We present the discovery of thieno[3,2-d]pyrimidine SGC-STK17B-1 (11s), a high-quality chemical probe for this understudied "dark" kinase. 11s is an ATP-competitive inhibitor that showed remarkable selectivity over other kinases including the closely related STK17A. X-ray crystallography of 11s and related thieno[3,2-d]pyrimidines bound to STK17B revealed a unique P-loop conformation characterized by a salt bridge between R41 and the carboxylic acid of the inhibitor. File list (9) download file view on ChemRxiv STK17B chemical probe final.pdf (4.28 MiB) download file view on ChemRxiv SI File 2.pdf (2.81 MiB) download file view on ChemRxiv SI combined final.pdf (1.64 MiB) download file view on ChemRxiv SI File 1.xlsx (32.16 KiB) download file view on ChemRxiv SI Movie 1.mp4 (36.75 MiB) download file view on ChemRxiv SI Movie 2.mp4 (32.23 MiB) download file view on ChemRxiv SI Movie 3.mp4 (56.17 MiB) download file view on ChemRxiv SI Movie 4.mp4 (58.45 MiB) download file view on ChemRxiv SI Movie 5.mp4 (62.15 MiB)

We present the discovery of thieno[3,2-<i>d</i>]pyrimidine <b>SGC-STK17B-1</b> (<b>11s</b>), a high-quality chemical probe for this understudied “dark” kinase. <b>11s</b> is an ATP-competitive inhibitor that showed remarkable selectivity over other kinases including the closely related STK17A. X-ray crystallography of <b>11s</b> and related thieno[3,2-<i>d</i>]pyrimidines bound to STK17B revealed a unique P-loop conformation characterized by a salt bridge between R41 and the carboxylic acid of the inhibitor.

Deep annotation of a library of 4‐anilinoquin(az)olines led to the identification of 7‐iodo‐N‐(3,4,5‐trimethoxyphenyl)quinolin‐4‐amine 16 as a potent inhibitor (IC50=14 nM) of Protein Kinase Novel 3 (PKN3) with micromolar activity in cells. Compound 16 is a potential tool compound to study the cell biology of PKN3 and its role in pancreatic and prostate cancer and T‐cell acute lymphoblastic leukemia. These 4‐anilinoquin(az)olines may also be useful tools to uncover the therapeutic potential of PKN3 inhibition in a broad range of diseases.

The development of a small library of 4anilinoquinolines led to the identification of 7-iodo-N-(3,4,5trimethoxyphenyl)quinolin-4-amine 16 as a potent inhibitor of Protein Kinase Novel 3 (PKN3) with an IC50 of 1.3 μM in cells. Compound 16 presents a useful potential tool compound to study the biology of PKN3 including links to pancreatic and prostate cancer, along with T-cell acute lymphoblastic leukemia. These compounds may be useful tools to explore the therapeutic potential of PKN3 inhibition in prevention of a broad range of infectious and systemic diseases.[a]

Leinamycin is a thiol dependent DNA alkylating agent which shows very potent activity against various human cancer cell lines (IC 50 values in the low nanomolar range). This natural compound forms guanine adducts (N7) in DNA which are converted into abasic sites and simultaneously generates Reactive Oxygen Species (ROS), to produce DNA strand breaks in human cancer cells. Our present study shows that leinamycin induces a group of DNA repair and transcription factor genes involved in DNA repair in a MDA-MB-231 human breast cancer cell line, which can mediate chemoresistance to leinamycin. In addition, N-acetylcysteine decreases leinamycin-mediated ROS production while increasing leinamycin mediated apoptotic cell death, without affecting the induction of repair genes. These data indicate that ROS is not a crucial player in leinamycin induced DNA damage and that a precursor of glutathione, N-acetylcysteine, can potentiate leinamycin mediated cytotoxicity by increasing the activation of leinamycin into its DNA reactive form.