Optimized Target Residence Time: Type†I1/2 Inhibitors for p38α MAP Kinase with Improved Binding Kinetics through Direct Interaction with the R-Spine.

Skepinone-L was recently reported to be a p38α MAP kinase inhibitor with high potency and excellent selectivity in vitro and in vivo. However, this class of compounds still act as fully ATP-competitive Type I binders which, furthermore, suffer from short residence times at the enzyme. We herein describe a further development with the first Type I1/2 binders for p38α MAP kinase. Type I1/2 inhibitors interfere with the R-spine, inducing a glycine flip and occupying both hydrophobic regions I and II. This design approach leads to prolonged target residence time, binding to both the active and inactive states of the kinase, excellent selectivity, excellent potency on the enzyme level, and low nanomolar activity in a human whole blood assay. This promising binding mode is proven by X-ray crystallography.

Design, Synthesis, and Biological Evaluation of Novel Type I1/2 p38α MAP Kinase Inhibitors with Excellent Selectivity, High Potency, and Prolonged Target Residence Time by Interfering with the R-Spine.

We recently reported 1a (skepinone-L) as a type I p38α MAP kinase inhibitor with high potency and excellent selectivity in vitro and in vivo. However, as a type I inhibitor, it is entirely ATP-competitive and shows just a moderate residence time. Thus, the scope was to develop a new class of advanced compounds maintaining the structural binding features of skepinone-L scaffold like inducing a glycine flip at the hinge region and occupying both hydrophobic regions I and II. Extending this scaffold with suitable residues resulted in an interference with the kinase's R-Spine. By synthesizing 69 compounds, we could significantly prolong the target residence time with one example to 3663 s, along with an excellent selectivity score of 0.006 and an outstanding potency of 1.0 nM. This new binding mode was validated by cocrystallization, showing all binding interactions typifying type I1/2 binding. Moreover, microsomal studies showed convenient metabolic stability of the most potent, herein reported representatives.

Dibenzosuberones as p38 mitogen-activated protein kinase inhibitors with low ATP competitiveness and outstanding whole blood activity.

p38α mitogen-activated protein (MAP) kinase is a main target in drug research concerning inflammatory diseases. Nevertheless, no inhibitor of p38α MAP kinase has been introduced to the market. This might be attributed to the fact that there is no inhibitor which combines outstanding activity in biological systems and selectivity. Herein an approach to the development of such inhibitors on the basis of the highly selective molecular probe Skepinone-L is described. Introduction of a "deep pocket" moiety addressing the DFG motif led to an increased activity of the compounds. Hydrophilic moieties, addressing the solvent-exposed area adjacent to hydrophilic region II, conserved a high activity of the compounds in a whole blood assay. Combined with their outstanding selectivity and low ATP competitiveness, these inhibitors are very interesting candidates for use in biological systems and in therapy.