The goal of this clinical trial is to treat male and female participants with two types of Multiple Sclerosis (MS) called primary progressive or secondary progressive MS.
The main questions the trial aims to answer are the following:
* Is TRX319 safe when administered to patients with progressive forms of MS? * At what dose does TRX319 work the best to treat participants with primary and or secondary progressive MS? * Is pre-conditioning (with Bendamustine) needed to allow TRX319 to better treat participants with primary and/or secondary progressive MS?
Participants will be asked to be on study for up 1 year and may receive up to 3 total administrations of TRX319. While on study, participants will have blood tests and other assessments (MRI scans and lumbar punctures) done to understand the safety of TRX319 and how it may benefit their multiple sclerosis.
Clinical diagnosis of MS with evidence of PPMS or SPMS according to 2025 McDonald criteria.
Expanded Disability Status Scale (EDSS) range ≥ 2.5 to ≤ 6.5.
Evidence of clinical disability progression within 2 years prior to enrollment.
Documented presence of CSF-restricted OCBs and/or elevated IgG index and/or κ free light chain.
MS clinical stability on disease modifying therapy.
Clinical relapse of MS in the 1 year prior to study entry.
Diseases other than MS to explain the first demyelinating event, including aquaporin 4 IgG or myelin oligodendrocyte glycoprotein-IgG seropositivity.
Prior treatment with CAR-T or gene therapy product directed at any target.
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Treatment groupsSee each treatment group below.