNS disorders.

Disclosure: Dr. Kandimalla has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc.. Dr. Daniel has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc. Dr. Mix has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc. Dr. Nallagatla has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc. Dr. Kentala has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Charles River Laboratories. Dr. Zasadny has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Invicro. Dr. Schook has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc.. Dr. Cedrone has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc. Dr. Marks has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Exicure, Inc.