ABA-101 in Participants With Progressive Multiple Sclerosis

Inclusion Criteria: * 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. Exclusion Criteria: * Presents with clinical or radiographic evidence of relapse within 24 months prior to or at Screening. * Is considered by the Investigator to be immunocompromised. * Current treatment with disease-modifying therapies (DMTs).