Sustained freedom from disease activity in secondary progressive multiple sclerosis by targeting invariant NKT cells: a phase 2 trial of OCH

Multiple sclerosis (MS) therapies primarily rely on lymphocyte depletion or trafficking blockade, carrying risks of systemic immunosuppression; however, such treatments have limited efficacy in secondary progressive multiple sclerosis (SPMS). Thus, drugs that target stage-specific inflammation without broad immunosuppression are an unmet clinical need. In this double-blind, placebo-controlled phase II trial, 30 patients with relapsing MS received weekly oral OCH or placebo for 24 weeks. In the pre-specified SPMS subgroup (n=12), OCH achieved complete relapse prevention (p=0.0003), prolonged relapse-free survival (p=0.0079), no new lesions (0/6), with no evidence of disease activity (NEDA-3) in 5/6 patients. In comparison, for the placebo-treated group, 5/6 patients suffered relapses, 2/6 patients developed new lesions, and no placebo-treated SPMS achieved NEDA-3. Invariant natural killer T (iNKT) cells, a regulatory lymphocyte population that is numerically and functionally impaired in MS, are a potential target for MS therapy. Glycolipid OCH is a selective iNKT cell stimulator, skewing the cytokine environment towards Th2. OCH treatment resulted in increased IL-4-producing Th cells in patient peripheral blood while decreasing pathogenic GM-CSF-producing Th cells. Parallel studies in mouse models of MS (EAE) corroborated this mechanism and further revealed that OCH activated gut iNKT cells. Disease amelioration by OCH depended on IL-4 and its efficacy was further enhanced by depletion of B cells. These data revealed the gut-brain axis mediation of progressive-stage pathology distinct from relapsing-remitting MS. Findings from this bidirectional translational study uncover mechanistic differences between SPMS and other types of MS and highlight divergent roles for B cells and Th cells. Furthermore, OCH exerts its therapeutic benefit via targeting mechanisms that are distinct from currently available drugs; exploiting iNKT cell regulatory potential to reprogram pathogenic T helper responses without lymphocyte depletion. The unique yet effective nature of OCH treatment positions it as an attractive future oral therapy for SPMS. One Sentence SummaryThe iNKT cell activating ligand OCH suppresses disease activity selectively in secondary progressive MS in a phase II clinical trial, revealing stage-specific IL-4-mediated immune cell interactions in MS pathology.