In vivo delivery of a fluorogenic antisense oligonucleotide into human leukocytes in a humanized mouse model system

Development of oligonucleotide-based therapeutics has been limited by the lack of effective <i>in vivo</i> delivery vehicles. We previously showed that the presence of an H-type excitonic dimer formed by the covalent binding of two fluorophores with significant transition dipoles on opposite ends of peptide or nucleic acid sequences of interest facilitated their delivery into live cells <i>in vitro.</i> Here, we evaluated delivery of a fluorogenic anti-sense oligonucleotide (ASO) complementary to β-actin (<i>ACTB</i>) mRNA into human leukocytes <i>in vivo</i> using a humanized mouse model. We observed delivery of the ASO into human leukocytes at a median of ≥94% in blood, spleen, bone marrow, and liver with half-lives of at least 72 h. Additionally, we detected the ASO in a significant proportion of human leukocytes within difficult-to-penetrate tissues such as brain and gut. The ASO localized to the perinuclear space within target cells and mediated reductions in bone marrow <i>ACTB</i> transcripts after a single intravenous injection. The delivery system described herein is a technology platform with the capacity for highly efficient systemic delivery of therapeutic oligonucleotides that will facilitate development of a new class of drugs for treatment of HIV and other pathologic conditions.