YM-08 is a Heat Shock Protein 70 (Hsp70) inhibitor that is blood-brain barrier permeable. YM-08 is a neutral derivative of the Hsp70 inhibitor MKT-077. MKT-077 reduces tau levels in cellular models, but it doesn′t penetrate the blood brain barrier. Although YM-08 was somewhat less effective than MKT-077 in anti-tau and anticancer assays, it selectively reduced pathogenic tau in brain slices, which MKT-077 did not. Furthermore,YM-08 was not retained in the kidney leading one to speculate that it would not have the nephrotoxicity that was a problem for MKT-077 in clinical trials.
