Progressive multiple sclerosis.

PURPOSE OF REVIEW: The purpose of this study is to highlight the pathological features and clinical aspects of progressive multiple sclerosis (PMS) and also the results of clinical trial experience to date and review ongoing clinical trials and prospective new treatment options. This study will explain the challenges of clinical trial design in PMS.

RECENT FINDINGS: Multiple sclerosis (MS) has been identified as a chronic immune mediated disease, and the progressive phase of the disease appears to have significant neurodegenerative mechanisms. The classification of the course of PMS has been reorganized into categories of active vs. inactive inflammatory disease and the presence vs. absence of gradual disease progression. This differentiation allows clearer conceptualization of PMS and possibly even more efficient recruitment of PMS patients into clinical trials. Clinical trial experience to date in PMS has been negative with anti-inflammatory medications used in relapsing MS. Simvastatin was recently tested in a phase II trial and showed a 43% reduction of annualized atrophy progression in secondary progressive MS. Ongoing PMS trials are currently being conducted with the phosphodiesterase inhibitor ibudilast, S1P modulator siponimod and anti-B-cell therapy ocrelizumab. Several efforts for development of outcome measures in PMS are ongoing.

SUMMARY: PMS represents a significant challenge, as the pathogenesis of the disease is not well understood, no validated outcome metrics have been established and clinical trial experience to date has been disappointing. Advances in the understanding of the disease and lessons learned in previous clinical trials are paving the way for successful development of disease-modifying agents for this disease.