Promising experimental drug for juvenile ALS shows success in mice with no side effects

Experimental treatments in medicine have a reputation for being risky. These divergent ideas, however, can often lead to revolutionary courses of treatment for life-threatening diseases. This is the case of a recent study out of Columbia University Irving Medical Center. An experimental drug, known informally as jacifusen, was used as a last-ditch effort to help a 25-year-old woman with juvenile ALS.

The study reports that the drug lowered levels of FUS, a toxic protein found in the woman’s neurons. The scientists also tested jacifusen in mice with ALS and found the same results.

Columbia has now advanced to a phase 3 clinical trial for the drug. The clinical trial will be pivotal in determining if the drug can slow the progression of juvenile ALS.

The study finds that jacifusen had “a profound effect, virtually eliminating the toxic proteins in the central nervous system and reducing the burden of FUS pathology dramatically,” says study leader Dr. Neil Shneider, of the Columbia University Vagelos College of Physicians and Surgeons, in a statement.

The name jacifusen receives its namesake from a young woman named Jaci Hermstad, and one that makes it personal for Shneider. Though the drug was already in development, Jaci was the first patient to receive the drug as a treatment for her diagnosis. ALS, or amyotrophic lateral sclerosis, is usually associated with adults, but a rare and aggressive form of the disease can affect individuals, like Jaci, in their teens or 20s. The disease attacks the patient’s motor neurons, which control the body’s muscles, until the patient can no longer move or breathe unassisted. Sneider himself received FDA permission to treat Jaci with the drug through the administration’s compassionate use program.

Several years ago, researchers discovered that most adolescents and young adults with ALS have mutations in the gene FUS.

In a study of a series of mouse models with ALS-related FUS mutations published in 2016, and in another series in the current study, Shneider found that the mutant FUS protein is toxic to motor neurons, suggesting that lowering FUS levels by silencing the gene that makes the protein might protect neurons in ALS patients with the mutation.

Jaci received the first of several doses of the drug in 2019. “We saw a significant slowdown in her functional decline, suggesting that the drug was working as intended, but sadly, her disease was already advanced by the time she began the treatment and she died about a year later,” Shneider says.

In his new study, Shneider shows that a single infusion of jacifusen at birth in a mouse model effectively silenced the FUS gene, reduced FUS protein levels in the brain and spinal cord, and delayed motor neuron degeneration in the mice—all with no apparent side effects. 

“This trial will determine if jacifusen is safe, and if it can effectively slow disease progression in symptomatic FUS-ALS patients.  If approved, jacifusen would be the first treatment for this highly aggressive form of early-onset ALS,” Shneider says. “This study is an example of truly personalized medicine in the 21st century.”

This study is published in Nature Medicine.

Article written by Rhonda Errabelli

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