 The purpose of this study is to evaluate the long-term safety and tolerability of multiple intravenous IV infusions of BIIB092 in participants with Progressive Supranuclear Palsy PSP. The study will also assess the pharmacodynamic PD effects of BIIB092 on cerebrospinal fluid CSF extracellular tau eTau, pharmacokinetics PK, and immunogenicity of BIIB092 in participants with PSP. 