A Phase I–IIA Study of Mogamulizumab for HTLV-1–Associated Myelopathy

Human T-lymphotropic virus type 1 (HTLV-1) causes HTLV-1–associated myelopathy–tropical spastic paraparesis (HAM–TSP). HAM–TSP presents with progressive myelopathy, thought to be through infection of CCR4+ T cells. Mogamulizumab is an anti-CCR4 monoclonal antibody approved in Japan for adult T-cell leukemia–lymphoma. Researchers conducted an open-label, phase I–IIA, dose escalation study to evaluate mogamulizumab's safety and effect on proviral load in 21 patients with HAM-TSP.

The first phase evaluated the maximum tolerated dose after a single dose per patient and showed that the maximum dose of 0.3 mg/kg was acceptable. In phase IIA, 19 individuals who completed phase I received the same dose of mogamulizumab as in phase I, administered ev…