Tubastatin A is a potent and selective HDAC6 inhibitor with IC50 of 15 nM in a cell-free assay. Tubastatin A is a very selective HDAC6 inhibitor with 100 to over 1000-fold selectivity for HDAC6 over other HDAC classes. Tubastatin A increases the total numbers of mitochondria and restores the number of moving mitochondria in DRG neurons. It reverses the axonal loss in peripheral neurons in the mouse model of Charcot-Marie-Tooth disease. Tubastatin A inhibits the deacetylation of α-tubulin in murine myoblasts.

JNJ-7706621, developed by Johnson & Johnson Pharmaceutical, is pan-CDK inhibitor with the highest potency on cyclin-dependent kinases: CDK1/2. Inhibition of CDK1 kinase activity, altered CDK1 phosphorylation status, and interference with downstream substrates such as retinoblastoma was also shown in human tumor cells following drug treatment. It also potently inhibits Aurora A/B and has no activity on Plk1 and Wee1. In human cancer cells, treatment with JNJ-7706621 inhibited cell growth independent of p53, retinoblastoma, or P-glycoprotein status; activated apoptosis; and reduced colony formation. At low concentrations, JNJ-7706621 slowed the growth of cells and at higher concentrations induced cytotoxicity. JNJ-7706621 is a unique inhibitor regulating cell cycle progression at multiple points, suggesting that it could be useful for cell cycle analysis and therapy of various cancers, including Ewing's sarcoma.