TOWARDS NEW ANTINFLAMMATORY AGENTS: DESIGN, SYNTHESIS AND EVALUATIONS OF MOLECULES TARGETING XIAP-BIR2 – NADAABIR

XIAP (X-chromosome-linked inhibitor of apoptosis protein) is involved in various cellular processes, such as apoptosis and the immune response. It also coordinates a series of events leading to the production of pro-inflammatory cytokines. Recently, the key role of XIAP in the NOD signalling pathway has been highlighted. This pathway is overexpressed in inflammatory diseases such as Crohn's disease and sarcoidosis. XIAP could therefore be a valuable target for developing new treatments for these NOD2-mediated inflammatory diseases. Indeed, it has been observed that the absence of XIAP in cells leads to defective ubiquitination of serine/threonine/tyrosine-protein kinase 2 (RIPK2), and reduces the production of pro-inflammatory cytokines, notably IL8. As the ubiquitination of RIPK2 is regulated by its binding to XIAP via its BIR2 domain, specific inhibitors of XIAP, binding to XIAP-BIR2, could disrupt XIAP/RIPK2 complex formation, and have therapeutic applications in chronic inflammatory diseases. The data in the literature also show that targeting XIAP via its BIR2 domain could result in more selective XIAP activity and avoid serious adverse effects.
The aim of this project is to design, synthesize, and evaluate synthetic small molecules both affine and selective for XIAP-BIR2. Preliminary results obtained by CERMN have identified two molecules (a fragment (hit1) and a molecule (hit2)) that are affine and selective for XIAP-BIR2. The hit2 molecule showed in cellulo its ability to disrupt the interaction between XIAP-BIR2 and RIPK2. On the basis of these results, we propose an applied multidisciplinary approach starting with structural studies of the interaction of hits 1 and 2 with XIAP-BIR2, accompanied by a study of the conformational flexibility of the entire XIAP protein induced by binding of the inhibitor. An in silico drug design strategy will then be initiated, followed by the synthesis of designed compounds via a fragment growing approach, to obtain molecules affine and selective for XIAP. An in vitro evaluation will enable us to assess their affinity for XIAP-BIR2, as well as their selectivity, by measuring their affinity for XIAP-BIR3 and cIAPs-BIR2. Early assessment of the druggability (solubility, logP, membrane passage) of the compounds will be carried out throughout the project. Finally, the molecules will be evaluated in cell models to determine their potential to disrupt the XIAP/RIPK2 interaction, and their anti-inflammatory potential, via the reduction of IL8 production.