Structure-Based Drug Design of Novel Indazole/Indolinone-Based Biaryl Derivatives as Oral IRAK4 Inhibitors for the Treatment of Inflammatory Diseases

Pathological inflammation in multiple diseases arises from dysregulated innate immune signaling, wherein the interleukin-1 receptor-associated kinase 4 (IRAK4) acts as a critical node that mediates pro-inflammatory cascades and cytokine release downstream of toll-like and interleukin-1 receptors (TLR/IL-1R). Consequently, the therapeutic inhibition of IRAK4 using small molecules has emerged as a promising strategy for these conditions, particularly, rheumatoid arthritis. In this study, we identified a series of novel IRAK4 inhibitors featuring an indazole/indolinone-based biaryl scaffold, and forty-seven novel compounds were designed and synthesized using structure-based rational drug design strategies. Notably, compound 43 exhibited potent molecular and cellular IRAK4 inhibitory activities as well as in vivo anti-inflammatory activities in both LPS-induced acute inflammation and collagen-induced arthritis models alongside favorable pharmacokinetic properties. These findings indicated that compound 43 is a valuable lead compound for further structural optimization and the development of novel IRAK4-targeted anti-inflammatory therapies.