Immunotherapy in progressive supranuclear palsy.

PURPOSE OF REVIEW: Progressive supranuclear palsy (PSP) is a progressive adult-onset neurodegenerative disease. Abnormally, phosphorylated forms of the microtubule-associated protein tau containing four repeat domains (4R-tau) aggregate in neurons. Additionally, increasing evidence suggests that secretion and uptake of fragments of abnormal 4R-tau may play a role in disease progression. This extracellular tau is a natural target for immunotherapy.

RECENT FINDINGS: Three monoclonal antibodies targeting extracellular tau are in clinical stages of development. ABBV-8E12 and BIIB092 were safe in Phase 1, but both Phase two studies recently failed futility analyses. UCB0107 recently reported (in abstract form) Phase 1 safety results, and a Phase 2 study is under consideration. Stem cell therapy and the infusion of plasma are also being explored clinically.

SUMMARY: The likely role of extracellular tau in the progression of PSP makes tau a natural target for targeted immunotherapy. Clinical trials are still in early stages, and although tau immunotherapy has largely been shown to be safe, efficacy has yet to be demonstrated.