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WVE-004, an investigational treatment for people with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) who carry C9orf72 gene mutations, lowered the production of disease-related molecules in the spinal cord and brains of mice, researchers reported.
Wave Life Sciences, the therapy’s developer, has applied for regulatory permission to move WVE-004 into clinical testing, and anticipates starting to dose people with C9orf72-associated ALS and TFD in a Phase 1b/2a study later this year.
Preclinical study results were shared by Wave scientist Yuanjing Liu, PhD, in the presentation “WVE-004, an investigational stereopure antisense oligonucleotide for the treatment of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD),” at the 2021 MDA Virtual Clinical and Scientific Conference.
The most common cause of inherited and sporadic forms of ALS and FTD is the GGGGCC repeat expansion in the C9orf72 gene (G stands for guanine and C for cytosine, two of the four building blocks of DNA).
Normally, different forms of the C9orf72 gene generate three specific messenger RNA (mRNA) molecules — called variant 1 (V1), V2, and V3 — that carry the gene’s instructions to make C9orf72 protein in various tissues. V2 levels are highest in the brain and spinal cord (central nervous system, CNS) relative to V1 and V3 levels.
However, repeat expansions occurring in V1 and V3 cause disease because they create by-products that lead to abnormal molecules called dipeptide repeat proteins (DPR), which form clumps, and RNA foci — altered forms of RNA that accumulate in a cell’s nucleus and become toxic.
WVE-004 is an antisense oligonucleotide (ASO), a small molecule designed to target and block V1 and V3 but spare V2, allowing healthy production of C9orf72 protein in the CNS without these disease-related by-products.
The purpose of this preclinical work, conducted and sponsored by Wave, was to evaluate the effects of WVE-004 on mRNA containing the repeat expansions, on DPR proteins, and total C9orf72 protein levels, as well as to measure the distribution of WVE-004 in tissues of the CNS.
Researchers first assessed the activity of WVE-004 in C9orf72 patient-derived, induced pluripotent stem cell (iPSC) motor neurons. These are essentially motor nerve cells derived from stem cells created from cells isolated from a patient.
WVE-004 was found to selectively lower V3 mRNA in a dose-dependent manner in cells carrying the C9orf72 repeat expansion. This reduction was not observed when a non-targeting ASO control was used.
Further experiments were conducted in mice altered to carry the complete human C9orf72 gene with the repeat expansion. WVE-004, or a saline solution, was injected into the fluid surrounding the CNS (cerebrospinal fluid) of these mice on days zero and seven, and tissue was analyzed eight weeks later.
Analysis revealed that WVE-004 was distributed in motor neurons of the spinal cord and the brain, with a clear signal in the cell nucleus, indicating that “the molecule has access to the cellular compartment where the C9orf72 repeat-containing [mRNAs] are located,” Liu said.
Mice were then given saline or WVE-004 at increasing doses, and examined six weeks later. A dose-dependent decrease in V3 mRNA and the DPR protein was observed in their spinal cords and brains.
This same experiment was repeated, but mice now were examined at four, 12, 18, and 24 weeks after the first dose. Compared with the saline control group, WVE-004’s use led to a 60–80% drop in the levels of V3 in the spinal cord, and a 40–50% reduction in the brain through 24 weeks. Scientists also saw a greater than 90% reduction in DPRs in the spinal cord, and more than 80% in the brain after 24 weeks.
Notably, after 24 weeks, total C9orf72 protein levels in the CNS were unaffected by WVE-004 treatment, “indicating the variant selectivity of the molecule,” Liu said.
“WVE-004 produces substantial reductions in repeat-containing C9orf72 [mRNA] and dipeptide repeat (DPR) proteins that are sustained for at least 6 months, without disrupting total protein expression,” the researchers wrote.
“These results support further development of WVE-004 and the potential for a potent, durable effect with preferential targeting of repeat-containing [mRNA] in patients with C9orf72-associated ALS and FTD,” they added.