Open-label Extension (OLE) Study of WVE-004 in Patients With C9orf72-associated Amyotrophic Lateral Sclerosis (ALS) and/or Frontotemporal Dementia (FTD)

Inclusion Criteria: * Patient successfully completed the Phase 1b/2a study with WVE-004, WVE-004-001. Exclusion Criteria: * Patient has a clinically significant medical finding on the physical examination other than C9orf72-associated ALS or FTD that, in the judgment of the Investigator or Sponsor, will make the patient unsuitable for participation in and/or completion of the trial procedures. * Patient received any other investigational drug, biological agent, or device within 1 month or 5 half-lives of study agent, whichever is longer. Patient received an investigational oligonucleotide within the past 6 months or 5 half-lives of the drug, whichever is longer.