This drug is structurally similar to MS-275, exerting its inhibitory effect by downregulating the anti-apoptotic proteins of Bcl-2 family, including Bim, PUMA and Bcl-xl (Table 1, 2).53,74 Spirachostatins A, B is a new drug with a specific inhibitory effect on HDAC in leukemia cell lines. This evidence concerns the gene HDAC9 and leukemia.