Discovery of Novel Potent and Fast BTK PROTACs for the Treatment of Osteoclasts-Related Inflammatory Diseases

Bruton's tyrosine kinase (BTK) is an attractive target in inflammatory and autoimmune diseases. However, the effectiveness of BTK inhibitors is limited by side effects and drug resistance. In this study, we report the development of novel BTK proteolysis targeting chimeras (PROTACs) with different classes of BTK-targeting ligands (e.g., spebrutinib) other than ibrutinib. Compound 23 was identified as a potent and fast BTK PROTAC degrader, exhibiting outstanding degradation potency and efficiency in Mino cells (DC50, 4 h = 1.29 ± 0.3 nM, t1/2, 20 nM = 0.59 ± 0.20 h). Furthermore, compound 23 forms a stable ternary complex, as confirmed by the HTRF assay. Notably, 23 down-regulated the BTK-PLCγ2-Ca2+-NFATc1 signaling pathway activated by RANKL, thus inhibiting osteoclastogenesis and attenuating alveolar bone resorption in a mouse periodontitis model. These findings suggest that compound 23 is a potent and promising candidate for osteoclast-related inflammatory diseases, expanding the potential of BTK PROTACs.