A Study to Evaluate the Safety and Pharmacokinetics of Single and Multiple Doses of Prosetin in Healthy Volunteers and Participants With ALS

PRO-101, Parts A and B, were completed in healthy volunteers. PRO-101, Parts C and D are ongoing in participants with ALS. Key eligibility criteria are summarized below: Key Inclusion Criteria - Part C * Adults ≥18 years of age * Diagnosis of ALS based on the Gold Coast diagnostic criteria * Slow Vital Capacity (SVC) \>50% predicted * If being concomitantly treated with riluzole and/or locally approved standard of care treatments, the participant must be on a stable dose for at least 30 days prior to screening and throughout the study * In the opinion of the Investigator, participant is able to swallow liquid in order to ingest the study medication. Key Exclusion Criteria - Part C * Active dementia, neurologic diseases other than ALS, or psychiatric illness that in the opinion of the investigator would affect participation in the current study. * Significant history or clinical manifestation of comorbid disease in any organ system that currently requires active treatment or is likely to require treatment during the study. * Any episodes of vertigo in the previous 12 months prior to screening. * Any medical history of seizures, or any clinically significant EEG finding at Screening or at Day -1. * A diagnosis of cancer or evidence of continued disease within five years before screening. Protocol-specified exceptions may be considered with approval from the Sponsor's Medical Monitor. * Participation in any other investigational study drug trial in which receipt of an investigational study drug occurred within 30 days prior to the first dose of study medication. * Prior exposure to any stem cell or gene therapies (investigational or off-label) for the treatment of ALS. Key Inclusion Criteria- Part D Participants who meet all of the following criteria may be included in Part D of the study: * Participants must have completed 14 days of blinded treatment in Part C. * Participants taking approved ALS standard-of-care medications must remain on stable doses through Day 28 of open-label treatment. * In the judgment of the Investigator, the participant's participation in the open-label portion of the study is medically appropriate Key Exclusion Criteria- Part D * Treatment with any other investigational drug or device throughout the duration of the study is excluded, with the exception of any COVID-19 vaccine or treatment with an emergency use authorization. NOTE: Other protocol-defined Inclusion/Exclusion Criteria may apply. Please contact trials@projenx.com with any questions about eligibility criteria.