Biology subjects

Alterman, J.

Publications and source records attributed to Alterman, J..

4 recordsLinked to original sources

bioRxiv2025

Lowering the HTT1a transcript as an effective therapy for Huntingtons disease

Lowering the levels of HTT transcripts has been a major focus of therapeutic development for Huntingtons disease (HD), but which transcript should be lowered? HD is caused by a CAG repeat expansion in exon 1 of the HTT gene, and the rate of somatic expansion of this CAG repeat throughout life is now known to drive the age of onset and rate of disease progression. As the CAG repeat expands, the extent to which the HTT mRNA is alternatively processed to generate the HTT1a transcript and highly aggregation-prone and pathogenic HTT1a protein increases. Several HTT-lowering modalities have entered clinical trials that either target both HTT and HTT1a together, or full-length HTT alone. We have developed siRNAs that target the Htt1a mouse transcript (634/486) and used these, together with a potent Htt-targeting siRNA (10150) to compare the efficacy of lowering either full-length Htt or Htt1a. zQ175 and wild-type mice were treated with 10150 or 634/486 alongside control groups at 2 months of age with treatment to 6 or 10 months, or at 6 months with treatment to 10 months. The siRNA potency and durability were most effective in the hippocampus. Whilst both strategies showed benefits, despite the greater potency of 10150, targeting Htt1a was more effective at delaying HTT aggregation and transcriptional dysregulation than targeting full-length Htt. These data support HTT-lowering strategies that are designed to target the HTT1a transcript, either alone, or together with lowering full-length HTT. One Sentence SummaryLowering HTT1a transcript levels delays the onset of molecular and neuropathological phenotypes in a knock-in mouse model of Huntingtons disease.

neuroscience↗

bioRxiv2024

Preventing acute neurotoxicity of CNS therapeutic oligonucleotides with the addition of Ca2+ and Mg2+ in the formulation

Oligonucleotide therapeutics (ASOs and siRNAs) have been explored for modulation of gene expression in the central nervous system (CNS), with several drugs approved and many in clinical evaluation. Administration of highly concentrated oligonucleotides to the CNS can induce acute neurotoxicity. We demonstrate that delivery of concentrated oligonucleotides to the CSF in awake mice induces acute toxicity, observable within seconds of injection. Electroencephalography (EEG) and electromyography (EMG) in awake mice demonstrated seizures. Using ion chromatography, we show that siRNAs can tightly bind Ca2+ and Mg2+ up to molar equivalents of the phosphodiester (PO)/phosphorothioate (PS) bonds independently of the structure or phosphorothioate content. Optimization of the formulation by adding high concentrations (above biological levels) of divalent cations (Ca2+ alone, Mg2+ alone, or Ca2+ and Mg2+) prevents seizures with no impact on the distribution or efficacy of the oligonucleotide. The data here establishes the importance of adding Ca2+ and Mg2+ to the formulation for the safety of CNS administration of therapeutic oligonucleotides.

neuroscience↗

bioRxiv2023

A programmable dual-targeting di-valent siRNA scaffold supports potent multi-gene modulation in the central nervous system

Di-valent short interfering RNA (siRNA) is a promising therapeutic modality that enables sequence-specific modulation of a single target gene in the central nervous system (CNS). To treat complex neurodegenerative disorders, where pathogenesis is driven by multiple genes or pathways, di-valent siRNA must be able to silence multiple target genes simultaneously. Here we present a framework for designing unimolecular "dual-targeting" di-valent siRNAs capable of co-silencing two genes in the CNS. We reconfigured di-valent siRNA - in which two identical, linked siRNAs are made concurrently - to create linear di-valent siRNA - where two siRNAs are made sequentially attached by a covalent linker. This linear configuration, synthesized using commercially available reagents, enables incorporation of two different siRNAs to silence two different targets. We demonstrate that this dual-targeting di-valent siRNA is fully functional in the CNS of mice, supporting at least two months of maximal target silencing. Dual-targeting di-valent siRNA is highly programmable, enabling simultaneous modulation of two different disease-relevant gene pairs (e.g., Huntingtons disease: MSH3 and HTT; Alzheimers disease: APOE and JAK1) with similar potency to a mixture of single-targeting di-valent siRNAs against each gene. This work potentiates CNS modulation of virtually any pair of disease-related targets using a simple unimolecular siRNA.

molecular biology↗

bioRxiv2023

Extended Nucleic Acid (exNA): A Novel, Biologically Compatible Backbone that Significantly Enhances Oligonucleotide Efficacy in vivo

Metabolic stabilization of therapeutic oligonucleotides requires both sugar and backbone modifications, where phosphorothioate (PS) is the only backbone chemistry used in the clinic. Here, we describe the discovery, synthesis, and characterization of a novel biologically compatible backbone, extended nucleic acid (exNA). Upon exNA precursor scale up, exNA incorporation is fully compatible with common nucleic acid synthetic protocols. The novel backbone is orthogonal to PS and shows profound stabilization against 3- and 5-exonucleases. Using small interfering RNAs (siRNAs) as an example, we show exNA is tolerated at most nucleotide positions and profoundly improves in vivo efficacy. A combined exNA-PS backbone enhances siRNA resistance to serum 3-exonuclease by [~]32-fold over PS backbone and >1000-fold over the natural phosphodiester backbone, thereby enhancing tissue exposure ([~]6-fold), tissues accumulation (4- to 20-fold), and potency both systemically and in brain. The improved potency and durability imparted by exNA opens more tissues and indications to oligonucleotide-driven therapeutic interventions.

biochemistry↗