Kinase experiment:

Inhibition of PAK1 kinase activity is measured using the Caliper assay. The assay is performed using 384-well microtiter plates. Compounds (NVS-PAK1-1) are tested as 8-point dose responses. The assays are prepared by addition of 50 nL of compound solution in 90% DMSO directly into the empty plate. Subsequently, 4.5 μL of the enzyme solution is added to each well and the resulting solution is pre-incubated at 30℃ for 60 min, followed by addition of 4.5 μL of the peptide/ATP-solution. After 60 min incubation at 30℃, reactions are terminated by addition of 16 μL per well of the stop solution. Plates with terminated kinase reactions are transferred to the Caliper LC3000 workstations for reading. Product formation is measured in a microfluidic mobility shift assay. IC50 values are derived from percent inhibition values at different compound concentrations by non-linear regression analysis[1].

NVS-PAK1-1 is a potent and selective allosteric PAK1 inhibitor with an IC50 of 5 nM.

NVS-PAK1-1 demonstrates high selectivity for inhibition of PAK1 over other PAK isoforms and the kinome in general. NVS-PAK1-1 has a biochemical PAK1 Kd of 7 nM and a PAK2 Kd of 400 nM. NVS-PAK1-1 shows excellent activity in biochemical assays and an exceptional selectivity profile against other known kinases. NVS-PAK1-1 at 6-20 μM inhibits the phosphorylation of the downstream substrate MEK1 Ser289. Consistent with the observation, NVS-PAK1-1 inhibits proliferation of Su86.86 cell line only above a concentration of 2 μM. In contrast, by applying a mixture of NVS-PAK1-1 and PAK2 shRNA, inhibition of downstream signaling and cell proliferation at a significantly lower 0.21 μM concentration are achieved[1].

NVS-PAK1-1 shows a relatively poor stability in rat liver microsomes (RLM) and this would limit its application for in vivo studies (t1/2 in RLM 3.5 min)[1].

[1]. Karpov AS, et al. Optimization of a Dibenzodiazepine Hit to a Potent and Selective Allosteric PAK1 Inhibitor. ACS Med Chem Lett. 2015 May 22;6(7):776-81.