Harnessing Glutamine-117 Plasticity toward Structure-Based Identification of Triazole IL-17 Inhibitors

The proinflammatory cytokine IL-17 is crucial for host defense but has also been linked to various inflammatory and autoimmune diseases. Antibody-based IL-17 inhibitors like secukinumab (Cosentyx) have demonstrated clinical success in psoriasis, psoriatic arthritis, and ankylosing spondylitis, sparking efforts to develop orally bioavailable small molecule alternatives. However, most small molecule IL-17 inhibitors failed in preclinical and clinical stages due to safety concerns and other challenges. This work describes the discovery of a 1,2,4-triazole scaffold that acts as an amide bioisostere. Its unique vector toward the Trp90 pocket, a key cavity for ligand binding, required the development of novel motifs. A structure-based library approach, considering the high plasticity of the Gln117 side chain, yielded structurally diverse Trp90 pocket binding motifs. The X-ray structures of the most potent hits guided subsequent optimization, resulting in triazole-based IL-17 inhibitors with low nanomolar cellular activity, which are promising leads for further development.