Delivery of mutant huntingtin-lowering antisense oligonucleotides to the brain by intranasally administered apolipoprotein A-I nanodisks

Huntington's Disease: Complex Pathogenesis and Therapeutic Strategies

Huntington's disease (HD) arises from the abnormal expansion of CAG repeats in the huntingtin gene (HTT), resulting in the production of the mutant huntingtin protein (mHTT) with a polyglutamine stretch in its N-terminus. The pathogenic mechanisms underlying HD are complex and not yet fully elucidated. However, mHTT forms aggregates and accumulates abnormally in neuronal nuclei and processes, leading to disruptions in multiple cellular functions. Although there is currently no effective curative treatment for HD, significant progress has been made in developing various therapeutic strategies to treat HD. In addition to drugs targeting the neuronal toxicity of mHTT, gene therapy approaches that aim to reduce the expression of the mutant HTT gene hold great promise for effective HD therapy. This review provides an overview of current HD treatments, discusses different therapeutic strategies, and aims to facilitate future therapeutic advancements in the field.

Systemic delivery of mutant huntingtin lowering antisense oligonucleotides to the brain using apolipoprotein A-I nanodisks for Huntington disease

Efficient delivery of therapeutics to the central nervous system (CNS) remains a major challenge for the treatment of neurological diseases. Huntington disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG trinucleotide expansion mutation in the HTT gene which codes for a toxic mutant huntingtin (mHTT) protein. Pharmacological reduction of mHTT in the CNS using antisense oligonucleotides (ASO) ameliorates HD-like phenotypes in rodent models of HD, with such therapies being investigated in clinical trials for HD. In this study, we report the optimization of apolipoprotein A-I nanodisks (apoA-I NDs) as vehicles for delivery of a HTT-targeted ASO (HTT ASO) to the brain and peripheral organs for HD. We demonstrate that apoA-I wild type (WT) and the apoA-I K133C mutant incubated with a synthetic lipid, 1,2-dimyristoyl-sn-glycero-3-phosphocholine, can self-assemble into monodisperse discoidal particles with diameters <20 nm that transmigrate across an in vitro blood-brain barrier model of HD. We demonstrate that apoA-I NDs are well tolerated in vivo, and that apoA-I K133C NDs show enhanced distribution to the CNS and peripheral organs compared to apoA-I WT NDs following systemic administration. ApoA-I K133C conjugated with HTT ASO forms NDs (HTT ASO NDs) that induce significant mHTT lowering in the liver, skeletal muscle and heart as well as in the brain when delivered intravenously in the BACHD mouse model of HD. Furthermore, HTT ASO NDs increase the magnitude of mHTT lowering in the striatum and cortex compared to HTT ASO alone following intracerebroventricular administration. These findings demonstrate the potential utility of apoA-I NDs as biocompatible vehicles for enhancing delivery of mutant HTT lowering ASOs to the CNS and peripheral organs for HD.