PrProfile: A Study to Assess the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of ION717

This is a first-in-human, multi-center study in participants with prion disease. The study will consist of a screening period of up to 6 weeks, a 30-week treatment period, a 142-week open-label extension period and a 32-week post-treatment period. Multiple dose levels will be tested.

The trial consists of three Regimens. Regimens 1 and 2 are fully enrolled. Participants in Regimens 1 and 2 received multiple doses of study drug (ION717 and placebo) during the 30-week double-blind treatment period; the order of doses (i.e. whether a given dose was ION717 or placebo) was blinded. The trial sites listed below are actively recruiting eligible participants for Regimen 3. Regimen 3 is open label.

Key Inclusion Criteria

• A confirmed diagnosis of probable or definite prion disease.
• Early-stage prion disease at the time of Screening.
• Willing to meet all study requirements, including travel to Study Center, procedures, measurements and visits.
• Patients must have a caregiver who is ≥ 18 years old and who is able and willing to facilitate the patient's involvement, to the best of their ability, for the duration of the trial; caregivers must also be able and willing to provide information about themselves and the patient for the duration of the trial.
• Aged ≥ 18 at the time of informed consent.

Key Exclusion Criteria

• Clinically significant abnormalities in medical history, laboratory tests or physical examination that would render a patient unsuitable for inclusion.
• Any contraindication or unwillingness to undergo an MRI.
• Obstructive hydrocephalus, presence of a functional ventriculoperitoneal shunt for the drainage of cerebrospinal fluid (CSF) or an implanted central nervous system (CNS) catheter.
• Known brain or spinal disease that would interfere with the LP process, CSF circulation or safety assessment.
• Have any other condition, which, in the opinion of the Investigator would make the patient unsuitable for inclusion or could interfere with the patient participating in or completing the study.