Active Motif's MS-275 is a potent and selective non-hydroxamate histone deacetylase (HDAC) inhibitor. It is considered to be a class I selective inhibitor, but it displays some selectivity amongst class I members; HDAC1 (IC50 = 0.3 M); HDAC3 (IC50 = 8 M) with no inhibition of HDAC 8 (at > 100 M).MS-275 induces hyperacetylation of nuclear histones in tumor cells resulting in inhibition of proliferation of a variety of human tumor cell lines. It protects p53-deficient mice against ischemic injury and supresses the p38 MAP kinase pathway in rheumatoid arthritic synovial fibroblasts. It is active in vivo.