Using a synthetic short chain of chemically modified nucleotides engineered at the Institute of RNA Therapeutics at UMass Chan School of Medicine, Robert H. The ALS gene known as C9ORF72 in a pilot study of a single patient. C9ORF72 is the most common cause of familial amyotrophic lateral sclerosis (ALS) and familial frontotemporal dementia (FTD). The results are published in nature medicineIt has the potential to stimulate research into treatments for ALS, FTD, and other neurodegenerative diseases.
Treatment, with an antisense oligonucleotide (ASO) injected into the spinal canal, significantly reduced ALS-related neurotoxins known as dipeptide repeat proteins (DPRs) in the experiment’s spinal fluid. Over the course of the trial, the subject’s functional ALS rating and other measures of effect were largely stable or little improved. The patient, who had weakness in the legs and feet prior to treatment, had no neurological or medical effects from the treatment.
“While other teams have documented that this gene can be inhibited in cells in culture, this is the first time this type of antisense oligonucleotide treatment has been demonstrated for C9ORF72 ALS in a person with ALS,” said Dr. Brown. Leo b. Theresa M. Lachance Chair in Medical Researchand Professor of Neuroscience at UMass Chan School of Medicine and lead author of nature medicine study. “The results are very encouraging. This means that this is a viable approach to suppress the mutant C9ORF72 protein that causes most cases of familial ALS. The next step is to launch a multi-person clinical trial to see if this treatment can slow the progression of the disease.”
Antisense oligonucleotides are short, synthetic, single-stranded oligonucleotides that can alter RNA and reduce, restore, or modify protein expression. The type of ASO used in this research inhibits gene expression by binding to strands of messenger RNA (mRNA). Once this association occurs, this hybrid sequence is targeted and naturally degraded by enzymes in the cell.
The allure of developing antiallergic oligonucleotides to treat ALS and other neurodegenerative diseases lies in its simplicity, according to Dr. Watts, associate professor of RNA Therapeutics and co-lead author of nature medicine study. “ASOs are essentially anti-messenger RNA agents. Using the genetic sequence you want to target, you can design an antisense oligonucleotide sequence that binds to this messenger RNA so that it does not make the mutant protein,” Watts explained. “Once you determine how ASO is delivered to a specific type of cell, it is theoretically possible to replicate with other neurodegenerative diseases. All you have to change is the nucleotide sequence.”
By eliminating the disease-causing protein from the cell, scientists believe this strategy can stop and even reverse disease progression. To date, four ASO-mediated therapies have received approval from the US Food and Drug Administration. Three of these are for Duchenne muscular dystrophy and one for spinal muscular atrophy.
ALS is a progressive neurodegenerative disorder that involves the loss of motor neurons that control voluntary muscles. About 10 percent of ALS is familial — inherited from a person’s parents — and results from a genetic mutation in a person’s DNA. The remaining 90 percent of cases are classified as sporadic and occur in cases with no family history of the disease. An estimated 6,000 people in the United States are diagnosed with ALS each year. It is not fully understood why motor neurons die in ALS, but this neurodegeneration is thought to involve a complex set of cellular and molecular processes.
Mutations in the C9ORF72 gene, a target nature medicine In the study, it accounts for 40 percent of familial cases of ALS, as well as about 10 percent of non-familial cases. These mutations also cause about 25 percent of familial cases of FTD. This overlap is important because it is among the pathogenic mechanisms that have been identified to link ALS and FTD. It also suggests that a similar treatment strategy may treat both diseases.
ALS patients with the C9ORF72 mutation have an abnormally long repeat pattern for a six-letter nucleotide sequence–GGGGCC–in their C9ORF72 gene sequence. In someone who does not have the mutation, there are usually fewer than 20-30 such repeats. But in people with the mutation, recurrence can occur hundreds of times. This repetitive sequence interferes with normal expression of a protein synthesized by C9ORF72, and also produces neurotoxins known as ribonucleoproteins.
While scientists have long believed that eliminating single gene mutations that lead to neurodegenerative diseases could have a therapeutic benefit, it has proven difficult to safely and efficiently deliver oligonucleotide agents into neurons. Therapeutic development of therapies has also been hampered, in some cases, by the need to eliminate mutant proteins while leaving enough functional proteins for cells to thrive.
We can’t just get rid of all C9ORF72 proteins from neurons because that runs the risk of damaging the cells. Any potential treatment would have to be more selective in its targeting.”
Jonathan Watts, Ph.D., UMass Chan School of Medicine
To do this, Watts and Brown targeted two specific isoforms of the C9ORF72 gene that generate toxic DPRs and identified several ASOs that knock down DPR levels. Once the ASOs were identified, Watts modified the ASO backbone to improve its integrity, distribution, and stability in the brain and spinal cord. Watts identified groups of various phosphates and sugars that allow cells to take up ASOs effectively and safely. “We used a ‘naked’ oligonucleotide,” Watts said. “Because the chemical modification pattern we used does not require a delivery medium, we can just inject ASO into the cerebrospinal fluid.”
“This study provides a proof-of-concept that ASO treatment in humans can effectively and safely suppress levels of expansion harboring the C9ORF72 protein,” Brown said. “That is, this intervention targets not only the mutant allele, but also missense transcripts and the DPR generated by that allele. This is the first report on C9ORF72 DPR repression in humans. Our findings strongly encourage the view that suppression of expression of the C9ORF72 mutant is possible and should explore it further for clinical benefits.”
Besides Brown and Watts, other study authors included Helen Tran, PhD, instructor of neuroscience at UMass Chan and Michael Moazami PhD, a former post-doctoral fellow at Watts Lab and currently a medical student at the University of Oxford Medical School, Oxford, UK, also as an experimental team. Intensive clinical. This study was funded by the Angel Fund for ALS Research, with additional support from the National Institutes of Health, ALS Finding a Cure, ALS ONE, the Max Rosenfeld ALS Research Fund and the Cellucci Fund for ALS Research.
University of Massachusetts College of Medicine
coloring., et al. (2021) Suppression of mutant C9orf72 expression by strong mixed backbone oligonucleotides. Nature medicine. doi.org/10.1038/s41591-021-01557-6.