Phase 3

FUSION trial

Industry trial

In this study we investigate the safety and efficacy of the study drug ‘ION363’ for the treatment of ALS caused by mutations in the FUS gene. About 1% to 5% of ALS cases are caused by FUS mutations. This study is sponsored by Ionis Pharmaceuticals.


The study drug (ION363) is designed to target the mutated FUS gene, which makes FUS protein. When FUS protein builds up in motor neurons, it may contribute to ALS. The study drug is designed to stop the FUS gene from making this protein, which may improve symptoms of ALS.

Study design

The FUSION trial is a phase 1-3 double-blind, randomized, placebo-controlled study. This means that the efficacy of ION363 is compared to a placebo. A placebo is a drug without an active ingredient. In Part 1 of the study, particpants will be randomly assigned to either the placebo or ION363. You will have a 2/3 chance of receiving ION363 in the first part of the study. Neither you nor your study doctor or the study staff will know which treatment you are receiving during that time. All participants will then have the opportunity to receive ION363 in Part 2 of the study.

You will receive the study drug or placebo as an injection through the spinal canal. The injection will take 1 to 3 minutes. You may receive local anesthesia to make the injection more comfortable.

The study consists of two parts. The total study duration is 3 years and 11 months. Part 1 of the study involves up to 2 weeks of a screening period, approximately 14 months for treatment (ION363 or placebo) and 3 months of post-treatment follow-up. During the treatment period, if your condition worsens significantly, you may be eligible to change early into Part 2 of the study where everyone receives ION363.

After completion of Part 1, you can continue to Part 2 which includes up to 20 months of treatment with ION363 followed by 9 months of post-treatment follow-up. After Part 2 of the study, you may continue to receive injections of ION363 for up to 3 additional years if the drug is not commercially available.

During the study there will be approximately 20 visits (9 visits for Part 1 and 11 visits for Part 2). The length of your visits will vary. One visit will require overnight stay and visits when the study drug is being administered will require at least 6 hours at the study site. You might have to stay overnight at the study site if your study doctor feels that it is best to observe you overnight for your safety.

Can I participate in the study?

The main criteria to participate in this study are:

  • You are at least 12 years old
  • You have ALS with a mutation in the FUS gene

Registration and more information

If you are interested in participating in the FUSION trial and fit the above profile, please contact one of the participating tricals centres below (contact details can be found by clicking on ‘read more’). They can provide you with more information and answer any questions you may have.