N-acetyl cysteine as a neuroprotective agent in progressive multiple sclerosis (NACPMS) trial: Study protocol for a randomized, double-blind, placebo-controlled add-on phase 2 trial

Introduction: Patients with progressive multiple sclerosis (PMS) experience relentless disability worsening. Cur-rent approved therapies have very modest effects on disability progression and purely focus on immunomodu-lation. While some inflammatory processes exist in non-active PMS, other biological processes such as neuronal injury from oxidative stress are likely more critical. N-acetyl cysteine (NAC) directly scavenges free radicals and restores neuronal glutathione, a major endogenous antioxidant. Our group has recently evaluated the safety of high dose NAC in a pilot trial in PMS with no tolerability concerns. We aim now to assess the safety, tolerability, and effect of NAC on progression of several MRI, clinical and biological markers in PMS patients.Methods: The NACPMS trial is a multi-site, randomized, double-blind, parallel-group, placebo-controlled add-on phase 2 trial. Ninety-eight PMS patients with EDSS 3.0-7.0 and aged 40-70 years will be randomized to NAC 1200 mg TID or matching placebo (1:1) as an add-on to the standard of care stratified by site and disease type during a 15-month intervention period. It is hypothesized that a reduction in oxidative stress injury will lessen brain atrophy estimated by MRI. The primary outcome analysis will compare the percent change over 12 months (Month 15 vs Month 3) between treatment and control arms using multivariable linear regression adjusted by age, sex, and disease duration.Ethics: This study was approved by the Institutional Review Board at the University of California, San Francisco (IRB21-34143), and an Investigational New Drug approval was obtained from the FDA (IND127184). Trial registration: NCT05122559.