Is ≥18 years old at signing of consent.

Has a diagnosis of MS per the 2017 revised McDonald criteria.

Has documented evidence of progression of disability independent of MS relapse activity (clinical or radiographic).

Expresses the HLA that matches the TCR restriction.

Presence of a radiographic biomarker of CNS inflammation as identified by MRI.

Meets Expanded Disability Status Scale (EDSS) criteria.

Meets the nine-hole peg test (9HPT) criteria.

ABA-101 in Participants With Progressive Multiple Sclerosis