This research project entails delivery of a personalized antisense oligonucleotide (ASO) drug designed for a single participant with dentatorubral-pallidoluysian atrophy (DRPLA) due to a heterozygous pathogenic CAG trinucleotide expansion in ATN1

This is an interventional study to evaluate the safety and efficacy of treatment with an individualized antisense oligonucleotide (ASO) treatment in a single participant with DRPLA due to a heterozygous pathogenic CAG trinucleotide expansion in ATN1

Inclusion Criteria:

• Informed consent/assent provided by the participant (when appropriate), and/or participant's parent(s) or legally authorized representative(s).
• Ability to travel to the study site and adhere to study-related follow-up examinations and/or procedures and provide access to participant's medical records.
• Clinical phenotype and neuroimaging consistent with a diagnosis of ATN1 mutation associated Dentatorubral-pallidoluysian atrophy (DRPLA).
• Documented genetic mutation in ATN1.

Exclusion Criteria:

• Participant has any known contraindication to or unwillingness to undergo lumbar puncture.
• Use of investigational medication within 5 half-lives of the drug at enrollment.
• Participant has any condition that in the opinion of the Site Investigator, would ultimately prevent the completion of study procedures.