July 29, 2026 —
Researchers at UMass Chan Medical School reported preclinical data showing that a single intravenous injection of an AAV-delivered microRNA gene therapy suppressed mutant SOD1 protein production, delayed disease onset, and extended survival in mouse models of SOD1-associated amyotrophic lateral sclerosis, or ALS.
The findings, published in Nature Communications, were led by Guangping Gao, PhD; Robert H. Brown Jr., DPhil, MD; Jun Xie, PhD; and Zuoshang Xu, MD, PhD. The therapy is designed to reduce production of mutant SOD1, a toxic gain-of-function protein that causes a subset of inherited ALS cases.
ALS is a fatal neurodegenerative disease characterized by progressive loss of motor neurons, muscle weakness, paralysis, and eventual respiratory failure. Most patients die within five years of disease onset. More than 40 genes have been linked to ALS, and approximately 10% of ALS cases have a known genetic driver. Mutations in SOD1 are estimated to account for 10% to 20% of inherited ALS cases.
In the study, a single IV administration of the AAV-microRNA therapy delayed disease onset by 60 days and extended lifespan by 100 days, more than tripling average survival time in the disease model. Treated animals also showed preservation of motor neurons and neuromuscular connections.
These effects translated into improved muscle and respiratory function, better motor performance, and longer survival in preclinical studies. The researchers described the therapeutic benefit as unprecedented among gene therapy approaches in this mouse model.
The therapy uses an adeno-associated virus, or AAV, vector to deliver an artificial microRNA targeting SOD1. The approach is intended to silence mutant SOD1 production after a single systemic administration.
A key feature of the design is that the artificial SOD1 microRNA, or amiR-SOD1, is embedded within the scaffold of miR-33, a cholesterol-associated microRNA. According to the researchers, this stem-loop structure helps avoid manufacturing challenges that have limited other gene-silencing strategies such as short hairpin RNAs and some artificial microRNAs.
The improved design may support more consistent and efficient AAV manufacturing, which is important for translating gene-silencing therapies into clinical development. The researchers noted that prior silencing constructs can interfere with AAV production, creating vector errors that may reduce consistency and therapeutic potency.
The AAV-delivered strategy may also offer a potential alternative or complement to antisense oligonucleotide therapies, which require repeated intrathecal injections into the spinal canal. If translated successfully, an AAV-based approach could provide longer-lasting SOD1 suppression after a single IV infusion.
The researchers said the next step toward clinical development will include a pre-investigational new drug meeting with the U.S. Food and Drug Administration. Further studies will be needed to evaluate dose, biodistribution, durability, safety, and translational relevance in humans.
While the findings remain preclinical, the study supports continued development of AAV-mediated gene silencing for SOD1-ALS and potentially other neurodegenerative diseases caused by toxic gain-of-function mutations.
