Targeting the transferrin receptor to transport antisense oligonucleotides across the mammalian blood-brain barrier.

Antisense oligonucleotides (ASOs) are promising therapeutics for treating various neurological disorders. However, ASOs are unable to readily cross the mammalian blood-brain barrier (BBB) and therefore need to be delivered intrathecally to the central nervous system (CNS). Here, we engineered a human transferrin receptor 1 (TfR1) binding molecule, the oligonucleotide transport vehicle (OTV), to transport a tool ASO across the BBB in human TfR knockin (TfR^mu/hu KI) mice and nonhuman primates. Intravenous injection and systemic delivery of OTV to TfR^mu/hu KI mice resulted in sustained knockdown of the ASO target RNA, Malat1, across multiple mouse CNS regions and cell types, including endothelial cells, neurons, astrocytes, microglia, and oligodendrocytes. In addition, systemic delivery of OTV enabled Malat1 RNA knockdown in mouse quadriceps and cardiac muscles, which are difficult to target with oligonucleotides alone. Systemically delivered OTV enabled a more uniform ASO biodistribution profile in the CNS of TfR^mu/hu KI mice and greater knockdown of Malat1 RNA compared with a bivalent, high-affinity TfR antibody. In cynomolgus macaques, an OTV directed against MALAT1 displayed robust ASO delivery to the primate CNS and enabled more uniform biodistribution and RNA target knockdown compared with intrathecal dosing of the same unconjugated ASO. Our data support systemically delivered OTV as a potential platform for delivering therapeutic ASOs across the BBB. Editor's summary: Antisense oligonucleotides (ASOs) show potential for treating several intractable neurological disorders, but because ASOs cannot cross the mammalian blood-brain barrier (BBB), they must be delivered intrathecally to the central nervous system. Barker et al. engineered a human transferrin receptor binding molecule to transport ASOs across the BBB of mice and macaques. They intravenously administered mice and macaques with this oligonucleotide transport vehicle (OTV) carrying a tool ASO and showed sustained knockdown of the ASO target (Malat1 RNA) in multiple brain and spinal cord regions. Furthermore, OTV enabled a more uniform ASO biodistribution and RNA target knockdown in the brain compared to intrathecal delivery of naked ASO. Thus, OTV may be an effective delivery modality for therapeutic ASOs to treat neurological disorders. —Orla Smith [ABSTRACT FROM AUTHOR]