Synthesis of the highly selective p38 MAPK inhibitor UR-13756 for possible therapeutic use in Werner syndrome

Background: UR-13756 is a potent and selective p38 mitogen-activated protein kinase (MAPK) inhibitor, reported to have good bioavailability and pharmacokinetic properties and, thus, is of potential use in the treatment of accelerated aging in Werner syndrome. Results and discussion: Irradiation of 2-chloroacrylonitrile and methylhydrazine in ethanol at 100 degrees C gives 1-methyl-3-aminopyrazole, which reacts with 4-fluorobenzaldehyde and a ketone, obtained by Claisen condensation of 4-picoline, in a Hantzsch-type 3-component heterocyclocondensation, to give the pyrazolopyridine UR-13756. UR-13756 shows p38 MAPK inhibitory activity in human telomerase reverse transcriptase-immortalized HCA2 dermal fibroblasts, with an IC(50) of 80 nm, as shown by ELISA, is 100% efficacious for up to 24 h at 1.0 mu m and displays excellent kinase selectivity-over the related stress-activated c-Jun kinases. In addition, UR-13756 is an effective p38 inhibitor at 1.0 mu m in Werner syndrome cells, as shown by immunoblot. Conclusion: The convergent synthesis of UR-13756 is realized using microwave dielectric heating and provides a highly selective inhibitor that shows excellent selectivity for p38 MAPK over c-Jun N-terminal kinase.