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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.

Vor kurzem wurde mit Skepinone-L ein p38α-MAP-Kinase-Inhibitor mit hoher Potenz und ausgezeichneter Selektivitat in vitro und in vivo beschrieben. Der Bindemodus dieser Substanzklasse entspricht allerdings dem eines ATP-kompetitiven Typ-I-Inhibitors mit kurzer Verweildauer am Enzym. Nun wurde Skepinone-L zu den ersten Typ-I1/2 -Inhibitoren der p38α-MAP-Kinase weiterentwickelt. Typ-I1/2 -Inhibitoren storen den Aufbau der R-Spine, induzieren einen Glycin-Flip und besetzen beide hydrophobe Bindetaschen, die hydrophobe Region I und II. Dieses Konzept fuhrte zu Inhibitoren mit verlangerter Verweildauer am Enzym, die sowohl die aktive als auch die inaktive Kinase binden. Des Weiteren kennzeichnet sie eine herausragende Selektivitat gegenuber anderen Kinasen sowie eine ausgezeichnete Wirkung am isolierten Enzym. Daruber hinaus reicht ihre Hemmwirkung in einem humanen Vollblut-Assay bis tief in den nanomolaren Bereich. Dieser neue Bindemodus konnte rontgenkristallographisch belegt werden.

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.