Efficacy and Safety of Tamibarotene (OAM80) for Alzheimer's Disease

Tamibarotene is a synthetic retinoid presently approved in Japan for the treatment of APL, which has a higher receptor selectivity and activity for the Retinoic Acid Receptor subtypes compared to the natural retinoid. Tamibarotene decreased insoluble amyloid-beta (Ab) 42 deposition in APP mice, and also increased TTR, VAChT and ACh in the brain of SAMP8 mice, which suggest the enhancement of neurotransmission. In the behavioral model such as reduced anxiety of SAMP8 mice and rat passive avoidance test, tamibarotene showed improvement. Tamibarotene as in other retinoids are known to moderate the immune system and reduce inflammatory cytokines and chemokines, which may control the excessive stimulation of astrocyte and microglia around the Ab plaque. Tamibarotene reduced cytokines and showed clinical efficacy in the rat experimental autoimmune encephalitis model. Furthermore, retinoids are known to have critical roles during the regeneration stage in the differentiation from neural stem cells (NSC). In spinal cord injured rats treated with tamibarotene showed better recovery compared to the control. By these preclinical results, we plan by this study to evaluate the efficacy together with the safety of tamibarotene to the patients of Alzheimer's Disease. Tamibarotene is used clinically in Japan since 2005. It's side effects are known to be similar to that of other clinically used retinoids.