Ionis Pharmaceuticals has initiated a Phase III clinical trial of antisense medicine ION363 in patients with amyotrophic lateral sclerosis (ALS) with mutations in the fused in sarcoma gene (FUS).

An investigational antisense medicine, ION363 targets the FUS RNA to lower the production of the FUS protein.

ALS is a rare, quickly progressing and fatal neurodegenerative disorder characterised by muscle weakness, movement loss, and difficulty in breathing and swallowing.

The global, multi-centre trial will enrol up to 64 FUS-ALS patients to assess the efficacy, safety, pharmacokinetics and pharmacodynamics of intrathecally administered ION363.

In part one of the trial, subjects will be randomised in a 2:1 ratio to receive a multi-dose regimen of ION363 or placebo for 29 weeks. It will be followed by a part two open-label trial, which will see all patients given ION363 for 73 weeks.

Analysing the clinical efficacy of ION363 on clinical function and survival in carriers of FUS-ALS will be the primary purpose of the trial.

Ionis Pharmaceuticals chief scientific officer and neurological programme franchise leader Frank Bennett said: “Advancement of ION363 to a pivotal trial is the latest example of the power of Ionis’ antisense technology to potentially target the root causes of neurological diseases.

“Driven by our experience in developing medicines for motor neuron diseases such as ALS and spinal muscular atrophy and our intimate connection to the ALS patient community, Ionis made the decision to advance ION363 to the clinic and, ultimately, to the market because we believe we are uniquely positioned to make it available to patients living with FUS-ALS.”

Columbia University Eleanor and Lou Gehrig ALS Center director Neil Shneider will lead the trial.

So far, through the US Food and Drug Administration’s expanded access pathway or compassionate use, several FUS-ALS patients were treated with ION363 under Shneider’s investigator-initiated study.