Cortistatin-29 is a neuropeptide that is structurally similar to somatostatin-28. It is produced by cleavage of preprocortistatin to procortistatin, which is cleaved at dibasic amino acids to form cortistatin-29 and cortistatin-14 as well as other partial cleavage products. Cortistatin mRNA is expressed in the human brain and in interneurons of the rat hippocampus and cerebral cortex. Cortistatin-29 binds to somatostatin (SST) receptors with IC50 values of 2.8, 7.1, 0.2, 3, and 13.7 nM for SST1-5, respectively. Cortistatin-29 is found at similar levels as cortistatin-14 in mouse AtT20 cells but is secreted at a lower level. Cortistatin-29 corresponds to residues 85-112 of the rat peptide sequence.
AZ5576 racemate is a racemic mixture of AZ5576 isomers. AZ5576 is a potent, highly selective, and orally bioavailable inhibitor of Cdk9 that inhibits Cdk9 enzyme activity with an IC50 <5nM and decreases phosphorlyation of Ser2-RNAPII in cells with an IC50 of 96nM. In the MLL-fusion containing acute myeloid leukemia (AML) line, MV411, short-term treatment with AZ5576 led to a rapid dose-dependent decrease in pSer2-RNAPII with concomitant loss of Mcl1 mRNA and protein, resulting in the cleavage and activation of caspase 3 and loss of cell viability.