Development of an HTS-compatible assay for the discovery of ASK1 signalosome inhibitors using alphascreen technology

Discovery of 2-arylquinazoline derivatives as a new class of ASK1 inhibitors

The development of a new series of apoptosis signal-regulating kinase 1 (ASK1) inhibitors is described. Starting from purine, pyrimidine and quinazoline scaffolds identified by high throughput screening, we used tools of structure-based drug design to develop a series of potent kinase inhibitors, including 2-arylquinazoline derivatives 12 and 23, with submicromolar inhibitory activities against ASK1. Kinetic analysis demonstrated that the 2-arylquinazoline scaffold ASK1 inhibitors described herein are ATP competitive.

Development of an HTS-Compatible Assay for the Discovery of Ulk1 Inhibitors

A rapidly accumulating body of work suggests the autophagy pathway is an attractive therapeutic target for neurodegenerative diseases and cancer. To validate autophagy as an anticancer strategy and to assess if systemic inhibition of the pathway will have deleterious effects on normal tissues and physiology, highly selective autophagy inhibitors are needed. While several inducers and inhibitors of autophagy are known, all are nonspecific and none target the enzymes that execute the pathway. A central upstream regulator of the autophagy pathway is the serine/threonine kinase Ulk1 (UNC-51-like kinase-1). Selective molecular probes that function as Ulk1-specific inhibitors are needed to improve our understanding of the autophagy pathway. To identify inhibitors of Ulk1 kinase activity, we developed an HTS-compatible, homogeneous biochemical assay using AlphaScreen technology. This novel assay design uses purified stress-activated Ulk1 and monitors phosphorylation of its full-length native substrate, Atg13. This assay was optimized and validated in a 384-well format by screening the Sigma LOPAC library. Here we report that the Ulk1 AlphaScreen assay is robust and reproducible, with a Z' factor value of 0.83 ± 0.02 and a signal to background ratio of 20 ± 1.2. Thus, this assay can be used to screen large chemical libraries to discover novel inhibitors of Ulk1.