A pathogenic proteolysis-resistant huntingtin isoform induced by an antisense oligonucleotide maintains huntingtin function.

Huntington's disease (HD) is a late-onset neurological disorder for which therapeutics are not available. Its key pathological mechanism involves the proteolysis of polyglutamine-expanded (polyQ-expanded) mutant huntingtin (mHTT), which generates N-terminal fragments containing polyQ, a key contributor to HD pathogenesis. Interestingly, a naturally occurring spliced form of HTT mRNA with truncated exon 12 encodes an HTT (HTTΔ12) with a deletion near the caspase-6 cleavage site. In this study, we used a multidisciplinary approach to characterize the therapeutic potential of targeting HTT exon 12. We show that HTTΔ12 was resistant to caspase-6 cleavage in both cell-free and tissue lysate assays. However, HTTΔ12 retained overall biochemical and structural properties similar to those of wt-HTT. We generated mice in which HTT exon 12 was truncated and found that the canonical exon 12 was dispensable for the main physiological functions of HTT, including embryonic development and intracellular trafficking. Finally, we pharmacologically induced HTTΔ12 using the antisense oligonucleotide (ASO) QRX-704. QRX-704 showed predictable pharmacology and efficient biodistribution. In addition, it was stable for several months and inhibited pathogenic proteolysis. Furthermore, QRX-704 treatments resulted in a reduction of HTT aggregation and an increase in dendritic spine count. Thus, ASO-induced HTT exon 12 splice switching from HTT may provide an alternative therapeutic strategy for HD.

Evaluation of eluforsen, a novel RNA oligonucleotide for restoration of CFTR function in in vitro and murine models of p.Phe508del cystic fibrosis.

Cystic fibrosis (CF) is caused by mutations in the gene encoding the epithelial chloride channel CF transmembrane conductance regulator (CFTR) protein. The most common mutation is a deletion of three nucleotides leading to the loss of phenylalanine at position 508 (p.Phe508del) in the protein. This study evaluates eluforsen, a novel, single-stranded, 33-nucleotide antisense oligonucleotide designed to restore CFTR function, in in vitro and in vivo models of p.Phe508del CF. The aims of the study were to demonstrate cellular uptake of eluforsen, and its efficacy in functional restoration of p.Phe508del-CFTR both in vitro and in vivo. In vitro, the effect of eluforsen was investigated in human CF pancreatic adenocarcinoma cells and human bronchial epithelial cells. Two mouse models were used to evaluate eluforsen in vivo. In vitro, eluforsen improved chloride efflux in CF pancreatic adenocarcinoma cell cultures and increased short-circuit current in primary human bronchial epithelial cells, both indicating restoration of CFTR function. In vivo, eluforsen was taken up by airway epithelium following oro-tracheal administration in mice, resulting in systemic exposure of eluforsen. In female F508del-CFTR mice, eluforsen significantly increased CFTR-mediated saliva secretion (used as a measure of CFTR function, equivalent to the sweat test in humans). Similarly, intranasal administration of eluforsen significantly improved nasal potential difference (NPD), and therefore CFTR conductance, in two CF mouse models. These findings indicate that eluforsen improved CFTR function in cell and animal models of p.Phe508del-CFTR-mediated CF and supported further development of eluforsen in human clinical trials, where eluforsen has also been shown to improve CFTR activity as measured by NPD.

PET imaging of disease progression and treatment effects in the experimental autoimmune encephalomyelitis rat model.

UNLABELLED: The experimental autoimmune encephalomyelitis model is a model of multiple sclerosis that closely mimics the disease characteristics in humans. The main hallmarks of multiple sclerosis are neuroinflammation (microglia activation, monocyte invasion, and T-cell infiltration) and demyelination. PET imaging may be a useful noninvasive technique for monitoring disease progression and drug treatment efficacy in vivo. METHODS: Experimental autoimmune encephalomyelitis was induced by myelin-oligodendrocyte glycoprotein immunization in female Dark Agouti rats. Experimental autoimmune encephalomyelitis rats were imaged at baseline and at days 6, 11, 15, and 19 after immunization to monitor monocyte and microglia activation ((11)C-PK11195) and demyelination ((11)C-MeDAS) during normal disease progression and during treatment with dexamethasone. RESULTS: (11)C-PK11195 PET detected activation of microglia and monocytes in the brain stem and spinal cord during disease progression. The uptake of (11)C-PK11195 was elevated in dexamethasone-treated animals that had shown mild clinical symptoms that had resolved at the time of imaging. Demyelination was not detected by (11)C-MeDAS PET, probably because of the small size of the lesions (average, 0.13 mm). CONCLUSION: PET imaging of neuroinflammation can be used to monitor disease progression and the consequences of treatment in the experimental autoimmune encephalomyelitis rat model. PET imaging was more sensitive than clinical symptoms for detecting inflammatory changes in the central nervous system.