Discovery of Potent Benzolactam IRAK4 Inhibitors with Robust in Vivo Activity

Abstract

IRAK4 kinase activity transduces signaling from multiple IL-1Rs and TLRs to regulate cytokines and chemokines implicated in inflammatory diseases. As such, there is high interest in identifying selective IRAK4 inhibitors for the treatment of these disorders. We previously reported the discovery of potent and selective dihydrobenzofuran inhibitors of IRAK4. Subsequent studies, however, showed inconsistent inhibition in disease-relevant pharmacodynamic models. Herein, we describe application of a human whole blood assay to the discovery of a series of benzolactam IRAK4 inhibitors. We identified potent molecule 19 that achieves robust in vivo inhibition of cytokines relevant to human disease.

Figure 1

(A) Examples of recently disclosed IRAK4 inhibitors and (B) co-crystal structure of 4 with IRAK4 (1.8 Å, PDB ID 6O95).

Figure 2

Comparison of 4 and 19 in HWB assays. (A) IC₅₀ and (B) MI for IL-6 and INFα. Each point reflects at least two donors.

Figure 3

X-ray cocrystal structure of lactam 19 (gold) bound to IRAK4 (green) (PDB ID 6UYA). Polar interactions between the ligand and protein are indicated by dashed lines.

Figure 4

Effect of compound 4 and 19 on the proinflammatory IFNα in an R848-induced mouse PD model. (A) Plasma concentration upon dosing a nanosuspension of either 4 or 19 in MCT, 2 h after compound treatment and 1 h after stimulation with R848. (B) IFNα levels as determined by ELISA, 2 h after compound treatment and 1 h after stimulation with R848.

Scheme 1. Synthesis of Benzolactam IRAK4 Inhibitors

Reagents and conditions: (a) NH₂R¹, triethylamine, methanol (48%-quant.); (b) NHR²R³, potassium carbonate (63%-quant.); (c) tin(II) chloride dihydrate, or Fe, ammonium chloride, or H₂, Pd/C (quant.); (d) 31, triethylamine, or 32, 7-azabenzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate, 2,4,5-trimethylpyridine (13% quant.).