Study of BIIB092 in Participants With Progressive Supranuclear Palsy

The Primary objective of the study is to evaluate the efficacy of BIIB092, compared to placebo, as measured by a change from baseline in the PSP Rating Scale (PSPRS) at Week 52 and to assess the safety and tolerability of BIIB092, relative to placebo, by measuring the frequency of deaths, SAEs, AEs leading to discontinuation, and Grade 3 \& 4 laboratory abnormalities. The Secondary objective of the study is to evaluate the efficacy of BIIB092, compared to placebo, as measured by a change in baseline in the Movement Disorder Society (MDS)-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part II at Week 52, to evaluate the efficacy of BIIB092, compared to placebo, as measured by the Clinical Global Impression of Change (CGI-C) at Week 52, to evaluate the efficacy of BIIB092, compared to placebo, as measured by a change in baseline in the Repeatable Battery for the Assessment of Neuropsychological Disease Severity (RBANS) at Week 52 and to assess the impact of BIIB092 on quality of life, relative to placebo, as measured by change from baseline on the Progressive Supranuclear Palsy Quality of Life scale (PSP-QoL) at Week 52.