A Study to Find Out How Nusinersen is Processed in the Body When Given Through the ThecaFlex DRx™ System in Adult and Pediatric Participants With Spinal Muscular Atrophy (PIERRE-PK)

Exclusion Criteria

• •Ongoing participation or participation within 6 months or 5 half-lives of the agent (whichever is longer) of enrollment in other interventional clinical trials for the treatment of SMA (except for the PIERRE study or interventional clinical trials of myostatin inhibitors \[e.g., apitegromab and taldefgrobep alfa\]).
• •Participant is naïve to nusinersen treatment.
• •Participant is receiving nusinersen at a dose other than 12 mg.
• •Participant has already undergone implantation of the ThecaFlex DRx system.
• •Participant is pregnant, currently breastfeeding, or intending to become pregnant during the study.